Abstract

The view that numerical difference entails qualitative difference has come under attack from various quarters. One classical attack, advanced by Black, involves possible worlds which are symmetrical. In a symmetrical world, it is claimed, the identity of indiscernibles is false. I argue that such attacks are mistaken, basically because they confuse epistemological issues (such as, how to specify a quality difference) with ontological ones (such as, whether there is such a quality difference). In brief, though there may be some reasons for doubting the necessity of the Identity of lndiscernibles, the possibility of a symmetrical world is not one of them.