I have seen "justification", "truth" and "belief" used a lot in Crash Course philosophy and would like to know some hard differences between the three.

  • See Knowledge as Justified True Belief. Feb 10, 2018 at 19:39
  • @MauroALLEGRANZA thanks for the article. I think now I 80% understand the subject. If you could produce an answer that compares the three it would be great.
    – Bar Akiva
    Feb 10, 2018 at 19:50
  • 1
    Truth has to do with what facts are, belief is what we take the facts to be, and justification concerns what our beliefs are based on. Suppose Jill is pregnant, but she hasn’t yet realized this. Then although it is true she is pregnant, she doesn’t yet believe this. Next, suppose that Jill’s fortune teller tells her she is pregnant, based on a tarot card reading. Then Jill (who is gullible) comes to believe she is pregnant, but her belief is not justified. On the other hand, if Jill takes a pregnancy test, her belief is justified.
    – MarkOxford
    Feb 10, 2018 at 21:12
  • @MarkOxford great analogy. Just what i was looking for. Go write this as an answer
    – Bar Akiva
    Feb 11, 2018 at 12:44

5 Answers 5


In a classic theory of knowledge, there are typically 3 conditions that must be fulfilled in order for something to be considered "known":

  1. Belief - pretty self-explanatory, you believe that what you think is true. Example: I believe an elephant has grey skin.

  2. Justification - you have a reason to think you belief is true. Example: I heard someone say elephant has grey skin.

  3. Truth - an after-the-fact kind of justification, you can say an objective true statement about your belief. Example: you saw an elephant, and you saw it actually has grey skin, so you can say objectively "elephant has grey skin".

Now keep in mind that every theory of knowledge build upon these 3 conditions and expand (because, as noted over the years, they are not enough - in the example, who says I didn't saw just a specific kind of elephant with grey skin, but there are actually more elephants with pink skin? Here comes Hume's famous induction problem, and that's just an example for the problem with keeping only those 3 conditions as they're presented here).


These words are often used very loosely in philosophy and cause much trouble. The reason is the common idea that ''truth' is the same as 'belief' where the belief is 'justified'. But a justified belief is a tentative belief and not a known truth, and if a truth is not known then we cannot call it a truth. Descartes saw this problem and chose his axiom accordingly.

A proper answer would be quite long and technical, but for now I'd just keep it simple. A belief is what we believe. A belief may be justified or unjustified depending on the strength of the evidence for it. If the evidence is strong then it may be considered a justified belief but cannot be considered a truth. A truth is something we know to be true such that we require no further evidence or justification and could not be wrong.

Much trouble comes from equating justified belief with truth, as in the phrase 'justified true belief'. I would ban this phrase from philosophical discourse as an unhelpful muddle of words, but regrettably I'm not in charge. .

  • "A truth is something we know to be true such that we require no further evidence or justification and could not be wrong." Surely there are unknown truths, right? There's a fact of the matter (i.e., a truth!) about whether or not the Goldbach conjecture is true, but nobody knows it. Feb 11, 2018 at 20:52
  • Further to what @possibleWorld said, whether a belief is true has little to do with whether it is justified. If I believe that Jill is pregnant because my crystal ball told me, my belief is not justified – but true, if Jill is pregnant. Also, nobody wants to equate truth with justified belief: JTB accounts (which claim that “justified true belief is knowledge”) hold that S knows that p iff (i) S believes that p, (ii) S’s belief is justified, and (iii) p is true. Here, (iii) is separate from (ii) and concerns how matters stand with the world - with p - and not how they stand with S's mind.
    – MarkOxford
    Feb 12, 2018 at 10:07
  • @MarkOxford - The confusion seems to be between belief and knowledge. Suppose x is true and we believe it. This would be a truth but it would not be knowledge unless we know it is true. Simply believing x is true would not make it knowledge even if it true. Thus it is not the truth-value of x that makes it knowledge, but whether we know it or not. I feel the confusion is unavoidable because we usually have no understanding of how we know things. Russell called it the most difficult philosophical question. .
    – user20253
    Feb 12, 2018 at 10:38
  • I’m not sure what confusion you are talking about. You say “it is not the truth-value of x that makes it knowledge, but whether we know it”. That strikes me as trivial: we know p only if we know it. The whole point of JTB-type accounts (and revisions thereof, such as Nozick’s) is that we can give a non-trivial analysis of knowledge. If you subscribe to the ‘Knowledge First’ paradigm (a la Tim Williamson), you’ll deny that such an analysis is available. Still, Williamson can say non-trivial things about knowledge – e.g. that knowledge is more than true belief.
    – MarkOxford
    Feb 12, 2018 at 11:06
  • @MarkOxford - It seems we have different ideas as to what is trivial. JTB is not an explanation of knowledge. Russell calls knowledge the most important and challenging problem in all of philosophy and gets nowhere with it, but he is talking about knowledge and not.JTB.
    – user20253
    Feb 22, 2018 at 12:14

I largely agree with the first answer. Knowledge is often taken to be a matter of justified true belief. 'Sasha knows that grass is green'. Suppose Sasha knows this. Then my own terms :


Acceptance of a proposition : Sasha accepts the proposition that grass is green.


Sasha has adequate evidence, sufficient grounds, for accepting the proposition that grass is green.


The proposition that grass is green fits the real world, corresponds to reality - to the fact that grass is green.

This invokes a so-called correspondence theory of truth. This has problems but it conveys a commonsense view of truth. Enough to make the difference between truth and belief & justification plain - I hope.


Truth is pervasive of all conditions.It is a fact,or a statement true in all respects. Truth is absoulte.

Belief is something personal.It is trusting a statement without necessarily demanding a proof.Belief may or may not be true and it can change with time. It is dependent on your faith and confidence in that statement.

while truth is more a matter of logic or thought,belief is related to trust and feelings.

Justification is a process of one party convincing one party,the validity of a statement to another party. Or the way to convince someone why your belief is true with some reasons or facts.


A belief is the acceptance of some proposition. For example, I believe that Napoleon lost at Waterloo. In other words, I think that the proposition "Napoleon lost at Waterloo" is true; I accept it. The belief is a state of my mind.

Truth is a property of a proposition. Of course, defining truth is a controversial and complicated philosophical topic. But to a first approximation, a proposition is true just in case reality is as the proposition says it is. "Napoleon lost at Waterloo" is a true proposition, because the man it speaks of (Napoleon) did, in fact, have the property it says he had (losing at Waterloo).

Hence, when I believe that Napoleon lost at Waterloo, I think the proposition is true, and it is true. So that's good!

But I might believe this for bad reasons. Perhaps I saw a piece of graffiti that said "Napoleon lost at Waterloo" and I decided to believe it. My reason for believing is "Because the graffiti said so." This is, intuitively, a bad reason for a belief. So a philosopher would say that even though I have a true belief, it is not a justified belief; I don't have a good enough reason for it.

So, in general, a belief is justified if there is a good reason for having it. Now, this is a fairly uninformative statement. In particular, there are two crucial things it doesn't tell us:

  1. It doesn't say what counts as a good reason for belief.
  2. For my belief to be justified, do I have to know the good reason, or it is sufficient that there simply be such a reason?

Philosophers since Descartes have been centrally preoccupied with justification, and a lot of their effort has been expended trying to answer those two questions.

Philosophers have also traditionally thought that knowledge is a very important concept, and they have tried to define it. A very famous and traditional answer is: I know that P just in case I have a justified true belief in P (where P can be any sentence). That is one historical reason philosophers care about the notions of justification, truth and belief.

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