P.S. even if we grant that God doesn't exist (for the sake of argument) it doesn't follow that there isn't life / survival after death.

For example... Lets say science advances to the point where they can make cells (incl neurones) out of silicon. Your brain is progressively replaced (and every cell in your body, I guess).

Functionalists say that what is crucial about mind is that mental states are states that play a certain functional role. The silicon allows your brain to continue playing that functional role. Hence you get immortality without God...