Kant's Critique of Pure Reason
TRANSCENDENTAL LOGIC, SECOND DIVISION: TRANSCENDENTAL
DIALECTIC
BOOK II: THE DIALECTICAL INFERENCES OF PURE REASON
Chapter III: THE IDEAL OF PURE REASON
Section 5: THE IMPOSSIBILITY OF A COSMOLOGICAL PROOF OF THE EXISTENCE OF GOD (p. 507)
The proof is as follows:
If anything exists, an absolutely necessary being must also exist.
I, at least, exist. Therefore, an absolutely necessary being exists.
The necessary being can be determined in one way only: by one out of each possible pair of opposed predicates.
It must therefore be completely determined through its own concept.
Now, there is only one possible concept which determines a thing completely a priori: ens realissimum. Therefore the concept of ens realissimum is the only concept
through which a necessary being can be thought. In other words, a supreme being
necessarily exists.
The cosmological proof retains the connection of absolute necessity with the highest reality, but instead of reasoning, like the ontological proof, from the highest reality to necessity of existence, it reasons from the previously given unconditioned necessity of some being to the unlimited reality of that being.
The cosmological proof uses experience only for a single step in the argument. What properties this being may have, the empirical premiss cannot tell us.
We are again presupposing that the concept of the highest reality is completely adequate to the concept of absolute necessity of existence. The same proposition used in the ontological proof.
Does not address the fact that there may be other worlds containing other ens realissimum.
There are a number of deceptive principles used in the proof:
The transcendental principle whereby from the contingent we infer a cause. This principle only applies to the sensible world.
The inference to a first cause from the impossibility of an infinite series of causes in the sensible world.
The unjustified self-satisfaction of reason in respect of the completion of this series.
The confusion between the logical possibility of a concept of all reality united into one and the transcendental possibility of such a reality.
In the same way, since the systematic unity of nature cannot be prescribed as a principle for the empirical employment of our reason, except in so far as we presuppose the idea of ens realissimum as the supreme cause, it is quite natural that this latter idea should be represented as an actual object, which, in its character of supreme condition, is also necessary - thus changing a regulative into a constitutive principle.