their motion. Thus, when his hand is moved, all its parts move, together with whatever is on it, such as a ring, and whatever is attached to it, such as a sleeve. These therefore follow the same rule as a continuous body when it moves. When one motion is separate from another, as when one foot moves before the other, temporal precedence is observable because of that separation. Where there is continuity, however, what is contiguous may be confused with what is simultaneous. In that case, any motion arising from what is continuous is contiguous with what precedes it, just as the successive portions of the time occupied by the motion are contiguous. There is therefore no simultaneity here.
If it is said concerning the sleeve’s motion, “It occurs at the same time as the hand’s motion,” as is likewise said of other things moving simultaneously, we do not concede that one of the two motions produces the other. At most, it is a condition for the other. A condition may coincide with what depends upon it, unlike an agent, which must precede the particular act it produces—even if action as a kind is assumed to be inseparable from it.
For example, if we suppose an eternal moving entity that has always been in motion, it will precede every individual portion of that motion. No portion of the motion will be coeval with the existence of the entity itself, even though motion as a kind is inseparable from it. Thus, whoever allows the existence of an eternal body that has always been moving does not say, “A particular motion is eternal.” Rather, he says, “Motion as a kind is eternal,” even though each individual motion comes into existence after not existing and is preceded by nonexistence.
Those who philosophize and maintain that something in the world is eternal have no evidence whatsoever for this. At most, their arguments establish the eternity of action as a kind. Yet the eternity of action as a kind does not entail the eternity of any particular act or any particular thing produced by an act. Rather, that is impossible.