Abstract

This paper concerns the question of which logical principles hold for real definitions. Recently, Samuel Elgin has presented five principles concerning real definitions that seem initially plausible. He has shown them to be jointly inconsistent. This gives rise to a puzzle that can only be solved by denying one of the principles. In this paper, I argue against Elgin's principle of expansion, which concerns substituting a definiens for its definiendum within the definiens of a further definition. I show that this principle fails for every irreflexive notion of definition and proposes a replacement that allows to restore consistency and solve the puzzle.