Pascal's Wager

Pascal's wager is an argument to believe in god. It goes like this: If god exists, and you believe, you'll go to heaven for eternity. If god exists, and you don't believe, you'll go to hell for eternity. If god doesn't exist, you'll neither gain nor lose anything by believing or not believing. Because the reward/punishment of heaven/hell is infinite, no matter how unlikely god's existence is, the cost/benefit analysis says that you should believe.

The first problem is: what if you pick the wrong god? Worship Zeus and Odin could damn you. Oops. Still, you might think it's better to choose some god, rather than none. Picking the wrong god gets the same punishment as picking no god, but picking a god gives some chance of getting the infinite reward.

But it goes further than that. There's no reason to think that any god would give you infinite reward for believing in it and infinite punishment for not believing in it. It's possible, sure. But it's just as possible for a god to punish anyone who believes in it, and reward anyone who doesn't believe in it. Or, the god could reward only those who truly believe, and not just play some silly game. Or, god could capriciously reward and punish people regardless of what they did in life. Or, some other scenario I haven't thought of.

Also, there is a cost to believing that's not incumbent on the non-believer; following the tenets of the religion you've chosen.

With all those different possibilities, there's no reason to think trying to believe in god is better than not trying to believe.