Suppose that Smith and Jones have applied for a certain job. And suppose that Smith has strong evidence for the following conjunctive proposition: (d) Jones is the man who will get the job, and Jones has ten coins in his pocket. Smith's evidence for (d) might be that the president of the company assured him that Jones would, in the end, be selected and that he, Smith, had counted the coins in Jones's pocket ten minutes ago. Proposition (d) entails: (e) The man who will get the job has ten coins in his pocket.

Let us suppose that Smith sees the entailment from (d) to (e), and accepts (e) on the grounds of (d), for which he has strong evidence. In this case, Smith is clearly justified in believing that (e) is true.

But imagine, further, that unknown to Smith, he himself, not Jones, will get the job. And, also, unknown to Smith, he himself has ten coins in his pocket. Proposition (e) is true, though proposition (d), from which Smith inferred (e), is false. In our example, then, all of the following are true: (i) (e) is true, (ii) Smith believes that (e) is true, and (iii) Smith is justified in believing that (e) is true. But it is equally clear that Smith does not know that (e) is true; for (e) is true in virtue of the number of coins in Smith's pocket, while Smith does not know how many coins are in his pocket, and bases his belief in (e) on a count of the coins in Jones's pocket, whom he falsely believes to be the man who will get the job.[1]

Edmund Gettier used this case and cases like this to demonstrate that Plato's description of knowledge was inadequate. That is that knowledge consists of true justified belief.

I don't see how Smith is justified in assuming some sort of inherent correlation between the coins and the job. Jones will get the Job if the business owner considers hiring Jones to be in the interest of himself, Jones or the business. Or in SOMEONE OR SOMETHINGS interest. Jones having 10 coins does nothing to improve his potential in fulfilling the interest of the Business or the business owner. It's clearly an irrelevant factor.

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    Isn't that the point? The fact that the conclusion is absurd shows that "justified true belief" is an absurd definition of knowledge
    – b a
    Commented Feb 4, 2021 at 16:02
  • Yeah but I take issue with the notion proposed by Gettier that Smith is justified in believing that the man with 10 coins will get the job (as if there is some correlation). Commented Feb 4, 2021 at 16:15
  • The proposition Smith believes is not that having 10 coins is correlated with getting the job; just that the same person both happens to have 10 coins and will happen to get the job. This follows logically from the belief that Jones has both these properties.
    – Schiphol
    Commented Feb 4, 2021 at 16:20
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    Here is an analogous example from history. Aristotle and others in antiquity believed that air has weight based on the fact that inflated bladder weighs more than the empty one. As we know today, the effect has to do with buoyancy and not with air's extra weight, which is too small to be detected by the balances they used. So they had a justified belief that happened to be true, but what they inferred it from had little to do with the real reason. So did they know that air has weight?
    – Conifold
    Commented Feb 4, 2021 at 20:51
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    @transitionsynthesis Thank you. There is one partial reason for it, and it operates in mathematics as well. One has an intuition about a flaw in a generalization, and contrives a counterexample to demonstrate it. But doing it first is hard, the first counterexample is rarely the most natural one, just like the first proof is rarely the most transparent one. Nonetheless, it gets picked up and repeated, especially in philosophy where there is greater concern about distorting author's point when "optimizing" it.
    – Conifold
    Commented Feb 5, 2021 at 5:33

3 Answers 3


Gettier's argument is an attempt to prove that "justified true belief" is inadequate as a definition of knowledge. He shows that one can believe something, the belief can be true and justified, yet one still doesn't know it.

Your problem is that the cases that Gettier brings of justified true belief are not truly "justified." That is, you are evaluating the justification for whether it's actually justified.

The reason why the criticism still holds, at least in the context of Plato's original argument, is that in defining knowledge as justified, the justification itself shouldn't be required to be justified. If it is so required, then the justification is itself is a kind of knowledge, and the definition of knowledge itself has to include "knowledge" because "true belief with a justification" would mean "true belief with knowledge." This leads to an infinite loop in defining knowledge (like the other definitions proffered earlier in the dialogue). This is the argument that leads Socrates to reject this definition in Plato's Theaetetus:

Then, it seems, if asked, “What is knowledge?” our leader will reply that it is right opinion with the addition of a knowledge of difference; for that would, according to him, be the addition of reason or explanation.

So it seems.

And it is utterly silly, when we are looking for a definition of knowledge, to say that it is right opinion with knowledge, whether of difference or of anything else whatsoever. So neither perception, Theaetetus, nor true opinion, nor reason or explanation combined with true opinion could be knowledge.

Theaetetus (210a-b).


What Gettier sets out to show is that someone does not have knowledge if it is only by chance that their justified true belief is true. I'd gently suggest that when we realise this, his examples are not and do not seem 'absurd and unconvincing'. But you are right to speak as you find. I am going to try to alter your perspective.

By ordinary standards, Smith has done everything he can to reach the truth. He has accepted what the president of the company has said, namely that Jones will get the job, where we can assume (as implicit in the example) that the president was in a position to know and was normally a reliable truth-teller. Jones had taken this evidence into account and by ordinary evidential criteria was justified in believing the president's statement that Jones would get the job.

He was also justified in believing by ordinary evidential criteria that Jones had ten coins in hs pocket. He had counted them.

Smith was further justified in inferring from his belief that Jones would get the job and his belief that Jones had ten coins in his pocket, that the man who would get the job had ten coins in his pocket.

It merely so happened that the president's statement that Brown would get the job was in fact false and it also merely so happened that Smith himself had ten coins in his pocket. We are confronted here just by things as they turned out, matters of coincidence. If Smith had actually had only nine coins in his pocket, he would still have believed and been justified in believing that the man who would get the job had ten coins in his pocket. It was only by chance, the chance of his happening to have ten coins in his own pocket, that Smith was justified in believing that the man who would get the job had ten coins in his pocket - namely, himself.

What this example leaves us with is a double possibility: either (1) justified true belief is not sufficient for knowledge, and an extra condition needs to be added (perhaps several extra conditions) or (2) justification must be reworked to make it sufficient for knowledge. One direction (2) could take would be the Cartesian route, and tighten the criteria for justification to the extent that one is not justified in accepting any belief unless it is immune from error, invulnerable to mistake. (2) has its attractions but it would have the result that we would be justified in believing hardly anything, if anything at all.


It's initially plausible that knowledge is something like justified true belief: if

  1. you believe that p
  2. on excellent grounds
  3. and p is the case

you would seem to count as someone who knows that p.

Now, you can think of Gettier cases as raising the following possibility: the grounds, excellent as they are, on which you believe that p might be perfectly unrelated to whatever it is that makes p true. This is obvious in retrospect, but it took Gettier's paper for everyone to notice. You now might want to somehow build the right kind of relation between the grounds in 2. and the truthmaker in 3. That's what much late XXth century epistemology tried to do.

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