The nature of truth has baffled people since ancient times, partly because people so often use the term true for ideas they find congenial and want to believe, and also because people so often disagree about which ideas are true.
Philosophers have attempted to define criteria for distinguishing between truth and error. But they disagree about what truth means and how to arrive at true ideas.
The correspondence theory holds that an idea is true if it corresponds to the facts or reality.
The pragmatic theory maintains that an idea is true if it works or settles the problem it deals with.
The coherence theory states that truth is a matter of degree and that an idea is true to the extent to which it coheres (fits together) with other ideas that one holds.
Skepticism claims that knowledge is impossible to attain and that truth is unknowable.