whatever it may be, of a spatial magnitude or of a thing that has magnitude, and to the end of each thing (and of this nature is that towards which the movement and the action are not that from which they are, though sometimes it is both, that from which and that to which the movement is and that for the sake of which), and to the substance of each thing, and the essence of each; for this is the limit of knowledge; and if of knowledge, of the thing also.