and an object moved; if such a cause is present the motor in that compound sets the other element in motion; in the absence of such a cause no motion takes place. Living beings do therefore not move continually, although each of them possesses an indivisible motive element; because this element is not constantly in motion, as it would be if it produced motion of its own accord. On the contrary, the things to which the action is due are separate from the motor. The action is caused either by desire for that which is agreeable, or by aversion from that which is disagreeable, or by some image, or by some ideal when the moving being has the capacity of conceiving it. When any of these causes are present then the motor acts; its motion is accidental, and must therefore come to an end (Prop. VIII.). If the motor of the sphere were of this kind the sphere could not move ad infinitum. Our opponent, however, holds that the spheres move continually ad infinitum; if this were the case, and it is in fact possible (Prop. XIII.), the efficient cause of the motion of the sphere must, according to the above division, be of the second kind, viz., something incorporeal and separate from the sphere.
It may thus be considered as proved that the efficient cause of the motion of the sphere, if that motion be eternal, is neither itself corporeal nor does it reside in a corporeal object; it must move neither of its own accord nor accidentally; it must be indivisible and unchangeable (Prop. VII. and Prop. V.). This Prime Motor of the sphere is God, praised be His name!
The hypothesis that there exist two Gods is inadmissible, because absolutely incorporeal beings cannot be counted (Prop. XVI.), except as cause and effect; the relation of time is not applicable to God (Prop. XV.), because motion cannot be predicated of Him.
The result of the above argument is consequently this: the sphere cannot move ad infinitum of its own accord; the Prime Motor is not corporeal, nor a force residing within a body; it is One, unchangeable, and in its existence independent of time. Three of our postulates are thus proved by the principal philosophers.
The philosophers employ besides another argument, based on the following proposition of Aristotle. If there be a thing composed of two elements, and the one of them is known to exist also by itself, apart from that thing, then the other element is likewise found in existence by itself separate from that compound. For if the nature of the two elements were such that they could only exist together – as, e.g., matter and form – then neither of them could in any way exist separate from the other. The fact that the one component is found also in a separate existence proves that the two elements are not indissolubly connected, and that the same must therefore be the case with the other component. Thus we infer from the existence of honey-vinegar and of honey by itself, that there exists also vinegar by itself. After having explained this proposition Aristotle continues thus: We notice many objects consisting of a motor and a motum, i.e., objects which set other things in motion, and whilst doing so are themselves set in motion by other things; such is clearly the case as regards all the middle members of a series of things in motion. We also see a thing that is moved, but does not itself move anything, viz., the last member of the series: consequently a motor must exist without being at the same time a motum, and that is the Prime Motor, which,
