The first of our present conclusions needs only a short explanation. When we say that in every creature there is a motive power which, considered in its absolute state, has no need of producing a momentum, we mean that in every creature there is an act which is a principle of activity, but that the exercise of this activity is not required for the substantial perfection and essential constitution of the creature itself, though it may be required for some other reason, as we shall see presently. In fact, every substance has its own complete being independently of accidents; and since the exertion of motive power is an accident, every substance is entitatively independent of it. We conceive that if God had created nothing but an element of matter, such an element would indeed (on its own part) be ready to act and to produce a momentum of movement; but, as there would be no subject capable of receiving a momentum, the motive power would remain in actu primo—that is, without actual exertion. And yet it is evident that the non-existence of other elements can have no bearing on the intrinsic constitution and substantial perfection of the element in the question. Therefore the power of an element of matter is a first act, which, as far as the entity of the element itself is concerned, has no need of producing any second act.
Nevertheless, since all creatures must in some manner glorify God as long as they exist, because such is the true and highest end of their existence, hence to every created power some proportionate term or subject corresponds, in which its exertion is received without interruption. In the same manner as the understanding never lacks an intelligible object, and the sense never lacks a sensible term, about which to exercise itself by immanent operation, the motive power of inferior beings never fails to meet a proportionate—that is, movable—term and to impress upon it a momentum of a certain intensity. Hence, when we regard, not the substance of natural things as such, but the natural necessity they are under of tending constantly to the ultimate end of their creation, we see that their first act of moving must always entail some second act, or momentum, in all the terms which it can reach according to its natural determination.
The second conclusion is self-evident; for, if the principle of real movement were not an objective reality, a real effect would proceed from an unreal cause—which is absurd. Nor does it matter that the power is only a “first” act. For, as we have explained above, it is first as compared with the acts which it can produce, but it is intrinsically complete in the entity of the agent, as it is terminated to its substantial term.
The third conclusion is nothing but a corollary of the well-known axiom that in all things the principle of operation is the substantial act: Forma est id quo agens agit, and Principium essendi est principium operandi. We have proved in another place[156] that no natural accident possesses active power or is actually concerned in any of the effects produced by the agent. This truth should be well understood by the modern scientists who very commonly mistake the conditions of the action for the active principle. Of course no creature can act independently of accidental conditions; but these conditions have no bearing on the active power itself—they only determine (formally and not efficiently) the mode of its application according to a constant law. Thus the distance of two material points has no active influence on their motive power or on their mutual action, but only constitutes the two points in a certain relation to one another; and when such a relation is altered, the action is changed, not because the power is modified, but because its determination to act—that is, its very nature—demands that it should in its application follow the Newtonian law of the inverse ratio of the squared distances.
The philosophers of the old school admitted, but never proved, that, although the substantial form is the main principle of activity in natural things, nevertheless this principle was in need of some accidental entity, that it might be proximately disposed to produce its act. This opinion, too, originated in the confusion of active power with the conditions on which the mode of its exertion depends. What they called “active qualities” is now acknowledged to be, not a new kind of active power superadded to the substantial forms, but merely a result of the concurrence of many simple powers acting under determinate conditions. The accidental change of the conditions entails the change of the result and action, but the active powers evidently remain the same. The ancients said also that the substantial forms were the active principles of substantial generations, whereas the “active qualities” were the active principles of mere alterations. As we have shown that the whole theory of substantial generations, as understood by the peripatetic school, is based on assumption and equivocation, and leads to impossibilities,[157] we may be dispensed from giving a new refutation of the opinion last mentioned.
Our fourth conclusion directly follows from the general principle that the act by which a thing has its first being is its principle of action: Quo aliquid primo est, eo agit. The substantial act, considered as to its absolute entity, does not connote action, but simply constitutes the being of which it is the act. In order to conceive it as an active power, we must refer to the effects which it virtually contains—that is, we must consider its virtuality. In this manner what is a second act with regard to the substance of the agent, will be conceived as a first act with reference to the effects it can produce, according to a received axiom: Actus secundus essendi est actus primus operandi.
The fifth conclusion, notwithstanding the contrary opinion of many philosophers, is quite certain. For all intrinsic modification is the result of passive reception or passion. Now, to produce a momentum of movement is action, not passion. Therefore, when such a momentum is produced, no other subject is intrinsically modified by it except the one which passively receives it. It is therefore the being which is acted on, not that which acts, that acquires an intrinsic modification. The power of the agent is not entitatively and intrinsically more actuated by action than by non-action. Its action is an extrinsic termination, and gives it nothing but the real denomination of agent, by which it is really related to the term acted on. The patient, by its reception of the momentum, becomes similarly related to the agent, as is evident. And the relation consists in this: that the patient acquires formally an act which the agent virtually contains. This relation is of accidental causality on the one side and of accidental dependence on the other. The foundation of the relation is the accidental action as coming from the one and terminating in the other.
As everything that is in movement must have received the motion from a distinct agent, according to the principle Omne quod movetur, ab alio movetur, it follows that whatever is in movement is accidentally dependent on an extrinsic mover; and, since all material elements are both movers and moved, they all have a mutual accidental causality and dependence.
Our sixth conclusion is sufficiently clear from what has been said concerning the sixth conclusion of the preceding series. The momentum of movement is evidently the second act of the motive power—that is, the extrinsic term of its exertion. The entitative distance between two momentums produced by the same mover is an extrinsic relation; for its foundation is the virtuality of the act by which the agent is, as has been explained above. But the same momentums, as possessing greater or less intensity, can also be compared with one another according to their intrinsic entity or degree; and thus they will be found to have a mutual relation arising from an intrinsic foundation.