But one motion is predicated in many ways; for the one is multifariously predicated. Motion, therefore, is one in genus according to the figures of category: for lation with all lation is one motion in genus; but change, according to quality, differs in genus from lation. And motion is one in species, when being one in genus, it is also in an individual species. Thus, there are differences of colour; and therefore, denigration and dealbation differ in species.. Hence, every dealbation will be the same in species with every dealbation; and every denigration, with every denigration, but not with every dealbation. On this account, dealbation is one motion in species with every dealbation. But if there are certain things, which are at the same time both genera and species; it is manifest that there will be, in a certain respect, one motion in species, but simply, that there will not be one in species; as for instance, discipline, if science is a species of hypolepsis, but the genus of the sciences. Some one, however, may doubt if there is one motion in species, when the same thing is changed from the same to the same; as for instance, one point, from this place to that, again and again. But if there is, circulation will be the same with rectilinear motion; and rolling with walking. Or is it determined that motion is different if that in which it is, is different in species? But the circular is different in species from the right-lined. Thus, therefore, there is one motion both in ganus and species. But the motion is simply one, which is one in essence, and in number. And what a motion of this kind is, will be manifest from division: for there are three things in number, about which we say, there is one motion, viz. that which, and in which, and when. I say that which, because it is necessary that there should be something which is moved; as for instance, man, or gold. And this must be moved in something; as in place, or in passive quality. There must also be when it is moved: for every thing is moved in time. But of these that motion is one in genus or in species, is caused by the thing in which it is moved; but the coherence is the effect of time; and that it is simply one is produced by all these: for that in which the motion is, ought to be one and an individual; as for instance, form. And again, the when; as that the time should be one and uninterrupted. It is also necessary that the thing moved should be one, not according to accident, (as when that which is white becomes black, and Coriscus walks; and Coriscus and that which is white are one, but according to accident) nor according to that which is common: for hvo men may at the same time be cured by the same method of cure, for instance, of an ophthalmy; but this is not one motion simply, but one in species. Suppose, however, that Socrates is changed, in quality, according to the same species of change in quality, but in another time, and again in another; if then it is possible that what is corrupted, may again become one in number, this motion also will be one; but if this is not possible, there will, indeed, be the same motion, but not one motion. There is also a doubt similar to this, whether there is one health essentially, and, in short, whether habits and passions are in essence, in bodies: for the possessors of these appear to be moved and to flow. If, however, the health is one and the same, which was in the morning, and now is, why, when a man recovers the health which he had lost, is not this one and the same in number? For the reason is the same; except that it differs in this; that if two things are, on this account, as one in number, it is also necessary that habits should be one in number; for one energy in number is of one thing in number. But if habit is one, perhaps it may not yet appear to some one, that there is also one energy: for when a man ceases to walk, there is no longer walking; but when he again walks, there will be walking. If, therefore, there is one and the same energy, one and the same thing rnay often perish, and often exist. These doubts, however, are foreign from the present speculation. But since all motion is continued, it is also necessary that the motion which is simply one, should be continued; if all motion is divisible, and if it is continued, it is one: for not every motion can be continuous to every motion; as neither can any thing else, to any thing else; but those things only are continued, whose extremes are one. Extremes, however, do not belong to some things, but not to others, being different in species, and homonymous: for how can the extremity of a line, and of walking, touch each other, or, become one? Motions, therefore, may be coherent, which are neither the same in species, nor in genus: for some one who is running, may immediately have a fever; and lation adheres, like a lamp, from succession; but is not continued: for it is admitted, that the continued is that, the extremes of which are one. So that motions adhere, and are successive, because time is continued; but they are continued, because the extremes of both become one. Hence, it is necessary, that the motion which is simply continued and one, should be the same in species, and of one thing, and in one time. In one time indeed, that a cessation of motion may not intervene; for in a cessation of motion; it is necessary to rest. Between many motions, therefore, and not one motion, there is rest. So that if any motion is stopped by permanency, it is neither one, nor a continued motion: but it is stopped if time intervenes. But that motion, which is not one in species, cannot be called one, though there should not be an intermission of time: for the time indeed is one, but the motion is different in species: for it is necessary that the motion, which is one, should also be one in species; but it is not necessary that this should be simply one. And thus we have shown, what the motion is which is simply one. Farther still, the motion also is said to be one which is perfect, whether it be according to genus or according to species, or according to essence; just as in other things the perfect and the whole are of one thing. Sometimes, however, though motion is imperfect it is said to be one, if it be only continucd. Again, after another manner, besides the modes which have been enumerated, the motion is said to be one which is equable: for the motion which is anomalous, in a certain respect does not appear to be one, but rather that which is equable, as a right line; for the anomalous is divisible. They appear, however, to differ, in the same manner as the more and the less. But in all motion there is either the equable, or the anomalous: for it may be equably varied, and borne along in an equable space, as for instance, in a circle, or a right line: and the like also may be said concerning increase, and diminution. But the difference of the inequability, is at one time in that in which a thing is moved; for it is impossible that motion should be equable upon a magnitude which is not equable; as for instance, the motion in a fractured, or spiral line, or in any other magnitude, every part of which does not accord with every part. But at another time, the inequability, is neither in the where, nor in the when, nor in that to which the motion tends, but in the manner; for sometimes it is defined by swiftness and slowness: for that motion, the celerity of which is the same, is equable; but that, of which the celerity is not the same, is anomalous. Hence, swiftness and slowness are neither species, nor differences of motion, because they are consequent to all motions which are different in species. Hence, neither do gravity and levity, which tend to the same thing, differ in species; as of earth to itself, or of fire to itself. Anomalous motion, therefore, is one because it is continued; but it is less one than equable motion; which, indeed, happens to fractured lation: but the less has always a mixture of the contrary. If, however, every motion which is one may be equable and not equable, motions which do not adhere according to species, cannot be one and continued: for how can the motion be equable, which is composed from change according to quality and lation? for it would be necessary that they should accord.
