The void is 'not-being,' and no part of 'what is' is a 'not-being,'; for what 'is' in the strict sense of the term is an absolute plenum. This plenum, however, is not 'one': on the contrary, it is a 'many' infinite in number and invisible owing to the minuteness of their bulk.

Every science seeks certain principles and causes for each of its objects—e.g. medicine and gymnastics and each of the other sciences, whether productive or mathematical. For each of these marks off a certain class of things for itself and busies itself about this as about something existing and real—not however qua real; the science that does this is another distinct from these.

A line is not made up of points. ... In the same way, time is not made up parts considered as indivisible 'nows.' Part of Aristotle's reply to Zeno's paradox concerning continuity.

We, on the other hand, must take for granted that the things that exist by nature are, either all or some of them, in motion.

For any two portions of fire, small or great, will exhibit the same ratio of solid to void; but the upward movement of the greater is quicker than that of the less, just as the downward movement of a mass of gold or lead, or of any other body endowed with weight, is quicker in proportion to its size.

Here and elsewhere we shall not obtain the best insight into things until we actually see them growing from the beginning.

He who thus considers things in their first growth and origin ... will obtain the clearest view of them.

Since we think we understand when we know the explanation, and there are four types of explanation (one, what it is to be a thing; one, that if certain things hold it is necessary that this does; another, what initiated the change; and fourth, the aim), all these are proved through the middle term.

The same thing may have all the kinds of causes, e.g. the moving cause of a house is the art or the builder, the final cause is the function it fulfils, the matter is earth and stones, and the form is the definitory formula.