Epistemology Greek ἐπιστήμη - episteme-, "knowledge, science" + λόγος, "logos") or theory of knowledge is the branch of philosophy concerned with the nature and scope (limitations) of knowledge. It addresses the questions:
- What is knowledge?
- How is knowledge acquired?
- What do people know?
- How do we know what we know?
Much of the debate in this field has focused on analyzing the nature of knowledge and how it relates to similar notions such as truth, belief, and justification. It also deals with the means of production of knowledge, as well as skepticism about different knowledge claims.
The term was introduced into English by the Scottish philosopher James Frederick Ferrier (1808–1864).
In epistemology in general, the kind of knowledge usually discussed is propositional knowledge, also known as "knowledge-that" as opposed to "knowledge-how." For example: in mathematics, it is known that 2 + 2 = 4, but there is also knowing how to add two numbers. Many (but not all) philosophers therefore think there is an important distinction between "knowing that" and "knowing how", with epistemology primarily interested in the former. This distinction is recognized linguistically in many languages, though not in modern Standard English (N.B. some languages related to English still do retain these verbs, as in Scots: "wit" and "ken").
In Personal Knowledge, Michael Polanyi articulates a case for the epistemological relevance of both forms of knowledge; using the example of the act of balance involved in riding a bicycle, he suggests that the theoretical knowledge of the physics involved in maintaining a state of balance cannot substitute for the practical knowledge of how to ride, and that it is important to understand how both are established and grounded.
In recent times, some epistemologists (Sosa, Greco, Kvanvig, Zagzebski) have argued that we should not think of knowledge this way.Template:Citation needed Epistemology should evaluate people's properties (i.e., intellectual virtues) instead of propositions' properties. This is, in short, because higher forms of cognitive success (i.e., understanding) involve features that can't be evaluated from a justified true belief view of knowledge.
Often, statements of "belief" mean that the speaker predicts something that will prove to be useful or successful in some sense—perhaps the speaker might "believe in" his or her favorite football team. This is not the kind of belief usually addressed within epistemology. The kind that is dealt with is when "to believe something" simply means any cognitive content held as true. For example, to believe that the sky is blue is to think that the proposition "The sky is blue" is true.
Knowledge entails belief, so the statement, "I know the sky is blue, but I don't believe it", is self-contradictory.
Belief is a subjective personal basis for individual behavior, while truth is an objective state independent of the individual.
Whether somebody's belief is true is not a prerequisite for someone to believe it. On the other hand, if something is actually known, then it categorically cannot be false. For example, a person believes that a particular bridge is safe enough to support them, and attempts to cross it; unfortunately, the bridge collapses under their weight. It could be said that they believed that the bridge was safe, but that this belief was mistaken. It would not be accurate to say that they knew that the bridge was safe, because plainly it was not. By contrast, if the bridge actually supported their weight then they might be justified in subsequently holding that he knew the bridge had been safe enough for his passage, at least at that particular time. For something to count as knowledge, it must actually be true. There is a sense that makes us feel that the truth should command our belief.
The Aristotelian definition of truth states:
"To say of something which is that it is not, or to say of something which is not that it is, is false. However, to say of something which is that it is, or of something which is not that it is not, is true."
In Plato's dialogue Theaetetus, Socrates considers a number of theories as to what knowledge is, the last being that knowledge is true belief that has been "given an account of" — meaning explained or defined in some way. According to the theory that knowledge is justified true belief, in order to know that a given proposition is true, one must not only believe the relevant true proposition, but one must also have a good reason for doing so. One implication of this would be that no one would gain knowledge just by believing something that happened to be true. For example, an ill person with no medical training, but a generally optimistic attitude, might believe that they will recover from their illness quickly. Nevertheless, even if this belief turned out to be true, the patient would not have known that they would get well since their belief lacked justification. The definition of knowledge as justified true belief was widely accepted until the 1960s. At this time, a paper written by the American philosopher Edmund Gettier provoked major widespread discussion. See theories of justification for other views on the idea.
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