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Proposed Definitions of Knowledge

Definitions of knowledge attempt to determine the essential features of knowledge.
Most definitions of knowledge in analytic philosophy focus on propositional knowledge or knowledge-that.
Disagreements about the precise nature of knowledge are still numerous and deep.
One standard definition of knowledge is justified true belief (JTB).
The JTB definition implies that knowledge is a mental state and that it is not possible to know something false.
The source of most disagreements regarding the nature of knowledge concerns what more is needed besides justification.
The JTB definition of knowledge came under severe criticism in the second half of the 20th century due to counterexamples given by Edmund Gettier.
Many theorists still agree that the JTB definition is on the right track and have proposed more moderate responses to deal with Gettier's counterexamples.
Not all forms of knowledge are propositional, and various definitions of different forms of non-propositional knowledge have also been proposed.
Different theorists have different goals in mind when trying to define knowledge, and there are also important methodological differences regarding how one arrives at and justifies one's definition.
The term "standard of knowledge" refers to how high the requirements are for ascribing knowledge to someone.
There is overwhelming agreement that knowledge implies truth, but some theorists have proposed that truth may not always be necessary for knowledge.Understanding Knowledge: Belief, Justification, Internalism and Externalism
Knowledge is usually understood as a form of belief, meaning that the agent accepts the proposition in question.
True belief by itself is not sufficient for knowledge, as there are counterexamples where a person holds a true belief in virtue of faulty reasoning or a lucky guess.
Justification is the third component of the JTB definition, which implies that having a true belief is not sufficient for knowledge, and beliefs based on dogmatic opinions, blind guesses, or erroneous reasoning do not constitute knowledge even if they are true.
The additional requirement for turning a true belief into knowledge is justification, which is a central question in epistemology.
There are many suggestions and deep disagreements within the academic literature about what the additional requirements are for knowledge.
Internalism and externalism are two theories of justification, with internalism being more commonly defended. Internalism holds that internal mental states of the subject justify beliefs, such as perceptual experiences, memories, rational intuition, or other justified beliefs.
Evidentialism is a particular form of internalism, which bases justification exclusively on the possession of evidence.
Externalism includes factors external to the person as well, such as the existence of a causal relation to the believed fact or to a reliable belief formation process, and a prominent theory in this field is reliabilism.
The JTB definition of knowledge was already rejected in Plato's Theaetetus, and the JTB definition came under severe criticism in the 20th century due to a series of counterexamples given by Edmund Gettier.
The Gettier problem includes cases in which a justified belief is true because of lucky circumstances, where the person's reason for the belief is irrelevant to its truth.
There have been various notable responses to the Gettier problem, typically involving substantial attempts to provide a new definition of knowledge that is not susceptible to Gettier-style objections, either by providing an additional fourth condition that justified true beliefs must meet to constitute knowledge or proposing a completely new set of necessary and sufficient conditions for knowledge.
Most contemporary philosophers deny the JTB definition of knowledge, at least in its exact form, and see the problems as insurmountable, proposing radical new conceptions of knowledge.Different Approaches to Defining Knowledge
The traditional definition of knowledge is justified true belief.
Many epistemologists have proposed a moderate departure from the traditional definition, arguing that justified true belief is necessary but not sufficient for knowledge.
JTB+X accounts of knowledge propose an additional fourth criterion needed for sufficiency.
Defeasibility theories of knowledge introduce the condition of defeasibility to avoid problems faced by JTB accounts.
Reliabilistic and causal theories are forms of externalism that modify the JTB definition of knowledge by reconceptualizing what justification means.
Virtue-theoretic approaches try to avoid the problem of cognitive luck by seeing knowledge as a manifestation of intellectual virtues.
The "no false premises" response to the Gettier problem proposes that a justified true belief must not have been inferred from a false belief.
The infallibilist response defines knowledge as a belief that is infallibly justified, but this response is incompatible with everyday knowledge ascriptions.
The tracking condition defines knowledge as a belief that tracks the truth, but externalist accounts of knowledge often reject closure in cases where it is intuitively valid.
The knowledge-first response argues that the concept of knowledge cannot be broken down into a set of other concepts through analysis—it is sui generis.
The merely true belief response argues that justification is an unnecessary criterion for knowledge.
Nyaya philosophy distinguishes between knowing and knowing that one knows, and proposes a sort of implicit inference that usually follows immediately the episode of knowing.Understanding the Concept of Knowledge
The concept of knowledge has been debated by philosophers for centuries.
A commonly accepted definition of knowledge is justified true belief.
However, some philosophers argue that this definition is not sufficient to capture the complexity of knowledge.
Some alternative definitions of knowledge include the ability to make correct assertions, superlative artifactual performance, and what entitles an agent to assert a fact or act as a trustworthy informant.
Anthropologists often define knowledge in a broad sense as equivalent to understanding or culture.
There are different types of knowledge, including propositional knowledge (knowledge-that), practical knowledge (knowledge-how), and knowledge by acquaintance.
Propositional knowledge refers to the possession of certain information and can be expressed using that-clauses.
Practical knowledge involves competence or the ability to do something and is expressed using formulations like "I know how to ride a bike."
Knowledge by acquaintance is a direct familiarity with an individual or object and does not necessarily require a that-clause.
The concept of knowledge is important in argumentation theory and the anthropology of knowledge.
Some philosophers argue that knowledge is grounded in awareness rather than belief.
The diversity of knowledge makes it difficult to define in terms of necessary and sufficient conditions.