Given

• Billions of people around the world all:
  • Pray to god or gods for wisdom, enlightenment, and guidance (e.g. “grace”)
  • Are at least somewhat serious in their prayer, and open to a response from their deity
• Most people are the religion of their parents
• Never in the history of the world has a religion spontaneously appeared in a second location (i.e. without a missionary or other cultural exchange)
• Every religion has had at least one prophet or person to whom the religion was revealed.

Proof by contradiction

Assume that a God exists who listens to people who pray to God as they know him and who at least sometimes answers prayers.

Then we would could God to answer prayers for religious enlightenment by revealing the true religion to the person praying to him, perhaps making that person a prophet, as he has done before.

However if that were true, we could expect not only a significant number of believers of every other religion converting to the one “true” religion, but we could expect this to happen without any exposure to said religion.

This does not match observations of the real world.

Therefore, no god exists who answers prayers for knowledge or enlightenment and, because this is such a basic request, it is likely no god answers prayers at all.

Disclaimer

I know it isn’t an ironclad or scientific proof, but it’s a hell of a lot stronger than “Isn’t the world pretty? It must be created by the gods in this particular holy book,” don’t you think?