Each piece, or part, of the whole of nature is always merely an approximation to the complete truth, or the complete truth so far as we know it. In fact, everything we know is only some kind of approximation, because we know that we do not know all the laws as yet. Therefore, things must be learned only to be unlearned again or, more likely, to be corrected. … The test of all knowledge is experiment. Experiment is the sole judge of scientific truth.

volume I; lecture 1, "Atoms in Motion"; section 1-1, "Introduction"; p. 1-1 - The Feynman Lectures on Physics (1964)