Kant is considered one of the greatest Philosophers of all time. His analysis of Theistic claims, and, how one cannot make them coherently because they "transend experience" is excellent. Here is how Kant Shows us that we can defeat the Cosmological and Teleological argument(s) for God's existence by showing the Ontological Argument to be fallacious.

First, let us use some terminology. Kant breaks propositions into four main categories: (1) A Priori, (2) A Prosteriori, (3) Analytic, and (4) Synthetic. I assume we all know what the first two mean. However, let me explain three and four. A proposition is thought to be analytic if the subject contains the predicate within the very concept. Hence, a proposition is analytic if the predicate adds nothing to the subject. If a proposition is synthetic, then the predicate is not contained within the subject, and it therefore the predicate adds something to the subject (if true).

Kant explains that where the Rationalists (like Descartes) went wrong was by assuming that all a priori propositions were analyic. Since they assumed this, they thought that these propositions could simply be proven by a reductio proof. This is all very abstract, so let me us a concrete example of an a priori analytic proposition:

"Bachlors are unmarried men." Now, this can be known without experience. We can tell this is true in virtue of knowing the meaning and relation of the words. Furthermore, the concept of "unmarried man" is contained within the meaning of Bachlor. Thus, if we assume this wasn't true, we would reach a contradiction.

Kant said that contray to the Rationalists assumption that all propositions are a priori analytic, metaphysical and mathematical propositions where synthetic a priori. This is all complicated, so I won't explain.

Kant critiques the Cosmological argument by saying in essence: look, without the ontological argument, the cosmological argument fails. Now, why is this? Lets look at how we understand and given explanations. If I say "man, my foot hurts" and you ask why, I give a causal explanation "well, I dropped a box of books on my foot." Hence, I am explaining my pain in terms of a causal relationship. Now, let me ask you, would you give a causal account for this proposition: "5 + 5 = 10"? Would you ask "how did 5 + 5 become such that it equaled 10"? Of course not...it just is.

God must be of this latter case. If God's existence is accounted for in terms of causation, then we have accomplished nothing by saying "God must be the cause of the universe." For one would have to explain God's cause, and God's cause's cause. But theists want to say "nope, the buck stops at God." Ok, so God must be a necessary being who's existence is not accounted for in terms of a causal relationship. Therefore, to argue for the Cosmological argument is to already presuppose the ontological argument. if the ontological argument fails, then we have a case like the old Indian theory of the earth sitting on turtles, and those turtles sitting on other turtles and so on.

I hope this is clear. if it isn't, just ask me questions.

Now, without the Cosmological argument, there cannot be any argument form design. For the argument from design says that life is so complex, it must have a designer who CAUSED it to be that way. Ok, but then what caused the universe? God presumably, and this is the cosmological argument. Hence, it all traces back to the cosmological argument, and, that rests upon the ontological argument. Therefore, it is imperitive that the Ontological argument work in order for these other three to work. however, as Kant said, the Ontological argument must fail. There cannot be a logically necessary being. Here is why:

Descartes claimed that God contained all perfections. Since existence is a perfection, God must contain existence within himself. Thus, to deny that God exists is to be lead into a contradiction. However, existence isn't a perfection. It is a place where perfections could presumably get instantiated. I mean, saying "I have read hair" is different that saying "I exist." hence, existence is where properties reside...but existence is not itself a property.