In this syllogism the major is evident. An active principle which, like the human soul, can, by immanent operations, assume at pleasure different attitudes towards the term of its action, and which masters the conditions and controls the intensity of its exertions, may perhaps be considered competent to originate actions of opposite kinds.[159] But a being which is destitute [pg 723] of immanent operations, and acts by an inherent necessity of its nature, has no power to modify itself or to alter its intrinsic determination; and its action is so ruled by its intrinsic determination that there is no chance of its being either transmuted into its opposite, or even partially suspended. Now, in a primitive being the principle of activity is nothing else than the simple act which formally determines its nature; and it is plain that wherever there is one simple formal act, there can be only one formal determination to act. And consequently a simple principle of activity which has no immanent operations cannot be the source of two opposite kinds of actions. Bodies and their molecules, on account of their physical composition, contain as many distinct principles of activity as they contain physical components or elements; hence we can easily account for their capability of originating opposite actions by admitting that among those elements some are attractive and others repulsive. But in a primitive element it is impossible to admit of two opposite active principles; for a primitive element is a being entitatively one, having only one essential act, and consequently only one active principle and one intrinsic determination to act. It would therefore be absurd to expect from such an element actions of such an opposite nature as are attraction and repulsion. For evidently, to enable the element to display two opposite powers, two opposite determinations would be necessary. Hence, if the intrinsic determination enables the primitive element to attract, such an element will always attract, and never repel; and if, on the contrary, the intrinsic determination enables the primitive element to repel, such an element will always repel, and never attract. In other terms, the attractive and the repulsive power cannot coexist in the same primitive element.
This conclusion, which affords the only possible basis for the speculations of molecular mechanics, is one of those which mere scientists cannot reach through their empirical and inductive method; but its truth is not less certain for that; it is rather all the more certain, as it is not founded on accidental facts, but on the unchangeable nature of things and the transcendental relation of the principles involved in the constitution of real beings.
Our proposition may be confirmed by reflecting that the change of attraction into repulsion, according to Boscovich, would depend on the diminution of the distance between the agent and the patient. Now, this view is inadmissible. For a change of distance, though necessarily accompanied by a change in the intensity of the action, cannot exercise any influence on the specific nature of the action. The intensity of the action is an accidental thing, and can change without in the [pg 724] least interfering with the nature of the agent; and for this reason it can, and must, depend on distance as a condition implied in the exercise of the active power. But the nature of the action always follows the nature of the substance from which it proceeds. Now, a change of distance does not change the nature of the substance. And accordingly the nature of the action must remain the same, even though the distance be indefinitely diminished.
Moreover, if there were any distance at which the action of a primitive element could change from attractive to repulsive, evidently the element, at such a distance, would be unable to exercise either attraction or repulsion, as Boscovich concedes; and therefore, at such a distance, the material element would have no activity. We may, then, ask: Whence does the attractive power emanate which is to have uncontrolled sway at all greater distances? Does it emanate from any point of space outside the element? Then it would not be the active power of the element, as it would have nothing to do with it. On the other hand, it is obvious that if it emanates from the element, it does not end at a distance from it. For, since the active power is really identical with the formal principle from which the primitive element receives its nature, it is as necessary for the elementary power to reach the very centre of the element as it is for the form to be intrinsically terminated to its matter. Whence it follows that the elementary power of attraction, which prevails at all great distances, must emanate from the very centre of the element. But if so, why shall it not prevail up to that very centre? Is it, forsooth, because in the neighborhood of the centre an opposite principle prevails? Were this the case, the same primitive being would have two formal acts, and it would be two beings and two natures; which is an evident contradiction. As long, therefore, as we adhere to the fundamental doctrine that a primitive being cannot have more than one simple principle of activity, we must admit that a primitive element, if attractive at any distance, is attractive at all molecular distances, and, if repulsive at molecular distances, is repulsive at all distances.
Against the existence of attractive and repulsive powers in distinct primitive elements some objections now and then have been made. It has been said, first, that what we call repulsion is only a result of certain vortical movements of the ether all around the molecules of ponderable bodies. This objection is based on a false supposition. We have already shown that the arbitrary theory of the vortices fails altogether to explain the great phenomenon of universal attraction; and we may easily show that it fails as completely in regard to molecular repulsion. In fact, the centrifugal forces which are developed by vortical movements, and which in this theory are assumed as the cause of the phenomena of molecular resistances, are not active powers. They are components of the vortical movements, and nothing more; that is to say, they do not efficiently produce movements, but are the formal principles of movements already produced. To ascribe to them the molecular resistances and the impenetrability of bodies is, therefore, to admit the effect without the cause.
Secondly, some authors object that the resistance called into play by pressure is not a real action, and [pg 725] requires no efficient repulsive powers. They consider it, according to the vulgar prejudice, as a merely passive resistance; for they imagine that a body, when pressed or impinged on, resists the progress of the obtruding body by its own inert matter, which with its materiality obstructs the way onward. This old explanation is still popular with the great mass of the uninstructed, but is scientifically and philosophically worthless. For whatever causes a real change really acts; now, a body resisting the advance of another body causes a real change in the rate of its movement; therefore a body resisting the advance of another body really acts. Its resistance is therefore active, and not passive; that is, it consists in an exertion of repulsive power, and not in a material obstruction of the path.
Hence what physicists call “force of inertia” is not a passive resistance proceeding from the inertia of matter, but an active exertion of the molecular powers, and has been so called only because, all other things being equal, its intensity is proportional to the mass of the inert body.[160] Evidently, inertia itself cannot resist or check the advance of an impinging body. Nothing but a positive action can do it; for nothing but a positive action can communicate to the advancing body that impetus in the opposite direction which alone is competent to neutralize the impetus of the advance. Physicists know this very well, though many of them, owing to the difficulty of analyzing and expressing certain things with philosophical accuracy, do not always use, in this particular, a very correct language—a thing which, after all, must not surprise us, as one can be well read in physics without necessarily being a profound philosopher.
The third objection is aimed at our argument against Boscovich's theory, in which we have said that attraction and repulsion are actions of opposite kinds. Boscovich, on the contrary, maintains that attraction and repulsion differ only as the greater from the less, and therefore cannot be considered as actions of a different kind. He says: “Both actions are of the same kind; for the one, as compared with the other, is negative; and negative things do not differ in kind from positive ones. That the one, as compared with the other, is negative, is evident from this: that they differ only in direction. That the negative and the positive belong to the same kind is evident from the principle, More and less do not differ in kind. In fact, from the positive, by a continued subtraction or diminution, we obtain first some smaller positive quantities, then zero, and lastly, if we still go on in our subtraction, negative quantities.”[161]
This argument, notwithstanding its speciousness, is not difficult to upset. It is not true, in the first place, that attraction and repulsion differ only in direction; on the contrary, they differ in everything except in direction. Two points A and B being given, there is only one direction from A to B, whether A be attractive or repulsive. If A is attractive, its attraction is directed from A to B; and if A is repulsive, its repulsion is no less directed from A to B. This is quite evident, as the action must in all cases proceed from the agent to [pg 726] the patient. It is evident, therefore, that the two actions must have the same direction. The movements of B will indeed have opposite directions, according as B is attracted or repelled; but this does not show that the actions themselves have opposite directions; it shows, on the contrary, that those actions, though directed in the same manner from A to B, are of a different nature, and proceed from opposite principles. And this conclusion may be confirmed by remarking that the direction is always from a point to a point, or from matter to matter; and consequently it is not the active power or the action, but only the position of the material centres, that can determine any direction. Accordingly, so long as such a position is not inverted, it is impossible to conceive two opposite directions from A to B. It is therefore evidently false that attraction and repulsion differ in direction.
It is not true, in the second place, that attraction and repulsion differ only as the positive differs from the negative, or the greater from the less. In the mathematical expression of mechanical relations, if we consider a movement as positive, the movement which points to an opposite direction must, of course, be affected by the negative sign. The same we must do with regard to forces and actions; for we estimate the actions by the movements which they produce, and we express them only in terms of movement—that is, by their effects. But this does not mean that there is either any movement or any action absolutely negative; for a negative movement would be no movement, and a negative action no action. It is in a relative and conventional sense only that movements are considered as positive or negative; and, moreover, either of the two opposite movements can be assumed as positive or as negative, at will; which shows very clearly that the negative and the positive do not differ in this case as the greater differs from the less, as Boscovich assumes; for either of the two can, at pleasure, be taken as positive, whereas it would be absurd to pretend that either of the two can, at pleasure, be pronounced to be the greater. Thus, when a stone is thrown up vertically, and abandoned to itself, if its ascent is taken as positive, its descent will be considered as negative. Now, according to Boscovich's reasoning, we should infer that the ascent is greater than the descent, though they are evidently equal. And in the same manner, if the ascent is taken as negative (which nothing forbids), the descent must be taken as positive; whence, according to Boscovich, we ought to infer also that the descent is greater than the ascent. Any argument which leads to such glaring contradictions must be radically false. And therefore it is false that attraction and repulsion differ from one another as the greater from the less.