Pascal presumes (for this argument) that reason cannot determine whether God exists, so reason alone cannot determine whether to believe in God.

	God exists	God doesn’t exist
Believe in God	Infinite payoff (heaven)	finite loss at most (Pascal: finite gain)
Don’t believe	Negative infinite?	finite gain at most

So, it is smart to bet that God exists.

This doesn’t prove that God exists. But it does (if sound) prove that it is a good idea to believe that God exists.