Introduction (from the Internet Encyclopaedia of Philosophy)

Aristotle’s Metaphysics is a difficult book, partly because of the language used, and the different translations offered.  It is recommended that you start by reading this introduction from the Internet Encylopaedia of Philosophy, part of which is reproduced below.  PB

All that is left in Aristotle’s array of possibilities is the unity of that of which the thinking or the knowing is one.

This thread of the investigation, which we may call for convenience the biological one, converges in Book 12 with a cosmological one. The animal and plant species take care of their own perpetuation by way of generation, but what the parents pass on to the offspring is an identity which must hold together thanks to a timeless activity of thinking. The cosmos holds together in a different way: it seems to be literally and directly eternal by way of a ceaseless repetition of patterns of locomotion. An eternal motion cannot result from some other motion, but must have an eternal, unchanging cause. Again, Aristotle lays out all the possibilities. What can cause a motion without undergoing a motion? A thing desired can, and so can a thing thought. Can you think of a third?

Aristotle says that there are only these two, and that, moreover, the first reduces to the second. When I desire an apple it is the fleshy apple and not the thought of it toward which I move, but it is the thought or imagining of the fleshy apple that moves me toward the apple. The desired object causes motion only as an object of thought. Just as the only candidate left to be the source of unity of form among the animals and plants was the activity of thinking, so again the only possible unmoved source for the endless circlings of the stars is an eternal activity of thinking. Because it is deathless and because the heavens and nature and all that is depend upon it, Aristotle calls this activity God. Because it is always altogether at work, nothing that is thought by it is ever outside or apart from it: it is of thinking, simply. Again, because it is always altogether at work, nothing of it is ever left over outside of or apart from its work of thinking: it is thinking, simply. It is the pure holding-together of the pure holdable-together, activity active, causality caused. The world is, in all its being most deeply, and in its deepest being wholly, intelligible.

So far is Aristotle from simply assuming the intelligibility of things, that he requires twelve books of argument to account for it. All being is dependent on the being of things; among things, the artificial are derived from the natural; because there is a cosmos, all natural things have being as living things; because all living things depend on either a species-identity or an eternal locomotion, there must be a self-subsisting activity of thinking.

[1069a] [18] The first two kinds of substance are sensible and immutable

Our inquiry is concerned with substance; for it is the principles and causes of substances that we are investigating. Indeed if the universe is to be regarded as a whole,  substance is its first part; and if it is to be regarded as a succession, even so substance is first, then quality, then quantity. Moreover, the latter hardly exist at all in the full sense, but are merely qualifications and affections of Being. Otherwise “not-white” and “not-straight” would also exist; at any rate we say that they too “are,” e.g., “it is not white.” Further, none of the other categories is separately existent. Even the ancients in effect testify to this, for it was of substance that they sought the principles and elements and causes. Present-day thinkers tend to regard universals as substance, because genera are universal, and they hold that these are more truly principles and substances because they approach the question theoretically; but the ancients identified substance with particular things, e.g. fire and earth, and not with body in general.

Now there are three kinds of substance. One is sensible (and may be either eternal or perishable; the latter, e.g. plants and animals, is universally recognized); of this we must apprehend the elements, whether they are one or many. Another is immutable , which certain thinkers hold to exist separately; some dividing it into two classes, others combining the Forms and the objects of mathematics into a single class, and others recognizing only the objects of mathematics as of this nature. The first two kinds of substance come within the scope of physics, since they involve motion;