 The idea that substantial forms are particulars is supported by Aristotle’s claims that a substance is “separable and this something ” (chôriston kai tode ti, Ζ.3), that there are no universals apart from their particulars (Ζ.13), and that universals are not substances (Ζ.13). On the other side, the idea that substantial forms are universals is supported by Aristotle’s claims that substances are, par excellence, the definable entities (Ζ.4), that definition is of the universal (Ζ.11), and that it is impossible to define particulars (Ζ.15).