Theories to test truth:

1. Pragmatic theory - e.g. "It is true because it works for me."
2. Correspondent theory - e.g. I say there is a yellow bird on the roof and you can check if what I say matches what you see.
3. Coherent theory: - e.g. "It is true if it fits in with what I already know."

Criteria for Truth:

1. Independent - exists on its own
2. Public - everyone knows it
3. Eternal - truth will never change