Whose wishes to describe anything whatsoever before proceeding to establish first its reality of existence, such a one is counted by the wise among those who deviate from the broad beaten track of perspicuous statement. It is incumbent upon us, therefore, to first set to work to establish the existence of the spiritual powers, before starting to define each one of them singly, and enlarge upon it. And whereas the most peculiar characteristics of spiritual properties are two—one of them Setting in Motion (Impulsion), and the other Perception—it is incumbent upon us to show that to every moving body there is a [A] moving cause (ground, reason, motive, pretence). Then it will become evident to us therefrom that bodies moving in motions over and above the natural motions—an example of natural motions is the sinking of the heavy, and the rising of the light—have moving [B] causes, which we call souls or spiritual powers; and that we further show that any body, in so far as it shows signs (traces) that it is perceptive, such perception by it cannot be validly ascribed to its body, except because of powers (faculties) in it that are capable of perception.