Pascal's wager

Pascal's wager is a way of thinking about whether or not to believe in God. It says that you might as well believe in God, because if you do, it might turn out to be true, and you'll get a reward for it (like getting to be with God in Heaven). But if you don't believe in God, and it turns out to be true, then you'll be in trouble. So it's better to believe in God even if you're not sure it's true, just to be safe.