Unity and Measure
To be one means ‘to be whole and indivisible’, being essentially one means a “this” and capable of being isolated in time, place, form or thought; but it means especially ‘to be the first measure of a kind’, and most strictly of quantity; for it is from this that it has been extended to the other categories. For measure is that by which quantity is known; and quantity qua quantity is known either by a ‘one’ or by a number, and all number is known by a one.
Unity, in the strictest sense, is a measure, and most properly of quantity, and secondly of quality. Some things are one if they are indivisible in quantity, and others if they are indivisible in quality; and so that which is one is indivisible, either absolutely or qua one.
Knowledge and perception, we call the measure of things, because we come to know something by them-while as a matter of fact they are measured rather than measure other things. But it is with us as if some one else measured us and we came to know how big we are by seeing that he applied the cubit-measure to such and such a fraction of us.
Changes and Matter
Changes are of four kinds-either in respect of the ‘what’ or of the quality or of the quantity or of the place, and change in respect of ‘thisness’ is simple generation and destruction, and change in quantity is increase and diminution, and change in respect of an affection is alteration, and change of place is motion, changes will be from given states into those contrary to them in these several respects.
Now if change proceeds from the contrary, there must be something underlying which changes into the contrary state; for the contraries do not change. Further, something persists, but the contrary does not persist; there is, then, some third thing besides the contraries, viz. the matter. The matter which changes must be capable of both states. And since that which ‘is’ has two senses, we must say that everything changes from that which is potentially to that which is actually. Therefore not only can a thing come to be, incidentally, out of that which is not, but also all things come to be out of that which is, but is potentially, and is not actually. This is the ‘One’ of Anaxagoras, instead of ‘all things were together’-and the ‘Mixture’ of Empedocles and Anaximander and Democritus.
Now all things that change have matter, but different matter; and of eternal things those which are not generable but are movable in space have matter-not matter for generation, however, but for motion from one place to another. It follows that there an infinity of matters, since otherwise why did an infinity of things come to be, and not one thing? For ‘reason’ is one, so that if matter also were one, that must have come to be in actuality which the matter was in potency.
The Unmoved Mover
Movement is continuous in the sense in which time is; for time is either the same thing as movement or an attribute of movement. And there is no continuous movement except movement in place, and of this only that which is circular is continuous.
The same things have always existed (either passing through a cycle of changes or obeying some other law), since nothing can come from nothing, actuality is prior to potency. If there is a constant cycle, something must always remain, acting in the same way. And if there is to be generation and destruction, there must be something else which is always acting in different ways. For it was the cause of eternal uniformity; and something else is the cause of variety, and evidently both together are the cause of eternal variety. This, accordingly, is the character which the motions actually exhibit.
And since that which moves and is moved is intermediate, there is something which moves without being moved, being eternal, substance, and actuality. And the object of desire and the object of thought move in this way; they move without being moved. The primary objects of desire and of thought are the same, viz. the good.