ABSTRACT
G. W. Leibniz, through his famous Principle of the Identity of Indiscernibles (PII), affirms that no two substances are completely alike, that every substance has a property, or properties, which no other substance has. Aristotle, on the other hand, neither affirms nor denies this, but for him individuation is accomplished by each substance having "different matter", rather than different properties. This chapter describes the Leibnizian view and dwells on the difficulties which might move one to seek an alternative account of individuation. It introduces the Principle of the Identity of Necessary Similarity (PINS), a PII-like principle which does not seem to be subject to the kind of objections that PII faces in connection with the problem of individuation. The chapter discusses Aristotle's view of matter as the principle of individuation and suggests that PINS can be viewed as a consequence of the Aristotelian position.
