The claim of Motion to be established as a genus will depend upon three conditions: first, that it cannot rightly be referred to any other genus; second, that nothing higher than itself can be predicated of it in respect of its essence; third, that by assuming differences it will produce species. These conditions satisfied, we may consider the nature of the genus to which we shall refer it. Clearly it cannot be identified with either the Substance or the Quality of the things which possess it. It cannot, further, be consigned to Action, for Passivity also comprises a variety of motions; nor again to Passivity itself, because many motions are actions: on the contrary, actions and passions are to be referred to Motion. Furthermore, it cannot lay claim to the category of Relation on the mere ground that it has an attributive and not a self-centred existence: on this ground, Quality too would find itself in that same category; for Quality is an attribute and contained in an external: and the same is true of Quantity. If we are agreed that Quality and Quantity, though attributive, are real entities, and on the basis of this reality distinguishable as Quality and Quantity respectively: then, on the same principle, since Motion, though an attribute has a reality prior to its attribution, it is incumbent upon us to discover the intrinsic nature of this reality. We must never be content to regard as a relative something which exists prior to its attribution, but only that which is engendered by Relation and has no existence apart from the relation to which it owes its name: the double, strictly so called, takes birth and actuality in juxtaposition with a yard's length, and by this very process of being juxtaposed with a correlative acquires the name and exhibits the fact of being double. What, then, is that entity, called Motion, which, though attributive, has an independent reality, which makes its attribution possible- the entity corresponding to Quality, Quantity and Substance? But first, perhaps, we should make sure that there is nothing prior to Motion and predicated of it as its genus. Change may be suggested as a prior. But, in the first place, either it is identical with Motion, or else, if change be claimed as a genus, it will stand distinct from the genera so far considered: secondly, Motion will evidently take rank as a species and have some other species opposed to it- becoming, say- which will be regarded as a change but not as a motion. What, then, is the ground for denying that becoming is a motion? The fact, perhaps, that what comes to be does not yet exist, whereas Motion has no dealings with the non-existent. But, on that ground, becoming will not be a change either. If however it be alleged that becoming is merely a type of alteration or growth since it takes place when things alter and grow, the antecedents of becoming are being confused with becoming itself. Yet becoming, entailing as it does these antecedents, must necessarily be a distinct species; for the event and process of becoming cannot be identified with merely passive alteration, like turning hot or white: it is possible for the antecedents to take place without becoming as such being accomplished, except in so far as the actual alteration has "come to be"; where, however, an animal or a vegetal life is concerned, becoming takes place only upon its acquisition of a Form. The contrary might be maintained: that change is more plausibly ranked as a species than is Motion, because change signifies merely the substitution of one thing for another, whereas Motion involves also the removal of a thing from the place to which it belongs, as is shown by locomotion. Even rejecting this distinction, we must accept as types of Motion knowledge and musical performance- in short, changes of condition: thus, alteration will come to be regarded as a species of Motion- namely, motion displacing.

Hence you inquire concerning the difference in the last things pertaining to them; but you leave uninvestigated such things as are first, and most hon...

Now in definitions, difference is assumed, which, in the definition, occupies the place of sign. The faculty of laughing, accordingly, being added to...

And of things without life, plants, they say, are moved by transposition in order to growth, if we will concede to them that plants are without life. ...

With respect to your inquiry, “ what the peculiarities are in each of the more excellent genera, by which they are separated from each other? ” if...

To which may be added, that it is dreadfully absurd to ascribe to bodies a principal power of giving a specific distinction to the first causes of the...

The genera of all things company with their own species; so that the genus is a class in its entirety, the species is part of a genus. The genus of th...

We divide, therefore, the genus of what is proposed for consideration into the species contained in it; as, in the case of man, we divide animal,...

For each of the species is either an essence; as when we say, Some substances are corporeal and some incorporeal; or how much, or what relation, or wh...

And then the name animal was reduced to definition, for the sake of perspicuity. But having discovered that it is distinguished from what is not an an...

Accordingly, while the definition is explanatory of the essence of the thing, it is incapable of accurately comprehending its nature. By means of the...

Accordingly we must first take the genus, in which are the points that are nearest those above; and after this the next difference. And the...

Of things stated, some are stated without connection; as, for example, "man" and "runs," and whatever does not complete a sentence, which is either...

Of this I'll give thee here on earth an instance, which the eye can see. Regard the animals down here - a man, for instance, swimming! The water...

After the body of the universe, also, many things are generated by the nature of it. For the concord of similars, and the contrariety of dissimilars,...

Besides, in addition to these ten human parts, the law appear to give its injunctions to sight, and hearing, and Smell, and touch, and taste, and to...

For these reasons are forms , and being simple and uniform, they receive no perturbation in themselves, and no departure from their proper mode of sub...

Now every single class of living thing, Asclepius, of whatsoever kind, or it be mortal or be rational, whether it be endowed with soul, or be without...

This little chapter is not without its special difficulty. Are we to read as a word implying motion, with as its determinative, or as implying...

These, also, may now be divided according to the difference of commixture. For mundane vapours are mingled with dæmons, and are unstably borne along,...

It is, necessary, however, to discuss these things particularly, and to show how they subsist, and what reason they possess. It is requisite,...