In the use of pure reason its concepts, or transcendental ideas, aim at unity of all conditions of thought. So all transcendental ideas may be arranged in three classes; the first containing the unity of the thinking subject; the second, the unity of the conditions of phenomena observed; the third, the unity of the objective conditions of thought.
This classification becomes clear if we note that the thinking subject is the object-matter of psychology; while the system of all phenomena (the world) is the object-matter of cosmology; and the Being of all Beings (God) is the object-matter of theology.
Hence we perceive that pure reason supplies three transcendental ideas, namely, the idea of a transcendental science of the soul (psychologia rationalis); of a transcendental science of the world (cosmologia rationalis); and, lastly, of a transcendental science of God (theologia transcendentalis). It is the glory of transcendental idealism that by it the mind ascends in the series of conditions till it reaches the unconditioned, that is, the principles. We thus progress from our knowledge of self to a knowledge of the world, and through it to a knowledge of the Supreme Being.
III.—The Antinomies of Pure Reason
Transcendental reason attempts to reconcile conflicting assertions. There are four of these antinomies, or conflicts.
First Antinomy. Thesis. The world has a beginning in time, and is also limited in regard to space. Proof. Were the world without a time-beginning we should have to ascribe a present limit to that which can have no limit, which is absurd. Again, were the world not limited in regard to space, it must be conceived as an infinite whole, yet it is impossible thus to conceive it.
Antithesis. The world has neither beginning in time, nor limit in space, but in both regards is infinite. Proof. The world must have existed from eternity, or it could never exist at all. If we imagine it had a beginning, we must imagine an anterior time when nothing was. But in such time the origin of anything is impossible. At no moment could any cause for such a beginning exist.
Second Antinomy. Thesis. Every composite substance in the world is composed of simple parts. This thesis seems scarcely to require proof. No one can deny that a composite substance consists of parts, and that these parts, if themselves composite, must consist of others less composite, till at length we come, by compulsion of thought, to the conception of the absolutely simple as that wherein the substantial consists.
Antithesis. No composite thing in the world consists of simple parts, and nothing simple exists anywhere in the world. Proof. Each simple part implied in the thesis must be in space. But this condition is a positive disproof of their possibility. A simple substance would have to occupy a simple portion of space; but space has no simple parts. The supposition of such a part is the supposition, not of space, but of the negation of space. A simple substance, in existing and occupying any portion of space, must contain a real multiplicity of parts external to each other, i.e., it must contradict its own nature, which is absurd.
Third Antinomy. Thesis. The causality of natural law is insufficient for the explanation of all the phenomena of the universe. For this end another kind of causality must be assumed, whose attribute is freedom. Proof. All so-called natural causes are effects of preceding causes, forming a regressive series of indefinite extent, with no first beginning. So we never arrive at an adequate cause of any phenomenon. Yet natural law has for its central demand that nothing shall happen without such a cause.