ABSTRACT
The principle of the Identity of Indiscernible makes us attend to the distinction between essential and inessential or "accidental" qualities. Furthermore, this way of being different needs to be continuous, because change is continuous, and one of our arguments for introducing a non-qualitative way of being different was in order to allow for the possibility of a thing's changing—that is, the same thing being different at different times. We thus have, in effect, a parameter, assigned to each individual, which distinguishes one individual from others qualitatively identical with it, which can take different values at different times, and which can vary continuously. This is what constitutes the philosopher's space. It is room for things to be different in; different from one another at any time, different from themselves at different times; and because in a sufficiently short time things can differ by as little as we please, space must be, like time, a continuum.
