The cosmological ideas cannot be fully attained without the aid of the categories. (1) So far as the quantity of the world is concerned, space and time are the original _quanta_ of all intuition. In a quantitative respect, therefore, the cosmological idea must hold fast to something concerning the totality of the times and spaces of the world. (2) In respect of quality, the divisibility of matter must be regarded. (3) In respect of relation, the complete series of causes must be sought for the existing effects in the world. (4) In respect of modality, the accidental according to its conditions, or the complete dependence of the accidental in the phenomenon must be conceived. When, now, the reason attempts to establish determinations respecting these problems, it finds itself at once entangled in a contradiction with itself. Directly contrary affirmations can be made with equal validity in reference to each of these four points. We can show, upon grounds equally valid, (1) the _thesis_, the world has a beginning in time and limits in space; and the _antithesis_, the world has neither beginning in time nor limit in space. (2) The thesis: every compound substance in the world consists of simple parts, and there exists nothing else than the simple and that which it composes; and the antithesis: no compound thing consists of simple parts, and there exists nothing simple in the world. (3) The thesis: causality according to the laws of nature, is not the only one from which the phenomena of the world may be deduced, but these may be explained through a causality in freedom; and the antithesis: there is no freedom, but every thing in the world happens only according to natural laws. Lastly, (4) the thesis: something belongs to the world either as its part or its cause, which is an absolutely necessary being; and the antithesis: there exists no absolutely necessary being as cause of the world, either in the world or without it. From this dialectic conflict of the cosmological ideas, there follows at once the worthlessness of the whole struggle.
(3.) _The ideal of the pure Reason or the idea of God._
Kant shows at first how the reason comes to the idea of a most real being, and then turns himself against the efforts of previous metaphysics to prove its valid existence. His critick of the arguments employed to prove the existence of a God, is essentially the following.