Pascal's Wager

God either exists, or he doesn't.
If you wager that God exists(and you place your trust in him), and God does indeed exist, you have won eternal life.
If God turns out to not exist, you have lost little.
If you wager that God does not exist, and in fact he does not exist, you have lost nothing.
But, if you wager that God does not exist, and it turns out that he does exist, you have lost eternal life.
The logic of the wager inevitably leads one to belief and trust in God.