Philosophy

=== Epistemology ===
{{Main|Epistemology}}
Epistemology is the branch of philosophy that studies knowledge. It is also known as ''theory of knowledge'' and aims to understand what knowledge is, how it arises, what its limits are, and what value it has. It further examines the nature of [[truth]], [[belief]], [[Justification (epistemology)|justification]], and [[Reason|rationality]].<ref>{{multiref |1={{harvnb|Martinich|Stroll|2023|loc=Lead Section, The Nature of Epistemology}} |2={{harvnb|Steup|Neta|2020|loc=Lead Section}} |3={{harvnb|Truncellito|loc=Lead Section}} |4={{harvnb|Greco|2021|loc=Article Summary}} }}</ref> Some of the questions addressed by epistemologists include "By what method(s) can one acquire knowledge?"; "How is truth established?"; and "Can we prove causal relations?"{{sfn|Mulvaney|2009|p=ix}}

Epistemology is primarily interested in [[declarative knowledge]] or knowledge of facts, like knowing that Princess Diana died in 1997. But it also investigates [[practical knowledge]], such as knowing how to ride a bicycle, and [[knowledge by acquaintance]], for example, knowing a celebrity personally.<ref>{{multiref |1={{harvnb|Steup|Neta|2020|loc=Lead Section, 2. What Is Knowledge?}} |2={{harvnb|Truncellito|loc=Lead Section, 1. Kinds of Knowledge}} |3={{harvnb|Colman|2009a|loc=[https://www.oxfordreference.com/display/10.1093/oi/authority.20110803095705926;jsessionid=A19D30BFCF6E02A0F21A87B805F10DEE Declarative Knowledge]}} }}</ref>

One area in epistemology is the ''[[analysis of knowledge]]''. It assumes that declarative knowledge is a combination of different parts and attempts to identify what those parts are. An influential theory in this area claims that knowledge has three components: it is a ''belief'' that is ''justified'' and ''true''. This theory is controversial and the difficulties associated with it are known as the [[Gettier problem]].<ref>{{multiref |1={{harvnb|Martinich|Stroll|2023|loc=The Nature of Knowledge}} |2={{harvnb|Truncellito|loc=Lead Section, 2. The Nature of Propositional Knowledge}} }}</ref> Alternative views state that knowledge requires additional components, like the absence of luck; different components, like the manifestation of [[Epistemic virtue|cognitive virtues]] instead of justification; or they deny that knowledge can be analyzed in terms of other phenomena.<ref>{{multiref |1={{harvnb|Ichikawa|Steup|2018|loc=[https://plato.stanford.edu/entries/knowledge-analysis/#GettProb § 3. The Gettier Problem, § 11. Knowledge First]}} |2={{harvnb|Truncellito|loc=§ 2d. The Gettier Problem}} }}</ref>

Another area in epistemology asks how people acquire knowledge. Often-discussed sources of knowledge are [[perception]], [[introspection]], [[memory]], [[inference]], and [[testimony]].<ref>{{multiref |1={{harvnb|Steup|Neta|2020|loc=5. Sources of Knowledge and Justification}} |2={{harvnb|Truncellito|loc=Lead Section, 4a. Sources of Knowledge}} }}</ref> According to [[empiricists]], all knowledge is based on some form of experience. Rationalists reject this view and hold that some forms of knowledge, like [[innate knowledge]], are not acquired through experience.<ref>{{multiref |1={{harvnb|Hetherington|loc=[https://iep.utm.edu/knowledg/#SH3c § 3c. Knowing Purely by Thinking]}} |2={{harvnb|Blackburn|2008|loc=[https://www.oxfordreference.com/display/10.1093/oi/authority.20110803095750220;jsessionid=BA317C21431AFF040A4F793D75E18752 Empiricism]}} |3={{harvnb|Blackburn|2008|loc=[https://www.oxfordreference.com/display/10.1093/oi/authority.20110803100405393;jsessionid=8337F6C845B873723233E9AEDB1025BC Rationalism]}} }}</ref> The [[regress problem]] is a common issue in relation to the sources of knowledge and the justification they offer. It is based on the idea that beliefs require some kind of reason or evidence to be justified. The problem is that the source of justification may itself be in need of another source of justification. This leads to an [[infinite regress]] or [[circular reasoning]]. [[Foundationalist]]s avoid this conclusion by arguing that some sources can provide justification without requiring justification themselves.<ref>{{multiref |1={{harvnb|Steup|Neta|2020|loc=4. The Structure of Knowledge and Justification}} |2={{harvnb|Truncellito|loc=3. The Nature of Justification}} }}</ref> Another solution is presented by [[coherentist]]s, who state that a belief is justified if it coheres with other beliefs of the person.{{sfn|Olsson|2021|loc=Lead Section, § 1. Coherentism Versus Foundationalism}}

Many discussions in epistemology touch on the topic of [[philosophical skepticism]], which raises doubts about some or all claims to knowledge. These doubts are often based on the idea that knowledge requires absolute certainty and that humans are unable to acquire it.<ref>{{multiref |1={{harvnb|Steup|Neta|2020|loc=6. The Limits of Cognitive Success}} |2={{harvnb|Truncellito|loc=4. The Extent of Human Knowledge}} |3={{harvnb|Johnstone|1991|p=[https://books.google.com/books?id=IBbQtkyrLE4C&pg=PA52 52]}} }}</ref>