The Catholic World, Vol. 19, April 1874‐September 1874

by Various

The Catholic World. Vol. XIX., No. 114.—September, 1874.

Matter.

II.

The activity displayed by matter in the production of natural phenomena is twofold, viz., attractive and repulsive; and the question has been raised whether these two kinds of activity can reside in one and the same subject, or, owing to their opposite nature, require separate subjects. With regard to molecules, it is quite certain, though some have thought otherwise, that in all ponderable bodies each molecule is in possession of both powers; but with regard to the primitive elements which enter into the constitution of a molecule, the question needs a special treatment, as no direct evidence is supplied by experimental science for an affirmative more than for a negative solution, and different views have been advanced which it is important to examine in the light of philosophical principles, that we may ascertain which of them has the best claim to adoption both in philosophy and in molecular mechanics.

Attractive and repulsive powers.

Since it is well known that all the phenomena of the material order, whether physical or chemical, ultimately depend on attractions and repulsions, we are compelled to admit the existence in nature of attractive and repulsive powers. Neither attractive powers alone nor repulsive powers alone would afford us a rational explanation of natural facts. If the primitive elements of matter were all repulsive, and nothing but repulsive, then neither the cohesion of material particles nor the gravitation of bodies would be possible; no solid and no liquid would exist; and all matter from the very beginning of its existence would have vanished in a state of extreme attenuation through the immensity of space. If, on the contrary, the primitive elements of matter were all attractive, and nothing [pg 722] but attractive, no expansive power would be found in nature; for the expansion of bodies evidently depends on a repulsion prevailing between their molecules. All solid and liquid bodies likewise proclaim the existence of repulsive powers by the resistance they oppose to compression. This resistance shows that their molecules are endowed with powers whose exertion impedes their mutual approach as soon as they have reached a certain limit of distance. It is plain that the power which impedes the approach under pressure must be a repulsive one. Thus both attractive and repulsive powers exist in nature.

But do they exist together in the same primitive element of matter? Boscovich answers in the affirmative; but his answer is not supported by any cogent reason. Having found no other means of accounting for the impenetrability of bodies, he assumed that every element of matter is so constituted as to be attractive at all great distances, according to the law of universal attraction, but that each element, at molecular distances, becomes repulsive in order to resist pressure, and again attractive in order to exercise chemical affinity, and then repulsive again, these alternations going on a certain number of times, till at last repulsivity alone prevails, which indefinitely increases when the distance of two elements indefinitely diminishes.

Yet this theory is by no means needed to account either for the impenetrability of bodies or for any other phenomenon; as what Boscovich ascribes to elements may be, and is in fact, a property of molecules—that is, of a compound system of elements. On the other hand, the theory is unnaturally complex, and the alternation of the attractive and repulsive exertions looks as unscientific as the epicycles of the old astronomers and other hypotheses once admitted as plausible, and now superseded by a fuller knowledge of natural laws. To a mind which examines the question of attractive and repulsive powers in the light of philosophy, it must be evident that each primitive element of matter cannot possess them both. If an element is attractive at any distance, it must be attractive at all distances, whether enormously great or indefinitely small; likewise, if an element is repulsive at any distance, it must be repulsive at all distances.

This proposition can be proved as follows: Opposite actions cannot originate from one and the same simple principle when such a principle has no control over itself, but acts by inherent necessity. But in each primitive element of matter there is but one simple principle of activity, which has no control over itself, as it acts by inherent necessity. And therefore no primitive element can be both attractive and repulsive, but is either attractive at all distances or at all distances repulsive.