This paper compares the roles classical and intuitionistic logic play in restricting the free use of truth principles in arithmetic. We consider fifteen of the most commonly used axiomatic principles of truth and classify every subset of them as either consistent or inconsistent over a weak purely intuitionistic theory of truth.

When my son Jason was an economics Ph.D. student at Harvard in the 1990s, he said: “I have observed that only two economists can push you around, Milton Friedman and Gary Becker.” I agreed but argued that it was a good thing. Everyone needed heroes, and Gary had only Milton. Milton had no one, except Ronald Reagan in the 1980s, but Reagan did not really qualify as an economist. Arthur Burns may...