Is knowledge justified true belief?

Is knowledge justified true belief?

This paper will demonstrate that the tripartite analysis of knowledge – justified true belief (JTB)– isa solid foundation for the definition of knowledge. Firstly a brief overview of JTB, Gettier-type counter-arguments and three types of response to the Gettier problem: The fourth premise, redefining the definition and scepticism. Than an argument against scepticism with two additional considerations regarding the analysis of knowledge. Firstly, knowledge is relative to the context of
would-be-knower's perception and secondly, the would-be-knower must be aware of limitations to their claims of knowledge. Based on this, it is possible to present a definition of knowledge that is encompassed by justified true belief.

The statement: “I know that it is raining, but I don't believe it” is a contradiction, as knowing encompasses an awareness of truth that assumes belief.1 It is clear that truth and belief are integral to knowledge, however, although true belief is necessary for knowledge it is not sufficient.2 The implication being that epistemological “luck” lacks evidence and thus could not be known to be
true.3 In response to these deficiencies, an alternative analysis of knowledge–justified true belief – emerged proposing that in addition to true belief the believer must have reasoning or good evidence to support the truth of their belief.4 The justified true belief analysis of knowledge can be written:5


S has knowledge of P if and only if:
1. P is true
2. S believes that P is true, and
3. S is justified in believing that P is true



The tripartite analysis of knowledge is frequently attributed to Greek philosopher Plato who wrote about it in his Theaetetus and was widely accepted until 1963 when Edmund Gettier provided two counter-examples in his paper “is justified true belief knowledge?.”6 His examples demonstrated cases that satisfied the conditions of Justified true belief, yet would not be regarded as genuine cases of knowledge because the conditions had only been met “by dumb luck, by accident, by coincidence, or by some means we intuitively regard as illegitimate”7 Most Gettier-type counters follow the same basic form:8

1. S justifiably believes that P
2. P is false
3. S correctly infers: if P is true Q is true
4. S believes Q justifiably
5. Q is true, but not by virtue of P
6. S has a justified true belief that Q


There have been numerous responses to the Gettier problem and this paper will cover three. Firstly, Alvin Goldman's “A causal theory of knowledge” detailing that for a belief to be knowledge there must be a causal connection between the belief and it's truth.9 That is to say that: the truth of P caused S's belief that P” or in Goldman's own words:10

S knows that P if and only if
“The fact P is causally connected in an “appropriate” way with S's believing P.”


Unfortunately Goldman's theory relied on the assumption that all Gettier counters were the result of 2 non-causal, incorrect, inferences.11 Carl Ginet disproved this idea with the now well-known “barnfacade” rebuttal where although the belief satisfied the requirements of causal theory, the believer did not have knowledge.12


Similarly Keith Lehrer and Tomas Paxton suggested the addition of a fourth premise:
“defeasibility.”13 Proposing that a justified true belief is knowledge if and only if no other truth would destroy the justification for the belief.14 That we do not know something if their exists a truth that would defeat it. Although this satisfies common claims of knowledge, if the would-be-knower is not privy to all the relevant information they could be said to not know all the truths that would defeat their belief.

Alternatively, Robert Nozick's “truth-tracking” theory seeks to redefine the JTB analysis of knowledge. Nozick described knowledge as a belief that reliably “tracks the truth”.15 Demonstrating that so long as justification of a belief reliably tracks the truth, it is valid.16 However, the tracking theory can be criticised for giving the status of knowledge to the process of knowledge acquisition, even if there is faulty reasoning.

Confronted with the continual attempts and subsequent difficulties resolving the Gettier problem, Richard Kirkham concluded that the only analysis of knowledge exclusive enough to exclude all Gettier-type counters is one that could not be inclusive of the beliefs we “commonly regard as knowledge.”17 Kirkham conceded that much of what we intuitively regard as knowledge is fallible and thus we cannot know much as even beliefs that seem infallible may not be.18


The justification that a belief is true requires another justified and true belief continuing ad. Infinitum.19 The need to “justify the justification.” forms the infinite regress argument against the tripartite analysis of knowledge. In an attempt to solve the regress problem foundationalist theorise that there are finite steps of justification that are logically reducible to “basic” beliefs that are axiomatic truths.20 Sceptics propose that these “foundational beliefs” are arbitrarily labelled and are not self-evident.21 Descartes provided a particularly compelling sceptical argument, beginning with perception as a foundational belief he constructed three simple counter arguments and systematically destroyed it.


(1)Firstly, Descartes highlighted how perceptions are often mistaken, for example: a straight stick appears bent in the water. However, he readily admitted that we often know when our perceptions are defective and thus we are able to correct perceptual errors.22


(2)Secondly he questioned: If sometimes a dream is mistaken for reality, could it be the case that reality is mistaken for a dream? If “being awake can [not] be distinguished from being asleep” then it can not be known that perceptions are true. Descartes acknowledged that objects in dreams and perceived reality still possessed certain attributes, Namely: they had shape, colour, could be counted and extended through time and in space.23

(3)Thirdly he imagined that there was a malicious demon that constantly and systematically deceived him, manipulating his mind, so that his perception of any external thing was a delusion. From this Descartes concluded that there was only one certain truth that remained: “I think, therefore I am.” That the act of thinking: “I exist” necessitates it's truth, for something must exist to be thinking.24


Although sceptical arguments can be labelled unlikely, irrelevant, void of common sense and guilty of toying with semantics25 it seems somewhat against philosophical enquiry to dismiss them in this way. In fact the sceptic's argument that all knowledge derived from perceptions is fallible, is an acceptable one, as no matter how complete the justification given for a belief the sceptic can continuously ad hoc counter-arguments that bring into question every perceptual connection with what “is.” Yet, the mere possibility of deception is not enough to render the senses as entirely untrustworthy.26 Since, at the very least, there seems to be cognitive interaction with what is being perceived, even if it is a delusion.


Consider the following thought experiment: Samantha is a “brain in a vat” and her entire world is constructed by a team of scientists who provide her with experiences. One such experience is her linear concept of time, such that she knows that while seated in her chair typing at the computer that some time will pass (sitting, chair, typing, computer and time are all of course illusions). So long as she accepts the possibility that her world is a manipulated reality; that she could be asleep, the subject of an evil demon's will or that she is a brain in a vat, which indeed she is. Then she is aware and accepts that she does not know anything outside of what she attains through her perceptions, which entails that her knowledge only pertains to what she has perceived or is perceiving; That her concept of “time” is only knowledge of something she perceives it in her reality. Thus, simply not knowing all the information does not render the perceptions she does have void.27 For indeed she is perceiving something and that leads her to formulate beliefs, those beliefs affect her actions and her actions causally interact with the world she has perceived. So long as her claims of knowledge only pertain to the coherent system of perception, then scepticism poses no threat to her capacity for knowledge.28


Brain in the vat type analogies may seem absurd, however, given that evolution has lead to perceiving the world in a humanised way it is not at all far-fetched to suggest that perception is, at the very least, subjective29 For example, when “seeing a colour” it is the eye's detection of certain wavelengths of electromagnetic radiation.30 In other words, colour, taste, feel and so forth, depend on the perceptual tools of the observer. What “is” only exists in a recognisable form when something exists to recognise it, thus, the perception of what “is” is influenced by the context of the observer.31 If the observer has evolved to understand what “is” through perceptions, language and language-based thought, then from these attributes it is possible to make logical inferences that are labelled as “knowledge.” It seems that scepticism is correct in questioning the “truth” of perception. However it does not follow that there cannot be “knowledge” as some types of knowledge are constructed from perception. Based on this, “knowledge” could be defined as a justified true belief logically deduced from, and coherent with, the plexus of all accessible information that is reducible to sensory input and is accepted provisionally until the discovery of an alternative truth which disproves it. Knowledge should also retain it's “knowledge status” so long as at the time of knowledge acquisition it was a justified true belief. As an item of “knowledge” only ever pertains to the specific combination of information that was present at it's acquisition and thus, remains knowledge when defeated. It is therefore possible to have “false knowledge” that is, knowledge which is no longer relevant to the plexus of information. This view is somewhat pragmatic, with an emphasis on the functionality of knowledge over it's actuality.

Revised definitions of knowledge struggle to demonstrate it's ambiguity and often try to bundle “types” of knowledge into a single analysis despite fundamental differences in their contextualised meanings and function. For example: scientific knowledge, day-to-day knowledge and scepticism, each require unique versions of a justified true belief.32 Thus, the would-be-knower needs to be aware of the limitations to their particular claim of knowledge in order for their justified true beliefs to qualify as a form of knowledge; even though it will not satisfy the requirements of every form of knowledge. However, “S knowing what P pertains to” is not a premise unto itself; if Samantha “knows the flower is red” than there is an unstated awareness that this knowledge only pertains to knowing the perception of redness. Thus, awareness and acceptance of these limitations is implicit to the justified true belief analysis, therefore, justified true belief is an adequate definition of knowledge.



1. Sober, Elliott. Core Questions in Philosophy. 2nd ed. Englewood Cliffs: Prentice-Hall, 1995.
2. Plato. “Knowledge is Something More Than True Belief.” In Core Questions in Philosophy, 2nd
ed. Edited by. Elliott Sober, 204- 211. Englewood Cliffs: Prentice-Hall, 1995.
3. ibid.
4. Philosophy Index. “Tripartite Theory of Knowledge” http://www.philosophyindex.
com/epistemology/knowledge/tripartite.php (accessed july 01, 2010).
5. O'Brien, Dan. The Theory of Knowledge. Cambridge: Polity Press, 2006.
6. Gettier, Edmund. “Is Justified True Belief Knowledge?” Analysis 23,(1963): 121-123.
7. Kirkman, Richard L. “Does the Gettier Problem Rest on a Mistake?” Mind, New Series 2, no.
372 (1984): 501-513.
8. Philosophy Index. “Gettier Counterexamples” http://www.philosophyindex.
com/gettier/counterexamples/ (accessed july 01, 2010).
9. Alvin Goldman "A Causal Theory of Knowing" in The Journal of Philosophy v. 64 (1967), pp.
357–372.
10. Ginet, Carl cited by Goldman, Alvin I. “Discrimination and Perceptual Knowledge” The
Journal of Philosophy 73.20 (1976): 771–791. Print.
11. ibid.
12. ibid.
13. Keith Lehrer and Thomas Paxton Knowledge: Undefeated Justified True Belief, in The Journal
of Philosophy v. 66 (1969), pp. 225–237.
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14. ibid.
15. Nozick, Robert. philosophical explanations Harvard University Press. 1981.
16. Fred dretske "Conclusive Reasons" in Australiasian Journal of Philosophy v. 49 (1971), pp. 1–
22.
17. Kirkman, Richard L. Op. Cit.
18. ibid.
19. Armstrong, D.M. 1973. Belief, Truth, and Knowledge. Cambridge: Cambridge University
Press.
20. Pence, Gregory. A Dictionary of Common Philosophical Terms. s.v “Foundationalism.” New
York: McGraw-Hill, 2000.
21. Chisholm, Roderick M. Theory of Knowledge. 3rd ed. Englewood Cliffs: Prentice-Hall, 1989.
22. Descartes, René. “Mediations on First Philosophy.” from The Philosophical Writings of
Descartes, vol. 2. Edited & translated by J. Cottingham, R. Stoothoff & D. Murdoch.
Cambride: Cambridge University Press, 1984.
23. ibid.
24. Descartes, René. “Second Mediations” from The Philosophical Writings of Descartes, vol. 2.
Edited & translated by J. Cottingham, R. Stoothoff & D. Murdoch. Cambride: Cambridge
University Press, 1984.
25. Fogelin, Robert j. “Contextualism and Externalism: Trading in One Form of Skepticism for
Another” Philosophical Issues, vol. 10, 2000, 43-57.
26. Lehrer, Keith. “Knowledge, Coherence and Skepticism” Philosophical Issues, Vol. 2,
Rationality in Epistemology, 1992, 171-192.
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27. ibid.
28. ibid.
29. Railton, Peter. “Truth, Reason, and the Regulation of Belief.” Philosophical Issues 5 (1994): 71-
93.
30. Weiten, Wayne. “Sensation and perception” in Psyhology: Themes and Variations, 8th ed.
Belmont: Wadsworth Cengage Learning, 2010, 129-184.
31. Railton, Peter. “Truth, Reason, and the Regulation of Belief.” Op. Cit
32. Feder, Kenneth L. Frauds, myths, and mysteries: science and pseudoscience in archaeology.
Mountain View, Calif.: Mayfield Publishing Company, 1990: p. 9-26 .
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