Metaphysics

Metaphysics

Overview
Metaphysics is a branch of philosophy
Philosophy
Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational...

 concerned with explaining the fundamental nature of being
Being
Being , is an English word used for conceptualizing subjective and objective aspects of reality, including those fundamental to the self —related to and somewhat interchangeable with terms like "existence" and "living".In its objective usage —as in "a being," or "[a] human being" —it...

 and the world
World
World is a common name for the whole of human civilization, specifically human experience, history, or the human condition in general, worldwide, i.e. anywhere on Earth....

, although the term is not easily defined. Traditionally, metaphysics attempts to answer two basic questions in the broadest possible terms:
  1. "What is there?"
  2. "What is it like?"


A person who studies metaphysics is called a metaphysicist or a metaphysician.
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Metaphysics is a branch of philosophy
Philosophy
Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational...

 concerned with explaining the fundamental nature of being
Being
Being , is an English word used for conceptualizing subjective and objective aspects of reality, including those fundamental to the self —related to and somewhat interchangeable with terms like "existence" and "living".In its objective usage —as in "a being," or "[a] human being" —it...

 and the world
World
World is a common name for the whole of human civilization, specifically human experience, history, or the human condition in general, worldwide, i.e. anywhere on Earth....

, although the term is not easily defined. Traditionally, metaphysics attempts to answer two basic questions in the broadest possible terms:
  1. "What is there?"
  2. "What is it like?"


A person who studies metaphysics is called a metaphysicist or a metaphysician. The metaphysician attempts to clarify the fundamental notions by which people understand the world, e.g., existence
Existence
In common usage, existence is the world we are aware of through our senses, and that persists independently without them. In academic philosophy the word has a more specialized meaning, being contrasted with essence, which specifies different forms of existence as well as different identity...

, object
Object (philosophy)
An object in philosophy is a technical term often used in contrast to the term subject. Consciousness is a state of cognition that includes the subject, which can never be doubted as only it can be the one who doubts, and some object or objects that may or may not have real existence without...

s and their properties
Property (philosophy)
In modern philosophy, logic, and mathematics a property is an attribute of an object; a red object is said to have the property of redness. The property may be considered a form of object in its own right, able to possess other properties. A property however differs from individual objects in that...

, space
Space
Space is the boundless, three-dimensional extent in which objects and events occur and have relative position and direction. Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of a boundless four-dimensional continuum...

 and time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

, cause and effect
Causality
Causality is the relationship between an event and a second event , where the second event is understood as a consequence of the first....

, and possibility.

A central branch of metaphysics is ontology
Ontology
Ontology is the philosophical study of the nature of being, existence or reality as such, as well as the basic categories of being and their relations...

, the investigation into the basic categories of being
Category of being
In metaphysics , the different kinds or ways of being are called categories of being or simply categories. To investigate the categories of being is to determine the most fundamental and the broadest classes of entities...

 and how they relate to each other.

Prior to the modern history of science
History of science
The history of science is the study of the historical development of human understandings of the natural world and the domains of the social sciences....

, scientific questions were addressed as a part of metaphysics known as natural philosophy
Natural philosophy
Natural philosophy or the philosophy of nature , is a term applied to the study of nature and the physical universe that was dominant before the development of modern science...

. The term science itself meant "knowledge" of, originating from epistemology. The scientific method
Scientific method
Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...

, however, transformed natural philosophy into an empirical
Empirical
The word empirical denotes information gained by means of observation or experimentation. Empirical data are data produced by an experiment or observation....

 activity deriving from experiment
Experiment
An experiment is a methodical procedure carried out with the goal of verifying, falsifying, or establishing the validity of a hypothesis. Experiments vary greatly in their goal and scale, but always rely on repeatable procedure and logical analysis of the results...

 unlike the rest of philosophy. By the end of the 18th century, it had begun to be called "science" to distinguish it from philosophy. Thereafter, metaphysics denoted philosophical enquiry of a non-empirical character into the nature of existence.

Etymology


The word "metaphysics" derives from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 words μετά (metá
Meta
Meta- , is a prefix used in English to indicate a concept which is an abstraction from another concept, used to complete or add to the latter....

)
("beyond" or "after") and φυσικά (physiká) ("physics"). It was first used as the title for several of Aristotle's works, because they were usually anthologized after the works on physics
Physics (Aristotle)
The Physics of Aristotle is one of the foundational books of Western science and philosophy...

 in complete editions. The prefix meta- ("beyond") indicates that these works come "after" the chapters on physics. However, Aristotle himself did not call the subject of these books "Metaphysics": he referred to it as "first philosophy." The editor of Aristotle's works, Andronicus of Rhodes
Andronicus of Rhodes
Andronicus of Rhodes was a Greek philosopher from Rhodes who was also the eleventh scholarch of the Peripatetic school.He was at the head of the Peripatetic school at Rome, about 58 BC, and was the teacher of Boethus of Sidon, with whom Strabo studied...

, is thought to have placed the books on first philosophy right after another work, Physics, and called them (ta meta ta physika biblia) or "the books that come after the [books on] physics". This was misread by Latin scholiasts, who thought it meant "the science of what is beyond the physical".

However, once the name was given, the commentators sought to find intrinsic reasons for its appropriateness. For instance, it was understood to mean "the science of the world beyond nature (phusis in Greek)," that is, the science of the immaterial. Again, it was understood to refer to the chronological or pedagogical order among our philosophical studies, so that the "metaphysical sciences would mean, those that we study after having mastered the sciences that deal with the physical world" (St. Thomas Aquinas, "In Lib, Boeth. de Trin.", V, 1).

There is a widespread use of the term in current popular literature, which replicates this error, i.e. that metaphysical means spiritual non-physical: thus, "metaphysical healing" means healing by means of remedies that are not physical.

Origins and nature of metaphysics


Although the
word "metaphysics" goes back to Aristotelean philosophy, Aristotle himself credited earlier philosophers with dealing with metaphysical questions. The first known philosopher, according to Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

, is Thales
Thales
Thales of Miletus was a pre-Socratic Greek philosopher from Miletus in Asia Minor, and one of the Seven Sages of Greece. Many, most notably Aristotle, regard him as the first philosopher in the Greek tradition...

 of Miletus
Miletus
Miletus was an ancient Greek city on the western coast of Anatolia , near the mouth of the Maeander River in ancient Caria...

, who taught that all things derive from a single first cause or
Arche
Arche
Arche is a Greek word with primary senses 'beginning', 'origin' or 'first cause' and 'power', 'sovereignty', 'domination' as extended meanings. This list is extended to 'ultimate underlying substance' and 'ultimate undemonstrable principle'...

.

Scientific questions in ancient Greece were addressed to metaphysicians, but by the 18th century, the skeptics'
How do you know? led to a new branch of philosophy called epistemology (how we know) to fill-out the metaphysics (what we know) and this led to science (Latin to know) and to the scientific method
Scientific method
Scientific method refers to a body of techniques for investigating phenomena, acquiring new knowledge, or correcting and integrating previous knowledge. To be termed scientific, a method of inquiry must be based on gathering empirical and measurable evidence subject to specific principles of...

 (the precision of which is still being debated). Skepticism evolved epistemology out of metaphysics. Thereafter, metaphysics denoted philosophical inquiry of a non-empirical character into the nature of existence.

Metaphysics as a discipline
Discipline
In its original sense, discipline is referred to systematic instruction given to disciples to train them as students in a craft or trade, or to follow a particular code of conduct or "order". Often, the phrase "to discipline" carries a negative connotation. This is because enforcement of order –...

 was a central part of academic inquiry and scholarly education even before the age of Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

, who considered it "the Queen of Sciences." Its issues were considered no less important than the other main formal subjects of physical science
Physical science
Physical science is an encompassing term for the branches of natural science and science that study non-living systems, in contrast to the life sciences...

, medicine
Medicine
Medicine is the science and art of healing. It encompasses a variety of health care practices evolved to maintain and restore health by the prevention and treatment of illness....

, mathematics
Mathematics
Mathematics is the study of quantity, space, structure, and change. Mathematicians seek out patterns and formulate new conjectures. Mathematicians resolve the truth or falsity of conjectures by mathematical proofs, which are arguments sufficient to convince other mathematicians of their validity...

, poetics
Poetics
Aristotle's Poetics is the earliest-surviving work of dramatic theory and the first extant philosophical treatise to focus on literary theory...

 and music
Music
Music is an art form whose medium is sound and silence. Its common elements are pitch , rhythm , dynamics, and the sonic qualities of timbre and texture...

. Since the beginning of modern philosophy
17th-century philosophy
17th-century philosophy in the Western world is generally regarded as being the start of modern philosophy, and a departure from the medieval approach, especially Scholasticism....

 during the seventeenth century, problems that were not originally considered within the bounds of metaphysics have been added to its purview, while other problems considered metaphysical for centuries are now typically subjects of their own separate regions in philosophy, such as philosophy of religion
Philosophy of religion
Philosophy of religion is a branch of philosophy concerned with questions regarding religion, including the nature and existence of God, the examination of religious experience, analysis of religious language and texts, and the relationship of religion and science...

, philosophy of mind
Philosophy of mind
Philosophy of mind is a branch of philosophy that studies the nature of the mind, mental events, mental functions, mental properties, consciousness and their relationship to the physical body, particularly the brain. The mind-body problem, i.e...

, philosophy of perception
Philosophy of perception
The philosophy of perception is concerned with the nature of perceptual experience and the status of perceptual data, in particular how they relate to beliefs about, or knowledge of, the world. Any explicit account of perception requires a commitment to one of a variety of ontological or...

, philosophy of language
Philosophy of language
Philosophy of language is the reasoned inquiry into the nature, origins, and usage of language. As a topic, the philosophy of language for analytic philosophers is concerned with four central problems: the nature of meaning, language use, language cognition, and the relationship between language...

, and philosophy of science
Philosophy of science
The philosophy of science is concerned with the assumptions, foundations, methods and implications of science. It is also concerned with the use and merit of science and sometimes overlaps metaphysics and epistemology by exploring whether scientific results are actually a study of truth...

.

In some cases, subjects of metaphysical scholarship have been found to be entirely physical and natural, thus making them part of science proper (cf. the theory of Relativity
Theory of relativity
The theory of relativity, or simply relativity, encompasses two theories of Albert Einstein: special relativity and general relativity. However, the word relativity is sometimes used in reference to Galilean invariance....

).

Aristotle's branching


Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

's Metaphysics
Metaphysics (Aristotle)
Metaphysics is one of the principal works of Aristotle and the first major work of the branch of philosophy with the same name. The principal subject is "being qua being", or being understood as being. It examines what can be asserted about anything that exists just because of its existence and...

was divided into three parts, which are now regarded as the proper branches of traditional Western metaphysics:

Ontology
Ontology
Ontology is the philosophical study of the nature of being, existence or reality as such, as well as the basic categories of being and their relations...

: The study of being
Being
Being , is an English word used for conceptualizing subjective and objective aspects of reality, including those fundamental to the self —related to and somewhat interchangeable with terms like "existence" and "living".In its objective usage —as in "a being," or "[a] human being" —it...

 and existence
Existence
In common usage, existence is the world we are aware of through our senses, and that persists independently without them. In academic philosophy the word has a more specialized meaning, being contrasted with essence, which specifies different forms of existence as well as different identity...

; includes the definition and classification of entities
Entity
An entity is something that has a distinct, separate existence, although it need not be a material existence. In particular, abstractions and legal fictions are usually regarded as entities. In general, there is also no presumption that an entity is animate.An entity could be viewed as a set...

, physical or mental, the nature of their properties, and the nature of change.

Natural Theology
Natural theology
Natural theology is a branch of theology based on reason and ordinary experience. Thus it is distinguished from revealed theology which is based on scripture and religious experiences of various kinds; and also from transcendental theology, theology from a priori reasoning.Marcus Terentius Varro ...

: The study of a God
God
God is the English name given to a singular being in theistic and deistic religions who is either the sole deity in monotheism, or a single deity in polytheism....

 or Gods; involves many topics, including among others the nature of religion and the world, existence of the divine
Divinity
Divinity and divine are broadly applied but loosely defined terms, used variously within different faiths and belief systems — and even by different individuals within a given faith — to refer to some transcendent or transcendental power or deity, or its attributes or manifestations in...

, questions about Creation, and the numerous religious or spiritual
Spirituality
Spirituality can refer to an ultimate or an alleged immaterial reality; an inner path enabling a person to discover the essence of his/her being; or the “deepest values and meanings by which people live.” Spiritual practices, including meditation, prayer and contemplation, are intended to develop...

 issues that concern humankind in general.

Universal science
Universal science
Universal science is a branch of Metaphysics. Originally, the idea of Universal Science came from Plato's system of idealism, formulated using the teachings of Socrates.-External sources:*...

: The study of first principles, such as the law of noncontradiction
Law of noncontradiction
In classical logic, the law of non-contradiction is the second of the so-called three classic laws of thought. It states that contradictory statements cannot both at the same time be true, e.g...

, which Aristotle believed were the foundation of all other inquiries.

Universal science or first philosophy treats of "being qua being"—that is, what is basic to all science before one adds the particular details of any one science. Essentially "being
qua being" may be translated as "being insofar as being goes" or as "being in terms of being." This includes topics such as causality, substance, species and elements, as well as the notions of relation, interaction, and finitude.

Central questions



Most positions that can be taken with regards to any of the following questions are endorsed by one or another notable philosopher. It is often difficult to frame the questions in a non-controversial manner.

Being, existence and reality


The nature of Being is a perennial topic in metaphysics. For instance, Parmenides
Parmenides
Parmenides of Elea was an ancient Greek philosopher born in Elea, a Greek city on the southern coast of Italy. He was the founder of the Eleatic school of philosophy. The single known work of Parmenides is a poem, On Nature, which has survived only in fragmentary form. In this poem, Parmenides...

 taught that reality was a single unchanging Being
Being
Being , is an English word used for conceptualizing subjective and objective aspects of reality, including those fundamental to the self —related to and somewhat interchangeable with terms like "existence" and "living".In its objective usage —as in "a being," or "[a] human being" —it...

. The 20th century philosopher Heidegger thought previous philosophers have lost sight of the question of Being (qua Being) in favour of the questions of beings (existing things), so that a return to the Parmenidean approach was needed. An ontological catalogue is an attempt to list the fundamental constituents of reality. The question of whether or not existence
Existence
In common usage, existence is the world we are aware of through our senses, and that persists independently without them. In academic philosophy the word has a more specialized meaning, being contrasted with essence, which specifies different forms of existence as well as different identity...

 is a predicate has been discussed since the Early Modern period, not least in relation to the ontological argument for the existence of God. Existence, that something is, has been contrasted with essence
Essence
In philosophy, essence is the attribute or set of attributes that make an object or substance what it fundamentally is, and which it has by necessity, and without which it loses its identity. Essence is contrasted with accident: a property that the object or substance has contingently, without...

, the question of what something is.
Since existence without essence seems blank, it associated with nothingness by philosophers such as Hegel.
Objects and their properties


The world seems to contain many individual things, both physical, like apples, and abstract such as love and the number 3; the former objects are called particular
Particular
In philosophy, particulars are concrete entities existing in space and time as opposed to abstractions. There are, however, theories of abstract particulars or tropes. For example, Socrates is a particular...

s. Particulars are said to have attributes, e.g. size, shape, color, location and two particulars may have some such attributes in common. Such attributes, are also termed Universals or Properties
Property (philosophy)
In modern philosophy, logic, and mathematics a property is an attribute of an object; a red object is said to have the property of redness. The property may be considered a form of object in its own right, able to possess other properties. A property however differs from individual objects in that...

; the nature of these, and whether they have any real existence and if so of what kind, is a long-standing issue, realism
Philosophical realism
Contemporary philosophical realism is the belief that our reality, or some aspect of it, is ontologically independent of our conceptual schemes, linguistic practices, beliefs, etc....

 and nominalism
Nominalism
Nominalism is a metaphysical view in philosophy according to which general or abstract terms and predicates exist, while universals or abstract objects, which are sometimes thought to correspond to these terms, do not exist. Thus, there are at least two main versions of nominalism...

 representing opposing views.

Metaphysicians concerned with questions about universals or particulars are interested in the nature of objects
Object (philosophy)
An object in philosophy is a technical term often used in contrast to the term subject. Consciousness is a state of cognition that includes the subject, which can never be doubted as only it can be the one who doubts, and some object or objects that may or may not have real existence without...

 and their properties, and the relationship between the two. Some, e.g. Plato, argue that properties are abstract objects, existing outside of space
Space
Space is the boundless, three-dimensional extent in which objects and events occur and have relative position and direction. Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of a boundless four-dimensional continuum...

 and time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

, to which particular objects bear special relations. David Armstrong holds that universals exist in time and space but only at their instantiation and their discovery is a function of science. Others maintain that particulars are a bundle
Bundle theory
Bundle theory, originated by the 18th century Scottish philosopher David Hume, is the ontological theory about objecthood in which an object consists only of a collection of properties, relations or tropes....

 or collection of properties (specifically, a bundle of properties they have).

Abstract objects and mathematics



Some philosophers endorse views according to which there are abstract objects such as numbers, or Universals. (Universals are properties that can be instantiated by multiple objects, such as redness or squareness.) Abstract objects are generally regarded as being outside of space and time, and/or as being causally inert. Mathematical objects and fictional entities and worlds are often given as examples of abstract objects. The view that there really are no abstract objects is called nominalism. Realism about such objects is exemplified by Platonism. Other positions include moderate realism, as espoused by Aristotle, and conceptualism.

The philosophy of mathematics overlaps with metaphysics because some positions are realistic in the sense that they hold that mathematical objects really exist, whether transcendentally, physically, or mentally. Platonic realism holds that mathematical entities are a transcendent realm of non-physical objects. The simplest form of mathematical empiricism claims that mathematical objects are just ordinary physical objects, i.e. that squares and the like physically exist. Plato rejected this view, among other reasons, because geometrical figures in mathematics have a perfection that no physical instantiation can capture. Modern mathematicians have developed many strange and complex mathematical structures with no counterparts in observable reality, further undermining this view. The third main form of realism holds that mathematical entities exist in the mind. However, given a materialistic conception of the mind, it does not have the capacity to literally contain the many infinities of objects in mathematics. Intuitionism, inspired by Kant, sticks with the idea that "there are no non-experienced mathematical truths". This involves rejecting as intuitionistically unacceptable anything that cannot be held in the mind or explicitly constructed. Intuitionists reject the law of the excluded middle and are suspicious of infinity, particularly of transfinite numbers.

Other positions such as formalism and fictionalism that do not attribute any existence to mathematical entities are anti-realist
Anti-realism
In analytic philosophy, the term anti-realism is used to describe any position involving either the denial of an objective reality of entities of a certain type or the denial that verification-transcendent statements about a type of entity are either true or false...

.

Cosmology and cosmogony



Metaphysical Cosmology is the branch of metaphysics that deals with the world
World
World is a common name for the whole of human civilization, specifically human experience, history, or the human condition in general, worldwide, i.e. anywhere on Earth....

 as the totality of all phenomena in space
Space
Space is the boundless, three-dimensional extent in which objects and events occur and have relative position and direction. Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of a boundless four-dimensional continuum...

 and time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

. Historically, it has had quite a broad scope, and in many cases was founded in religion. The ancient Greeks did not draw a distinction between this use and their model for the cosmos. However, in modern times it addresses questions about the Universe
Universe
The Universe is commonly defined as the totality of everything that exists, including all matter and energy, the planets, stars, galaxies, and the contents of intergalactic space. Definitions and usage vary and similar terms include the cosmos, the world and nature...

 beyond the scope of physical science. It is distinguished from religious cosmology in that it approaches these questions using philosophical methods (e.g. dialectic
Dialectic
Dialectic is a method of argument for resolving disagreement that has been central to Indic and European philosophy since antiquity. The word dialectic originated in Ancient Greece, and was made popular by Plato in the Socratic dialogues...

s).
Cosmogony
Cosmogony
Cosmogony, or cosmogeny, is any scientific theory concerning the coming into existence or origin of the universe, or about how reality came to be. The word comes from the Greek κοσμογονία , from κόσμος "cosmos, the world", and the root of γίνομαι / γέγονα "to be born, come about"...

deals specifically with the origin of the universe.

Modern metaphysical cosmology and cosmogony try to address questions such as:
  • What is the origin of the Universe? What is its first cause? Is its existence necessary? (see monism
    Monism
    Monism is any philosophical view which holds that there is unity in a given field of inquiry. Accordingly, some philosophers may hold that the universe is one rather than dualistic or pluralistic...

    , pantheism
    Pantheism
    Pantheism is the view that the Universe and God are identical. Pantheists thus do not believe in a personal, anthropomorphic or creator god. The word derives from the Greek meaning "all" and the Greek meaning "God". As such, Pantheism denotes the idea that "God" is best seen as a process of...

    , emanationism
    Emanationism
    Emanationism is an idea in the cosmology or cosmogony of certain religious or philosophical systems. Emanation, from the Latin emanare meaning "to flow from" or "to pour forth or out of", is the mode by which all things are derived from the First Reality, or Principle...

     and creationism
    Creationism
    Creationism is the religious beliefthat humanity, life, the Earth, and the universe are the creation of a supernatural being, most often referring to the Abrahamic god. As science developed from the 18th century onwards, various views developed which aimed to reconcile science with the Genesis...

    )
  • What are the ultimate material components of the Universe? (see mechanism
    Mechanism (philosophy)
    Mechanism is the belief that natural wholes are like machines or artifacts, composed of parts lacking any intrinsic relationship to each other, and with their order imposed from without. Thus, the source of an apparent thing's activities is not the whole itself, but its parts or an external...

    , dynamism
    Dynamism (metaphysics)
    Dynamism is a metaphysical concept conceived by Gottfried Leibniz and developed into a full system of cosmology. Dynamism in metaphysical cosmology explains the material world in terms of active, pointlike forces, with no extension but with action at a distance...

    , hylomorphism, atomism
    Atomism
    Atomism is a natural philosophy that developed in several ancient traditions. The atomists theorized that the natural world consists of two fundamental parts: indivisible atoms and empty void.According to Aristotle, atoms are indestructible and immutable and there are an infinite variety of shapes...

    )
  • What is the ultimate reason for the existence of the Universe? Does the cosmos have a purpose? (see teleology
    Teleology
    A teleology is any philosophical account which holds that final causes exist in nature, meaning that design and purpose analogous to that found in human actions are inherent also in the rest of nature. The word comes from the Greek τέλος, telos; root: τελε-, "end, purpose...

    )

Determinism and free will



Determinism
Determinism
Determinism is the general philosophical thesis that states that for everything that happens there are conditions such that, given them, nothing else could happen. There are many versions of this thesis. Each of them rests upon various alleged connections, and interdependencies of things and...

 is the philosophical
Philosophy
Philosophy is the study of general and fundamental problems, such as those connected with existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing such problems by its critical, generally systematic approach and its reliance on rational...

 proposition
Proposition
In logic and philosophy, the term proposition refers to either the "content" or "meaning" of a meaningful declarative sentence or the pattern of symbols, marks, or sounds that make up a meaningful declarative sentence...

 that every event, including human cognition, decision and action, is causally
Causality
Causality is the relationship between an event and a second event , where the second event is understood as a consequence of the first....

 determined by an unbroken chain of prior occurrences. It holds that no random
Randomness
Randomness has somewhat differing meanings as used in various fields. It also has common meanings which are connected to the notion of predictability of events....

, spontaneous, stochastic
Stochastic
Stochastic refers to systems whose behaviour is intrinsically non-deterministic. A stochastic process is one whose behavior is non-deterministic, in that a system's subsequent state is determined both by the process's predictable actions and by a random element. However, according to M. Kac and E...

, mysterious, or miraculous
Miracle
A miracle often denotes an event attributed to divine intervention. Alternatively, it may be an event attributed to a miracle worker, saint, or religious leader. A miracle is sometimes thought of as a perceptible interruption of the laws of nature. Others suggest that a god may work with the laws...

 events occur. The principal consequence of the deterministic claim is that it poses a challenge to the existence of free will
Free will
"To make my own decisions whether I am successful or not due to uncontrollable forces" -Troy MorrisonA pragmatic definition of free willFree will is the ability of agents to make choices free from certain kinds of constraints. The existence of free will and its exact nature and definition have long...

.

The problem of free will
Free will
"To make my own decisions whether I am successful or not due to uncontrollable forces" -Troy MorrisonA pragmatic definition of free willFree will is the ability of agents to make choices free from certain kinds of constraints. The existence of free will and its exact nature and definition have long...

 is the problem of whether rational agents exercise control over their own actions and decisions. Addressing this problem requires understanding the relation between freedom and causation, and determining whether the laws of nature are causally deterministic. Some philosophers, known as Incompatibilists
Incompatibilism
Incompatibilism is the view that a deterministic universe is completely at odds with the notion that people have a free will. Strictly speaking, there is a dichotomy between determinism and free will where philosophers must choose one or the other...

, view determinism and free will as mutually exclusive
Mutually exclusive
In layman's terms, two events are mutually exclusive if they cannot occur at the same time. An example is tossing a coin once, which can result in either heads or tails, but not both....

. If they believe in determinism, they will therefore believe free will to be an illusion, a position known as Hard Determinism. Proponents range from Baruch Spinoza
Baruch Spinoza
Baruch de Spinoza and later Benedict de Spinoza was a Dutch Jewish philosopher. Revealing considerable scientific aptitude, the breadth and importance of Spinoza's work was not fully realized until years after his death...

 to Ted Honderich
Ted Honderich
Ted Honderich is a Canadian-born British philosopher, Grote Professor Emeritus of the Philosophy of Mind and Logic, University College London and Visiting Professor, University of Bath...

.

Others, labeled Compatibilists
Compatibilism
Compatibilism is the belief that free will and determinism are compatible ideas, and that it is possible to believe both without being logically inconsistent. It may, however, be more accurate to say that compatibilists define 'free will' in a way that allows it to co-exist with determinism...

 (or "Soft Determinists"), believe that the two ideas can be coherently reconciled. Adherents of this view include Thomas Hobbes
Thomas Hobbes
Thomas Hobbes of Malmesbury , in some older texts Thomas Hobbs of Malmsbury, was an English philosopher, best known today for his work on political philosophy...

 and many modern philosophers.

Incompatibilists who accept free will
Free will
"To make my own decisions whether I am successful or not due to uncontrollable forces" -Troy MorrisonA pragmatic definition of free willFree will is the ability of agents to make choices free from certain kinds of constraints. The existence of free will and its exact nature and definition have long...

 but reject determinism are called Libertarians
Libertarianism (metaphysics)
Libertarianism is one of the main philosophical positions related to the problems of free will and determinism, which are part of the larger domain of metaphysics. In particular, libertarianism, which is an incompatibilist position, argues that free will is logically incompatible with a...

, a term not to be confused with the political sense. Robert Kane
Robert Kane (philosopher)
Robert Hilary Kane is an American philosopher. He is Distinguished Teaching Professor of Philosophy at the University of Texas at Austin, and is currently on phased retirement....

 is a modern defender of this theory.

It is believed that determinism necessarily entails that humanity or individual humans have no influence on the future and its events (a position known as Fatalism
Fatalism
Fatalism is a philosophical doctrine emphasizing the subjugation of all events or actions to fate.Fatalism generally refers to several of the following ideas:...

). Determinists believe a human being's future depends on present and past events beyond the individual's influence.

Quantum physics


Proponents of the Copenhagen Interpretation
Copenhagen interpretation
The Copenhagen interpretation is one of the earliest and most commonly taught interpretations of quantum mechanics. It holds that quantum mechanics does not yield a description of an objective reality but deals only with probabilities of observing, or measuring, various aspects of energy quanta,...

 of quantum mechanics
Quantum mechanics
Quantum mechanics, also known as quantum physics or quantum theory, is a branch of physics providing a mathematical description of much of the dual particle-like and wave-like behavior and interactions of energy and matter. It departs from classical mechanics primarily at the atomic and subatomic...

 believe that Determinism was proven incorrect with the Heisenberg Uncertainty Principle, which states that certain corresponding physical quantities (such as position and momentum, energy and time, eigenstates of spin in non-parallel directions) cannot be determined simultaneously to an arbitrarily small error. For example, the more precisely a particle's position is measured, the less precisely one can know its momentum from the same measurement. If the momentum is more precisely measured to account for this, the uncertainty in the position will rise. This counter-intuitive result is a consequence of the wave-like behavior of subatomic particles. The Heisenberg Uncertainty Principle is thus a statement providing an inverse correlation between the uncertainties of certain corresponding measurements.

This result has led physicists to develop Quantum field theory
Quantum field theory
Quantum field theory provides a theoretical framework for constructing quantum mechanical models of systems classically parametrized by an infinite number of dynamical degrees of freedom, that is, fields and many-body systems. It is the natural and quantitative language of particle physics and...

 and use the "wave function" to describe physical systems. While differential equations govern the evolution of the wave function, the wave function itself only specifies the probability of an event to be measured. Thus, while the evolution of the wave function is deterministic, the history of a particle is not. The widely held view amongst physicists regards the apparent determinism of Newtonian dynamics, for example, as the limiting behavior of inherently probabilistic phenomena. Classical physics is then considered a convenient and sufficiently accurate description of nature only at macroscopic scales. A large enough scale is usually thought of as much larger than the Compton wavelength
Compton wavelength
The Compton wavelength is a quantum mechanical property of a particle. It was introduced by Arthur Compton in his explanation of the scattering of photons by electrons...

 of the object considered.

Alternative interpretations of quantum theory
Interpretation of quantum mechanics
An interpretation of quantum mechanics is a set of statements which attempt to explain how quantum mechanics informs our understanding of nature. Although quantum mechanics has held up to rigorous and thorough experimental testing, many of these experiments are open to different interpretations...

, such as de Broglie–Bohm theory and the many-worlds interpretation
Many-worlds interpretation
The many-worlds interpretation is an interpretation of quantum mechanics that asserts the objective reality of the universal wavefunction, but denies the actuality of wavefunction collapse. Many-worlds implies that all possible alternative histories and futures are real, each representing an...

, provide a deterministic theoretical framework that is consistent with empirical observation of quantum mechanical phenomena. Notable physicists, such as Albert Einstein
Albert Einstein
Albert Einstein was a German-born theoretical physicist who developed the theory of general relativity, effecting a revolution in physics. For this achievement, Einstein is often regarded as the father of modern physics and one of the most prolific intellects in human history...

 and Erwin Schrödinger
Erwin Schrödinger
Erwin Rudolf Josef Alexander Schrödinger was an Austrian physicist and theoretical biologist who was one of the fathers of quantum mechanics, and is famed for a number of important contributions to physics, especially the Schrödinger equation, for which he received the Nobel Prize in Physics in 1933...

, never believed that Quantum Mechanics was a fundamental theory. Einstein is famous for believing that while Quantum Mechanics provided good experimental predictions, it should ultimately be replaced with a deterministic theory that could account for the seemingly probabilistic nature of the atomic regime. In a letter to Max Born
Max Born
Max Born was a German-born physicist and mathematician who was instrumental in the development of quantum mechanics. He also made contributions to solid-state physics and optics and supervised the work of a number of notable physicists in the 1920s and 30s...

, Einstein wrote, "Quantum mechanics is certainly imposing. But an inner voice tells me that it is not yet the real thing. The theory says a lot, but does not really bring us any closer to the secret of the 'old one'. I, at any rate, am convinced that He does not throw dice." This quote is commonly paraphrased "God does not play dice" or "God does not play dice with the universe", and other slight variants.

Though there remains skepticism, there is a scientific consensus that the laws of Quantum Mechanics correctly describe the universe up to current experimental bounds, and that it is necessary for the very consistency of the subject that our observations be probabilistic in nature (see Bell's Theorem
Bell's theorem
In theoretical physics, Bell's theorem is a no-go theorem, loosely stating that:The theorem has great importance for physics and the philosophy of science, as it implies that quantum physics must necessarily violate either the principle of locality or counterfactual definiteness...

).

Identity and change


The Greeks took some extreme positions on the nature of change: Parmenides
Parmenides
Parmenides of Elea was an ancient Greek philosopher born in Elea, a Greek city on the southern coast of Italy. He was the founder of the Eleatic school of philosophy. The single known work of Parmenides is a poem, On Nature, which has survived only in fragmentary form. In this poem, Parmenides...

 denied that change occurs at all, while Heraclitus
Heraclitus
Heraclitus of Ephesus was a pre-Socratic Greek philosopher, a native of the Greek city Ephesus, Ionia, on the coast of Asia Minor. He was of distinguished parentage. Little is known about his early life and education, but he regarded himself as self-taught and a pioneer of wisdom...

 thought change was ubiquitous: "[Y]ou cannot step into the same river twice".

Identity, sometimes called Numerical Identity, is the relation that a "thing" bears to itself, and which no "thing" bears to anything other than itself (cf. sameness). According to Leibniz
Gottfried Leibniz
Gottfried Wilhelm Leibniz was a German philosopher and mathematician. He wrote in different languages, primarily in Latin , French and German ....

, if some object x is identical to some object y, then any property that x has, y will have as well. However, it seems, too, that objects can change over time. If one were to look at a tree one day, and the tree later lost a leaf, it would seem that one could still be looking at that same tree. Two rival theories to account for the relationship between change and identity
Identity and change
The relationship between identity and change in the philosophical field of metaphysics seems, at first glance, deceptively simple, and belies the complexity of the issues involved. This article explores "the problem of change and identity".- Change :...

 are Perdurantism
Perdurantism
Perdurantism or perdurance theory is a philosophical theory of persistence and identity. The perdurantist view is that an individual has distinct temporal parts throughout its existence....

, which treats the tree as a series of tree-stages, and Endurantism
Endurantism
Endurantism or endurance theory is a philosophical theory of persistence and identity. According to the endurantist view material objects are persisting three-dimensional individuals wholly present at every moment of their existence...

, which maintains that the tree—the same tree—is present at every stage in its history.

Mind and matter



The nature of matter
Hyle
In philosophy, hyle refers to matter or stuff. It can also be the material cause underlying a change in Aristotelian philosophy. The Greeks originally had no word for matter in general, as opposed to raw material suitable for some specific purpose or other, so Aristotle adapted the word for...

 was a problem in its own right in early philosophy. Aristotle himself introduced the idea of matter in general to the Western world, adapting the term hyle
Hyle
In philosophy, hyle refers to matter or stuff. It can also be the material cause underlying a change in Aristotelian philosophy. The Greeks originally had no word for matter in general, as opposed to raw material suitable for some specific purpose or other, so Aristotle adapted the word for...

, which originally meant "lumber." Early debates centered on identifying a single underlying principle. Water was claimed by Thales
Thales
Thales of Miletus was a pre-Socratic Greek philosopher from Miletus in Asia Minor, and one of the Seven Sages of Greece. Many, most notably Aristotle, regard him as the first philosopher in the Greek tradition...

, air by Anaximenes
Anaximenes of Miletus
Anaximenes of Miletus was an Archaic Greek Pre-Socratic philosopher active in the latter half of the 6th century BC. One of the three Milesian philosophers, he is identified as a younger friend or student of Anaximander. Anaximenes, like others in his school of thought, practiced material monism...

,
Apeiron
Apeiron (cosmology)
Apeiron is a Greek word meaning unlimited, infinite or indefinite from ἀ- a-, "without" and πεῖραρ peirar, "end, limit", the Ionic Greek form of πέρας peras, "end, limit, boundary".-Apeiron as an origin:...

 (the Boundless) by Anaximander, fire by Heraclitus
Heraclitus
Heraclitus of Ephesus was a pre-Socratic Greek philosopher, a native of the Greek city Ephesus, Ionia, on the coast of Asia Minor. He was of distinguished parentage. Little is known about his early life and education, but he regarded himself as self-taught and a pioneer of wisdom...

. Democritus
Democritus
Democritus was an Ancient Greek philosopher born in Abdera, Thrace, Greece. He was an influential pre-Socratic philosopher and pupil of Leucippus, who formulated an atomic theory for the cosmos....

, in conjunction with his mentor, Leucippus
Leucippus
Leucippus or Leukippos was one of the earliest Greeks to develop the theory of atomism — the idea that everything is composed entirely of various imperishable, indivisible elements called atoms — which was elaborated in greater detail by his pupil and successor, Democritus...

, conceived of an atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...

ic theory many centuries before it was accepted by modern science. It is worth noting, however, that the grounds necessary to ensure validity to the proposed theory's veridical nature were not scientific, but just as philosophical as those traditions espoused by Thales and Anaximander.

The nature of the mind
Mind
The concept of mind is understood in many different ways by many different traditions, ranging from panpsychism and animism to traditional and organized religious views, as well as secular and materialist philosophies. Most agree that minds are constituted by conscious experience and intelligent...

 and its relation to the body has been seen as more of a problem as science has progressed in its mechanistic understanding of the brain and body. Proposed solutions often have ramifications about the nature of mind as a whole. René Descartes
René Descartes
René Descartes ; was a French philosopher and writer who spent most of his adult life in the Dutch Republic. He has been dubbed the 'Father of Modern Philosophy', and much subsequent Western philosophy is a response to his writings, which are studied closely to this day...

 proposed substance dualism, a theory in which mind and body are essentially different, with the mind having some of the attributes traditionally assigned to the soul, in the seventeenth century. This creates a conceptual puzzle about how the two interact (which has received some strange answers, such as occasionalism
Occasionalism
Occasionalism is a philosophical theory about causation which says that created substances cannot be efficient causes of events. Instead, all events are taken to be caused directly by God...

). Evidence of a close relationship between brain and mind, such as the Phineas Gage
Phineas Gage
Phineas P. Gage was an American railroad construction foreman now remembered for his improbablesurvival of an accident in which a large iron rod was driven completely through his head, destroying much of his brain's left frontal lobe, and for that injury's reported effects on his personality and...

 case, have made this form of dualism increasingly unpopular.

Another proposal discussing the mind-body problem is idealism
Idealism
In philosophy, idealism is the family of views which assert that reality, or reality as we can know it, is fundamentally mental, mentally constructed, or otherwise immaterial. Epistemologically, idealism manifests as a skepticism about the possibility of knowing any mind-independent thing...

, in which the material is sweepingly eliminated in favor of the mental. Idealists, such as George Berkeley
George Berkeley
George Berkeley , also known as Bishop Berkeley , was an Irish philosopher whose primary achievement was the advancement of a theory he called "immaterialism"...

, claim that material objects do not exist unless perceived and only as perceptions. The "German idealists" such as Fichte, Hegel and Schopenhauer took Kant
Immanuel Kant
Immanuel Kant was a German philosopher from Königsberg , researching, lecturing and writing on philosophy and anthropology at the end of the 18th Century Enlightenment....

 as their starting-point, although it is debatable how much of an idealist Kant himself was. Idealism is also a common theme in Eastern philosophy. Related ideas are panpsychism
Panpsychism
In philosophy, panpsychism is the view that all matter has a mental aspect, or, alternatively, all objects have a unified center of experience or point of view...

 and panexperientialism, which say everything has a mind rather than everything exists in a mind. Alfred North Whitehead
Alfred North Whitehead
Alfred North Whitehead, OM FRS was an English mathematician who became a philosopher. He wrote on algebra, logic, foundations of mathematics, philosophy of science, physics, metaphysics, and education...

 was a twentieth-century exponent of this approach.

Idealism
Idealism
In philosophy, idealism is the family of views which assert that reality, or reality as we can know it, is fundamentally mental, mentally constructed, or otherwise immaterial. Epistemologically, idealism manifests as a skepticism about the possibility of knowing any mind-independent thing...

 is a monistic
Monism
Monism is any philosophical view which holds that there is unity in a given field of inquiry. Accordingly, some philosophers may hold that the universe is one rather than dualistic or pluralistic...

 theory that holds there is a single universal substance or principles. Neutral monism
Neutral monism
Neutral monism, in philosophy, is the metaphysical view that the mental and the physical are two ways of organizing or describing the same elements, which are themselves "neutral," that is, neither physical nor mental. This view denies that the mental and the physical are two fundamentally...

, associated in different forms with Baruch Spinoza
Baruch Spinoza
Baruch de Spinoza and later Benedict de Spinoza was a Dutch Jewish philosopher. Revealing considerable scientific aptitude, the breadth and importance of Spinoza's work was not fully realized until years after his death...

 and Bertrand Russell
Bertrand Russell
Bertrand Arthur William Russell, 3rd Earl Russell, OM, FRS was a British philosopher, logician, mathematician, historian, and social critic. At various points in his life he considered himself a liberal, a socialist, and a pacifist, but he also admitted that he had never been any of these things...

, seeks to be less extreme than idealism, and to avoid the problems of substance dualism. It claims that existence consists of a single substance that in itself is neither mental nor physical, but is capable of mental and physical aspects or attributes thus it implies a dual-aspect theory.

For the last one hundred years, the dominant metaphysics has without a doubt been materialistic monism
Materialism
In philosophy, the theory of materialism holds that the only thing that exists is matter; that all things are composed of material and all phenomena are the result of material interactions. In other words, matter is the only substance...

. Type identity theory, token identity theory, functionalism
Functionalism (philosophy of mind)
Functionalism is a theory of the mind in contemporary philosophy, developed largely as an alternative to both the identity theory of mind and behaviourism. Its core idea is that mental states are constituted solely by their functional role — that is, they are causal relations to other mental...

, reductive physicalism, nonreductive physicalism, eliminative materialism
Eliminative materialism
Eliminative materialism is a materialist position in the philosophy of mind. Its primary claim is that people's common-sense understanding of the mind is false and that certain classes of mental states that most people believe in do not exist...

, anomalous monism
Anomalous monism
Anomalous monism is a philosophical thesis about the mind-body relationship. It was first proposed by Donald Davidson in his 1970 paper Mental events. The theory is twofold and states that mental events are identical with physical events, and that the mental is anomalous, i.e. under their mental...

, property dualism
Property dualism
Property dualism describes a category of positions in the philosophy of mind which hold that, although the world is constituted of just one kind of substance - the physical kind - there exist two distinct kinds of properties: physical properties and mental properties...

, epiphenomenalism
Epiphenomenalism
In philosophy of mind, epiphenomenalism, also known as Type-E Dualism, is a view that "mental" states do not have any influence on "physical" states.-Background:...

 and emergence
Emergence
In philosophy, systems theory, science, and art, emergence is the way complex systems and patterns arise out of a multiplicity of relatively simple interactions. Emergence is central to the theories of integrative levels and of complex systems....

 are just some of the candidates for a scientifically informed account of the mind. (It should be noted that while many of these positions are dualisms, none of them are substance dualism.)

Prominent recent philosophers of mind include David Armstrong
David Malet Armstrong
David Malet Armstrong , often D. M. Armstrong, is an Australian philosopher. He is well-known for his work on metaphysics and the philosophy of mind, and for his defence of a factualist ontology, a functionalist theory of the mind, an externalist epistemology, and a necessitarian conception of the...

, Ned Block, David Chalmers
David Chalmers
David John Chalmers is an Australian philosopher specializing in the area of philosophy of mind and philosophy of language, whose recent work concerns verbal disputes. He is Professor of Philosophy and Director of the Centre for Consciousness at the Australian National University...

, Patricia
Patricia Churchland
Patricia Smith Churchland is a Canadian-American philosopher noted for her contributions to neurophilosophy and the philosophy of mind. She has been a Professor at the University of California, San Diego since 1984...

 and Paul Churchland
Paul Churchland
Paul Churchland is a philosopher noted for his studies in neurophilosophy and the philosophy of mind. He is currently a Professor at the University of California, San Diego, where he holds the Valtz Chair of Philosophy. Churchland holds a joint appointment with the Cognitive Science Faculty and...

, Donald Davidson
Donald Davidson (philosopher)
Donald Herbert Davidson was an American philosopher born in Springfield, Massachusetts, who served as Slusser Professor of Philosophy at the University of California, Berkeley from 1981 to 2003 after having also held teaching appointments at Stanford University, Rockefeller University, Princeton...

, Daniel Dennett
Daniel Dennett
Daniel Clement Dennett is an American philosopher, writer and cognitive scientist whose research centers on the philosophy of mind, philosophy of science and philosophy of biology, particularly as those fields relate to evolutionary biology and cognitive science. He is currently the Co-director of...

, Douglas Hofstadter
Douglas Hofstadter
Douglas Richard Hofstadter is an American academic whose research focuses on consciousness, analogy-making, artistic creation, literary translation, and discovery in mathematics and physics...

, Jerry Fodor
Jerry Fodor
Jerry Alan Fodor is an American philosopher and cognitive scientist. He holds the position of State of New Jersey Professor of Philosophy at Rutgers University and is the author of many works in the fields of philosophy of mind and cognitive science, in which he has laid the groundwork for the...

, David Lewis
David Kellogg Lewis
David Kellogg Lewis was an American philosopher. Lewis taught briefly at UCLA and then at Princeton from 1970 until his death. He is also closely associated with Australia, whose philosophical community he visited almost annually for more than thirty years...

, Thomas Nagel
Thomas Nagel
Thomas Nagel is an American philosopher, currently University Professor of Philosophy and Law at New York University, where he has taught since 1980. His main areas of philosophical interest are philosophy of mind, political philosophy and ethics...

, Hilary Putnam
Hilary Putnam
Hilary Whitehall Putnam is an American philosopher, mathematician and computer scientist, who has been a central figure in analytic philosophy since the 1960s, especially in philosophy of mind, philosophy of language, philosophy of mathematics, and philosophy of science...

, John Searle
John Searle
John Rogers Searle is an American philosopher and currently the Slusser Professor of Philosophy at the University of California, Berkeley.-Biography:...

, John Smart
J. J. C. Smart
John Jamieson Carswell "Jack" Smart AC is an Australian philosopher and academic who is currently Emeritus Professor of Philosophy at Monash University, Australia...

, Ludwig Wittgenstein
Ludwig Wittgenstein
Ludwig Josef Johann Wittgenstein was an Austrian philosopher who worked primarily in logic, the philosophy of mathematics, the philosophy of mind, and the philosophy of language. He was professor in philosophy at the University of Cambridge from 1939 until 1947...

, and Fred Alan Wolf
Fred Alan Wolf
Fred Alan Wolf is an American theoretical physicist specializing in quantum physics and the relationship between physics and consciousness. He is a former physics professor at San Diego State University, and more recently has helped to popularize science on the Discovery Channel...

.

Necessity and possibility



Metaphysicians investigate questions about the ways the world could have been. David Lewis
David Kellogg Lewis
David Kellogg Lewis was an American philosopher. Lewis taught briefly at UCLA and then at Princeton from 1970 until his death. He is also closely associated with Australia, whose philosophical community he visited almost annually for more than thirty years...

, in "On the Plurality of Worlds," endorsed a view called Concrete Modal realism
Modal realism
Modal realism is the view, notably propounded by David Kellogg Lewis, that all possible worlds are as real as the actual world. It is based on the following tenets: possible worlds exist; possible worlds are not different in kind from the actual world; possible worlds are irreducible entities; the...

, according to which facts about how things could have been are made true by other concrete worlds, just like ours, in which things are different. Other philosophers, such as Gottfried Leibniz
Gottfried Leibniz
Gottfried Wilhelm Leibniz was a German philosopher and mathematician. He wrote in different languages, primarily in Latin , French and German ....

, have dealt with the idea of possible worlds as well. The idea of necessity is that any necessary fact is true across all possible world
Possible world
In philosophy and logic, the concept of a possible world is used to express modal claims. The concept of possible worlds is common in contemporary philosophical discourse and has also been disputed.- Possibility, necessity, and contingency :...

s; that is, we could not imagine it to be otherwise. A possible fact is true in some possible world, even if not in the actual world. For example, it is possible that cats could have had two tails, or that any particular apple
Apple (symbolism)
Apples appear in many religious traditions, often as a mystical or forbidden fruit. One of the problems identifying apples in religion, mythology and folktales is that as late as the 17th century, the word "apple" was used as a generic term for all fruit other than berries, but including nuts...

 could have not existed. By contrast, certain propositions seem necessarily true, such as analytic propositions, e.g. "All bachelors are unmarried." The particular example of analytic truth being necessary is not universally held among philosophers. A less controversial view might be that self-identity is necessary, as it seems fundamentally incoherent to claim that for any x, it is not identical to itself; this is known as the law of identity, a putative "first principle". Aristotle describes the principle of non-contradiction, "It is impossible that the same quality should both belong and not belong to the same thing . . . This is the most certain of all principles . . . Wherefore they who demonstrate refer to this as an ultimate opinion. For it is by nature the source of all the other axioms."

Religion and spirituality


Theology
Theology
Theology is the systematic and rational study of religion and its influences and of the nature of religious truths, or the learned profession acquired by completing specialized training in religious studies, usually at a university or school of divinity or seminary.-Definition:Augustine of Hippo...

 is the study of a God or gods and the nature of the divine. Whether there is a god (monotheism
Monotheism
Monotheism is the belief in the existence of one and only one god. Monotheism is characteristic of the Baha'i Faith, Christianity, Druzism, Hinduism, Islam, Judaism, Samaritanism, Sikhism and Zoroastrianism.While they profess the existence of only one deity, monotheistic religions may still...

), many gods (polytheism
Polytheism
Polytheism is the belief of multiple deities also usually assembled into a pantheon of gods and goddesses, along with their own mythologies and rituals....

) or no gods (atheism
Atheism
Atheism is, in a broad sense, the rejection of belief in the existence of deities. In a narrower sense, atheism is specifically the position that there are no deities...

), or whether it is unknown or unknowable whether any gods exist (agnosticism
Agnosticism
Agnosticism is the view that the truth value of certain claims—especially claims about the existence or non-existence of any deity, but also other religious and metaphysical claims—is unknown or unknowable....

), and whether the Divine intervenes directly in the world (theism
Theism
Theism, in the broadest sense, is the belief that at least one deity exists.In a more specific sense, theism refers to a doctrine concerning the nature of a monotheistic God and God's relationship to the universe....

), or its sole function is to be the first cause of the universe (deism
Deism
Deism in religious philosophy is the belief that reason and observation of the natural world, without the need for organized religion, can determine that the universe is the product of an all-powerful creator. According to deists, the creator does not intervene in human affairs or suspend the...

); these and whether a God or gods and the World are different (as in panentheism
Panentheism
Panentheism is a belief system which posits that God exists, interpenetrates every part of nature and timelessly extends beyond it...

 and dualism
Dualism
Dualism denotes a state of two parts. The term 'dualism' was originally coined to denote co-eternal binary opposition, a meaning that is preserved in metaphysical and philosophical duality discourse but has been diluted in general or common usages. Dualism can refer to moral dualism, Dualism (from...

), or are identical (as in pantheism
Pantheism
Pantheism is the view that the Universe and God are identical. Pantheists thus do not believe in a personal, anthropomorphic or creator god. The word derives from the Greek meaning "all" and the Greek meaning "God". As such, Pantheism denotes the idea that "God" is best seen as a process of...

), are some of the primary metaphysical questions concerning philosophy of religion.

Within the standard Western philosophical tradition, theology reached its peak under the medieval school of thought known as scholasticism
Scholasticism
Scholasticism is a method of critical thought which dominated teaching by the academics of medieval universities in Europe from about 1100–1500, and a program of employing that method in articulating and defending orthodoxy in an increasingly pluralistic context...

, which focused primarily on the metaphysical aspects of Christianity
Christianity
Christianity is a monotheistic religion based on the life and teachings of Jesus as presented in canonical gospels and other New Testament writings...

. The work of the scholastics is still an integral part of modern philosophy, with key figures such as Thomas Aquinas
Thomas Aquinas
Thomas Aquinas, O.P. , also Thomas of Aquin or Aquino, was an Italian Dominican priest of the Catholic Church, and an immensely influential philosopher and theologian in the tradition of scholasticism, known as Doctor Angelicus, Doctor Communis, or Doctor Universalis...

 still playing an important role in the philosophy of religion
Philosophy of religion
Philosophy of religion is a branch of philosophy concerned with questions regarding religion, including the nature and existence of God, the examination of religious experience, analysis of religious language and texts, and the relationship of religion and science...

.

Space and time


In Book XI of the Confessions
Confessions (St. Augustine)
Confessions is the name of an autobiographical work, consisting of 13 books, by St. Augustine of Hippo, written between AD 397 and AD 398. Modern English translations of it are sometimes published under the title The Confessions of St...

, Saint Augustine of Hippo
Augustine of Hippo
Augustine of Hippo , also known as Augustine, St. Augustine, St. Austin, St. Augoustinos, Blessed Augustine, or St. Augustine the Blessed, was Bishop of Hippo Regius . He was a Latin-speaking philosopher and theologian who lived in the Roman Africa Province...

 asked the fundamental question about the nature of time. A traditional realist
Philosophical realism
Contemporary philosophical realism is the belief that our reality, or some aspect of it, is ontologically independent of our conceptual schemes, linguistic practices, beliefs, etc....

 position in ontology is that time and space have existence apart from the human mind. Idealists, including Kant
Immanuel Kant
Immanuel Kant was a German philosopher from Königsberg , researching, lecturing and writing on philosophy and anthropology at the end of the 18th Century Enlightenment....

, claim that space and time are mental constructs used to organize perceptions, or are otherwise surreal.

Suppose that one is sitting at a table, with an apple in front of him or her; the apple exists in space
Space
Space is the boundless, three-dimensional extent in which objects and events occur and have relative position and direction. Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of a boundless four-dimensional continuum...

 and in time
Time
Time is a part of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify rates of change such as the motions of objects....

, but what does this statement indicate? Could it be said, for example, that space is like an invisible three-dimensional grid in which the apple is positioned? Suppose the apple, and all physical objects in the universe, were removed from existence entirely. Would space as an "invisible grid" still exist? René Descartes
René Descartes
René Descartes ; was a French philosopher and writer who spent most of his adult life in the Dutch Republic. He has been dubbed the 'Father of Modern Philosophy', and much subsequent Western philosophy is a response to his writings, which are studied closely to this day...

 and Leibniz believed it would not, arguing that without physical objects, "space" would be meaningless because space is the framework upon which we understand how physical objects are related to each other. Newton
Isaac Newton
Sir Isaac Newton PRS was an English physicist, mathematician, astronomer, natural philosopher, alchemist, and theologian, who has been "considered by many to be the greatest and most influential scientist who ever lived."...

, on the other hand, argued for an absolute
Absolute time and space
Originally introduced by Sir Isaac Newton in the Philosophiæ Naturalis Principia Mathematica, the concepts of absolute time and space provided a theoretical foundation that facilitated Newtonian mechanics...

 "container" space
Container space
The container theory of space is a metaphysical theory according to which space is a background against which objects rest and move, with the implication that it can continue to exist in the absence of matter. Its opposite is the relational theory. Newton favoured absolute time and space and the...

. The pendulum swung back to relational space
Relational space
The relational theory of space is a metaphysical theory according to which space is composed of relations between objects, with the implication that it cannot exist in the absence of matter. Its opposite is the container theory...

 with Einstein and Ernst Mach
Ernst Mach
Ernst Mach was an Austrian physicist and philosopher, noted for his contributions to physics such as the Mach number and the study of shock waves...

.

While the absolute/relative debate, and the realism debate are equally applicable to time and space, time presents some special problems of its own. The flow of time has been denied in ancient times by Parmenides
Parmenides
Parmenides of Elea was an ancient Greek philosopher born in Elea, a Greek city on the southern coast of Italy. He was the founder of the Eleatic school of philosophy. The single known work of Parmenides is a poem, On Nature, which has survived only in fragmentary form. In this poem, Parmenides...

 and more recently by J. M. E. McTaggart
J. M. E. McTaggart
John McTaggart was an idealist metaphysician. For most of his life McTaggart was a fellow and lecturer in philosophy at Trinity College, Cambridge. He was an exponent of the philosophy of Hegel and among the most notable of the British idealists.-Personal life:J. M. E. McTaggart was born in 1866...

 in his paper
The Unreality of Time
The Unreality of Time
The Unreality of Time is the best-known philosophical work of the Cambridge idealist J. M. E. McTaggart. In the paper, first published in 1908 in Mind 17: 457-73, McTaggart argues that time is unreal because our descriptions of time are either contradictory, circular, or insufficient...

.

The
direction of time, also known as "time's arrow
Arrow of time
The arrow of time, or time’s arrow, is a term coined in 1927 by the British astronomer Arthur Eddington to describe the "one-way direction" or "asymmetry" of time...

", is also a puzzle, although physics is now driving the debate rather than philosophy. It appears that fundamental laws are time-reversible and the arrow of time must be an "emergent
Emergentism
In philosophy, emergentism is the belief in emergence, particularly as it involves consciousness and the philosophy of mind, and as it contrasts with reductionism. A property of a system is said to be emergent if it is in some sense more than the "sum" of the properties of the system's parts...

" phenomenon, perhaps explained by a statistical understanding of thermodynamic entropy
Entropy (arrow of time)
Entropy is the only quantity in the physical sciences that requires a particular direction for time, sometimes called an arrow of time. As one goes "forward" in time, the second law of thermodynamics says, the entropy of an isolated system will increase...

.

Common-sense tells us that objects persist across time, that there is some sense in which you are the same person you were yesterday, in which the oak is the same as the acorn, in which you perhaps even can step into the same river twice. Philosophers have developed two rival theories for how this happens, called "endurantism
Endurantism
Endurantism or endurance theory is a philosophical theory of persistence and identity. According to the endurantist view material objects are persisting three-dimensional individuals wholly present at every moment of their existence...

" and "perdurantism
Perdurantism
Perdurantism or perdurance theory is a philosophical theory of persistence and identity. The perdurantist view is that an individual has distinct temporal parts throughout its existence....

". Broadly speaking, endurantists hold that a whole object exists at each moment of its history, and the same object exists at each moment. Perdurantists believe that objects are four-dimensional entities made up of a series of temporal parts
Temporal parts
Temporal parts is a concept used in contemporary metaphysics in the debate over the persistence of material objects. Objects typically have parts that exist in space—a human body, for example, has spatial parts like hands, feet, and legs. Some metaphysicians believe objects have temporal parts as...

 like the frames of a movie.

Styles and methods of metaphysics

  • Rational versus empirical. Rationalism
    Rationalism
    In epistemology and in its modern sense, rationalism is "any view appealing to reason as a source of knowledge or justification" . In more technical terms, it is a method or a theory "in which the criterion of the truth is not sensory but intellectual and deductive"...

     is a method or a theory "in which the criterion of the truth is not sensory but intellectual and deductive" (Bourke 263). Rationalist metaphysicians aim to deduce the nature of reality by armchair, a priori reasoning. Empiricism
    Empiricism
    Empiricism is a theory of knowledge that asserts that knowledge comes only or primarily via sensory experience. One of several views of epistemology, the study of human knowledge, along with rationalism, idealism and historicism, empiricism emphasizes the role of experience and evidence,...

     holds that the senses are the primary source of knowledge about the world.
  • Analytical versus systemic. The "system building" style of metaphysics attempts to answer all the important questions in a comprehensive and coherent way, providing a theory of everything
    Theory of everything (philosophy)
    In philosophy, a theory of everything or TOE is an ultimate, all-encompassing explanation of nature or reality. Adopting the term from physics, where the search for a theory of everything is ongoing, philosophers have discussed the viability of the concept and analyzed its properties and...

     or complete picture of the world. The contrasting approach is to deal with problems piecemeal.
  • Dogmatic versus critical. Under the scholastic
    Scholasticism
    Scholasticism is a method of critical thought which dominated teaching by the academics of medieval universities in Europe from about 1100–1500, and a program of employing that method in articulating and defending orthodoxy in an increasingly pluralistic context...

     approach of the Middle Ages, a number of themes and ideas were not open to be challenged. Kant and others thought this "dogmatism" should be replaced by a critical
    Critical thinking
    Critical thinking is the process or method of thinking that questions assumptions. It is a way of deciding whether a claim is true, false, or sometimes true and sometimes false, or partly true and partly false. The origins of critical thinking can be traced in Western thought to the Socratic...

     approach.
  • Individual versus collective. Scholasticism and Analytical philosophy are examples of collaborative approaches to philosophy. Many other philosophers expounded individual visions.
  • Parsimonious versus Adequate. Should a metaphysical system posit as little as possible, or as much as needed?
  • Descriptive versus revisionary. Peter Strawson makes the distinction between descriptive metaphysics, which sets out to investigate our deepest assumptions, and revisionary metaphysics, which sets out to improve or rectify them.

Pre-Socratic metaphysics in Greece


The first known philosopher, according to Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

, is Thales
Thales
Thales of Miletus was a pre-Socratic Greek philosopher from Miletus in Asia Minor, and one of the Seven Sages of Greece. Many, most notably Aristotle, regard him as the first philosopher in the Greek tradition...

 of Miletus
Miletus
Miletus was an ancient Greek city on the western coast of Anatolia , near the mouth of the Maeander River in ancient Caria...

. Rejecting mythological and divine explanations, he sought for a single first cause or Arche
Arche
Arche is a Greek word with primary senses 'beginning', 'origin' or 'first cause' and 'power', 'sovereignty', 'domination' as extended meanings. This list is extended to 'ultimate underlying substance' and 'ultimate undemonstrable principle'...

 (origin or beginning) under which all phenomena could be explained, and concluded that this first cause was in fact moisture or water. Thales also taught that the world is harmonious, has a harmonious structure, and thus is intelligible to rational understanding. Other Miletians, such as Anaximander
Anaximander
Anaximander was a pre-Socratic Greek philosopher who lived in Miletus, a city of Ionia; Milet in modern Turkey. He belonged to the Milesian school and learned the teachings of his master Thales...

 and Anaximenes
Anaximenes of Miletus
Anaximenes of Miletus was an Archaic Greek Pre-Socratic philosopher active in the latter half of the 6th century BC. One of the three Milesian philosophers, he is identified as a younger friend or student of Anaximander. Anaximenes, like others in his school of thought, practiced material monism...

, also had a monistic
Monism
Monism is any philosophical view which holds that there is unity in a given field of inquiry. Accordingly, some philosophers may hold that the universe is one rather than dualistic or pluralistic...

 conception of the first cause.

Another school was the Eleatics
Eleatics
The Eleatics were a school of pre-Socratic philosophers at Elea , a Greek colony in Campania, Italy. The group was founded in the early fifth century BCE by Parmenides. Other members of the school included Zeno of Elea and Melissus of Samos...

, Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...

. The group was founded in the early fifth century BCE by Parmenides
Parmenides
Parmenides of Elea was an ancient Greek philosopher born in Elea, a Greek city on the southern coast of Italy. He was the founder of the Eleatic school of philosophy. The single known work of Parmenides is a poem, On Nature, which has survived only in fragmentary form. In this poem, Parmenides...

, and included Zeno of Elea
Zeno of Elea
Zeno of Elea was a pre-Socratic Greek philosopher of southern Italy and a member of the Eleatic School founded by Parmenides. Aristotle called him the inventor of the dialectic. He is best known for his paradoxes, which Bertrand Russell has described as "immeasurably subtle and profound".- Life...

 and Melissus of Samos
Melissus of Samos
Melissus of Samos was the third and last member of the ancient school of Eleatic philosophy, whose other members included Zeno and Parmenides. Little is known about his life except that he was the commander of the Samian fleet shortly before the Peloponnesian War. Melissus’ contribution to...

. Methodologically, the Eleatics were broadly rationalist, rejecting the epistemological validity of sense experience, and instead took logical standards of clarity and necessity to be the criteria of truth
Truth
Truth has a variety of meanings, such as the state of being in accord with fact or reality. It can also mean having fidelity to an original or to a standard or ideal. In a common usage, it also means constancy or sincerity in action or character...

. Parmenides' chief doctrine was that reality is a single unchanging and universal Being. Zeno used reductio ad absurdum
Reductio ad absurdum
In logic, proof by contradiction is a form of proof that establishes the truth or validity of a proposition by showing that the proposition's being false would imply a contradiction...

, to demonstrate the illusory nature of change and time in his paradoxes
Zeno's paradoxes
Zeno's paradoxes are a set of problems generally thought to have been devised by Greek philosopher Zeno of Elea to support Parmenides's doctrine that "all is one" and that, contrary to the evidence of our senses, the belief in plurality and change is mistaken, and in particular that motion is...

.

Heraclitus
Heraclitus
Heraclitus of Ephesus was a pre-Socratic Greek philosopher, a native of the Greek city Ephesus, Ionia, on the coast of Asia Minor. He was of distinguished parentage. Little is known about his early life and education, but he regarded himself as self-taught and a pioneer of wisdom...

 of Ephesus
Ephesus
Ephesus was an ancient Greek city, and later a major Roman city, on the west coast of Asia Minor, near present-day Selçuk, Izmir Province, Turkey. It was one of the twelve cities of the Ionian League during the Classical Greek era...

, in contrast, made change central, teaching that "all things flow". His philosophy, expressed in brief aphorisms, is quite cryptic. For instance, he also taught the unity of opposites
Unity of opposites
The unity of opposites was first suggested by Heraclitus a pre-Socratic Greek philosopher.Philosophers had for some time been contemplating the notion of opposites. Anaximander posited that every element was an opposite, or connected to an opposite...

.

Democritus
Democritus
Democritus was an Ancient Greek philosopher born in Abdera, Thrace, Greece. He was an influential pre-Socratic philosopher and pupil of Leucippus, who formulated an atomic theory for the cosmos....

 and his teacher Leucippus
Leucippus
Leucippus or Leukippos was one of the earliest Greeks to develop the theory of atomism — the idea that everything is composed entirely of various imperishable, indivisible elements called atoms — which was elaborated in greater detail by his pupil and successor, Democritus...

, are known for formulating an atomic theory
Atomic theory
In chemistry and physics, atomic theory is a theory of the nature of matter, which states that matter is composed of discrete units called atoms, as opposed to the obsolete notion that matter could be divided into any arbitrarily small quantity...

 for the cosmos. They are considered forerunners of the scientific method.

Socrates and Plato


Socrates
Socrates
Socrates was a classical Greek Athenian philosopher. Credited as one of the founders of Western philosophy, he is an enigmatic figure known chiefly through the accounts of later classical writers, especially the writings of his students Plato and Xenophon, and the plays of his contemporary ...

 is known for his dialectic
Dialectic
Dialectic is a method of argument for resolving disagreement that has been central to Indic and European philosophy since antiquity. The word dialectic originated in Ancient Greece, and was made popular by Plato in the Socratic dialogues...

 or questioning approach to philosophy rather than a positive metaphysical doctrine.
His pupil, Plato
Plato
Plato , was a Classical Greek philosopher, mathematician, student of Socrates, writer of philosophical dialogues, and founder of the Academy in Athens, the first institution of higher learning in the Western world. Along with his mentor, Socrates, and his student, Aristotle, Plato helped to lay the...

 is famous for his theory of forms (which he confusingly places in the mouth of Socrates in the dialogues he wrote to expound it). Platonic realism
Platonic realism
Platonic realism is a philosophical term usually used to refer to the idea of realism regarding the existence of universals or abstract objects after the Greek philosopher Plato , a student of Socrates. As universals were considered by Plato to be ideal forms, this stance is confusingly also called...

 (also considered a form of idealism) is principally a solution to the problem of universals
Problem of universals
The problem of universals is an ancient problem in metaphysics about whether universals exist. Universals are general or abstract qualities, characteristics, properties, kinds or relations, such as being male/female, solid/liquid/gas or a certain colour, that can be predicated of individuals or...

; what particular horses have in common is that they partake in the Form of the Horse.
The theory has a number of other aspects:
  • Epistemological: knowledge of the Forms is more certain than mere sensory data.
  • Ethical. The Form of the Good sets an objective standard for morality.
  • Time and Change: The world of the Forms is eternal and unchanging. Time and change belong only to the lower sensory world. "Time is a moving image of Eternity".
  • Abstract objects and mathematics: Numbers, geometrical figures, etc., exist mind-independently in the World of Forms.


Platonism developed into Neoplatonism
Neoplatonism
Neoplatonism , is the modern term for a school of religious and mystical philosophy that took shape in the 3rd century AD, based on the teachings of Plato and earlier Platonists, with its earliest contributor believed to be Plotinus, and his teacher Ammonius Saccas...

, a philosophy with a monotheistic and mystical flavour that survived well into the early Christian era.

Aristotle


Plato's pupil Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

 wrote widely on almost every subject, including metaphysics
Metaphysics (Aristotle)
Metaphysics is one of the principal works of Aristotle and the first major work of the branch of philosophy with the same name. The principal subject is "being qua being", or being understood as being. It examines what can be asserted about anything that exists just because of its existence and...

. His solution to the problem of universals contrasts with Plato's. Whereas Platonic Forms exist in a separate realm, and can exist uninstantiated in visible things, Aristotelean essences "indwell" in particulars.

Potentiality and Actuality
Potentiality and actuality
In philosophy, Potentiality and Actuality are principles of a dichotomy which Aristotle used throughout his philosophical works to analyze motion, causality, ethics, and physiology in his Physics, Metaphysics, Ethics and De Anima .The concept of potentiality, in this context, generally refers to...

 are principles of a dichotomy
Dichotomy
A dichotomy is any splitting of a whole into exactly two non-overlapping parts, meaning it is a procedure in which a whole is divided into two parts...

 which Aristotle
Aristotle
Aristotle was a Greek philosopher and polymath, a student of Plato and teacher of Alexander the Great. His writings cover many subjects, including physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology, and zoology...

 used throughout his philosophical works to analyze motion
Motion (physics)
In physics, motion is a change in position of an object with respect to time. Change in action is the result of an unbalanced force. Motion is typically described in terms of velocity, acceleration, displacement and time . An object's velocity cannot change unless it is acted upon by a force, as...

, causality
Four causes
Four Causes refers to a principle in Aristotelian science that is used to understand change. Aristotle described four different types of causes, or ways in which an object could be explained: "we do not have knowledge of a thing until we have grasped its why, that is to say, its cause", He argued...

 and other issues.

The Aristotelean theory of change and causality stretches to four causes
Four causes
Four Causes refers to a principle in Aristotelian science that is used to understand change. Aristotle described four different types of causes, or ways in which an object could be explained: "we do not have knowledge of a thing until we have grasped its why, that is to say, its cause", He argued...

: the material, formal, efficient and final. The efficient cause corresponds to what is now known as a cause simpliciter. Final causes are explicitly teleological, a concept now regarded as controversial in science. The Matter/Form dichotomy was to become highly influential in later philosophy as the substance/essence distinction.

Scholasticism and the Middle Ages


Between about 1100 and 1500, philosophy as a discipline took place as part of the Catholic church's teaching system, known as scholasticism
Scholasticism
Scholasticism is a method of critical thought which dominated teaching by the academics of medieval universities in Europe from about 1100–1500, and a program of employing that method in articulating and defending orthodoxy in an increasingly pluralistic context...

. Scholastic philosophy took place within an established
framework blending Christian theology with Aristotelean teachings. Although fundamental orthodoxies could not be challenged, there were nonetheless deep metaphysical disagreements, particularly over the problem of universals
Problem of universals
The problem of universals is an ancient problem in metaphysics about whether universals exist. Universals are general or abstract qualities, characteristics, properties, kinds or relations, such as being male/female, solid/liquid/gas or a certain colour, that can be predicated of individuals or...

, which engaged Duns Scotus
Duns Scotus
Blessed John Duns Scotus, O.F.M. was one of the more important theologians and philosophers of the High Middle Ages. He was nicknamed Doctor Subtilis for his penetrating and subtle manner of thought....

 and Pierre Abelard. William of Ockham
William of Ockham
William of Ockham was an English Franciscan friar and scholastic philosopher, who is believed to have been born in Ockham, a small village in Surrey. He is considered to be one of the major figures of medieval thought and was at the centre of the major intellectual and political controversies of...

 is remembered for his principle of ontological parsimony.

Continental rationalism


In the early modern period (17th and 18th centuries), the system-building scope of philosophy is often linked to the rationalist method of philosophy, that is the technique of deducing the nature of the world by pure reason. The scholastic concepts of substance and accident were employed.
  • Leibniz proposed in his Monadology
    Monadology
    The Monadology is one of Gottfried Leibniz’s best known works representing his later philosophy. It is a short text which sketches in some 90 paragraphs a metaphysics of simple substances, or monads.- Text :...

     a plurality of non-interacting substances.
  • Descartes is famous for his Dualism
    Dualism
    Dualism denotes a state of two parts. The term 'dualism' was originally coined to denote co-eternal binary opposition, a meaning that is preserved in metaphysical and philosophical duality discourse but has been diluted in general or common usages. Dualism can refer to moral dualism, Dualism (from...

     of material and mental substances.
  • Spinoza believed reality was a single substance
    Monism
    Monism is any philosophical view which holds that there is unity in a given field of inquiry. Accordingly, some philosophers may hold that the universe is one rather than dualistic or pluralistic...

     of God-or-nature.

British empiricism


British empiricism marked something of a reaction to rationalist and system-building philosophy, or speculative metaphysics as it was pejoratively termed. The sceptic David Hume
David Hume
David Hume was a Scottish philosopher, historian, economist, and essayist, known especially for his philosophical empiricism and skepticism. He was one of the most important figures in the history of Western philosophy and the Scottish Enlightenment...

 famously declared that most metaphysics should be consigned to the flames (see below). Hume was notorious among his contemporaries as one of the first philosophers to openly doubt religion, but is better known now for his critique of causality. John Stuart Mill
John Stuart Mill
John Stuart Mill was a British philosopher, economist and civil servant. An influential contributor to social theory, political theory, and political economy, his conception of liberty justified the freedom of the individual in opposition to unlimited state control. He was a proponent of...

, Thomas Reid
Thomas Reid
The Reverend Thomas Reid FRSE , was a religiously trained Scottish philosopher, and a contemporary of David Hume, was the founder of the Scottish School of Common Sense, and played an integral role in the Scottish Enlightenment...

 and John Locke
John Locke
John Locke FRS , widely known as the Father of Liberalism, was an English philosopher and physician regarded as one of the most influential of Enlightenment thinkers. Considered one of the first of the British empiricists, following the tradition of Francis Bacon, he is equally important to social...

 were less sceptical, embracing a more cautious style of metaphysics based on realism, common sense
Common sense
Common sense is defined by Merriam-Webster as, "sound and prudent judgment based on a simple perception of the situation or facts." Thus, "common sense" equates to the knowledge and experience which most people already have, or which the person using the term believes that they do or should have...

 and science. Other philosophers, notably George Berkely were led from empiricism to idealistic metaphysics.

Kant


Immanuel Kant
Immanuel Kant
Immanuel Kant was a German philosopher from Königsberg , researching, lecturing and writing on philosophy and anthropology at the end of the 18th Century Enlightenment....

 attempted a grand synthesis and revision of the trends already mentioned: scholastic philosophy, systematic metaphysics, and sceptical empiricism, not to forget the burgeoning science of his day. Like the systems builders, he had an overarching framework in which all questions were to be addressed. Like Hume, who famously woke him from his 'dogmatic slumbers', he was suspicious of metaphysical speculation, and also places much emphasis on the limitations of the human mind.

Kant saw rationalist philosophers as aiming for a kind of metaphysical knowledge he defined as the synthetic apriori — that is knowledge that does not come from the senses (it is a apriori) but is nonetheless about reality (synthetic). Inasmuch as it is about reality, it is unlike abstract mathematical propositions (which he terms analytical apriori), and being apriori it is distinct from empirical, scientific knowledge (which he terms synthetic aposteriori). The only synthetic apriori knowledge we can have is of how our minds organise the data of the senses; that organising framework is space and time, which for Kant have no mind-independent existence, but nonetheless operate uniformly in all humans. Apriori knowledge of space and time is all that remains of metaphysics as traditionally conceived. There is a reality beyond sensory data or phenomena, which he calls the realm of noumena
Noumena
Noumena is a melodic death metal band from Finland. The band's name comes from the word noumenon, a philosophical term used by Immanuel Kant. The band consists of five members: vocalist Antti Haapanen, guitarists Tuukka Tuomela and Ville Lamminaho, bass guitarist Hannu Savolainen and drummer Ilkka...

; however, we cannot know it as it is in itself, but only as it appears to us. He allows himself to speculate that the origins of God, morality, and free will
might exist in the noumenal realm, but these possibilities have to be set against its basic unknowability for humans. Although he saw himself as having disposed of metaphysics, in a sense, he has generally been regarded in retrospect, as having a metaphysics of his own.

19th Century philosophy was overwhelmingly influenced by Kant and his successors. Schopenhauer, Schelling
Friedrich Wilhelm Joseph Schelling
Friedrich Wilhelm Joseph Schelling , later von Schelling, was a German philosopher. Standard histories of philosophy make him the midpoint in the development of German idealism, situating him between Fichte, his mentor prior to 1800, and Hegel, his former university roommate and erstwhile friend...

, Fichte and Hegel all purveyed their own panoramic versions of German Idealism
German idealism
German idealism was a philosophical movement that emerged in Germany in the late 18th and early 19th centuries. It developed out of the work of Immanuel Kant in the 1780s and 1790s, and was closely linked both with romanticism and the revolutionary politics of the Enlightenment...

, Kant's own caution about metaphysical speculation, and refutation of idealism, having fallen by the wayside. The idealistic impulse continued into the early 20th century with British idealists such as F. H. Bradley
F. H. Bradley
Francis Herbert Bradley, OM, was a British idealist philosopher.- Life :Bradley was born at Clapham, Surrey, England . He was the child of Charles Bradley, an evangelical preacher, and Emma Linton, Charles's second wife. A. C. Bradley was his brother...

 and J. M. E. McTaggart
J. M. E. McTaggart
John McTaggart was an idealist metaphysician. For most of his life McTaggart was a fellow and lecturer in philosophy at Trinity College, Cambridge. He was an exponent of the philosophy of Hegel and among the most notable of the British idealists.-Personal life:J. M. E. McTaggart was born in 1866...

.

Followers of Karl Marx
Karl Marx
Karl Heinrich Marx was a German philosopher, economist, sociologist, historian, journalist, and revolutionary socialist. His ideas played a significant role in the development of social science and the socialist political movement...

 took Hegel's dialectic view of history and re-fashioned it as materialism
Dialectical materialism
Dialectical materialism is a strand of Marxism synthesizing Hegel's dialectics. The idea was originally invented by Moses Hess and it was later developed by Karl Marx and Friedrich Engels...

.

Early analytical philosophy and positivism


During the period when idealism was dominant in philosophy, science had been making great advances. The arrival of a new generation of scientifically minded philosophers led to a sharp decline in the popularity of idealism during the 1920s.

Analytical philosophy was spearheaded by Bertrand Russell
Bertrand Russell
Bertrand Arthur William Russell, 3rd Earl Russell, OM, FRS was a British philosopher, logician, mathematician, historian, and social critic. At various points in his life he considered himself a liberal, a socialist, and a pacifist, but he also admitted that he had never been any of these things...

 and G. E. Moore. Russell and William James
William James
William James was a pioneering American psychologist and philosopher who was trained as a physician. He wrote influential books on the young science of psychology, educational psychology, psychology of religious experience and mysticism, and on the philosophy of pragmatism...

 tried to compromise between idealism and materialism with the theory of neutral monism
Neutral monism
Neutral monism, in philosophy, is the metaphysical view that the mental and the physical are two ways of organizing or describing the same elements, which are themselves "neutral," that is, neither physical nor mental. This view denies that the mental and the physical are two fundamentally...

.

The early to mid 20th century philosophy also saw a trend to reject metaphysical questions as meaningless. The driving force behind this tendency was the unabashedly materialist philosophy of Logical Positivism
Logical positivism
Logical positivism is a philosophy that combines empiricism—the idea that observational evidence is indispensable for knowledge—with a version of rationalism incorporating mathematical and logico-linguistic constructs and deductions of epistemology.It may be considered as a type of analytic...

 as espoused by the Vienna Circle
Vienna Circle
The Vienna Circle was an association of philosophers gathered around the University of Vienna in 1922, chaired by Moritz Schlick, also known as the Ernst Mach Society in honour of Ernst Mach...

. See "The Value and Future of Metaphysics" below.

At around the same time, the American pragmatists were steering a middle course between materialism and idealism.
System-building metaphysics, with a fresh inspiration from science, was revived by A. N. Whitehead and Charles Hartshorne
Charles Hartshorne
Charles Hartshorne was a prominent American philosopher who concentrated primarily on the philosophy of religion and metaphysics. He developed the neoclassical idea of God and produced a modal proof of the existence of God that was a development of St. Anselm's Ontological Argument...

.

Continental philosophy


The forces that shaped analytical philosophy — the break with idealism, and the influence of science — were much less significant outside the English speaking world, although there was a shared turn toward language. Continental philosophy continued in a trajectory from post Kantianism.

The phenomenology of Husserl and others was intended as a collaborative project for the investigation of the features and structure of consciousness common to all humans, in line with Kant's basing his synthetic apriori on the uniform operation of consciousness. It was officially neutral with regards to ontology, but was nonetheless to spawn a number of metaphysical systems. Brentano
Franz Brentano
Franz Clemens Honoratus Hermann Brentano was an influential German philosopher and psychologist whose influence was felt by other such luminaries as Sigmund Freud, Edmund Husserl, Kazimierz Twardowski and Alexius Meinong, who followed and adapted his views.-Life:Brentano was born at Marienberg am...

's concept of intentionality
Intentionality
The term intentionality was introduced by Jeremy Bentham as a principle of utility in his doctrine of consciousness for the purpose of distinguishing acts that are intentional and acts that are not...

 would become widely influential, including on analytical philosophy.

Heidegger, author of Being and Time
Being and Time
Being and Time is a book by the German philosopher Martin Heidegger. Although written quickly, and despite the fact that Heidegger never completed the project outlined in the introduction, it remains his most important work and has profoundly influenced 20th-century philosophy, particularly...

, saw himself as re-focusing on Being-qua-being, introducing the novel concept of Dasein
Dasein
Dasein is a German word famously used by Martin Heidegger in his magnum opus Being and Time, which generally translates to being in its ontological and philosophical sense Dasein is a German word famously used by Martin Heidegger in his magnum opus Being and Time, which generally translates to...

in the process. Classing himself an existentialist, Sartre wrote an extensive study of "Being and Nothingness.

The speculative realism
Speculative realism
Speculative realism is an emerging movement in contemporary philosophy which defines itself loosely in its stance of metaphysical realism against the dominant forms of post-Kantian philosophy or what it terms correlationism. Speculative realism takes its name from a conference held at Goldsmiths...

 movement marks a return to full blooded realism.

Later analytical philosophy


While early analytic philosophy tended to reject metaphysical theorizing, under the influence of logical positivism, it was revived in the second half of the twentieth century. Philosophers such as David Kellogg Lewis
David Kellogg Lewis
David Kellogg Lewis was an American philosopher. Lewis taught briefly at UCLA and then at Princeton from 1970 until his death. He is also closely associated with Australia, whose philosophical community he visited almost annually for more than thirty years...

 and David Armstrong
David Malet Armstrong
David Malet Armstrong , often D. M. Armstrong, is an Australian philosopher. He is well-known for his work on metaphysics and the philosophy of mind, and for his defence of a factualist ontology, a functionalist theory of the mind, an externalist epistemology, and a necessitarian conception of the...

 developed elaborate theories on a range of topics such as universals, causation, possibility and necessity and abstract objects. However, the focus of analytical philosophy is generally away from the construction of all-encompassing systems and towards close analysis of individual ideas.

Among the developments that led to the revival of metaphysical theorizing were Quine's
Willard Van Orman Quine
Willard Van Orman Quine was an American philosopher and logician in the analytic tradition...

 attack on the analytic-synthetic distinction, which was generally taken to undermine Carnap's
Rudolf Carnap
Rudolf Carnap was an influential German-born philosopher who was active in Europe before 1935 and in the United States thereafter. He was a major member of the Vienna Circle and an advocate of logical positivism....

 distinction between existence questions internal to a framework and those external to it.

The philosophy of fiction, the problem of empty names, and the debate over existence's status as a property have all risen out of relative obscurity to become central concerns, while perennial issues such as free will, possible worlds, and the philosophy of time have had new life breathed into them.

The value and future of metaphysics


A number of individuals have suggested that metaphysics as a whole should be rejected.

David Hume
David Hume
David Hume was a Scottish philosopher, historian, economist, and essayist, known especially for his philosophical empiricism and skepticism. He was one of the most important figures in the history of Western philosophy and the Scottish Enlightenment...

 argued with his empiricist principle that all knowledge involves either relations of ideas or matters of fact:
However, Hume's assertion may be self-defeating
Self-refuting idea
Self-refuting ideas are ideas or statements whose falsehood is a logical consequence of the act or situation of holding them to be true. Many ideas are accused by their detractors of being self-refuting, and such accusations are therefore almost always controversial, with defenders claiming that...

 if it itself is not self-evident or empirically verifiable.

Immanuel Kant
Immanuel Kant
Immanuel Kant was a German philosopher from Königsberg , researching, lecturing and writing on philosophy and anthropology at the end of the 18th Century Enlightenment....

 prescribed a limited role to the subject and argued against knowledge progressing beyond the world of our representations, except to knowledge that the noumena
Noumenon
The noumenon is a posited object or event that is known without the use of the senses.The term is generally used in contrast with, or in relation to "phenomenon", which refers to anything that appears to, or is an object of, the senses...

exist:
Proceeding from Kant's statement about antinomy
Antinomy
Antinomy literally means the mutual incompatibility, real or apparent, of two laws. It is a term used in logic and epistemology....

, A.J. Ayer
Alfred Ayer
Sir Alfred Jules "Freddie" Ayer was a British philosopher known for his promotion of logical positivism, particularly in his books Language, Truth, and Logic and The Problem of Knowledge ....

 in Language, Truth and Logic using the verifiability theory of meaning concluded that metaphysical propositions were neither true nor false but strictly meaningless, as were religious views. However, Karl Popper
Karl Popper
Sir Karl Raimund Popper, CH FRS FBA was an Austro-British philosopher and a professor at the London School of Economics...

 argued that metaphysical statements are not meaningless statements, but rather not fallible, testable or provable statements i.e. neither empirical observations nor logical arguments could falsify metaphysical statements to show them to be true or false. Hence, a metaphysical statement usually implies an idea about the world or about the universe, which may be reasonable but is ultimately not empirically testable.

Rudolf Carnap
Rudolf Carnap
Rudolf Carnap was an influential German-born philosopher who was active in Europe before 1935 and in the United States thereafter. He was a major member of the Vienna Circle and an advocate of logical positivism....

, in his book Philosophy and Logical Syntax, used the concept of verifiability to reject metaphysics.
John Locke
John Locke
John Locke FRS , widely known as the Father of Liberalism, was an English philosopher and physician regarded as one of the most influential of Enlightenment thinkers. Considered one of the first of the British empiricists, following the tradition of Francis Bacon, he is equally important to social...

, a founder of empiricism
Empiricism
Empiricism is a theory of knowledge that asserts that knowledge comes only or primarily via sensory experience. One of several views of epistemology, the study of human knowledge, along with rationalism, idealism and historicism, empiricism emphasizes the role of experience and evidence,...

, expressed that most of the doctrine of innate ideas in the metaphysics, such as Cartesian dualism
Dualism (philosophy of mind)
In philosophy of mind, dualism is a set of views about the relationship between mind and matter, which begins with the claim that mental phenomena are, in some respects, non-physical....

 and the Platonic realm
Theory of Forms
Plato's theory of Forms or theory of Ideas asserts that non-material abstract forms , and not the material world of change known to us through sensation, possess the highest and most fundamental kind of reality. When used in this sense, the word form is often capitalized...

 were ridiculous and nonsensical.

See also



  • Afterlife
    Afterlife
    The afterlife is the belief that a part of, or essence of, or soul of an individual, which carries with it and confers personal identity, survives the death of the body of this world and this lifetime, by natural or supernatural means, in contrast to the belief in eternal...

  • Alchemy
    Alchemy
    Alchemy is an influential philosophical tradition whose early practitioners’ claims to profound powers were known from antiquity. The defining objectives of alchemy are varied; these include the creation of the fabled philosopher's stone possessing powers including the capability of turning base...

  • Concerning existence of material things, and real distinction between mind and body (Descartes)
  • Essence
    Essence
    In philosophy, essence is the attribute or set of attributes that make an object or substance what it fundamentally is, and which it has by necessity, and without which it loses its identity. Essence is contrasted with accident: a property that the object or substance has contingently, without...

  • Ethereal being
    Ethereal being
    Ethereal beings, according to some belief systems and occult theories, are mystic entities that usually are not made of ordinary matter. Despite the fact that they are believed to be essentially incorporeal, they do interact in physical shapes with the material universe and travel between the...

  • Logic
    Logic
    In philosophy, Logic is the formal systematic study of the principles of valid inference and correct reasoning. Logic is used in most intellectual activities, but is studied primarily in the disciplines of philosophy, mathematics, semantics, and computer science...

  • Metaethics
  • Mind–body problem
  • Nihilism
    Nihilism
    Nihilism is the philosophical doctrine suggesting the negation of one or more putatively meaningful aspects of life. Most commonly, nihilism is presented in the form of existential nihilism which argues that life is without objective meaning, purpose, or intrinsic value...

  • Parapsychology
    Parapsychology
    The term parapsychology was coined in or around 1889 by philosopher Max Dessoir, and originates from para meaning "alongside", and psychology. The term was adopted by J.B. Rhine in the 1930s as a replacement for the term psychical research...

  • Personal identity (philosophy)
  • Philosophical logic
    Philosophical logic
    Philosophical logic is a term introduced by Bertrand Russell to represent his idea that the workings of natural language and thought can only be adequately represented by an artificial language; essentially it was his formalization program for the natural language...

  • Philosophical realism
    Philosophical realism
    Contemporary philosophical realism is the belief that our reality, or some aspect of it, is ontologically independent of our conceptual schemes, linguistic practices, beliefs, etc....

  • Philosophical theology
    Philosophical Theology
    Philosophical theology is the disciplined employment of philosophical methods in developing or analyzing theological concepts. It therefore includes natural theology as well as philosophical treatments of orthodox and heterodox theology....

  • Philosophy of Mathematics
    Philosophy of mathematics
    The philosophy of mathematics is the branch of philosophy that studies the philosophical assumptions, foundations, and implications of mathematics. The aim of the philosophy of mathematics is to provide an account of the nature and methodology of mathematics and to understand the place of...

  • Philosophy of physics
    Philosophy of physics
    In philosophy, the philosophy of physics studies the fundamental philosophical questions underlying modern physics, the study of matter and energy and how they interact. The philosophy of physics begins by reflecting on the basic metaphysical and epistemological questions posed by physics:...

  • Pluralism (philosophy of mind)
    Pluralism (philosophy of mind)
    Pluralism is a term used in philosophy, meaning "doctrine of multiplicity", often used in opposition to monism and dualism . The term has different connotations in metaphysics and epistemology...

  • Substance theory
    Substance theory
    Substance theory, or substance attribute theory, is an ontological theory about objecthood, positing that a substance is distinct from its properties. A thing-in-itself is a property-bearer that must be distinguished from the properties it bears....

  • Time travel
    Time travel
    Time travel is the concept of moving between different points in time in a manner analogous to moving between different points in space. Time travel could hypothetically involve moving backward in time to a moment earlier than the starting point, or forward to the future of that point without the...



Further reading


External links