empirical evidence

{{main|Evidence}}

The concept of evidence is of central importance in epistemology and in philosophy of science but plays different roles in these two fields.{{cite web |last1=DiFate |first1=Victor |title=Evidence |url=https://iep.utm.edu/evidence/ |website=Internet Encyclopedia of Philosophy |access-date=11 June 2021 |archive-date=25 June 2021 |archive-url=https://web.archive.org/web/20210625124049/https://iep.utm.edu/evidence/ |url-status=live }}{{cite web |last1=Kelly |first1=Thomas |title=Evidence |url=https://plato.stanford.edu/entries/evidence/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=11 June 2021 |date=2016 |archive-date=8 September 2021 |archive-url=https://web.archive.org/web/20210908185254/https://plato.stanford.edu/entries/evidence/ |url-status=live }} In epistemology, evidence is what justifies beliefs or what determines whether holding a certain doxastic attitude is rational.{{cite web |last1=Steup |first1=Matthias |last2=Neta |first2=Ram |title=Epistemology |url=https://plato.stanford.edu/entries/epistemology/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=15 June 2021 |date=2020 |archive-date=21 July 2020 |archive-url=https://web.archive.org/web/20200721023728/https://plato.stanford.edu/entries/epistemology/ |url-status=live }}{{cite web |last1=Mittag |first1=Daniel M. |title=Evidentialism |url=https://iep.utm.edu/evidenti/ |website=Internet Encyclopedia of Philosophy |access-date=15 June 2021 |archive-date=29 July 2021 |archive-url=https://web.archive.org/web/20210729002312/https://iep.utm.edu/evidenti/ |url-status=live }}{{cite book |last1=Gage |first1=Logan Paul |title=Objectivity and Subjectivity in Epistemology: A Defense of the Phenomenal Conception of Evidence |chapter=1. Introduction: Two Rival Conceptions of Evidence |date=2014 |publisher=Baylor University |url=https://philpapers.org/rec/GAGOAS |type=PhD Thesis |access-date=2021-06-21 |archive-date=2021-06-16 |archive-url=https://web.archive.org/web/20210616042929/https://philpapers.org/rec/GAGOAS |url-status=live }} For example, the olfactory experience of smelling smoke justifies or makes it rational to hold the belief that something is burning. It is usually held that for justification to work, the evidence has to be possessed by the believer. The most straightforward way to account for this type of evidence possession is to hold that evidence consists of the private mental states possessed by the believer.{{cite book |last1=Conee |first1=Earl |last2=Feldman |first2=Richard |title=Epistemology: New Essays |date=2008 |publisher=Oxford University Press |url=https://philpapers.org/rec/CONE |chapter=Evidence |access-date=2021-06-21 |archive-date=2021-06-24 |archive-url=https://web.archive.org/web/20210624201400/https://philpapers.org/rec/CONE |url-status=live }}{{cite journal |last1=Piazza |first1=Tommaso |title=Evidentialism and the Problem of Stored Beliefs |journal=Philosophical Studies |date=2009 |volume=145 |issue=2 |pages=311–324 |doi=10.1007/s11098-008-9233-1 |s2cid=56299607 |url=https://philpapers.org/rec/PIAEAT |access-date=2021-06-21 |archive-date=2021-06-16 |archive-url=https://web.archive.org/web/20210616043049/https://philpapers.org/rec/PIAEAT |url-status=live }}

Some philosophers restrict evidence even further, for example, to only conscious, propositional or factive mental states. Restricting evidence to conscious mental states has the implausible consequence that many simple everyday beliefs would be unjustified. This is why it is more common to hold that all kinds of mental states, including stored but currently unconscious beliefs, can act as evidence. Various of the roles played by evidence in reasoning, for example, in explanatory, probabilistic and deductive reasoning, suggest that evidence has to be propositional in nature, i.e. that it is correctly expressed by propositional attitude verbs like "believe" together with a that-clause, like "that something is burning".{{cite book |last1=Williamson |first1=Timothy |title=Evidence |year=2002 |publisher=Oxford University Press |doi=10.1093/019925656X.001.0001 |isbn=978-0-19-159867-8 |url=https://oxford.universitypressscholarship.com/view/10.1093/019925656X.001.0001/acprof-9780199256563-chapter-10 |access-date=2021-06-21 |archive-date=2021-06-16 |archive-url=https://web.archive.org/web/20210616043041/https://oxford.universitypressscholarship.com/view/10.1093/019925656X.001.0001/acprof-9780199256563-chapter-10 |url-status=live }}{{cite web |title=Philosophy of mind – Propositional attitudes |url=https://www.britannica.com/topic/philosophy-of-mind/Propositional-attitudes |website=Encyclopedia Britannica |access-date=2 April 2021 |language=en |archive-date=19 July 2020 |archive-url=https://web.archive.org/web/20200719083018/https://www.britannica.com/topic/philosophy-of-mind/Propositional-attitudes |url-status=live }} But it runs counter to the common practice of treating non-propositional sense-experiences, like bodily pains, as evidence.{{cite web |last1=Huemer |first1=Michael |title=Sense-Data |url=https://plato.stanford.edu/entries/sense-data/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=15 June 2021 |date=2019 |archive-date=11 June 2018 |archive-url=https://web.archive.org/web/20180611154837/https://plato.stanford.edu/entries/sense-data/ |url-status=live }} Its defenders sometimes combine it with the view that evidence has to be factive, i.e. that only attitudes towards true propositions constitute evidence. In this view, there is no misleading evidence. The olfactory experience of smoke would count as evidence if it was produced by a fire but not if it was produced by a smoke generator. This position has problems in explaining why it is still rational for the subject to believe that there is a fire even though the olfactory experience cannot be considered evidence.

In philosophy of science, evidence is understood as that which confirms or disconfirms scientific hypotheses and arbitrates between competing theories.{{cite web |last1=Crupi |first1=Vincenzo |title=Confirmation |url=https://plato.stanford.edu/entries/confirmation/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=13 June 2021 |date=2021 |archive-date=17 May 2021 |archive-url=https://web.archive.org/web/20210517040548/https://plato.stanford.edu/entries/confirmation/ |url-status=live }} Measurements of Mercury's "anomalous" orbit, for example, constitute evidence that plays the role of neutral arbiter between Newton's and Einstein's theory of gravitation by confirming Einstein's theory. For scientific consensus, it is central that evidence is public and uncontroversial, like observable physical objects or events and unlike private mental states. This way it can act as a shared ground for proponents of competing theories. Two issues threatening this role are the problem of underdetermination and theory-ladenness. The problem of underdetermination concerns the fact that the available evidence often provides equal support to either theory and therefore cannot arbitrate between them.{{cite web |last1=Stanford |first1=Kyle |title=Underdetermination of Scientific Theory |url=https://plato.stanford.edu/entries/scientific-underdetermination/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=15 June 2021 |date=2017 |archive-date=21 May 2021 |archive-url=https://web.archive.org/web/20210521021947/https://plato.stanford.edu/entries/scientific-underdetermination/ |url-status=live }}{{cite web |title=Philosophy of science – Underdetermination |url=https://www.britannica.com/topic/philosophy-of-science/Underdetermination |website=Encyclopedia Britannica |access-date=15 June 2021 |language=en |archive-date=16 June 2021 |archive-url=https://web.archive.org/web/20210616042926/https://www.britannica.com/topic/philosophy-of-science/Underdetermination |url-status=live }} Theory-ladenness refers to the idea that evidence already includes theoretical assumptions. These assumptions can hinder it from acting as neutral arbiter. It can also lead to a lack of shared evidence if different scientists do not share these assumptions.{{cite book |last1=Andersen |first1=Hanne |last2=Green |first2=Sara |title=Encyclopedia of Systems Biology |date=2013 |publisher=Springer |isbn=978-1-4419-9863-7 |pages=2165–2167 |url=https://link.springer.com/referenceworkentry/10.1007%2F978-1-4419-9863-7_86 |language=en |chapter=Theory-Ladenness |doi=10.1007/978-1-4419-9863-7_86 |access-date=2021-06-21 |archive-date=2022-04-08 |archive-url=https://web.archive.org/web/20220408024855/https://link.springer.com/referenceworkentry/10.1007%2F978-1-4419-9863-7_86 |url-status=live }} Thomas Kuhn is an important advocate of the position that theory-ladenness concerning scientific paradigms plays a central role in science.{{harvnb|Kuhn|1970}}{{harvnb|Bird|2013}}

A thing is evidence for a proposition if it epistemically supports this proposition or indicates that the supported proposition is true. Evidence is empirical if it is constituted by or accessible to sensory experience. There are various competing theories about the exact definition of the terms evidence and empirical. Different fields, like epistemology, the sciences or legal systems, often associate different concepts with these terms. An important distinction among theories of evidence is whether they identify evidence with private mental states or with public physical objects. Concerning the term empirical, there is a dispute about where to draw the line between observable or empirical objects in contrast to unobservable or merely theoretical objects.

The traditional view proposes that evidence is empirical if it is constituted by or accessible to sensory experience. This involves experiences arising from the stimulation of the sense organs, like visual or auditory experiences, but the term is often used in a wider sense including memories and introspection.{{cite web |title=Empiricism |url=https://www.britannica.com/topic/empiricism |website=Encyclopedia Britannica |access-date=17 June 2021 |language=en |archive-date=3 May 2021 |archive-url=https://web.archive.org/web/20210503102847/https://www.britannica.com/topic/empiricism |url-status=live }} It is usually seen as excluding purely intellectual experiences, like rational insights or intuitions used to justify basic logical or mathematical principles.{{cite web |last1=Baehr |first1=Jason S. |title=A Priori and A Posteriori |url=https://iep.utm.edu/apriori/ |website=Internet Encyclopedia of Philosophy |access-date=18 June 2021 |archive-date=4 October 2019 |archive-url=https://web.archive.org/web/20191004061905/https://www.iep.utm.edu/apriori/ |url-status=live }} The terms empirical and observable are closely related and sometimes used as synonyms.{{cite journal |last1=Willer |first1=David |last2=Webster |first2=Murray |title=Theoretical Concepts and Observables |journal=American Sociological Review |date=1970 |volume=35 |issue=4 |pages=748–757 |doi=10.2307/2093949 |jstor=2093949 |url=https://www.jstor.org/stable/2093949 |issn=0003-1224 |access-date=2021-06-21 |archive-date=2021-06-25 |archive-url=https://web.archive.org/web/20210625051552/https://www.jstor.org/stable/2093949 |url-status=live }}

There is an active debate in contemporary philosophy of science as to what should be regarded as observable or empirical in contrast to unobservable or merely theoretical objects. There is general consensus that everyday objects like books or houses are observable since they are accessible via unaided perception, but disagreement starts for objects that are only accessible through aided perception. This includes using telescopes to study distant galaxies,{{cite book |editor-last1=Churchland |editor-first1=Paul M. |editor-last2=Hooker |editor-first2=Clifford A. |title=Images of Science: Essays on Realism and Empiricism |last=Churchland |first=Paul M. |chapter=The Ontological Status of Observables: In Praise of the Superempirical Virtues |publisher=University of Chicago Press |date=1985}} microscopes to study bacteria or using cloud chambers to study positrons.{{cite book |last=van Fraassen |first=Bas |title=The Scientific Image |publisher=Oxford University Press |date=1980 |pages=16–17}} So the question is whether distant galaxies, bacteria or positrons should be regarded as observable or merely theoretical objects. Some even hold that any measurement process of an entity should be considered an observation of this entity. In this sense, the interior of the Sun is observable since neutrinos originating there can be detected.{{cite journal |last1=Schickore |first1=Jutta |title=Sehen, Sichtbarkeit Und Empirische Forschung |journal=Journal for General Philosophy of Science |date=1999 |volume=30 |issue=2 |pages=273–287 |doi=10.1023/A:1008374032737 |s2cid=119357187 |url=https://philpapers.org/rec/SCHSSU |access-date=2021-06-21 |archive-date=2021-06-24 |archive-url=https://web.archive.org/web/20210624203132/https://philpapers.org/rec/SCHSSU |url-status=live }}{{cite journal |last1=Shapere |first1=Dudley |title=The Concept of Observation in Science and Philosophy |journal=Philosophy of Science |date=1982 |volume=49 |issue=4 |pages=485–525 |doi=10.1086/289075 |s2cid=224832408 |url=https://philpapers.org/rec/SHATCO-3 |access-date=2021-06-21 |archive-date=2021-06-28 |archive-url=https://web.archive.org/web/20210628011740/https://philpapers.org/rec/SHATCO-3 |url-status=live }} The difficulty with this debate is that there is a continuity of cases going from looking at something with the naked eye, through a window, through a pair of glasses, through a microscope, etc.{{cite journal |last1=Malik |first1=Saira |title=Observation Versus Experiment: An Adequate Framework for Analysing Scientific Experimentation? |journal=Journal for General Philosophy of Science |date=2017-03-01 |volume=48 |issue=1 |pages=71–95 |doi=10.1007/s10838-016-9335-y |language=en |issn=1572-8587|doi-access=free }}{{cite book |last1=Okasha |first1=Samir |title=Philosophy of Science: Very Short Introduction |publisher=Oxford University Press |isbn=978-0-19-180764-0 |edition=2nd |url=https://www.veryshortintroductions.com/view/10.1093/actrade/9780198745587.001.0001/actrade-9780198745587-chapter-4 |chapter=4. Realism and anti-realism |year=2016 |access-date=2021-06-21 |archive-date=2021-06-24 |archive-url=https://web.archive.org/web/20210624202547/https://www.veryshortintroductions.com/view/10.1093/actrade/9780198745587.001.0001/actrade-9780198745587-chapter-4 |url-status=live }} Because of this continuity, drawing the line between any two adjacent cases seems to be arbitrary. One way to avoid these difficulties is to hold that it is a mistake to identify the empirical with what is observable or sensible. Instead, it has been suggested that empirical evidence can include unobservable entities as long as they are detectable through suitable measurements.{{cite journal |last1=Boyd |first1=Nora Mills |title=Evidence Enriched |journal=Philosophy of Science |date=2018 |volume=85 |issue=3 |pages=403–421 |doi=10.1086/697747 |s2cid=224833831 |url=https://philpapers.org/rec/BOYEE-5 |access-date=2021-06-21 |archive-date=2021-06-24 |archive-url=https://web.archive.org/web/20210624203700/https://philpapers.org/rec/BOYEE-5 |url-status=live }} A problem with this approach is that it is rather far from the original meaning of "empirical", which contains the reference to experience.

{{main|A priori and a posteriori}}

Knowledge or the justification of a belief is said to be a posteriori if it is based on empirical evidence. A posteriori refers to what depends on experience (what comes after experience), in contrast to a priori, which stands for what is independent of experience (what comes before experience).{{cite web |last1=Russell |first1=Bruce |title=A Priori Justification and Knowledge |url=https://plato.stanford.edu/entries/apriori/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=20 June 2021 |date=2020 |archive-date=12 August 2021 |archive-url=https://web.archive.org/web/20210812143105/https://plato.stanford.edu/entries/apriori/ |url-status=live }} For example, the proposition that "all bachelors are unmarried" is knowable a priori since its truth only depends on the meanings of the words used in the expression. The proposition "some bachelors are happy", on the other hand, is only knowable a posteriori since it depends on experience of the world as its justifier.{{cite book |last1=Gensler |first1=Harry J. |title=Introduction to Logic |year=2012 |publisher=Routledge |isbn=978-1-136-99452-4 |url=https://books.google.com/books?id=HnRekA0qkPsC |language=en |chapter=3.7 A priori and a posteriori}} Immanuel Kant held that the difference between a posteriori and a priori is tantamount to the distinction between empirical and non-empirical knowledge.{{harvnb|Craig|2005|p=1}}

Two central questions for this distinction concern the relevant sense of "experience" and of "dependence". The paradigmatic justification of knowledge a posteriori consists in sensory experience, but other mental phenomena, like memory or introspection, are also usually included in it. But purely intellectual experiences, like rational insights or intuitions used to justify basic logical or mathematical principles, are normally excluded from it. There are different senses in which knowledge may be said to depend on experience. In order to know a proposition, the subject has to be able to entertain this proposition, i.e. possess the relevant concepts.{{cite journal |last1=Siebel |first1=Mark |title=A Puzzle About Concept Possession |journal=Grazer Philosophische Studien |date=2005 |volume=68 |issue=1 |pages=1–22 |doi=10.1163/18756735-068001001 |url=https://philpapers.org/rec/SIEAPA |access-date=2021-06-21 |archive-date=2021-06-28 |archive-url=https://web.archive.org/web/20210628013945/https://philpapers.org/rec/SIEAPA |url-status=live }} For example, experience is necessary to entertain the proposition "if something is red all over then it is not green all over" because the terms "red" and "green" have to be acquired this way. But the sense of dependence most relevant to empirical evidence concerns the status of justification of a belief. So experience may be needed to acquire the relevant concepts in the example above, but once these concepts are possessed, no further experience providing empirical evidence is needed to know that the proposition is true, which is why it is considered to be justified a priori.

In its strictest sense, empiricism is the view that all knowledge is based on experience or that all epistemic justification arises from empirical evidence. This stands in contrast to the rationalist view, which holds that some knowledge is independent of experience, either because it is innate or because it is justified by reason or rational reflection alone.{{harvnb|Feldman|2001|p=293}}{{cite web |last1=Markie |first1=Peter |title=Rationalism vs. Empiricism |url=https://plato.stanford.edu/entries/rationalism-empiricism/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=20 June 2021 |date=2017 |archive-date=9 August 2019 |archive-url=https://web.archive.org/web/20190809193416/https://plato.stanford.edu/entries/rationalism-empiricism/ |url-status=live }}{{cite book |last1=Alston |first1=William P. |title=Routledge Encyclopedia of Philosophy |date=1998 |publisher=Taylor and Francis |url=https://www.rep.routledge.com/articles/thematic/empiricism/v-1 |language=en |chapter=Empiricism |doi=10.4324/9780415249126-P014-1 |isbn=978-0415250696 |access-date=2021-06-21 |archive-date=2021-06-24 |archive-url=https://web.archive.org/web/20210624202816/https://www.rep.routledge.com/articles/thematic/empiricism/v-1 |url-status=live }}{{cite book |author-link= Peter Markie|last1=Markie |first1=Peter J. |title=Routledge Encyclopedia of Philosophy |date=1998 |publisher=Taylor and Francis |url=https://www.rep.routledge.com/articles/thematic/rationalism/v-1 |language=en |chapter=Rationalism |doi=10.4324/9780415249126-P041-1 |isbn=978-0415250696 |access-date=2021-06-21 |archive-date=2021-06-24 |archive-url=https://web.archive.org/web/20210624203959/https://www.rep.routledge.com/articles/thematic/rationalism/v-1 |url-status=live }} Expressed through the distinction between knowledge a priori and a posteriori from the previous section, rationalism affirms that there is knowledge a priori, which is denied by empiricism in this strict form.{{cite journal |last1=Teixeira |first1=Célia |title=How Not to Reject the a Priori |journal=Kriterion: Journal of Philosophy |date=2018 |volume=59 |issue=140 |pages=365–384 |doi=10.1590/0100-512x2018n14002ct |doi-access=free }} One difficulty for empiricists is to account for the justification of knowledge pertaining to fields like mathematics and logic, for example, that 3 is a prime number or that modus ponens is a valid form of deduction. The difficulty is due to the fact that there seems to be no good candidate of empirical evidence that could justify these beliefs. Such cases have prompted empiricists to allow for certain forms of knowledge a priori, for example, concerning tautologies or relations between our concepts. These concessions preserve the spirit of empiricism insofar as the restriction to experience still applies to knowledge about the external world. In some fields, like metaphysics or ethics, the choice between empiricism and rationalism makes a difference not just for how a given claim is justified but for whether it is justified at all. This is best exemplified in metaphysics, where empiricists tend to take a skeptical position, thereby denying the existence of metaphysical knowledge, while rationalists seek justification for metaphysical claims in metaphysical intuitions.{{cite book |last1=Friedman |first1=Michael |title=The Cambridge Companion to Carnap |date=2007 |publisher=Cambridge University Press |isbn=978-0-521-84015-6 |pages=129–152 |url=https://www.cambridge.org/core/books/cambridge-companion-to-carnap/aufbau-and-the-rejection-of-metaphysics/5B8EE3CA519506849902DBAA1388C73E |chapter=The Aufbau and the rejection of metaphysics |access-date=2021-06-21 |archive-date=2021-06-30 |archive-url=https://web.archive.org/web/20210630140117/https://www.cambridge.org/core/books/cambridge-companion-to-carnap/aufbau-and-the-rejection-of-metaphysics/5B8EE3CA519506849902DBAA1388C73E |url-status=live }}{{cite journal |last1=Chakravartty |first1=Anjan |title=Stance Relativism: Empiricism Versus Metaphysics |journal=Studies in History and Philosophy of Science Part A |date=2004 |volume=35 |issue=1 |pages=173–184 |doi=10.1016/j.shpsa.2003.12.002 |url=https://philpapers.org/rec/CHASRE-4 |access-date=2021-06-21 |archive-date=2021-06-29 |archive-url=https://web.archive.org/web/20210629105007/https://philpapers.org/rec/CHASRE-4 |url-status=live }}

{{Main|Scientific evidence}}

Scientific evidence is closely related to empirical evidence. Some theorists, like Carlos Santana, have argued that there is a sense in which not all empirical evidence constitutes scientific evidence. One reason for this is that the standards or criteria that scientists apply to evidence exclude certain evidence that is legitimate in other contexts. For example, anecdotal evidence from a friend about how to treat a certain disease constitutes empirical evidence that this treatment works but would not be considered scientific evidence.{{cite journal |last1=Santana |first1=Carlos |title=Why Not All Evidence is Scientific Evidence |journal=Episteme |date=2018 |volume=15 |issue=2 |pages=209–227 |doi=10.1017/epi.2017.3 |s2cid=152066892 |url=https://philpapers.org/rec/SANWNA-2 |access-date=2021-06-21 |archive-date=2021-06-27 |archive-url=https://web.archive.org/web/20210627233619/https://philpapers.org/rec/SANWNA-2 |url-status=live }}{{cite journal |last1=Browning |first1=Heather |title=Anecdotes Can Be Evidence Too |journal=Animal Sentience |date=2017 |volume=2 |issue=16 |pages=13 |doi=10.51291/2377-7478.1246 |url=https://philpapers.org/rec/BROACB-3 |doi-access=free |access-date=2021-06-21 |archive-date=2021-06-29 |archive-url=https://web.archive.org/web/20210629002215/https://philpapers.org/rec/BROACB-3 |url-status=live }} Others have argued that the traditional empiricist definition of empirical evidence as perceptual evidence is too narrow for much of scientific practice, which uses evidence from various kinds of non-perceptual equipment.{{cite book |last1=Bogen |first1=James |author-link1=James Bogen |date=2016 |chapter=Empiricism and After |editor1-last=Humphreys |editor1-first=Paul |editor1-link=Paul Humphreys (philosopher) |editor2-last=Chakravartty |editor2-first=Anjan |editor2-link=Anjan Chakravartty |editor3-last=Morrison |editor3-first=Margaret |editor3-link=Margaret Morrison (philosopher) |editor4-last=Woody |editor4-first=Andrea |title=The Oxford Handbook of Philosophy of Science |series=Oxford Handbooks in Philosophy |location=Oxford; New York |publisher=Oxford University Press |pages=779–795 |isbn=978-0199368815 |oclc=933596096 |doi=10.1093/oxfordhb/9780199368815.013.12}}

Central to scientific evidence is that it was arrived at by following scientific method in the context of some scientific theory.{{cite book |last=Bunge |first=Mario |author-link=Mario Bunge |date=1998 |orig-year=1967 |title=Philosophy of Science: Volume 1, From Problem to Theory |edition=Revised |series=Science and Technology Studies |location=New Brunswick, NJ |publisher=Transaction Publishers |page=[https://archive.org/details/philosophyofscie0001bung/page/21 21] |isbn=9780765804136 |oclc=37156799 |url=https://archive.org/details/philosophyofscie0001bung/page/21 |url-access=registration |quote=... empirical information is not weighed in a theoretical vacuum: every piece of evidence must be judged in the light of the theory employed in the design and implementation of the technique used to gather that information. Just as no factual theory stands by itself, so no datum constitutes an evidence for or against a theory unless it is gathered and interpreted with the help of some scientific theory.}} But people rely on various forms of empirical evidence in their everyday lives that have not been obtained this way and therefore do not qualify as scientific evidence. One problem with non-scientific evidence is that it is less reliable, for example, due to cognitive biases like the anchoring effect,{{cite journal |last1=Tversky |first1=Amos |last2=Kahneman |first2=Daniel |title=Judgment under Uncertainty: Heuristics and Biases |journal=Science |date=1974-09-27 |volume=185 |issue=4157 |pages=1124–1131 |doi=10.1126/science.185.4157.1124 |pmid=17835457 |bibcode=1974Sci...185.1124T |s2cid=143452957 |url=https://www.science.org/doi/10.1126/science.185.4157.1124 |language=en |issn=0036-8075 |access-date=2022-06-30 |archive-date=2022-07-15 |archive-url=https://web.archive.org/web/20220715004933/https://www.science.org/doi/10.1126/science.185.4157.1124 |url-status=live }} in which information obtained earlier is given more weight, although science done poorly is also subject to such biases, as in the example of p-hacking.

In the philosophy of science, it is sometimes held that there are two sources of empirical evidence: observation and experimentation.{{harvnb|Pickett|2011|loc=Empirical}} The idea behind this distinction is that only experimentation involves manipulation or intervention: phenomena are actively created instead of being passively observed.{{cite journal |last1=Malik |first1=Saira |title=Observation Versus Experiment: An Adequate Framework for Analysing Scientific Experimentation? |journal=Journal for General Philosophy of Science |date=2017 |volume=48 |issue=1 |pages=71–95 |doi=10.1007/s10838-016-9335-y |url=https://philpapers.org/rec/MALOVE |doi-access=free |access-date=2021-06-21 |archive-date=2021-06-24 |archive-url=https://web.archive.org/web/20210624204023/https://philpapers.org/rec/MALOVE |url-status=live }}{{cite book |last1=González |first1=Wenceslao J. |title=New Methodological Perspectives on Observation and Experimentation in Science |year=2010 |publisher=Netbiblo |isbn=978-84-9745-530-5 |url=https://books.google.com/books?id=xZuOHU4aAh8C |language=en |chapter=1. Recent approaches on Observation and Experimentation}}{{cite web |last1=Boyd |first1=Nora Mills |last2=Bogen |first2=James |title=Theory and Observation in Science |url=https://plato.stanford.edu/entries/science-theory-observation/ |website=The Stanford Encyclopedia of Philosophy |publisher=Metaphysics Research Lab, Stanford University |access-date=21 June 2021 |date=2021 |archive-date=14 June 2021 |archive-url=https://web.archive.org/web/20210614180115/https://plato.stanford.edu/entries/science-theory-observation/ |url-status=live }} For example, inserting viral DNA into a bacterium is a form of experimentation while studying planetary orbits through a telescope belongs to mere observation.{{cite journal |last1=Okasha |first1=S. |title=Experiment, Observation and the Confirmation of Laws |journal=Analysis |date=2011 |volume=71 |issue=2 |pages=222–232 |doi=10.1093/analys/anr014 |url=https://philpapers.org/rec/OKAEOA |hdl=1983/79e68032-e432-47de-adb5-e7ca3ff2841d |hdl-access=free |access-date=2021-06-21 |archive-date=2021-06-24 |archive-url=https://web.archive.org/web/20210624202034/https://philpapers.org/rec/OKAEOA |url-status=live }} In these cases, the mutated DNA was actively produced by the biologist while the planetary orbits are independent of the astronomer observing them. Applied to the history of science, it is sometimes held that ancient science is mainly observational while the emphasis on experimentation is only present in modern science and responsible for the scientific revolution. This is sometimes phrased through the expression that modern science actively "puts questions to nature". This distinction also underlies the categorization of sciences into experimental sciences, like physics, and observational sciences, like astronomy. While the distinction is relatively intuitive in paradigmatic cases, it has proven difficult to give a general definition of "intervention" applying to all cases, which is why it is sometimes outright rejected.

Empirical evidence is required for a hypothesis to gain acceptance in the scientific community. Normally, this validation is achieved by the scientific method of forming a hypothesis, experimental design, peer review, reproduction of results, conference presentation, and journal publication. This requires rigorous communication of hypothesis (usually expressed in mathematics), experimental constraints and controls (expressed in terms of standard experimental apparatus), and a common understanding of measurement. In the scientific context, the term semi-empirical is used for qualifying theoretical methods that use, in part, basic axioms or postulated scientific laws and experimental results. Such methods are opposed to theoretical ab initio methods, which are purely deductive and based on first principles. Typical examples of both ab initio and semi-empirical methods can be found in computational chemistry.

{{col div|colwidth=30em}}

• Empirical distribution function
• Empirical formula
• Empirical measure
• Empirical relationship
• Empirical research
• Experiential knowledge
• Ground truth
• Phenomenology (philosophy)

{{colend}}

{{Reflist}}

• {{cite encyclopedia|last=Bird|first=Alexander|editor-last=Zalta|editor-first=Edward N.|date=2013|title=Thomas Kuhn|at=Section 4.2 Perception, Observational Incommensurability, and World-Change |encyclopedia=Stanford Encyclopedia of Philosophy|url=http://plato.stanford.edu/archives/fall2013/entries/thomas-kuhn/#4.2|access-date=25 January 2012}}
• {{cite encyclopedia|last=Craig|first=Edward|encyclopedia=The Shorter Routledge Encyclopedia of Philosophy|year=2005|publisher= Routledge|isbn=978-0415324953|title=a posteriori}}
• {{cite encyclopedia|last=Feldman|first=Richard|editor-last=Audi|editor-first=Robert|title=Evidence|encyclopedia=The Cambridge Dictionary of Philosophy|edition=2nd|year=2001|orig-year=1999|isbn=978-0521637220|publisher=Cambridge University Press|location=Cambridge, UK|pages=293–294}}
• {{cite book|last=Kuhn|first=Thomas S.|author-link=Thomas S. Kuhn|title=The Structure of Scientific Revolutions|publisher=University of Chicago Press|location=Chicago|year=1970|edition=2nd|orig-year=1962|isbn=978-0226458045|url-access=registration|url=https://archive.org/details/structureofscie000kuhn }}
• {{cite encyclopedia|editor-last=Pickett|editor-first=Joseph P.|title=The American Heritage Dictionary of the English Language|publisher=Houghton Mifflin|year=2011|edition=5th|isbn=978-0-547-04101-8}}

• {{wiktionary-inline|empirical}}
• {{wiktionary-inline|evidence}}
• {{cite IEP |url-id=apriori |title=A Priori and A Posteriori}}

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Category:Empiricism