Metaphysics is one of the principal works of Aristotle and the first major work of the branch of philosophy with the same name. The principal subject is "being qua being", or being understood as being. It examines what can be asserted about anything that exists just because of its existence and not because of any special qualities it has. Also covered are different kinds of causation, form and matter, the existence of mathematical objects, and a prime-mover God.

Book X Chapter 72015-04-29
Since contraries admit of an intermediate and in some cases have it, intermediates must be composed of the contraries. For (1) all intermediates are in the same genus as the things between which they stand. For we call those things intermediates, into which that which changes must change first; e. g.
Book X Chapter 82015-04-29
That which is other in species is other than something in something, and this must belong to both; e. g. If it is an animal other in species, both are animals. The things, then, which are other in species must be in the same genus. For by genus I mean that one identical thing which is predicated of b
Book X Chapter 92015-04-28
One might raise the question, why woman does not differ from man in species, when female and male are contrary and their difference is a contrariety; and why a female and a male animal are not different in species, though this difference belongs to animal in virtue of its own nature, and not as pale
Book X Chapter 102015-04-28
Since contraries are other in form, and the perishable and the imperishable are contraries (for privation is a determinate incapacity), the perishable and the imperishable must be different in kind. Now so far we have spoken of the general terms themselves, so that it might be thought not to be neces
Book XI Chapter 12015-04-27
THAT Wisdom is a science of first principles is evident from the introductory chapters, in which we have raised objections to the statements of others about the first principles; but one might ask the question whether Wisdom is to be conceived as one science or as several. If as one, it may be objec
Book XI Chapter 22015-04-27
Further, must we suppose something apart from individual things, or is it these that the science we are seeking treats of? But these are infinite in number. Yet the things that are apart from the individuals are genera or species; but the science we now seek treats of neither of these. The reason wh
Book XI Chapter 32015-04-26
Since the science of the philosopher treats of being qua being universally and not in respect of a part of it, and being has many senses and is not used in one only, it follows that if the word is used equivocally and in virtue of nothing common to its various uses, being does not fall
Book XI Chapter 42015-04-26
Since even the mathematician uses the common axioms only in a special application, it must be the business of first philosophy to examine the principles of mathematics also. That when equals are taken from equals the remainders are equal, is common to all quantities, but mathematics studies a part o
Book XI Chapter 52015-04-25
There is a principle in things, about which we cannot be deceived, but must always, on the contrary recognize the truth,-viz. that the same thing cannot at one and the same time be and not be, or admit any other similar pair of opposites. About such matters there is no proof in the full sense, thoug
Book XI Chapter 62015-04-25
The saying of Protagoras is like the views we have mentioned; he said that man is the measure of all things, meaning simply that that which seems to each man also assuredly is. If this is so, it follows that the same thing both is and is not, and is bad and good, and that the contents of all other o
Book XI Chapter 72015-04-24
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 rea
Book XI Chapter 82015-04-24
Since being in general has several senses, of which one is being by accident, we must consider first that which is in this sense. Evidently none of the traditional sciences busies itself about the accidental. For neither does architecture consider what will
Book XI Chapter 92015-04-23
Some things are only actually, some potentially, some potentially and actually, what they are, viz. In one case a particular reality, in another, characterized by a particular quantity, or the like. There is no movement apart from things; for change is always according to the categories of being, an
Book XI Chapter 102015-04-23
The infinite is either that which is incapable of being traversed because it is not its nature to be traversed (this corresponds to the sense in which the voice is invisible), or that which admits only of incomplete traverse or scarcely admits of traverse, or that which, though it natu
Book XI Chapter 112015-04-22
Of things which change, some change in an accidental sense, like that in which the musical may be said to walk, and others are said, without qualification, to change, because something in them changes, i. e. the things that change in parts; the body becomes healthy, because the eye does
Book XI Chapter 122015-04-22
If the categories are classified as substance, quality, place, acting or being acted on, relation, quantity, there must be three kinds of movement-of quality, of quantity, of place. There is no movement in respect of substance (because there is nothing contrary to substance), nor of relation (for it
Book XII Chapter 12015-04-21
The subject of our inquiry is substance; for the principles and the causes we are seeking are those of substances. For if the universe is of the nature of a whole, substance is its first part; and if it coheres merely by virtue of serial succession, on this view also substance is first, and is succe
Book XII Chapter 22015-04-21
Sensible substance is changeable. Now if change proceeds from opposites or from intermediates, and not from all opposites (for the voice is not-white, (but it does not therefore change to white)), but from the contrary, there must be something underlying which changes into the contrary state; for th
Book XII Chapter 32015-04-20
Note, next, that neither the matter nor the form comes to be-and I mean the last matter and form. For everything that changes is something and is changed by something and into something. That by which it is changed is the immediate mover; that which is changed, the matter; that into which it is chan
Book XII Chapter 42015-04-20
The causes and the principles of different things are in a sense different, but in a sense, if one speaks universally and analogically, they are the same for all. For one might raise the question whether the principles and elements are different or the same for substances and for relative terms, and
Book XII Chapter 52015-04-19
Some things can exist apart and some cannot, and it is the former that are substances. And therefore all things have the same causes, because, without substances, modifications and movements do not exist. Further, these causes will probably be soul and body, or reason and desire and body. And in yet
Book XII Chapter 62015-04-19
Since there were three kinds of substance, two of them physical and one unmovable, regarding the latter we must assert that it is necessary that there should be an eternal unmovable substance. For substances are the first of existing things, and if they are all destructible, all things are destructi
Book XII Chapter 72015-04-18
Since (1) this is a possible account of the matter, and (2) if it were not true, the world would have proceeded out of night and all things together and out of non-being, these difficulties may be taken as solved. There is, then, something which is always moved with an unceasing motion
Book XII Chapter 82015-04-18
It is clear, then, why these things are as they are. But we must not ignore the question whether we have to suppose one such substance or more than one, and if the latter, how many; we must also mention, regarding the opinions expressed by others, that they have said nothing about the number of the
Book XII Chapter 92015-04-17
The nature of the divine thought involves certain problems; for while thought is held to be the most divine of things observed by us, the question how it must be situated in order to have that character involves difficulties. For if it thinks of nothing, what is there here of dignity? It is just lik