Intuitionism and the liar paradox

Abstract

The concept of informal mathematical proof considered in intuitionism is apparently vulnerable to a version of the liar paradox. However, a careful reevaluation of this concept reveals a subtle error whose correction blocks the contradiction. This leads to a general resolution of the classical semantic paradoxes. This paper is an expanded version of parts of my earlier paper "Constructive truth and circularity" [arXiv:0905.1681].