Enneads VI.1: Of the Ten Aristotelian and Four Stoic Categories
Neither Is Time a Quantity
Let us pass to time. If it exist in what measures, that which measures must be examined; it is doubtless the soul, or the present instant. If it exist in what is measured, it is a quantity so far as it has a quantity; as, for instance, it may be a year. But, so far as it is time, it has another nature; for what has such a quantity, without (essentially) being a quantity, is not any the less such a quantity.
QUANTITY AS EQUAL AND UNEQUAL DOES NOT REFER TO THE OBJECTS.
As to (Aristotle’s) assertion that the property of quantity is to be both equal and unequal, this property belongs to quantity itself, and not to the objects which participate in quantity, unless it be by accident, so far as one does not consider these objects in themselves. A three foot object, for instance, is a quantity so far as it is taken in its totality; but it does not form a kind with quantity itself; only, along with it, it is traced back to a kind of unity, a common category.