Gettier problem
The Gettier problem, in the field of epistemology, is a landmark philosophical problem concerning the understanding of descriptive knowledge. Attributed to American philosopher Edmund Gettier, Gettier-type counterexamples challenge the long-held justified true belief account of knowledge. The JTB account holds that knowledge is equivalent to justified true belief; if all three conditions are met of a given claim, then there is knowledge of that claim. In his 1963 three-page paper titled "Is Justified True Belief Knowledge?", Gettier attempts to illustrate by means of two counterexamples that there are cases where individuals can have a justified true belief regarding a claim but still fail to know it because the reasons for the belief, while justified, turn out to be false. Thus, Gettier claims to have shown that the JTB account is inadequate because it does not account for all of the necessary and sufficient conditions for knowledge.
The terms "Gettier problem", "Gettier case", or even the adjective "Gettiered", are sometimes used to describe any case in the field of epistemology that purports to repudiate the JTB account of knowledge.
Responses to Gettier's paper have been numerous. Some reject Gettier's examples as inadequate justification, while others seek to adjust the JTB account of knowledge and blunt the force of these counterexamples. Gettier problems have even found their way into sociological experiments in which researchers have studied intuitive responses to Gettier cases from people of varying demographics.
History
The question of what constitutes "knowledge" is as old as philosophy itself. Early instances are found in Plato's dialogues, notably Meno and Theaetetus. Gettier himself was not actually the first to raise the problem named after him; its existence was acknowledged by both Alexius Meinong and Bertrand Russell, the latter of whom discussed the problem in his book Human Knowledge: Its scope and limits. In fact, the problem has been known since the Middle Ages, and both Indian philosopher Dharmottara and scholastic logician Peter of Mantua presented examples of it.Dharmottara, in his commentary on Dharmakirti's Ascertainment of Knowledge, gives the following two examples:
Various theories of knowledge, including some of the proposals that emerged in Western philosophy after Gettier in 1963, were debated by Indo-Tibetan epistemologists before and after Dharmottara. In particular, Gaṅgeśa in the 14th century advanced a detailed causal theory of knowledge.
Russell's case, called the stopped clock case, goes as follows: Alice sees a clock that reads two o'clock and believes that the time is two o'clock. It is, in fact, two o'clock. There's a problem, however: unknown to Alice, the clock she's looking at stopped twelve hours ago. Alice thus has an accidentally true, justified belief. Russell provides an answer of his own to the problem. Edmund Gettier's formulation of the problem was important as it coincided with the rise of the sort of philosophical naturalism promoted by W. V. O. Quine and others, and was used as a justification for a shift towards externalist theories of justification. John L. Pollock and Joseph Cruz have stated that the Gettier problem has "fundamentally altered the character of contemporary epistemology" and has become "a central problem of epistemology since it poses a clear barrier to analyzing knowledge".
Alvin Plantinga rejects the historical analysis:
Despite this, Plantinga does accept that some philosophers before Gettier have advanced a JTB account of knowledge, specifically C. I. Lewis and A. J. Ayer.
Knowledge as justified true belief (JTB)
The JTB account of knowledge is the claim that knowledge can be conceptually analyzed as justified true belief, which is to say that the meaning of sentences such as "Smith knows that it rained today" can be given with the following set of conditions, which are necessary and sufficient for knowledge to obtain:The JTB account was first credited to Plato, though Plato argued against this very account of knowledge in the Theaetetus. This account of knowledge is what Gettier subjected to criticism.
Gettier's two original counterexamples
Gettier's paper used counterexamples to argue that there are cases of beliefs that are both true and justified—therefore satisfying all three conditions for knowledge on the JTB account—but that do not appear to be genuine cases of knowledge. Therefore, Gettier argued, his counterexamples show that the JTB account of knowledge is false, and thus that a different conceptual analysis is needed to correctly track what we mean by "knowledge".Gettier's case is based on two counterexamples to the JTB analysis, both involving a fictional character named Smith. Each relies on two claims. Firstly, that justification is preserved by entailment, and secondly that this applies coherently to Smith's putative "belief". That is, that if Smith is justified in believing P, and Smith realizes that the truth of P entails the truth of Q, then Smith would also be justified in believing Q. Gettier calls these counterexamples "Case I" and "Case II":
Case I
Case II
False premises and generalized Gettier-style problems
In both of Gettier's actual examples, the justified true belief came about, if Smith's purported claims are disputable, as the result of entailment from justified false beliefs that "Jones will get the job", and that "Jones owns a Ford". This led some early responses to Gettier to conclude that the definition of knowledge could be easily adjusted, so that knowledge was justified true belief that does not depend on false premises. The interesting issue that arises is then of how to know which premises are in reality false or true when deriving a conclusion, because as in the Gettier cases, one sees that premises can be very reasonable to believe and be likely true, but unknown to the believer there are confounding factors and extra information that may have been missed while concluding something. The question that arises is therefore to what extent would one have to be able to go about attempting to "prove" all premises in the argument before solidifying a conclusion.The generalized problem
In a 1966 scenario known as "The sheep in the field", Roderick Chisholm asks us to imagine that someone, X, is standing outside a field looking at something that looks like a sheep. X believes there is a sheep in the field, and in fact, X is right because there is a sheep behind the hill in the middle of the field. Hence, X has a justified true belief that there is a sheep in the field.Another scenario by Brian Skyrms is "The Pyromaniac", in which a struck match lights not for the reasons the pyromaniac imagines but because of some unknown "Q radiation".
A different perspective on the issue is given by Alvin Goldman in the "fake barns" scenario. In this one, a man is driving in the countryside, and sees what looks exactly like a barn. Accordingly, he thinks that he is seeing a barn. In fact, that is what he is doing. But what he does not know is that the neighborhood generally consists of many fake barns—barn facades designed to look exactly like real barns when viewed from the road. Since, if he had been looking at one of them, he would have been unable to tell the difference, his "knowledge" that he was looking at a barn would seem to be poorly founded.
Objections to the "no false premises" approach
The "no false premises" solution which was proposed early in the discussion has been criticized, as more general Gettier-style problems were then constructed or contrived in which the justified true belief is said to not seem to be the result of a chain of reasoning from a justified false belief. For example:It is argued that it seems as though Luke does not "know" that Mark is in the room, even though it is claimed he has a justified true belief that Mark is in the room, but it is not nearly so clear that the perceptual belief that "Mark is in the room" was inferred from any premises at all, let alone any false ones, nor led to significant conclusions on its own; Luke did not seem to be reasoning about anything; "Mark is in the room" seems to have been part of what he seemed to see.
Constructing Gettier problems
The main idea behind Gettier's examples is that the justification for the belief is flawed or incorrect, but the belief turns out to be true by sheer luck. Linda Zagzebski shows that any analysis of knowledge in terms of true belief and some other element of justification that is independent from truth, will be liable to Gettier cases. She offers a formula for generating Gettier cases:start with a case of justified false belief;
amend the example, making the element of justification strong enough for knowledge, but the belief false by sheer chance;
amend the example again, adding another element of chance such that the belief is true, but which leaves the element of justification unchanged;
This will generate an example of a belief that is sufficiently justified to be knowledge, which is true, and which is intuitively not an example of knowledge. In other words, Gettier cases can be generated for any analysis of knowledge that involves a justification criterion and a truth criterion, which are highly correlated but have some degree of independence.
Responses to Gettier
The Gettier problem is formally a problem in first-order logic, but the introduction by Gettier of terms such as believes and knows moves the discussion into the field of epistemology. Here, the sound arguments ascribed to Smith then need also to be valid and convincing if they are to issue in the real-world discussion about justified true belief.Responses to Gettier problems have fallen into three categories:
- Affirmations of the JTB account: This response affirms the JTB account of knowledge, but rejects Gettier cases. Typically, the proponent of this response rejects Gettier cases because, they say, Gettier cases involve insufficient levels of justification. Knowledge actually requires higher levels of justification than Gettier cases involve.
- Fourth condition responses: This response accepts the problem raised by Gettier cases, and affirms that JTB is necessary for knowledge. A proper account of knowledge, according to this type of view, will contain at least fourth condition. With the fourth condition in place, Gettier counterexamples will not work, and we will have an adequate set of criteria that are both necessary and sufficient for knowledge.
- Justification replacement response: This response also accepts the problem raised by Gettier cases. However, instead of invoking a fourth condition, it seeks to replace justification itself with some other third condition that will make counterexamples obsolete.
Other epistemologists accept Gettier's conclusion. Their responses to the Gettier problem, therefore, consist of trying to find alternative analyses of knowledge.