The Principle of the Identity of Indiscernibles, commonly attributed to Leibniz, has given rise to much discussion and debate. Thus philosophers have argued over how it should be formulated, whether it is true, and what, if any, metaphysical consequences it has.It is not my intention to add to these discussions here, having done so elsewhere. Rather, I intend to introduce and defend a closely related principle which I shall, for want of a better name, refer to as The Principle of (...) the Identity of Necessary Similarity’.In section II, I briefly recapitulate some of the distinctions and other relevant points which are customarily made in connection with. This is all too familiar material, but it is necessary in order to provide a general framework of concepts in terms of which we can discuss in an intelligible fashion. (shrink)