Aristotle, Nicomachean Ethics
H. Rackham, Ed.

And the same is true of walking and the other forms of locomotion. For if locomotion is motion from one point in space to another, and if this is of different kinds, flying, walking, leaping and the like, and not only so, but if there are also differences in walking itself （for the terminal points of a race course are not the same as those of a portion of the course, nor are those of one portion the same as those of another; nor is traversing this line the same as traversing that one,¹ for the runner does not merely travel along a certain line but travels along a line that is in a certain place, and this line is in a different place from that）—however, for a full treatment of the subject of motion I must refer to another work,² but it appears that a motion is not perfect at every moment, but the many movements which make up the whole are imperfect; and different from each other in kind, inasmuch as the terminal points of a movement constitute a specific quality.