RE: Why God Doesn't Exist
I don't like saying something doesn't exist when you can't be sure, because this is purely speculation. It's like Schrödinger's cat, where a cat, a flask of poison, and a radioactive source are placed in a sealed box. If an internal monitor detects radioactivity (i.e. a single atom decaying), the flask is shattered, releasing the poison that kills the cat. The Copenhagen interpretation of quantum mechanics implies that after a while, the cat is simultaneously alive and dead. Yet, when one looks in the box, one sees the cat either alive or dead, not both alive and dead. This poses the question of when exactly quantum superposition ends and reality collapses into one possibility or the other.
This isn't to say God may have once been alive but died, but that there's no way of knowing if he exists. You could argue that throughout history, religion hasn't been used to enlighten its followers, but to control the masses, i.e. people were (and still are in some places) prosecuted and/or killed for not having the same religious belief as the general population or leader. If you've read James Orwell's book "1984" this idea connects to the Party and how what they tell you to believe must be believed or you will be tortured. Winston, the main character who was against the Party, was asked what 2+2 was. He answered "4". He was then asked "if the Party tells you 2+2=5, what is the answer?" Winston answered "4" and was tortured.
This is not to say that's how all of religion is, especially today, but these are just some ideas.