Answering Gettier

[ work in progress ] [ completed 1/15/11 ]

Plato’s justified-true-belief definition of knowledge, maintained by critical realists, besides requiring that a belief be justified by evidence and true by correspondence, says 1) whether or not a belief is true has no bearing on whether or not it is justified, and 2) a belief is true or not regardless whatever justification we are (un)able to find for it. To violate 1 is to commit David Hume’s is-ought fallacy, and to violate 2 is to commit its reverse. The skeptic’s argument from error confirms that justification does not equate to truth (ought=/=is) when it notes that sometimes what we thought was justified turns out to have been false. Edmund Gettier’s problem examples also note this, but they also confirm that truth does not equate to justification (is=/=ought) when they show that sometimes we are right for the wrong reasons (and really the skeptic’s argument from error could also be saying this). Hume thought his is-ought fallacy leads to skepticism about knowledge (originally, moral knowledge), but this is prevented by following the requirement that a belief (i.e., an ethical theory) be justified by evidence and true by correspondence. However, Gettier’s point with his problem examples, in Christopher Norris’ words, “is that people can hold beliefs which are indeed justified and true, but which for various reasons intuitively strike us as not meeting the requirements for genuine knowledge,” (p. 140). Where Gettier goes wrong is when he allows wrong reasons to pass as justification—his whole basis for challenging the justified-true-belief definition of knowledge.

Some object, saying that Gettier did not go wrong in allowing wrong reasons to count as justification. But, if any old reason will do, then any old belief will do—it doesn’t need to be justified. But the criterion is “justified, true belief”. It is ‘not’ possible for a falsehood to justify a belief, but Gettier-style examples depend on it. Richard Feldman summarizes the requirements of stating a Gettier-style example: “First one has to find a case of a justified false belief. …One then identifies some truth that logically follows from that falsehood. …The example proceeds by having the believer deduce this truth from the justified false belief. …The resulting belief will be a justified true belief that is not knowledge,” (p. 28, Epistemology). However, being right for the wrong reasons means one’s belief is not justified. Some think this means hardly any beliefs are justified, but this claim is unjustified in light of leaps and bounds in scientific progress. To see how Gettier’s problem examples rely on wrong reasons for justification, one must actually examine the two problem examples, referred to as Case I and Case II, in the one short paper Gettier has published, titled “Is justified true belief knowledge?”

In Case I, Smith believes the true belief “The man who will get the job has ten coins in his pocket,” based on his (what turns out to be) false belief “Jones is the man who will get the job” and his true (but irrelevant) belief “Jones has ten coins in his pocket”. Since Smith gets hired instead and just so happens to have ten coins he had no idea were in his pocket, his belief “Jones is the man who will get the job,” is a false belief, and “Jones has ten coins in his pocket” is an irrelevant belief, both of which Gettier says justify the true belief “The man who will get the job has ten coins in his pocket,” challenging the justified-true-belief definition of knowledge. However, the challenge goes away when one stops allowing wrong or irrelevant reasons (like, “Jones is the man who will get the job” and “Jones has ten coins in his pocket,” respectively) to count as justification.

In Case II, Smith believes the true belief “Either Jones owns a Ford, or Brown is in Barcelona” but he believes it based on his false belief “Jones owns a Ford” (by the way, he also believes two false beliefs based on that false belief: “Either Jones owns a Ford, or Brown is in Boston,” and “Either Jones owns a Ford, or Brown is in Brest-Litovsk”—and he could have rightly named every place in the universe besides the place Brown is actually in, if he had been right that Jones owns a Ford). Smith believes “or Brown is in Barcelona” (which is true), but he does not believe Brown is in Barcelona (though s/he is), because he believes “Jones owns a Ford,” a false belief Gettier says justifies the (as it turns out) true belief “Either Jones owns a Ford, or Brown is in Barcelona,” challenging the justified-true-belief definition of knowledge. Again, the challenge goes away when one stops allowing wrong reasons (like “Jones owns a Ford”) to count as justification (“Brown is in Barcelona” cannot count as an irrelevant reason, because he does not believe it, and if he did, he would not say “Either Jones owns a Ford, or Brown is in Barcelona” because he believes “Jones owns a Ford” and hopefully is not in the habit of believing either/or at the same time he believes both/and is the case). It is interesting to note that the equivalent (almost) of “Brown is in Barcelona” in Case II, is “Jones has ten coins in his pocket” in Case I, except that in Case I, Smith believes it, and in Case II, Smith does not believe it. I’d be willing to bet Gettier was trying for more symmetry (perhaps he thought he achieved it, including “Brown is in Barcelona” with “Either Jones owns a Ford, or Brown is in Barcelona”), which, agreed (assuming I’m right), would have been beautiful.

Richard Feldman points out in “Epistemology” a couple principles referred to, though not by name, in Gettier’s paper: The Justified Falsehood Principle (“JF”) and the Justified Deduction Principle (“JD”). The JF states that “It is possible for a person to be justified in believing a false [belief].” In Case I, Smith was justified (assuming not by false grounds) in believing the false belief that Jones will get the job. In Case II, Smith was justified (assuming not by false grounds) in believing the false belief that Jones owns a Ford. However, though it is possible to believe a justified falsehood (JF), it is not possible for a falsehood to justify a belief (whether true or false), as the JD would have it. If a belief is based on any false grounds, it can only be justified if there are also true grounds which do the actual justifying [so this is not related to the No False Grounds (NFG) modified account of knowledge mentioned by Feldman and proposed by Michael Clark, who considered it necessary to add a fourth condition that a belief’s justification rely on no false grounds whatsoever]. Admitting that false grounds are false grounds is admitting they are non-justifiers. The mistake the JD makes is committing the is-ought fallacy. A belief’s being justified, does not make it true grounds! Beliefs are not justified by other justified beliefs; they are justified by true grounds (evidence). Feldman mentions that The Same Evidence Principle (SE) seems to show how weird it is to deny the JD and say Smith is justified in believing a false belief, but not justified in believing anything deduced from it. Feldman thinks the SE shows this is weird, since the false belief and the belief deduced from it both rely on the same evidence. However, any belief deduced from the false belief uses the evidence grounding the false belief, “plus” the false belief itself—so it isn’t exactly ‘just’ the same evidence.

Lehrer-Paxson’s No Defeaters (ND) Theory (a.k.a. defeasibility analysis), like Michael Clark’s No False Grounds Theory just mentioned, is an attempt to modify the justified-true-belief account of knowledge. “The idea is that one has knowledge when there are no truths that defeat one’s justification,” (p. 34, Feldman’s “Epistemology”). How is this different from the No False Grounds theory? It allows for a false ground, as long as disbelieving it (in response to a truth which defeats it), does not result in disbelieving the conclusion it grounds. This modification seems to avoid the Gettier problem because if Smith had stopped believing the truth-defeated beliefs that Jones would get the job (Case I) and owns a Ford (Case 2), he would stop believing “The man who will get the job has ten coins in his pocket,” (Case I) and “Either Jones owns a Ford, or Brown is in Barcelona” (and the other two similarly random beliefs in Case II). However, Feldman points out a couple problems with this modification. 1) To paraphrase an example, Smith knows his radio is off and he does not know what is playing on the radio. However, if Smith was justified in knowing that the radio is playing Neil Diamond’s “Girl, You’ll Be a Woman Soon” then (all other methods of learning ruled out) Smith’s radio would have to be on, which would defeat his knowing that it is off. 2) There can be false defeaters, like a true statement about a lie [“Tom’s mother said that Tom’s twin took the tape” (p. 35, Feldman’s “Epistemology”), when “Tom’s twin took the tape” is a lie], which make us think we were wrong, when actually we were right.

Feldman notes that even believing a true statement about a falsehood involves implicit dependence of the final conclusion upon a falsehood. He mentions the EDF modification which adds the requirement that a belief’s justification not ‘e’ssentially ‘d’epend on a ‘f’alsehood. Paul K. Moser, in the article “Gettier problem” in Dancy and Sosa’s “A Companion to Epistemology,” proposes a modification he calls evidential truth-sustenance (ETS), which basically says that as long as there are true beliefs (essentially) justifying a conclusion, the (non-essential) false beliefs do not make the conclusion less justified. But such a requirement is already housed within the ‘justified’ aspect of the justified-true-belief account of knowledge (which would also be true of NFG and ND, if they were accurate). Admitting that false grounds are false grounds is admitting they are non-justifiers, so that Gettier’s problem examples do not involve instances of justified, true belief, and so do not challenge Plato’s justified-true-belief account of knowledge.



Edmund Gettier’s paper, “Is justified true belief knowledge?” (1963)
Plato’s “Theaetetus” (360 B.C.E.)
Christopher Norris’ “Epistemology” (2005)
Feldman’s “Epistemology” (2003)
David Hume’s “A Treatise of Human Nature” (1748)
Dancy&Sosa’s “A Companion to Epistemology” (2004)
–Paul K. Moser’s “Gettier problem” article therein

This entry was posted in Gettier Problem, Is-Ought Fallacy, Justified True Belief, Norris' Epistemology, Reviews and Interviews. Bookmark the permalink.

8 Responses to Answering Gettier

  1. Jonathan H says:

    Hi Maryann,

    As I understand it, you're arguing that the justified true belief model of truth is not defeated by Gettier – only that the requirement “reason for justification matches reason for proposition's truth” is added to the justified true belief model. Am I right about your statement?


  2. Nope, nothing is added. It stands as-is. What you said is encapsulated in the “justification” requirement–as long as you see that it is the 'belief' that is justified, not the truth. The important point is that a belief is not justified if it is based on falsehoods (even strongly convincing ones).

  3. What about the following variation?

    Smith believes that Jones is arriving on a bus at 7:30. In fact, Smith just finished looking at the bus schedule, and he said to a co-worker, “I know that Jones will be arriving at 7:30.” Unfortunately, the bus schedule was misprinted, and the bus Jones is on was supposed to arrive at 6:30. However, by an odd coincidence, the bus was delayed, and Jones did not arrive until 7:30. Hence, it was true that Jones would arrive at 7:30 when Smith said this to his co-worker.

    It seems to me that Smith has no false beliefs (or need not have any) in his evidential base for his belief that Jones will arrive at 7:30. He might have such a belief, e.g. if he believes that the schedule is correctly printed. But I don't think he strictly has to have such a belief. He might have the following two beliefs instead: (1) bus schedules are generally reliable and (2) this schedule says that Jones' bus arrives at 7:30. Given those true beliefs, he infers to the (as it turns out) true claim that Jones arrives at 7:30.

    But I still don't want to count this as an instance of knowledge. Am I missing something or does my variant stand up to a no-false-grounds challenge?

  4. Hi Jonathan (Livengood). Two things. One, the no false grounds challenge is flawed, because as long as your belief depends 'essentially' on the right reasons, it is okay if some of your reasons are flawed. Two, the bus schedule time was a mis-print, thus a false ground. The attempted “alternative route” through “This bus schedule says that Jones' bus arrives at 7:30” (still based on a mis-print) is a route w/ no end if in this case he is not concluding from it that “Jones will arrive at 7:30”. If he still holds the conclusion, the conclusion is still based on a mis-print, and his holding it is still unjustified, though true.

  5. I don't understand your reply. Suppose Smith has the following beliefs:

    (P1) If 99% of Xs assert only truths and this X asserts p, then (all else equal) p.
    (P2) 99% of bus schedules assert only truths.
    (P3) This is a bus schedule and asserts that Jones' bus arrives at 7:30.

    From these, Smith may conclude that Jones' bus arrives at 7:30, which turns out to be true.

    Which of the beliefs P1-P3 fails to be justified on your view and why?

  6. It's not about whether they are justified, it's about whether they are true/false–and there is a very important “hidden premise” (given Smith does in fact conclude that Jones' bus arrives at 7:30)–the assumption that this bus schedule is not of the 1% of bus schedules that have misprints (given your percentages are accurate). It is that falsehood upon which the conclusion is essentially based, and therefore the conclusion (though true) is not justified.

  7. The premisses as I've stated them are all true in the context of the story, unless you have serious concerns about the version of statistical syllogism given in (P1).

    In any event, the whole point of the story was to put teeth into a *denial* that Smith has to believe a falsehood at some stage of a Gettier case. As the story is set up, Smith has true and justified beliefs from which he validly infers a true conclusion. The inference he makes *does not* pass through a falsehood. I claim that his conclusion is not essentially based on a falsehood. (One might imagine an alternative story in which Smith believes the falsehood you suggest, but what I am saying is that having such a false belief is not essential for drawing the conclusion that he draws.)

  8. How can he draw the conclusion unless he believes his bus schedule is not of the 1% of bus schedules that have misprints?

    Regarding the syllogism, as long as stating “(all else equal)p” does not mean “p is necessarily true” then I'm cool w/ it, as long as it doesn't involve some sort of ad hominem fallacy (centered around the Xs)(because the mere fact that something is asserted by X does not 'make' it true).

Tell it:

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s