 In our opinion, the indefinability of particulars makes it impossible for substantial forms to be particulars. If there were a substantial form that is unique to some sensible particular, say Callias, then the definition corresponding to that form, or essence, would apply uniquely to Callias—it would define him, which is precisely what Aristotle says cannot be done. The question, then, is whether the evidence against substantial forms being universals can be countered. This is less clear, but the following considerations are relevant. (1) Aristotle’s claim that a substantial form is an individual (tode ti) does not exclude its being a universal (katholou). Universals are contrasted with particulars (kath’ hekasta), not individuals (although Aristotle does sometimes ignore the distinction between tode ti and kath’ hekaston). What makes something a tode ti is its being a fully determinate thing, not further differentiable; what makes something a kath’ hekaston is its being a particular thing, unrepeatable, and not predicated of anything else. There is thus the possibility of a universal tode ti—a fully determinate universal not further divisible into lower-level universals, but predicated of numerous particulars. (2) The claim that there are no universals apart from particulars needs to be understood in context. When Aristotle asserts (1038b33) that “there is not some animal … beyond the particular ones (ta tina)” he is just as likely to be referring to the particular kinds of animals as he is to particular specimens. If so, his point may be that a generic kind, such as animal, is ontologically dependent on its species, and hence on the substantial forms that are the essences of those species. (3) The arguments of Ζ.13 against the substantiality of universals are presented as part of a give-and-take investigation of the perplexities involved in the notion of substantial form. It is not clear, therefore, whether the blanket claim “No universal is a substance” is intended to be accepted without qualification. Indeed, a closer examination of the arguments may show that qualifications are required if the arguments are to be cogent. For example, the argument at 1038b11–15 is based on the premise that the substance of x is peculiar (idion) to x. It then draws the conclusion that a universal cannot be the substance of all of its instances (for it could not be idion to all of them), and concludes that it must be the substance “of none.” But note that this conclusion does not say that no universal can be a substance, but only that no universal can be the substance of any of its instances (cf. Code 1978). Aristotle’s point may be that since form is predicated of matter, a substantial form is predicated of various clumps of matter. But it is not the substance of those clumps of matter, for it is predicated accidentally of them. The thing with which it is uniquely correlated, and of which it is the substance, is not one of its instances, but is the substantial form itself. This conclusion should not be surprising in light of Aristotle’s claim in Ζ.6 that “each substance is one and the same as its essence.” A universal substantial form just is that essence.