Epistemology/Justified true belief

In this chapter, we will introduce and discuss the tripartite (or "JTB") analysis of knowledge. The tripartite analysis of knowledge has been held by many philosophers throughout history and can trace its origins all the way back to Plato's discussion of a tripartite analysis of knowledge in the Theaetetus. The tripartite analysis of knowledge is often called JTB knowledge after its conditions of justification, truth and belief. Each of these conditions is claimed to be individually necessary for knowledge and together they are said to form the jointly sufficient conditions for knowledge.

The tripartite analysis of knowledge: A subject S knows that p if and only if
  1. S is justified in believing that p,
  2. p is true, and
  3. S believes that p

where p is a proposition.

Attacks of the JTB analysis have come in two main forms: (a) in this chapter, we will discuss objections to the individual necessity of each of the conditions and (b) in the next chapter, we will discuss a famous attempt to show that these conditions cannot always guarantee us knowledge and so are not jointly sufficient.

Justification edit


The justification condition is placed on knowledge to make sure that we don't know things by pure luck. It is reasonable to say that without any reasons one way or the other to believe a proposition is true or false, we would not have no rational way to judge whether it is true or not and so we can only be right about that proposition by luck alone. Justification can be thought of as anything that gives us those good reasons that we need to legitimately believe that a proposition is true. To understand why philosophers see "lucky knowledge" as a problematic concept, let's look at the following example:

  • You and a friend are playing a game where you try to guess the outcome of a coin flip
  • Your friend shouts out that they know that the coin is going to land heads up
  • By pure chance the coin does land on heads
  • But the coin could just have easily landed on tails making them completely wrong!

This example aims to show that there is something faulty in the idea that we can know things without having the right kind of justification because if we don't have justification for our belief, all that matters is whether our beliefs happen to come true or not. There is no difference between an expert undertaking complicated research in an area to come to a conclusion and a person that makes a random guess on the subject so long as they both happen to be right in the end. All it takes to change the guesser to a knower is the toss of a coin (until we add a justification condition to our analysis, of course!).

Attempts to argue against the necessity of justification to knowledge have attempted to create an equivalence between the JTB analysis of knowledge and true belief so that true belief alone is really all that is needed. For example, consider this passage by Plato from the Meno:

Soc. If a man knew the way to Larisa, or anywhere else, and went to the place and led others thither, would he not be a right and good guide?

Men. Certainly.

Soc. And a person who had a right opinion about the way, but had never been and did not know, might be a good guide also, might he not?

Men. Certainly.

Soc. And while he has true opinion about that which the other knows, he will be just as good a guide if he thinks the truth, as he who knows the truth?

Men. Exactly.

Soc. Then true opinion is as good a guide to correct action as knowledge

Opponents of the tripartite account could use this argument to make the claim that there is no meaningful difference between justified true belief and true belief and so justification isn't needed. However, even though true belief and justified true belief are both good guides to action, this doesn't mean that there is no meaningful difference between them. As we saw from the coin flip/expert research example, the difference between a person who merely has right opinion and somebody who has justified true belief is that the person who has justified true belief has a certain sense of epistemic legitimacy. If we want the status of knowledge not to be granted to people who happen to believe true things but are motivated by ignorance, intolerance or epistemic laziness, then our analysis of knowledge must make sure that it guarantees a certain bare minimum of epistemic legitimacy.

Truth edit

Most philosophers believe that truth is the most secure and uncontroversial of the conditions on knowledge. To understand why, let's reconsider our previous example:

  • You and a friend are playing a game where you try to guess the outcome of a coin flip
  • Your friend shouts out that they know that the coin is going to land heads up
  • Unlucky for them the coin lands heads down

If your friend were to continue to claim that they knew that the coin would land heads up after it lands the opposite way, you would probably think they'd gone a little bit insane.

The basic point is, you can't know something is it isn't even true in the first place – knowledge simply aims at the truth.

Belief edit


Augustine defined belief as "to think with assent". In other words, belief can be defined simply as thinking that something is true. If you were to hear somebody say that they believe that ghosts exist but they don't really think it's true that they exist, you might think that they don't really believe in ghosts at all. Now let's consider what reaction we would have if we were to hear somebody say "I know that ghosts exist but I don't really believe that they do." It seems like the rational reaction to this statement would be similarly to think that this person doesn't really know that ghosts are real, for how could they possibly know something that they don't even believe.

However, a counterexample by Colin Radford has attempted to show that not all of our knowledge needs to be believed, some of it may be known implicitly or subconsciously.

  • Albert learned that Queen Elizabeth died in 1603 at school years ago.
  • When asked when Queen Elizabeth died, Albert doesn’t believe she died in 1603 because he can’t remember being taught about her at all. He doesn’t have any belief about which year she died because he is uncertain.
  • Randomly guessing, he answers 1603 and he can also answer many more similar history questions correctly with accuracy far better than chance.
  • Radford argues that Albert must know subconsciously and that this is an example of knowledge without belief.

Somebody who believed in the JTB analysis of knowledge could deny that this counts as an example of knowledge, but they would have to provide an explanation for how Albert could possibly get so many questions right without knowledge (for it seems very plausible that this example really could happen in real life).

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