“10th. A vacuum, whether of a large or of a small extent, whether accumulated or scattered, is an absolute impossibility.”[117]
These assertions form the substance of Balmes’ theory of space. But he wisely adds: “The apparent absurdity of some of these conclusions, and of others which I shall mention hereafter, leads me to believe either that the principle on which my reasonings rest is not altogether free from error, or that there is some latent blunder in the process of the deduction.”[118]
Lastly, to omit other suppositions which do not much differ from the ones we have mentioned, Kant and his followers are of opinion that space is nothing but a subjective form of our mind, and an intuition a priori. Hence, according to them, no real and objective space can be admitted.
Amid this variety and discord of opinions, we can hardly hope to ascertain the truth, and satisfy ourselves of its reality, unless we settle a few preliminary questions. It is necessary for us to know, first, whether any vacuum is or is not to be admitted in nature; then, we must know whether such a vacuum is or is not an objective reality. For, if it can be established that vacuum is mere nothingness, the consequence will be that all real space is necessarily and essentially filled with matter, as Balmes and others teach; if, on the contrary, it can be established that vacuum exists in nature, and has an objective reality, then it will follow that the reality of space does not arise from the presence of bodies, and cannot be confounded with their extension. In this case, Balmes’ theory will fall to the ground, and we shall have to borrow from Lessius and Fénelon, if not the whole solution of the question, at least the main conceptions on which it rests.
Existence of Void Space.—The first thing we must ascertain is the existence or non-existence of vacuum in nature. Is there any space in the world not occupied by matter?
Our answer must be affirmative, for many reasons. First, because without vacuum local movement would be impossible. In fact, since matter does not compenetrate matter, no movement can take place in a space full of matter unless the matter which lies on the way gives room to the advancing body. But such a matter cannot give room without moving; and it cannot move unless some other portion of matter near it vacates its place to make room for it. This other portion of matter, however, cannot make room without moving; and it cannot move unless another portion of matter makes room for it; and so on without end, or at least till we reach the outward limits of the material world. Hence, if there is no vacuum, a body cannot begin to move before it has shaken the whole material world throughout and compelled it to make room for its movement. Now, to make the movement of a body dependent on such a condition is absurd; for the condition can never be fulfilled. In fact, whilst the movement of the body cannot begin before room is made for it, no room is made for it before the movement has begun; for it is by moving that the body would compel the neighboring matter to give way. The condition is therefore contradictory, and can never be fulfilled, and therefore, if there is no vacuum, no local movement is possible.
Secondly, it has been proved in one of our articles on matter[119] that there is no such thing in the world as material continuity, and that therefore all natural bodies ultimately consist of simple and unextended elements. It is therefore necessary to admit that bodies owe their extension to the intervals of space intercepted between their primitive elements, and therefore there is a vacuum between all the material elements. This reason is very plain and cannot be questioned, as the impossibility of continuous matter has been established by such evident arguments as defy cavil.
Thirdly, bodies are compressible, and, when compressed, occupy less space—that is, their matter or mass is reduced to a less volume. Now, such a reduction in the volume of a body does not arise from material compenetration. It must therefore depend on a diminution of the distances, or void intervals, between the neighboring particles of matter.
Fourthly, it is well known that equal masses can exist under unequal volumes, and vice versa—that is, equal quantities of matter may occupy unequal spaces, and unequal quantities of matter may occupy equal spaces. This shows that one and the same space can be more or less occupied, according as the density of the body is greater or less. But the same space cannot be more or less occupied if there is no vacuum. For, if there is no vacuum, the space is entirely occupied by the matter, and does not admit of different degrees of occupation. It is therefore evident that without vacuum it is impossible to account for the specific weights and unequal densities of bodies.