Chapter I. The Phenomenology of Force
Immanuel Kant (1724-1804)
Among Kant's many works, there is one not very popular or well-known that relates directly to our topic. It is titled Metaphysical Foundations of Natural Science. In it, the philosopher considers the different forms of matter's motion. Of particular interest to us is the second chapter: Metaphysical Foundations of Dynamics, where motion is investigated as pertaining to the quality of matter that is called the original moving force. It should be said that in the first part the discourse is about motion as a purely quantitative value that ignores the quality of the motive matter. That is, motion is regarded here as if without matter, for "That space which is itself movable is called material, or also relative, space."
Proposition 1 in the second chapter goes: "Matter fills a space, not by its mere existence, but by a special moving force." In his subsequent proofs, Kant says: "the cause of a motion is called moving force."
This extremely important claim implies nonetheless certain admissions: matter can exist without a special moving force, for example, when it does not need to fill a space. Moreover, if there is a moving force, there can also be a non-moving force, some sort of passive force. Kant himself, though, ignores these admissions.
Kant does identify, naturally, the "Attractive force" and the "Repulsive force" which he calls the two moving forces of matter that cannot be separated from each other in the concept of matter. But then Kant poses the question: "Why is impenetrability given immediately with the concept of matter, while attraction is not thought in the concept, but only attributed to it by inference." It is because these phenomena cannot be sensed; they are hidden too deeply in the essence of things, and for that reason they can only be thought. This is precisely the answer begged by the question.
For this "mind-conclusion”, Kant was criticized by Hegel who noted that "…a determination which belongs to the concept of anything must be truly contained in it." Kant is consistent here, though, from the perspective of his general philosophical conception. He believes that what is verified by experience and senses (the force of repulsion) is contained in the concept of matter, while that which is outside senses and experience is included in the concept of matter, but not contained in it. The most important thing is this: all motion and, accordingly, all moving forces are perceived through senses, i.e. they are given only as phenomena, that is, reflections about things, but not as things themselves, which are, according to Kant, unknowable (agnosticism flows from here).
Hegel criticized Kant also for his conclusions regarding the interaction of forces. In Explication 7 Kant stated: "A moving force by which matters can directly act on one another only at the common surface of contact, I call a superficial force; but that whereby one matter can directly act on the parts of another beyond the surface of contact, a penetrative force." Hegel analyzes this topic in detail, connecting the superficial force to the force of repulsion, and the penetrative force to the force of attraction. This definition by Kant is obviously unfortunate, since it does not specify the location and the work mechanism of the "penetrative force" outside "the parts in contact" which is supposedly the sphere of action of the "superficial force". This is a step backwards even from Leibniz who saw the internal, primary forces as being in contradiction with the accidental, external forces; it is the interaction between these forces that moves matter (the spirit). Kant sees them as interacting only with external forces ("Every change in matter has an external cause").
Nonetheless, despite the imprecision in his definitions of reflection and substance, and the inconsistencies in the description of the "superficial" and other forces, Kant's central thought is important: "The concept of matter is reduced to nothing but moving forces; this could not be expected to be otherwise, because in space no activity and no change can be thought of but mere motion." The idealist Hegel, strangely enough, approves strongly of precisely this materialistic treatment of the movement of forces offered by Kant: "…namely, the derivation of matter from these two opposite determinations as its fundamental forces, must always be highly esteemed."
What is important to us is that Kant tied together matter, motion and force in one whole.
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