Why God Exists, From an Atheist

I don't believe in God. I don't believe that there's some old guy sitting up in a cloud looking down on us and deciding who to kill and who to rain gifts on. But God exists. Why? Because people believe in him. By people believing in him, and using his ideals to motivate them to do great good and great evil, God exists. He exists as an idea in the mind of the religious, and causes them to act. God, an unreal thing, has shaped human existence for the past 5,000 years and counting. If that does not make him real than what does?

Here's a little food for thought about God, that proves he doesn't exist beyond an idea:
If God is all powerful, can he make a rock so big, that he can't lift it?

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