Knowledge is often understood as awareness of facts or as practical skills, and may also mean familiarity with objects or situations. Knowledge of facts, also called propositional knowledge, is often defined as true belief that is distinct from opinion or guesswork by virtue of justification. While there is wide agreement among philosophers that propositional knowledge is a form of true belief, many controversies in philosophy focus on justification: whether it is needed at all, how to understand it, and whether something else besides it is needed. These controversies intensified due to a series of thought experiments by Edmund Gettier and have provoked various alternative definitions. Some of them deny that justification is necessary and replace it, for example, with reliability or the manifestation of cognitive virtues. Others contend that justification is needed but formulate additional requirements, for example, that no defeaters of the belief are present or that the person would not have the belief if it was false.
knowledge
Knowledge can be produced in many different ways. The most important source of empirical knowledge is perception, which refers to the usage of the senses. Many theorists also include introspection as a source of knowledge, not of external physical objects, but of one's own mental states. Other sources often discussed include memory, rational intuition, inference, and testimony. According to foundationalism, some of these sources are basic in the sense that they can justify beliefs without depending on other mental states. This claim is rejected by coherentists, who contend that a sufficient degree of coherence among all the mental states of the believer is necessary for knowledge.
Many different aspects of knowledge are investigated and it plays a role in various disciplines. It is the primary subject of the field of epistemology, which studies what we know, how we come to know it, and what it means to know something. The problem of the value of knowledge concerns the question of why knowledge is more valuable than mere true belief. Philosophical skepticism is the controversial thesis that we lack any form of knowledge or that knowledge is impossible. Formal epistemology studies, among other things, the rules governing how knowledge and related states behave and in what relations they stand to each other. Science tries to acquire knowledge using the scientific method, which is based on repeatable experimentation, observation, and measurement. Many religions hold that humans should seek knowledge and that God or the divine is the source of knowledge.
Numerous definitions of knowledge have been suggested.[1][2][3] Most definitions of knowledge in analytic philosophy recognize three fundamental types. "Knowledge-that", also called propositional knowledge, can be expressed using that-clauses as in "I know that Dave is at home".[4][5][6] "Knowledge-how" (know-how) expresses practical competence, as in "she knows how to swim". Finally, "knowledge by acquaintance" refers to a familiarity with the known object based on previous direct experience.[5][7][8] Analytical philosophers usually aim to identify the essential features of propositional knowledge in their definitions.[8] There is wide, though not universal, agreement among philosophers that knowledge involves a cognitive success or an epistemic contact with reality, and that propositional knowledge is a form of true belief.[9][10]
Despite the agreement about the general characteristics of knowledge listed above, many deep disagreements remain regarding its exact definition. These disagreements relate to the goals and methods within epistemology and other fields, or to differences concerning the standards of knowledge that people intend to uphold. Some theorists focus on knowledge's most salient features in their attempt to give a practically useful definition.[11] Others try to provide a theoretically precise definition by listing the conditions that are individually necessary and jointly sufficient. The term "analysis of knowledge" (or equivalently, "conception of knowledge" or "theory of knowledge") is often used for this approach.[1][12][13] It can be understood in analogy to how chemists analyze a sample by seeking a list of all the chemical elements composing it.[1][14][15] An example of this approach is characterizing knowledge as justified true belief (JTB), which is seen by many philosophers as the standard definition.[4][16] Others seek a common core among diverse examples of knowledge,[10] such as Paul Silva's "awareness first" epistemology[17] or Barry Allen's definition of knowledge as "superlative artifactual performance".[18][19]
Methodological differences concern whether researchers base their inquiry on abstract and general intuitions or on concrete and specific cases, referred to as methodism and particularism, respectively.[20][21][22] Another source of disagreement is the role of ordinary language in one's inquiry: the weight given to how the term "knowledge" is used in everyday discourse.[6][13] According to Ludwig Wittgenstein, for example, there is no clear-cut definition of knowledge since it is just a cluster of concepts related through family resemblance.[23] Different conceptions of the standards of knowledge are also responsible for various disagreements. Some epistemologists hold that knowledge demands very high requirements, like infallibility, and is therefore quite rare. Others see knowledge as a rather common phenomenon, prevalent in many everyday situations, without excessively high standards.[1][5][24]
In analytic philosophy, knowledge is usually understood as a mental state possessed by an individual person, but the term is sometimes used to refer to a characteristic of a group of people as group knowledge, social knowledge, or collective knowledge.[25][26] In a slightly different sense, it can also mean knowledge stored in documents, as in "knowledge housed in the library"[27][28] or the knowledge base of an expert system.[29][30]
Many philosophers define knowledge as justified true belief (JTB). This definition characterizes knowledge through three essential features: as (1) a belief that is (2) true and (3) justified.[4][16] In the dialogue Theaetetus by the ancient Greek philosopher Plato, Socrates pondered the distinction between knowledge and true belief but rejected the JTB definition of knowledge.[31][32] The most widely accepted feature is truth: one can believe something false but one cannot know something false.[5][6] A few ordinary language philosophers have raised doubts that knowledge is a form of belief based on everyday expressions like "I do not believe that; I know it".[4][5][33] Most theorists reject this distinction and explain such expressions through ambiguities of natural language.[4][5]
The main controversy surrounding the JTB definition concerns its third feature: justification.[1][4][34] This component is often included because of the impression that some true beliefs are not forms of knowledge. Specifically, this covers cases of superstition, lucky guesses, or erroneous reasoning. The corresponding beliefs may even be true but it seems there is more to knowledge than just being right about something.[4][5][13] The JTB definition solves this problem by identifying proper justification as the additional component needed, which is absent in the above-mentioned cases. Many philosophers have understood justification internalistically (internalism): a belief is justified if it is supported by another mental state of the person, such as a perceptual experience, a memory, or a second belief. This mental state has to constitute a sufficiently strong evidence or reason for the believed proposition. Some modern versions modify the JTB definition by using an externalist conception of justification instead. This means that justification depends not just on factors internal to the subject but also on external factors. They can include, for example, that the belief was produced by a reliable process or that the believed fact caused the belief.[1][4][5]
The JTB definition came under severe criticism in the 20th century, when Edmund Gettier gave a series of counterexamples.[35] They purport to present concrete cases of justified true beliefs that fail to constitute knowledge. The reason for their failure is usually a form of epistemic luck: the justification is not relevant to the truth.[4][5][34] In a well-known example, there is a country road with many barn facades and only one real barn. The person driving is not aware of this, stops by a lucky coincidence in front of the real barn, and forms the belief that he is in front of a barn. It has been argued that this justified true belief does not constitute knowledge since the person would not have been able to tell the difference without the fortuitous accident.[36][37][38] So even though the belief is justified, it is a lucky coincidence that it is also true. The responses to these counterexamples have been diverse. According to some, they show that the JTB definition of knowledge is deeply flawed and that a radical reconceptualization of knowledge is necessary, often by denying justification a role.[1] This can happen, for example, by replacing justification with reliability or by understanding knowledge as the manifestation of cognitive virtues. Other approaches include defining it in regard to the cognitive role it plays in providing reasons for doing or thinking something or seeing it as the most general factive mental state operator.[a][10] Various theorists are diametrically opposed to the radical reconceptualization and either deny that Gettier cases pose problems or they try to solve them by making smaller modifications to how justification is defined. Such approaches result in a minimal modification of the JTB definition.[1]
Between these two extremes, some philosophers have suggested various moderate departures. They agree that the JTB definition is a step in the right direction: justified true belief is a necessary condition of knowledge. However, they disagree that it is a sufficient condition. They hold instead that an additional criterion, some feature X, is necessary for knowledge. For this reason, they are often referred to as JTB+X definitions of knowledge.[1][40] A closely related approach speaks not of justification but of warrant and defines warrant as justification together with whatever else is necessary to arrive at knowledge.[4][41] Many candidates for the fourth feature have been suggested. In this regard, knowledge may be defined as justified true belief that does not depend on any false beliefs, that there are no defeaters[b] present, or that the person would not have the belief if it was false.[13][38] Such and similar definitions are successful at avoiding many of the original Gettier cases. However, they often fall prey to newly conceived counterexamples.[43] To avoid all possible cases, it may be necessary to find a criterion that excludes all forms of epistemic luck. It has been argued that such a criterion would set the required standards of knowledge very high: the belief has to be infallible to succeed in all cases.[5][44] This would mean that very few of our beliefs amount to knowledge, if any.[5][45][46] For example, Richard Kirkham suggests that our definition of knowledge requires that the evidence for the belief necessitates its truth.[47] There is still very little consensus in the academic discourse as to which of the proposed modifications or reconceptualizations is correct.[1][48][10] 2ff7e9595c
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