Truth is not knowledge. Truth is the property of knowledge being actually correct. "Valid" is a determination of the correctness of knowledge based on the rigorous application of logic and the self-evident axioms upon which logic itself is predicated.

This does leave open the possibility of valid knowledge not being true, which statistically must occur from time to time. But we don't get to work with truth, only knowledge, and science provides a basis for dealing with previously valid knowledge that becomes known to be invalid. Religion doesn't.