XV—Remarks on Definitions and the Concept of Truth

I wish to present a view of concepts (and, in particular, of the concept of truth) that Nuel Belnap and I have come, after much hesitation, to believe is true.2 We were led to consider the view by a striking parallel that we noticed between the behaviour of the concept of truth and that of certain kinds of definitions. I think I can best explain the view if I begin by sketching this parallel. The relevant behaviour of the concept of truth is well known: while some (perhaps most) of its uses are unproblematic (e.g., its use in 'some things Russell said about Wittgenstein are true') some others are not (e.g., its implicit use in Epimenides' assertion of the Liar 'all Cretans are liars', and its use in the Truth-Teller 'this very sentence is true').3 We have no difficulty in assigning a truth-value to the former, unproblematic, sentences (assuming that we know the relevant facts) but with the latter, pathological, ones we encounter a variety of difficulties. Sometimes, as in the Liar example, every possible assignment of truth-value seems to lead to contradictions.