Scientific evidence
Encyclopedia
Scientific evidence has no universally accepted definition but generally refers to evidence
which serves to either support or counter a scientific
theory
or hypothesis
. Such evidence is generally expected to be empirical
and properly documented in accordance with scientific method
such as is applicable to the particular field of inquiry. Standards for evidence may vary according to whether the field of inquiry is among the natural science
s or social sciences
. Evidence may involve understanding all steps of a process, or one or a few observations, or observation and statistical analysis of many samples without necessarily understanding the mechanism.
s, coupled with principles of inference
(the act or process of deriving a conclusion), that make information relevant to the support or negation of a hypothesis
. Scientific evidence is evidence where the dependence of the evidence on principles of inference is not conceded, enabling others to examine the background beliefs or assumptions employed to determine if facts are relevant to the support of or falsification of a hypothesis.
A person’s assumptions or beliefs about the relationship between alleged facts and a hypothesis will determine whether that person takes the facts as evidence. Consider, for example alternative uses of the observation that day and night alternate at a steady rate. In an environment where the observer makes a causal connection between exposure to the sun and day, the observer may take the observation of day and night as evidence for a theory of cosmology. Without an assumption or belief that a causal connection exists between exposure to the sun and the observance of day, the observation of day will be discounted as evidence of a cosmological theory.
A person’s assumptions or beliefs about the relationship between alleged facts and a hypothesis will also determine how a person utilizes the facts as evidence. Continuing with the same example, in an environment where geocentric cosmology is prevalent, the observation of day and night may be taken as evidence that the sun moves about the earth. Alternatively, in an environment where heliocentric cosmology is prevalent, the same observation may be taken as evidence that the earth is spinning about an axis. In summary, beliefs or assumptions about causal relationships are utilized to determine whether facts are evidence of a hypothesis.
Background beliefs differ. As a result, where observers operate under different paradigms, rational observers may find different meaning in scientific evidence from the same event. For example, Priestley
, working with phlogiston theory
, took his observations about the decomposition of what we know today as mercuric oxide as evidence of the phlogiston. In contrast, Lavoisier
, developing the theory of elements, took the same facts as evidence for oxygen. Note that a causal relationship between the facts and hypothesis does not exist to cause the facts to be taken as evidence, but rather the causal relationship is provided by the person seeking to establish facts as evidence.
A more formal method to characterize the effect of background beliefs is Bayesianism. Bayesian theory provides that one’s beliefs depend on evidence to which one is exposed and one’s prior experiences (probability distribution, in Bayesian terms). As a result, two observers of the same event will rationally arrive at different evidence, given the same facts, because their priors (previous experiences) differ.
The importance of background beliefs in the determination of what facts are evidence can be illustrated using as provided by Aristotle
's syllogistic logic. A standard syllogism
is a triad where two propositions jointly imply the conclusion:
If either of the propositions is not accepted as true, the conclusion will not be deemed to follow from them (it may or may not be true).
within which scientific evidence plays a central role. In summary, Popper provides that a scientist creatively develops a theory which may be falsified by testing the theory against evidence or known facts. Popper’s theory presents an asymmetry in that evidence can prove a theory wrong, by establishing facts that are inconsistent with the theory. In contrast, evidence cannot prove a theory correct because other evidence, yet to be discovered, may exist that is inconsistent with the theory. See falsificationism for more on this view of scientific evidence.
, as an example of a scientific approach, provides factors (clarity of the data, replication by others, consistency with results arrived at by alternative methods and consistency with plausible theories) useful for determination if facts rise to the level of scientific evidence.
A variety of philosophical approaches are available for the evaluation of evidence, many of which focus on the relationship between the evidence and the hypothesis, to determine if the facts rise to the level of evidence. Carnap recommends distinguishing such theories of evidence using three concepts: whether the theory is classificatory (does the evidence confirm the hypothesis), comparative (does the evidence support a first hypothesis more than an alternative hypothesis) or quantitative (the degree to which the evidence supports a hypothesis). Achinstein
provides a concise presentation by prominent philosophers on evidence, including Carl Hempel (Confirmation), Nelson Goodman
(of grue fame), R. B. Braithwaite
, Norwood Russell Hanson
, Wesley C. Salmon
, Clark Glymour and Rudolf Carnap
Based on the philosophical assumption of the Strong Church-Turing Universe Thesis, a mathematical criterion for evaluation of evidence has been proven, with the criterion having a resemblance to the idea of Occam's Razor
that the simplest comprehensive description of the evidence is most likely correct. It states formally, "The ideal principle states that the prior probability associated with the hypothesis should be given by the algorithmic universal probability, and the sum of the log universal probability of the model plus the log of the probability of the data given the model should be minimized."
Evidence
Evidence in its broadest sense includes everything that is used to determine or demonstrate the truth of an assertion. Giving or procuring evidence is the process of using those things that are either presumed to be true, or were themselves proven via evidence, to demonstrate an assertion's truth...
which serves to either support or counter a scientific
Science
Science is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe...
theory
Theory
The English word theory was derived from a technical term in Ancient Greek philosophy. The word theoria, , meant "a looking at, viewing, beholding", and referring to contemplation or speculation, as opposed to action...
or hypothesis
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...
. Such evidence is generally expected to be empirical
Empirical
The word empirical denotes information gained by means of observation or experimentation. Empirical data are data produced by an experiment or observation....
and properly documented in accordance with 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...
such as is applicable to the particular field of inquiry. Standards for evidence may vary according to whether the field of inquiry is among the natural science
Natural science
The natural sciences are branches of science that seek to elucidate the rules that govern the natural world by using empirical and scientific methods...
s or social sciences
Social sciences
Social science is the field of study concerned with society. "Social science" is commonly used as an umbrella term to refer to a plurality of fields outside of the natural sciences usually exclusive of the administrative or managerial sciences...
. Evidence may involve understanding all steps of a process, or one or a few observations, or observation and statistical analysis of many samples without necessarily understanding the mechanism.
Principles of inference
Evidence is information, such as factFact
A fact is something that has really occurred or is actually the case. The usual test for a statement of fact is verifiability, that is whether it can be shown to correspond to experience. Standard reference works are often used to check facts...
s, coupled with principles of inference
Inference
Inference is the act or process of deriving logical conclusions from premises known or assumed to be true. The conclusion drawn is also called an idiomatic. The laws of valid inference are studied in the field of logic.Human inference Inference is the act or process of deriving logical conclusions...
(the act or process of deriving a conclusion), that make information relevant to the support or negation of a hypothesis
Hypothesis
A hypothesis is a proposed explanation for a phenomenon. The term derives from the Greek, ὑποτιθέναι – hypotithenai meaning "to put under" or "to suppose". For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it...
. Scientific evidence is evidence where the dependence of the evidence on principles of inference is not conceded, enabling others to examine the background beliefs or assumptions employed to determine if facts are relevant to the support of or falsification of a hypothesis.
A person’s assumptions or beliefs about the relationship between alleged facts and a hypothesis will determine whether that person takes the facts as evidence. Consider, for example alternative uses of the observation that day and night alternate at a steady rate. In an environment where the observer makes a causal connection between exposure to the sun and day, the observer may take the observation of day and night as evidence for a theory of cosmology. Without an assumption or belief that a causal connection exists between exposure to the sun and the observance of day, the observation of day will be discounted as evidence of a cosmological theory.
A person’s assumptions or beliefs about the relationship between alleged facts and a hypothesis will also determine how a person utilizes the facts as evidence. Continuing with the same example, in an environment where geocentric cosmology is prevalent, the observation of day and night may be taken as evidence that the sun moves about the earth. Alternatively, in an environment where heliocentric cosmology is prevalent, the same observation may be taken as evidence that the earth is spinning about an axis. In summary, beliefs or assumptions about causal relationships are utilized to determine whether facts are evidence of a hypothesis.
Background beliefs differ. As a result, where observers operate under different paradigms, rational observers may find different meaning in scientific evidence from the same event. For example, Priestley
Joseph Priestley
Joseph Priestley, FRS was an 18th-century English theologian, Dissenting clergyman, natural philosopher, chemist, educator, and political theorist who published over 150 works...
, working with phlogiston theory
Phlogiston theory
The phlogiston theory , first stated in 1667 by Johann Joachim Becher, is an obsolete scientific theory that postulated the existence of a fire-like element called "phlogiston", which was contained within combustible bodies and released during combustion...
, took his observations about the decomposition of what we know today as mercuric oxide as evidence of the phlogiston. In contrast, Lavoisier
Antoine Lavoisier
Antoine-Laurent de Lavoisier , the "father of modern chemistry", was a French nobleman prominent in the histories of chemistry and biology...
, developing the theory of elements, took the same facts as evidence for oxygen. Note that a causal relationship between the facts and hypothesis does not exist to cause the facts to be taken as evidence, but rather the causal relationship is provided by the person seeking to establish facts as evidence.
A more formal method to characterize the effect of background beliefs is Bayesianism. Bayesian theory provides that one’s beliefs depend on evidence to which one is exposed and one’s prior experiences (probability distribution, in Bayesian terms). As a result, two observers of the same event will rationally arrive at different evidence, given the same facts, because their priors (previous experiences) differ.
The importance of background beliefs in the determination of what facts are evidence can be illustrated using as provided by 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 syllogistic logic. A standard syllogism
Syllogism
A syllogism is a kind of logical argument in which one proposition is inferred from two or more others of a certain form...
is a triad where two propositions jointly imply the conclusion:
All men are mortal,
and
Aristotle is a man;
therefore
Aristotle is mortal.
If either of the propositions is not accepted as true, the conclusion will not be deemed to follow from them (it may or may not be true).
Utility of scientific evidence
Philosophers, such as Karl R. Popper, have provided influential theories of the scientific methodScientific 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...
within which scientific evidence plays a central role. In summary, Popper provides that a scientist creatively develops a theory which may be falsified by testing the theory against evidence or known facts. Popper’s theory presents an asymmetry in that evidence can prove a theory wrong, by establishing facts that are inconsistent with the theory. In contrast, evidence cannot prove a theory correct because other evidence, yet to be discovered, may exist that is inconsistent with the theory. See falsificationism for more on this view of scientific evidence.
Philosophic versus scientific views of scientific evidence
The Philosophic community has invested extensive resources to address logical requirements for scientific evidence by examination of the relationship between evidence and hypotheses, in contrast to scientific approaches which focus on the candidate facts and their context. BechtelWilliam Bechtel
William Bechtel is a professor of Philosophy in the Department of Philosophy and the Science Studies Program at the University of California, San Diego. He was a Professor of Philosophy at Washington University in St. Louis from 1994 until 2002...
, as an example of a scientific approach, provides factors (clarity of the data, replication by others, consistency with results arrived at by alternative methods and consistency with plausible theories) useful for determination if facts rise to the level of scientific evidence.
A variety of philosophical approaches are available for the evaluation of evidence, many of which focus on the relationship between the evidence and the hypothesis, to determine if the facts rise to the level of evidence. Carnap recommends distinguishing such theories of evidence using three concepts: whether the theory is classificatory (does the evidence confirm the hypothesis), comparative (does the evidence support a first hypothesis more than an alternative hypothesis) or quantitative (the degree to which the evidence supports a hypothesis). Achinstein
Peter Achinstein
Peter Achinstein is a distinguished American Philosopher of Science. He is the author of numerous influential books and articles. He is the Jay and Jeanie Schottenstein University Professor of Philosophy at Yeshiva University, director of the Yeshiva Center for History and Philosophy of Science,...
provides a concise presentation by prominent philosophers on evidence, including Carl Hempel (Confirmation), Nelson Goodman
Nelson Goodman
Henry Nelson Goodman was an American philosopher, known for his work on counterfactuals, mereology, the problem of induction, irrealism and aesthetics.-Career:...
(of grue fame), R. B. Braithwaite
R. B. Braithwaite
Richard Bevan Braithwaite was an English philosopher who specialized in the philosophy of science, ethics, and the philosophy of religion. He was a lecturer in moral science at the University of Cambridge from 1934 to 1953, then Knightbridge Professor of Moral Philosophy there from 1953 to 1967...
, Norwood Russell Hanson
Norwood Russell Hanson
Norwood Russell Hanson was a philosopher of science. Hanson was a pioneer in advancing the argument that observation is theory-laden – that observation language and theory language are deeply interwoven – and that historical and contemporary comprehension are similarly deeply interwoven...
, Wesley C. Salmon
Wesley C. Salmon
Wesley C. Salmon was a metaphysician and contemporary philosopher of science concerned primarily with the topics of causation and explanation....
, Clark Glymour and 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....
Based on the philosophical assumption of the Strong Church-Turing Universe Thesis, a mathematical criterion for evaluation of evidence has been proven, with the criterion having a resemblance to the idea of Occam's Razor
Occam's razor
Occam's razor, also known as Ockham's razor, and sometimes expressed in Latin as lex parsimoniae , is a principle that generally recommends from among competing hypotheses selecting the one that makes the fewest new assumptions.-Overview:The principle is often summarized as "simpler explanations...
that the simplest comprehensive description of the evidence is most likely correct. It states formally, "The ideal principle states that the prior probability associated with the hypothesis should be given by the algorithmic universal probability, and the sum of the log universal probability of the model plus the log of the probability of the data given the model should be minimized."