justified true belief
A belief is the acceptance of a
proposition. A true belief is one that has been examined by
the believer and remains a belief. We often accept propositions, only to discover later that we were wrong. Being wrong can be the result of many things: lack of other knowledge that would have caused disbelief; a persuasive argument that you later reject; the proposition was rational-sounding but it was a fallacy.A rational proposition that is not a fallacy has justification, that is, it is 'justified'. This means the logic is sound and it has a correspondence to facts of reality. (See 'correspondence truth').Therefore, a 'justified true belief' is one that has been shown to be logically sound, or is accepted as logically sound.It may or may not be 'defeasible', in other words, defeatable, by a better argument. The Copernican Revolution was the defeat of Catholic justified true belief, by the arguments of
Galileo who used the mathematics of
Copernicus. (See 'defeator arguments' or 'defeasors')