We turn now to the task of providing a precise formulation of Quine's criterion. This task is none too easy: formulations that keep within the strictures of Quine's overall philosophy are woefully inadequate; the farther one is allowed to stray from Quinean strictures, the better things look; but, by the time one gets to a defensible criterion, one has left Quine far behind. I will consider in turn extensional, metalinguistic, and modal formulations.