It may be objected that non-presence in a subject is not peculiar to Substance, inasmuch as the differentia of a substance is no more present in a subject than the substance itself; but this objection results from taking a part of the whole substance, such as “two-footed” in our example, and asserting that this part is not present in a subject: if we take, not “two-footed” which is merely an aspect of Substance, but “two-footedness” by which we signify not Substance but Quality, we shall find that this “two-footedness” is indeed present in a subject.
We may be told that neither Time nor Place is present in a subject. But if the definition of Time as the measure of Motion be regarded as denoting something measured, the “measure” will be present in Motion as in a subject, while Motion will be present in the moved: if, on the contrary, it be supposed to signify a principle of measurement, the “measure” will be present in the measurer.
Place is the limit of the surrounding space, and thus is present in that space.
The truth is, however, that the “Substance” of our enquiry may be apprehended in directly opposite ways: it may be determined by one of the properties we have been discussing, by more than one, by all at once, according as they answer to the notions of Matter, Form and the Couplement.