Atheism/Religion in the creation of man/it’s own existence

“The other argument which is founded upon a man’s knowledge of his own existence, stands thus. — A man knows not only that he now is, but that there was a time when he did not exist; consequently there must have been a cause. But what does this prove? We can only infer from effects causes exactly adequate to those effects; — But there certainly is a generative power which is effected by certain instruments; we cannot prove that it is inherent in these instruments, nor is the contrary hypothesis capable of demonstration: we admit that the generative power is incomprehensible, but to suppose that the same effect is produced by an eternal, omniscient, Almighty Being, leaves the cause in the [same] obscurity, but renders it more incomprehensible.”

http://knarf.english.upenn.edu/PShelley/atheism.html