challenged traditional epistemology with his philosophy of naturalised epistemology.|alt=A photograph of W. V. Quine, he is wearing glasses and smiling at the camera, in the background it can be seen that Quine is on a boat. Epistemology is commonly defined as the "theory of knowledge". In this sense, it investigates the nature of knowledge and how far it extends, but epistemologists also investigate other concepts such as
justification,
understanding and
rationality. To account for this diversity of interests, epistemology is sometimes characterised as two connected projects:
gnoseology concerned with the theory of knowledge, and
intellectual ethics concerned with guiding inquiry according to proper intellectual norms. As the central focus of epistemology, knowledge is generally understood in terms of full
belief, but
credences or degrees of belief are also important concepts. These are the subjective probabilities people attach to different possible claims and feature most prominently in
Bayesian epistemology, which uses formal mathematical methods to investigate epistemological questions. Epistemology is traditionally viewed as an
a priori discipline focused on reflective thought rather than
empirical evidence, and as autonomous from the results and methods of the sciences. It is also generally seen as a
normative discipline, evaluating beliefs as either justified or unjustified and prescribing the proper way to form beliefs. Alternative views of epistemology may deny some or all of the traditional features of epistemology. For example, naturalistic epistemology denies the autonomy of epistemology, holding that epistemology should be informed by either the methods or
ontology of science. In its most radical form, associated in particular with the
naturalised epistemology of
W. V. Quine, it claims that epistemology should be replaced with empirical disciplines such as
psychology or
cognitive science. Advocates of experimental philosophy claim that epistemology should use
a posteriori methods such as experiments and empirical data, either as additional methods alongside traditional philosophical techniques or as a complete replacement. Methods associated with traditional epistemology include the use of
intuitions about particular cases or
thought experiments to support epistemological theories or ideas. A prominent example in epistemology is the use of intuitions regarding
Gettier cases to test theories of knowledge. These are hypothetical cases in which candidate conditions for knowledge are met but intuitively do not appear to count as knowledge due to luck being involved. Intuitions are also used in the process of
reflective equilibrium, in which conflicting intuitions are brought into alignment by modifying or removing intuitions until they form a coherent system of beliefs. .|alt=A greyscale photograph of Edmund Gettier, he is facing the camera, wearing a shirt, tie and cardigan. Related to the use of intuitions is the method of analysis to clarify epistemic terms. Traditionally, analysis in epistemology has been seen as
conceptual analysis, which attempts to clarify concepts such as knowledge by providing
necessary and sufficient conditions for their use. A similar view sees analysis as semantic or
linguistic analysis, in which the way terms are actually used is tracked to try and reveal their meaning. However, particularly due to problems associated with Gettier cases, philosophers including
Timothy Williamson and
Hilary Kornblith have argued that epistemologists should be concerned with the underlying phenomena of epistemology rather than words and concepts. According to this viewpoint, analysis in epistemology should be
metaphysical analysis, which aims at understanding the nature of the thing being investigated. An alternative methodology to philosophical analysis is
explication. Explication aims to clarify a term by replacing it with a more precisely defined technical term. The technical term should remain close in meaning to the original term but can deviate from intuitions to fulfil theoretical or practical goals. For example, the scientific term "fish" excludes whales to better capture the facts of biology, even if whales may be included in the colloquial or pre-scientific meaning of the word. Practical explication, also known as a function-first approach, identifies the purpose or function of a term to clarify its meaning. Proposed functions of the term
knowledge, for example, include its role in identifying reliable sources of information and in marking an end-point for inquiry. This approach is associated with the
pragmatism of
Charles Sanders Peirce and
neopragmatists such as Mark Kaplan and
Edward Craig. Inspired by Craig, Jonathan Weinberg has proposed an explicitly metaepistemological pragmatism that allows epistemic concepts to be redesigned to fulfil practical goals, resulting in a method of "analysis-by-imagined-reconstruction". Another methodological issue in epistemology is the debate between
particularists and
generalists. According to particularists, particular cases of knowledge need to be identified before the general principles underlying knowledge can be understood. Generalists, on the other hand, argue that the principles underlying knowledge are required to reliably identify cases. This debate is made more complicated by the fact that each question seems to depend on the other; a general theory of knowledge is needed to know if particular cases count as knowledge, but a theory of knowledge is potentially arbitrary without being tested against particular cases. This is known as the
problem of the criterion. Generalism was popular in
modern philosophy, but by the middle of the 20th century, particularism was the dominant view. In the 21st century, particularism became less dominant after a period driven by responses to Gettier cases, and epistemic methodology widened to include considerations regarding the
value of knowledge and the relationships between knowledge and related concepts such as
assertion. The value of knowledge can be used in the methodology of epistemology to test theories of knowledge. For example, any theory that fails to explain why knowledge is so valuable can be seen as failing to explain what knowledge truly is. This is because such a theory cannot explain why knowledge is more valuable than mere true opinions. One explanation for the value of knowledge dating back to
Plato is that knowledge is fixed onto the truth whilst true opinions can be unstable. Another theory,
virtue epistemology, espoused by philosophers such as
Ernest Sosa and
Linda Zagzebski, argues that knowledge is the result of virtuous
character traits—like open-mindedness and keen perception—and this explains the value of knowledge. One controversy surrounding this point of view, deriving from
situationism in psychology, is whether character traits are fixed or stable. has argued that epistemic concepts should be reformulated from a feminist lens to remove androcentric bias.|alt=A photo of Sally Haslanger delivering a talk or lecture at a whiteboard. According to
feminist epistemology, epistemology has been historically rooted in
androcentric bias. An example cited by some
feminist philosophers is epistemology's focus on
propositional knowledge and devaluing of
emotional and
practical forms of knowledge stereotyped as feminine. Feminists typically argue that this bias should be replaced with feminist values rather than a value-free or "disinterested" methodology, and have attempted to show that feminist values are preferable. For example,
Louise Antony has embraced feminist naturalised epistemology and argued that feminist ideals produce empirically better theories. Meanwhile,
Sally Haslanger has argued from a pragmatist perspective that epistemic concepts can be reformed based on feminist values to better serve their purposes within epistemology. == Epistemic realism and anti-realism ==