Aristotle, Nicomachean Ethics
H. Rackham, Ed.

and is a means to an end, for instance the process of building a house; and it is perfect when it has effected its end. Hence a motion is perfect either when viewed over the whole time of its duration, or at the moment when its end has been achieved. The several motions occupying portions of the time of the whole are imperfect, and different in kind from the whole and from each other. For instance, in building a temple the fitting together of the stones is a different process from the fluting of a column, and both are different from the construction of the temple as a whole; and whereas the building of the temple is a perfect process, for nothing more is required to achieve the end proposed, laying the foundation and constructing the triglyphs are imperfect processes, since each produces only a part of the design; they are therefore specifically different from the construction of the whole, and it is not possible to lay one's finger on a motion specifically perfect at any moment of the process of building, but only, if at all, in the whole of its duration. [3]

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