Aristotle, the master of common sense in philosophy, defined what ordinary people mean by truth as “saying of what is that it is and of what is not that it is not.” Truth means the correspondence of what you know or say to was is. Truth means “telling it like it is.” …
Alternative theories of truth:
1. The Pragmatic Theory of Truth: “Truth is what works.”
Since “what works” is subjective and relative (what you think works, or what works for you), pragmatism is a form of subjectivism and relativism. G.E. Moore proved (in his essay “William James’s Pragmatism”) that the pragmatic theory of truth is based on a linguistic confusion. There is a perfectly good word in the language for “what works.” that word is “efficient” or “effective” or “practical.” If we reduce truth to “what works,” we lose a different, distinctive, independent meaning of truth as “saying what is.” Moore shows quite simply and conclusively that truth cannot mean “what works” or “what is practical,” because what is true is not always practical (e.g., death) and what is practical is not always true (e.g., a “successful” lie).
Chesterton refuted pragmatism by saying that “man’s most pragmatic need is to be something more than a pragmatist.” For without an end, no one will work for any practical means. “Means” means “means-to-an-end.” Without a more-than-pragmatic end, no one can be pragmatic. Pragmatism doesn’t work, it isn’t practical.
-Kreeft and Tacelli in The Handbook of Christian Apologetics, p. 364-365.