Reading: Is Justified True Belief Knowledge? by Edmund Gettier

Is Justified True Belief Knowledge? by Edmund Gettier

Gettier, Edmund L. “Is Justified True Belief Knowledge?” Analysis, vol. 23, no. 6, 1963, p. 121., doi: 10.2307/3326922.

 

Various attempts have been made in recent years to state necessary and sufficient conditions for someone's knowing a given proposition. The attempts have often been such that they can be stated in a form similar to the following:¹

(a) S knows that P IFF             

(i) P is true,

(ii) S believes that P, and

(iii) S is justified in believing that P.

For example, Chisholm has held that the following gives the necessary and suf­ficient conditions for knowledge:²

(b) S knows that P IFF             

(i) S accepts P,

(ii) S has adequate evidence for P, and

(iii) P is true.

Ayer has stated the necessary and sufficient conditions for knowledge as follows:³

(c) S knows that P IFF             

(i) P is true,

(ii) S is sure that P is true, and

(iii) S has the right to be sure that P is true.

I shall argue that (a) is false in that the conditions stated therein do not constitute a sufficient condition for the truth of the proposition that S knows that P. The same argument will show that (b) and (c) fail if 'has adequate evidence for' or 'has the right to be sure that' is substituted for 'is justified in believing that' throughout.

I shall begin by noting two points. First, in that sense of 'justified' in which S's being justified in believing P is a necessary condition of S's knowing that P, it is possible for a person to be justified in believing a proposition that is in fact false. Secondly, for any proposition P, if S is justified in believing P, and P entails Q, and S deduces Q from P and accepts Q as a result of this deduction, then S is justified in believing Q. Keeping these two points in mind, I shall now present two cases in which the conditions stated in (a) are true for some proposition, though it is at the same time false that the person in question knows that proposition.

 

Case 1:

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, farther, 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 then 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 Smith's 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.

Case 2:

Let us suppose that Smith has strong evidence for the following proposition:

(f) Jones owns a Ford.

Smith's evidence might be that Jones has at all times in the past within Smith's memory owned a car, and always a Ford, and that Jones has just offered Smith a ride while driving a Ford. Let us imagine, now, that Smith has another friend, Brown, of whose whereabouts he is totally ignorant. Smith selects three place-names quite at random, and constructs the following three propositions:

(g) Either Jones owns a Ford, or Brown is in Boston;

(h) Either Jones owns a Ford, or Brown is in Barcelona;

(i) Either Jones owns a Ford, or Brown is in Brest-Litovsk.

Each of these propositions is entailed by (f). Imagine that Smith realizes the entail­ment of each of these propositions he has constructed by (f), and proceeds to accept (g), (h), and (i) on the basis of (f). Smith has correctly inferred (g), (h), and (i) from a proposition for which he has strong evidence. Smith is therefore completely justified in believing each of these three propositions. Smith, of course, has no idea where Brown is.

But imagine now that two further conditions hold. First, Jones does "not own a Ford, but is at present driving a rented car. And secondly, by the sheerest coinci­dence, and entirely unknown to Smith, the place mentioned in proposition (h) happens really to be the place where Brown is. If these two conditions hold then Smith does not know that (h) is true, even though (i ) (h) is true, (ii ) Smith does relieve that (h) is true, and (iii) Smith is justified in believing that (h) is true.

These two examples show that definition (a) does not state a sufficient condition for someone's knowing a given proposition. The same cases, with appropriate changes, will suffice to show that neither definition (b) nor definition (c) do so either.

1. Plato seems to be considering some such definition at Theaetetus 201, and perhaps accepting one at Meno 98.
2. Roderick M. Chisholm, Perceiving: a Philosophical Study, Cornell University Press (Ithaca, New York, 1957),  p. 16. 

3. A. ]. Ayer, The Problem of Knowledge, Macmillan (London, 1956), p. 34.

 

  

Basic Questions (Optional)

This is an optional, non-graded, non-credit area. Explore the following for a better understanding of philosophy. Answers to these question can be found in the video and in the reading.

1. Traditionally, what are the necessary and sufficient conditions for knowledge?
2. Is Gettier arguing that belief, truth, and justification are not necessary for knowledge?
3. True or False: The traditional definition of knowledge provides necessary, but not sufficient conditions for knowledge.
4. In Gettier's two examples, Smith is justified in believing a certain proposition P and reasons from P to another proposition Q, which Gettier say Smith does not know. Does Smith know P?

Advanced Questions (Optional)

This is an optional, non-graded, non-credit area. Explore the following for a better understanding of philosophy.

1. How would you explain the lack of knowledge in Gettier's job seekers thought experiment?
2. Assuming that the proposition "Jones owns a Ford" is true, why does it logically follow that "Jones owns a Ford or Brown is in Boston" is also true?
3. Why is the traditional definition of knowledge inadequate? What would you add to the traditional definition of knowledge so that we can be sure that S knows that P?
4. Suppose you have bought a lottery ticket. The odds oy your winning are 290 million to one. The winning ticket has been selected and it's not yours, but the number has not yet been announced on television. You're sure that you've lost. Do you know that you've lost? Assuming you don't know that you've lost, how does this case differ from Gettier's two examples?

 

Additional Considerations (Optional)

This is an optional, non-graded, non-credit area. Explore the following for a better understanding of philosophy.

This Simple Philosophical Puzzle Shows How Difficult It Is to Know Something

BY BRIAN GALLAGHER

What is knowledge? Well, thinkers for thousands of years had more or less taken one definition for granted: Knowledge is “justified true belief.” But Edmund Gettier showed, using little short stories, that this intuitive definition of knowledge was flawed.

In the 1960s, the American philosopher Edmund Gettier devised a thought experiment that has become known as a “Gettier case.” It shows that something’s “off” about the way we understand knowledge. This ordeal is called the “Gettier problem,” and 50 years later, philosophers are still arguing about it. Jennifer Nagel, a philosopher of mind at the University of Toronto, sums up its appeal. “The resilience of the Gettier problem,” she says, “suggests that it is difficult (if not impossible) to develop any explicit reductive theory of knowledge.” 

What is knowledge? Well, thinkers for thousands of years had more or less taken one definition for granted: Knowledge is “justified true belief.” The reasoning seemed solid: Just believing something that happens to be true doesn’t necessarily make it knowledge. If your friend says to you that she knows what you ate last night (say it’s veggie pizza), and happens to be right after guessing, that doesn’t mean she knew. That was just a lucky guess—a mere true belief. Your friend would know, though, if she said veggie pizza because she saw you eat it—that’s the “justification” part. Your friend, in that case, would have good reason to believe you ate it.

The reason the Gettier problem is renowned is because Gettier showed, using little short stories, that this intuitive definition of knowledge was flawed. His 1963 paper, titled “Is Justified True Belief Knowledge?” resembles an undergraduate assignment. It’s just three pages long. But that’s all Gettier needed to revolutionize his field, epistemology, the study of the theory of knowledge.

The “problem” in a Gettier problem emerges in little, unassuming vignettes. Gettier had his, and philosophers have since come up with variations of their own. Try this version, from the University of Birmingham philosopher Scott Sturgeon:

Suppose I burgle your house, find two bottles of Newcastle Brown Ale in the kitchen, drink and replace them. You remember purchasing the ale and come to believe there will be two bottles waiting for you at home. Your belief is justified and true, but you do not know what’s going on.

Does it seem odd to say that you would know that there are two Newcastles in your fridge? Sure, you’re confident they’re there. But the only reason they’re there is because this burglar evidently had a change of heart. You, though, believe two are there because you put them there. You’re right that you’ve got beer in the fridge, and you’ve got good reason to believe they’d be there once you get back—but doesn’t your true and justified belief that you have two Newcastles waiting for you seem lucky somehow? After all, your belief is true only because the burglar replaced the beer. Can lucking into a true and justified belief be considered knowledge?

You might be wondering what Gettier thinks of all this. It turns out, not much—or, if he does have an opinion, he hasn’t cared enough to share it. Indeed, he’s never published any other paper besides “Is Justified True Belief Knowledge?” and he turns 90 in October. To the question, “Why not?” he said, “I have nothing more to say.”

Gallagher, Brian. “This Simple Philosophical Puzzle Shows How Difficult It Is to Know Something - Facts So Romantic.” Nautilus, 6 Aug. 2017, nautil.us/blog/-this-simple-philosophical-puzzle-shows-how-difficult-it-is-to-know-something.

 

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