The
principle of sufficient reason states that anything that happens does so for a definite
reasonReason is the mental faculty that is able to generate conclusions from assumptions or premisses.Reason in this sense is often contrasted with authority, intuition, emotion, mysticism, superstition, and faith, and is thought by rationalists to be more reliable than these in discovering what is true...
. In virtue of which no fact can be real or no statement true unless it has sufficient reason why it should not be otherwise. It is usually attributed to
Gottfried LeibnizGottfried Wilhelm Leibniz was a German philosopher, polymath and mathematician who wrote primarily in Latin and French....
, although the first person to use it was Anaximander of Miletus.
The principle has a variety of expressions, all of which are perhaps best summarized by the following:
- For every entity x, if x exists, then there is a sufficient explanation why x exists.
- For every event e, if e occurs, then there is a sufficient explanation why e occurs.
- For every proposition p, if p is true, then there is a sufficient explanation why p is true.
A sufficient explanation may be understood either in terms of
reasons or
causes for like many philosophers of the period, Leibniz did not carefully distinguish between the two.
The
principle of sufficient reason states that anything that happens does so for a definite
reasonReason is the mental faculty that is able to generate conclusions from assumptions or premisses.Reason in this sense is often contrasted with authority, intuition, emotion, mysticism, superstition, and faith, and is thought by rationalists to be more reliable than these in discovering what is true...
. In virtue of which no fact can be real or no statement true unless it has sufficient reason why it should not be otherwise. It is usually attributed to
Gottfried LeibnizGottfried Wilhelm Leibniz was a German philosopher, polymath and mathematician who wrote primarily in Latin and French....
, although the first person to use it was Anaximander of Miletus.
Formulation
The principle has a variety of expressions, all of which are perhaps best summarized by the following:
- For every entity x, if x exists, then there is a sufficient explanation why x exists.
- For every event e, if e occurs, then there is a sufficient explanation why e occurs.
- For every proposition p, if p is true, then there is a sufficient explanation why p is true.
A sufficient explanation may be understood either in terms of
reasons or
causes for like many philosophers of the period, Leibniz did not carefully distinguish between the two. The resulting principle is very different, however, depending on which interpretation is given.
Leibniz's view
In fact Leibniz opposed
fatalismFatalism is a philosophical doctrine emphasizing the subjugation of all events or actions to fate or inevitable predetermination.Fatalism generally refers to several of the following ideas:...
and had a more nuanced and characteristic version of the principle, in which the contingent was admitted on the basis of infinitary reasons, to which
GodGod is a deity in theistic and deistic religions and other belief systems, representing either the sole deity in monotheism, or a principal deity in polytheism....
had access but humans did not. He explained this while discussing the problem of future contingents:
We have said that the concept of an individual substance [Leibniz also uses the term haecceityHaecceity is a term from medieval philosophy first coined by Duns Scotus which denotes the discrete qualities, properties or characteristics of a thing which make it a particular thing...
] includes once for all everything which can ever happen to it and that in considering this concept one will be able to see everything which can truly be said concerning the individual, just as we are able to see in the nature of a circle all the properties which can be derived from it. But does it not seem that in this way the difference between contingent and necessary truths will be destroyed, that there will be no place for human liberty, and that an absolute fatality will rule as well over all our actions as over all the rest of the events of the world? To this I reply that a distinction must be made between that which is certain and that which is necessary. (§13, Discourse on MetaphysicsThe Discourse on Metaphysics is a short book by Gottfried Leibniz in which he develops a philosophy concerning physical substance, motion and resistance of bodies, and God's role within the universe. It is divided into 37 chapters...
)
Without this qualification, the principle can be seen as a description of a certain notion of
closed systemA closed system is a system in the "state of being isolated from its surrounding environment." The term often refers to an idealized system in which closure is perfect. In reality no system can be completely closed; there are only varying degrees of closure....
, in which there is no 'outside' to provide unexplained events with causes. It is also in tension with the paradox of
Buridan's assBuridan's ass is a paradox in philosophy. It refers to a hypothetical situation wherein an ass, placed exactly in the middle between two stacks of hay of equal size and quality, will starve to death since it cannot make any rational decision to start eating one rather than the other...
.
As a Law of Thought
The principle was one of the four recognised laws of thought, that held a place in European
pedagogyPedagogy is the study of being a teacher. The term generally refers to strategies of instruction, or a style of instruction.Pedagogy is also sometimes referred to as the correct use of teaching strategies . For example, Paulo Freire referred to his method of teaching adults as "critical pedagogy"...
of
logicLogic, from the Greek λογική is the art and science of reasoning. More specifically, it is defined by the Penguin Encyclopedia to be "The formal systematic study of the principles of valid inference and correct reasoning". As a discipline, logic dates back to Aristotle, who established its...
and
reasoningReasoning is the cognitive process of looking for reasons for beliefs, conclusions, actions or feelings.Humans have the ability to engage in reasoning about their own reasoning. Different forms of such reflection on reasoning occur in different fields...
(and, to some extent,
philosophyPhilosophy is the study of general and fundamental problems concerning matters such as existence, knowledge, values, reason, mind, and language. Philosophy is distinguished from other ways of addressing these questions by its critical, generally systematic approach and its reliance on reasoned...
in general) in the eighteenth and nineteenth century. It was influential in the thinking of
Leo TolstoyLeo Tolstoy, or Count Lev Nikolayevich Tolstoy , was a Russian writer widely regarded as among the greatest of novelists. His masterpieces War and Peace and Anna Karenina represent in their scope, breadth and vivid depiction of 19th-century Russian life and attitudes, the peak of realist...
, amongst others, in the elevated form that
historyHistory is the study of the human past, with special attention to the written record. Scholars who write about history are called historians. It is a field of research which uses a narrative to examine and analyse the sequence of events, and it often attempts to investigate objectively the patterns...
could not be accepted as random.
Schopenhauer's Four Forms
According to Schopenhauer's
On the Fourfold Root of the Principle of Sufficient ReasonOn the Fourfold Root of the Principle of Sufficient Reason was originally published as a doctoral dissertation in 1813. The German philosopher Arthur Schopenhauer revised this important work and re-published it in 1847....
, there are four distinct forms of the principle.
Principle of Sufficient Reason of Becoming: If a new state of one or several real objects appears, another state must have preceded it upon which the new state follows regularly.
Principle of Sufficient Reason of Knowing: If a judgment is to express a piece of knowledge, it must have a sufficient ground. By virtue of this quality, it receives the predicate
true. Truth is therefore the reference of a judgment to something different therefrom.
Principle of Sufficient Reason of Being: The position of every object in space and the succession of every object in time is conditioned by another object's position in space and succession in time.
Principle of Sufficient Reason of Acting: Every human decision is the result of an object that necessarily determines the human's will by functioning as a motive.
Violations
- Quantum mechanics
Quantum mechanics is a set of principles describing the physical reality at the atomic level of matter and the subatomic . These descriptions include the simultaneous wave-like and particle-like behavior of both matter and radiation...
, it has been argued, violates the Principle (especially the "event" version) because elementary particles exhibit behavior without any observable external cause, and no internal mechanisms have yet been observed within them. This lack of observable causes for spontaneous quantum events is one of the properties of quantum mechanics that most disturbed Albert EinsteinAlbert Einstein was a theoretical physicist. His many contributions to physics include the special and general theories of relativity, the founding of relativistic cosmology, the first post-Newtonian expansion, explaining the perihelion advance of Mercury, prediction of the deflection of...
. The Bell test experimentsThe Bell test experiments serve to investigate the validity of the entanglement effect in quantum mechanics by using some kind of Bell inequality...
, testing the Einstein-Podolsky-Rosen ParadoxIn quantum mechanics, the EPR paradox is a thought experiment which challenged long-held ideas about the relation between the observed values of physical quantities and the values that can be accounted for by a physical theory...
, have several times verified that quantum systems behave in a manner inconsistent with either the Principle of Sufficient Reason, or the Axiom of CausalityThe Axiom of Causality is the proposition that everything in the universe has a cause and is thus an effect of that cause. This means that if a given event occurs, then this is the result of a previous, related event. If an object is in a certain state, then it is in that state as a result of...
.
Counter Argument
- The above is not an entirely accurate picture of the relationship between the PSR and quantum mechanics
Quantum mechanics is a set of principles describing the physical reality at the atomic level of matter and the subatomic . These descriptions include the simultaneous wave-like and particle-like behavior of both matter and radiation...
. Quantum theory does not allow for an event without a cause/reason. Even virtual particles occur because the potential for their occurrence is contained in the relevant LagrangianThe Lagrangian, L, of a dynamical system is a function that summarizes the dynamics of the system. It is named after Joseph Louis Lagrange. The concept of a Lagrangian was originally introduced in a reformulation of classical mechanics known as Lagrangian mechanics. In classical mechanics, the...
. A true example of a violation of the PSR would be the occurrence of a physical event that did not have a corresponding term in the governing LagrangianThe Lagrangian, L, of a dynamical system is a function that summarizes the dynamics of the system. It is named after Joseph Louis Lagrange. The concept of a Lagrangian was originally introduced in a reformulation of classical mechanics known as Lagrangian mechanics. In classical mechanics, the...
. What quantum mechanics does allow is a cause without necessarily having an effect. For example, throwing a particle at a barrier may or may not cause it to reflect back. However, without some sort of barrier it will never bounce back. Another example is Schroedinger's cat - if the cat is observed to be dead there is a reason (it was poisoned). If it is observed to be alive there is a reason (it was not poisoned). Quantum mechanics forces us to amend our understanding of effect, not cause, and therefore the PSR is not at all violated.
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