The proof of the existence of God may be attempted in three ways: we may argue the existence of a supreme cause either by starting from a definite experience (the special constitution and order of the sense-world, that is, its purposiveness), or from an indefinite experience (any existence whatever), or, finally, abstracting from all experience, from mere concepts a priori. But neither the empirical nor the transcendent nor the intermediate line of thought leads to the goal. The most impressive and popular of the proofs is the physico-theological argument. But even if we gratuitously admit the analogy of natural products with the works of human art (for the argument is not able to prove that the purposive arrangement of the things in the world, which we observe with admiration, is contingent, and could only have been produced by an ordering, rational principle, not self-produced by their own nature according to general mechanical laws), this can yield an inference only to an intelligent author of the purposive form of the world, and not to an author of its matter, only, therefore, to a world-architect, not to a world-creator. Further, since the cause must be proportionate to the effect, this argument can prove only a very wise and wonderfully powerful, but not an omniscient and omnipotent, designer, and so cannot give any definite concept of the supreme cause of the world. In leaping from the contingency of the purposive order of the world to the existence of something absolutely necessary and thence to an all-comprehensive reality, the teleological argument abandons the ground of experience and passes over into the cosmological argument, which in its turn is merely a concealed ontological argument (these two differ only in the fact that the cosmological proof argues from the antecedently given absolute necessity of a being to its unlimited reality, and the ontological, conversely, from supreme reality to necessary existence). The weaknesses of the cosmological argument in its first half consist in the fact that, in the inference from the contingent to a cause for it, it oversteps the boundary of the