Page:Popular Science Monthly Volume 3.djvu/570

554 tension, which determines the body to pass continually from one to the other of these points; that is to say, the power by which this body, considered at any instant in its course, differs from the identical body at rest. Evidently this something which is in one of these two bodies and is not in the other, this something that mathematicians call the quantity of motion, which is transformed, on a sudden stop-page of motion, into a certain quantity of heat, this something is a reality, distinct from the trajectory itself; and yet nothing, absolutely nothing, outside of the inner revelation of our soul, gives us the means of understanding what this initial cause of the motive forces may be. The distinguished founder of the mechanical theory of heat, Robert Mayer, defines force to be "whatever may be converted into motion." There is no formula that so well expresses the fact of the independence and preëminence of force, nor so completely includes the assertion of the essential reality of a cause preëxisting motion. The idea of force is one of those elementary forms of thought from which we cannot escape, because it is the necessary conclusion, the fixed and undestroyable residue from the analysis of the world in the alembic of our minds. The soul does not find it out by discursive reasoning, nor prove it to itself by way of theorem or experiment; it knows it, it clings to it by natural and unconquerable affinity. We must say of force what Pascal said of certain fundamental notions of the same order: "Urging investigation further and further, we necessarily arrive at primitive words which cannot be defined, or at principles so clear that we can find no others which are clearer." When we have reached these principles, nothing remains but to study one's self with profoundest meditation, not striving to give an image to those things whose essence is that they cannot be imagined. From the most general and abstract point of view, then, matter is at once form and force, that is, there is no essential difference between these two modes of substance. Form is simply force circumscribed, condensed. Force is simply form indefinite, diffused. Such is the net result of the methodical inquiries of modern science, and one which forces itself on our minds, apart from any systematic premeditation. It is of consequence to add that the merit of having formulated it very clearly and noted its importance belongs to French contemporary philosophers, particularly to Charles Lévèque and Paul Janet.

If the web of things, the essence of matter, is one single substance, who was the Orpheus under whose spell these materials gathered, ranged, and diversified themselves into natures of so many kinds? And, first of all, how can the extension of bodies proceed from an assembling of unextended principles? The answer to this first question does not seem difficult to us. Extension exists prior to matter. They are two distinct things, without any relation of causality or