philosophers are mostly interested in factual knowledge because they are trying to understand how we can achieve truth about the world. one of the first philosophers to attempt a definition of knowledge was the ancient greek philosopher, plato.
one of Plato’s main concerns was to distinguish knowledge from belief.
plato made the theory known as Justified True Belief theory, which argues that for a factual claim to be knowledge, it has to be a belief which is true and justified.
for example, i know that paris is a city if and only if:
- i believe it
- it is true
- i can offer justification for my belief (have evidence)
so, plato made the JTB theory.
the JTB theory says that if you believe something, if and only if, with justification, and it is true
however, the JTB theory is not logically complete, as illustrated in the gettier problem
justification
in order to know a thing, it is not enough to merely correctly believe it to be true, or to do lucky guesses; one must also have a good reason for doing so - one must have justification
truth
If one knows a thing then it must be true. No matter how well justified or sincere a belief, if it is not true that it cannot constitute knowledge. If a long-held belief is discovered to be false, then one must concede that what was thought to be known was in fact not known.
belief
unless one believes a thing, one cannot know it. Even if something is true, and one has excellent reasons for believing that it is true, one cannot know it without believing it.