“Being” means (1.) accidental being, (2.) absolute being. (1.) E.g., we say that the upright person “is” cultured, and that the man “is” cultured, and that the cultured person “is” a man; very much as we say that the cultured person builds, because the builder happens to be cultured, or the cultured person a builder; for in this sense “X is Y” means that Y is an accident of X. And so it is with the examples cited above; for when we say that “the man is cultured” and “the cultured person is a man” or “the white is cultured” or “the cultured is white,” in the last two cases it is because both predicates are accidental to the same subject, and in the first case because the predicate is accidental to what is ; and we say that “the cultured is a man” because “the cultured” is accidental to a man. (Similarly “not-white” is said to “be,” because the subject of which “not-white” is an accident, is .) These, then, are the senses in which things are said to “be” accidentally: either because both predicates belong to the same subject, which is ; or because the predicate belongs to the subject, which is ; or because the subject to which belongs that of which it is itself predicated itself is . (2.) The senses of essential being are those which are indicated by the figures of predication¹; for “being” has as many senses as there are ways of predication. Now since some predicates indicate (a) what a thing is, and others its (b) quality, (c) quantity, (d) relation, (e) activity or passivity, (f) place, (g) time, to each of these corresponds a sense of “being.” There is no difference between “the man is recovering” and “the man recovers”; or between “the man is walking” or “cutting” and “the man walks” or “cuts”; and similarly in the other cases. (3.) Again, “to be” and “is” mean that a thing is true, and “not to be” that it is false. Similarly too in affirmation and negation; e.g., in “ Socrates is cultured” “is” means that this is true; or in “Socrates is not-white” that this is true; but in “the diagonal is not commensurable”²“is not” means that the statement is false. 1017b(4.) Again, “to be” 〈or “is”〉 means that some of these statements can be made in virtue of a potentiality and others in virtue of an actuality. For we say that both that which sees potentially and that which sees actually is “a seeing thing.” And in the same way we call “understanding” both that which can use the understanding, and that which does ; and we call “tranquil” both that in which tranquillity is already present, and that which is potentially tranquil. Similarly too in the case of substances. For we say that Hermes is in the stone,³ and the half of the line in the whole; and we call “corn” what is not yet ripe. But when a thing is potentially existent and when not, must be defined elsewhere.⁴

“Substance” means (a) simple bodies, e.g. earth, fire, water and the like; and in general bodies, and the things, animal or divine, including their parts, which are composed of bodies. All these are called substances because they are not predicated of any substrate, but other things are predicated of them. (b) In another sense, whatever, being immanent in such things as are not predicated of a substrate, is the cause of their being; as, e.g., the soul is the cause of being for the animal. (c) All parts immanent in things which define and indicate their individuality, and whose destruction causes the destruction of the whole; as, e.g., the plane is essential to the body (as some⁵ hold) and the line to the plane. And number in general is thought by some⁶ to be of this nature, on the ground that if it is abolished nothing exists, and that it determines everything. (d) Again, the essence , whose formula is the definition, is also called the substance of each particular thing. Thus it follows that “substance” has two senses: the ultimate subject, which cannot be further predicated of something else; and whatever has an individual and separate existence. The shape and form of each particular thing is of this nature.

“The same” means (a) accidentally the same. E.g., “white” and “cultured” are the same because they are accidents of the same subject; and “man” is the same as “cultured,” because one is an accident of the other; and “cultured” is the same as “man” because it is an accident of “man”; and “cultured man” is the same as each of the terms “cultured” and “man,” and vice versa; for both “man” and “cultured” are used in the same way as “cultured man,” and the latter in the same way as the former. Hence none of these predications can be made universally. For it is not true to say that every man is the same as “the cultured”; because universal predications are essential to things, 1018abut accidental predications are not so, but are made of individuals and with a single application. “ Socrates” and “cultured Socrates” seem to be the same; but “ Socrates” is not a class-name, and hence we do not say “every Socrates” as we say “every man.” Some things are said to be “the same” in this sense, but (b) others in an essential sense, in the same number of senses as “the one” is essentially one; for things whose matter is formally or numerically one, and things whose substance is one, are said to be the same. Thus “sameness” is clearly a kind of unity in the being, either of two or more things, or of one thing treated as more than one; as, e.g., when a thing is consistent with itself; for it is then treated as two. Things are called “other” of which either the forms or the matter or the definition of essence is more than one; and in general “other” is used in the opposite senses to “same.” Things are called “different” which, while being in a sense the same, are “other” not only numerically, but formally or generically or analogically; also things whose genus is not the same; and contraries; and all things which contain “otherness” in their essence. Things are called “like” which have the same attributes in all respects; or more of those attributes the same than different; or whose quality is one. Also that which has a majority or the more important of those attributes of something else in respect of which change is possible (i.e. the contraries) is like that thing. And “unlike” is used in the opposite senses to “like.”

The term “opposite” is applied to (a) contradiction; (b) contraries; (c) relative terms; (d) privation; (e) state; (f) extremes; e.g. in the process of generation and destruction. And (g) all things which cannot be present at the same time in that which admits of them both are called opposites; either themselves or their constituents. “Grey” and “white” do not apply at the same time to the same thing, and hence their constituents are opposite. “Contrary” means: (a) attributes, generically different, which cannot apply at the same time to the same thing. (b) The most different attributes in the same genus; or (c) in the same subject; or (d) falling under the same faculty. (e) Things whose difference is greatest absolutely, or in genus, or in species. Other things are called “contrary” either because they possess attributes of this kind, or because they are receptive of them, or because they are productive of or liable to them, or actually produce or incur them, or are rejections or acquisitions or possessions or privations of such attributes. And since “one” and “being” have various meanings, all other terms which are used in relation to “one” and “being” must vary in meaning with them; and so “same,” “other” and “contrary” must so vary, and so must have a separate meaning in accordance with each category. Things are called “other in species” (a) which belong to the same genus and are not subordinate one to the other; 1018bor (b) which are in the same genus and contain a differentia; or (c) which contain a contrariety in their essence. (d) Contraries, too (either all of them or those which are called so in a primary sense), are “other in species” than one another; and (e) so are all things of which the formulae are different in the final species of the genus (e.g., “man” and “horse” are generically indivisible, but their formulae are different); and (f) attributes of the same substance which contain a difference. “The same in species” has the opposite meanings to these.

“Prior” and “posterior” mean: (1.) (a) In one sense (assuming that there is in each genus some primary thing or starting-point) that which is nearer to some starting-point, determined either absolutely and naturally, or relatively, or locally, or by some agency; e.g., things are prior in space because they are nearer either to some place naturally determined, such as the middle or the extreme, or to some chance relation; and that which is further is posterior. (b) In another sense, prior or posterior in time . Some things are prior as being further from the present, as in the case of past events (for the Trojan is prior to the Persian war, because it is further distant from the present); and others as being nearer the present, as in the case of future events (for the Nemean are prior to the Pythian games because they are nearer to the present, regarded as a starting-point and as primary). (c) In another sense, in respect of motion (for that which is nearer to the prime mover is prior; e.g., the boy is prior to the man). This too is a kind of starting point in an absolute sense. (d) In respect of potency; for that which is superior in potency, or more potent, is prior. Such is that in accordance with whose will the other, or posterior, thing must follow, so that according as the former moves or does not move, the latter is or is not moved. And the will is a “starting-point.” (e) In respect of order; such are all things which are systematically arranged in relation to some one determinate object. E.g., he who is next to the leader of the chorus is prior to him who is next but one, and the seventh string is prior to the eighth⁷; for in one case the leader is the starting-point, and in the other the middle⁸ string. In these examples “prior” has this sense; but (2.) in another sense that which is prior in knowledge is treated as absolutely prior; and of things which are prior in this sense the prior in formula are different from the prior in perception . Universals are prior in formula, but particulars in perception. And in formula the attribute is prior to the concrete whole: e.g. “cultured” to “the cultured man”; for the formula will not be a whole without the part. Yet “cultured” cannot exist apart from some cultured person. Again, (3.) attributes of prior subjects are called prior; e.g., straightness is prior to smoothness, 1019abecause the former is an attribute of the line in itself, and the latter of a surface. Some things, then, are called prior and posterior in this sense; but others (iv.) in virtue of their nature and substance, namely all things which can exist apart from other things, whereas other things cannot exist without them. This distinction was used by Plato.⁹(And since “being” has various meanings, (a) the substrate, and therefore substance, is prior; (b) potential priority is different from actual priority. Some things are prior potentially, and some actually; e.g., potentially the half-line is prior to the whole, or the part to the whole, or the matter to the substance; but actually it is posterior, because it is only upon dissolution that it will actually exist.) Indeed, in a sense all things which are called “prior” or “posterior” are so called in this connection; for some things can exist apart from others in generation (e.g. the whole without the parts), and others in destruction (e.g. the parts without the whole). And similarly with the other examples.