 Widely accepted as it is, however, IDT is not obviously true. Shoemaker (1980) considers a key’s disposition to open his front door and points out that it could lose this disposition without undergoing any intrinsic change, for example, by the lock on his door being replaced by one of a different kind. It would seem, then, that the disposition to open Shoemaker’s front door is not an intrinsic property of the key, and so IDT is false.