Atheism worships a dead god.

[Existentialist]

God almost certainly doesn't exist. He's about as likely as Santa Claus. There's no reason to worry about God's existence.

If God exists then the reality is true to both the existentialist and the atheist. There's no reason to worry about it either way.

What reality? If the rationalistic atheist meets God, he meets someone whose non-existence defines human freedom, therefore human freedom disappears at the meeting. An existential atheist meets someone who makes no difference to human freedom one way or another. That's the reason to worry about it. Not that either the rationalistic atheist nor the existentialist atheist thinks that God does exist. It's just, what would happen if he did? Denial of the question is the easiest route for the rationalist, not least because most people seem happy with it!

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Santa Claus is at least based on some historical person (Saint Nicholus, if I recall correctly). That's means "Santa Claus" is at least based on someone who may be a real person.
That's more than some of hte most prominant people in the bible.

True, but then, aren't we veering further away from the most important question - what would it mean to us if, contrary to all our expectations, god really does exist?