Pascal's Wager is a famous argument to believe in God. While you may not have heard it called that, you have probably heard it in one form or another. If nothing else, someone may have asked you: "What have you got to lose by believing in God?"
In essence, you are asked to analyze the question of God's existence in terms of a bet, that is to say, in terms of the odds of winning and the payoff. If there is no God, it doesn't matter what you bet: you are worm food either way. If there is a God, and you believe, then you go to heaven; and you don't believe, you go to hell.
In a normal betting situation, you need to compare what it costs to play to the odds of winning and the payoff. This is not a normal betting situation. The payoff is infinite and the cost is finite. As long as there is any chance at all, no matter how small, it is best to bet for God. You have nothing to lose, and infinitely much to gain. Or so the reasoning goes.
Bait and Switch
Let me begin by making it clear that Pascal's wager is not really about believing in God, it's about accepting religion. It might be an old religion with lots of cathedrals and a globe-spanning ministry, or a tiny little cult that meets in someone's front room. At the very least it will be a definition of God that you must accept, along with the infrastructure needed to propagate that definition.
Don't believe me? Next time some Mighty Zombie asks if you believe in God tell them this: "Sure: I believe God is sex, and I definitely believe in sex." If they're cute and you're available, wink.
Suppose I decided that Pascal is right, that I should "get religion" just in case. Which one should I choose? On a worldwide basis, roughly equal numbers of people are Catholic, Protestant, Muslim, and Hindu, each having roughly one billion adherents. Another billion have some religion other than one of the big four. The remaining billion or so have no religion. None of the religions call to me. I have no basis for choosing one over the other. When I knelt and prayed for guidance God told me he didn't exist.
All-Powerful = All-Stupid?
If God does exist, presumably He'll know I don't really believe in Him, that I'm pretending to believe in him on the off chance that He might really exist. If He's willing to accept me if I just "Go through the motions" then I suspect just being a good person will also be enough. Pascal's own answer to this point was that this is why we have churches, to help us grow in faith. In other words, if I submit to a church-approved brainwashing program, they can make me believe. I do not find this comforting.
The cost to "place the bet" is not as low as some would claim. Tithes and other contributions are just the beginning. People are dying, now, as I type, because of their religion, or because of somebody else's religion. There are people refusing medical treatment because it's "against their religion". There are people killing other people over religion. The "ethnic cleansing" in Eastern Europe was very much a religious war between Christians and Muslims. Similar conflicts are taking place in Indonesia. And let's not forget 9/11.
If You Bet, Bet Responsibly
Let's suppose someone offers you the following wager: Roll a single die. If it comes up a six, they will give you ten thousand dollars. If it comes up 1 through 5, you give them one thousand dollars. Should you take the bet? The odds of winning are 1:6 and the payoff is 10:1. If you've got a thousand bucks to spare, it's a good bet. But if that money is supposed to go towards rent and utilities, then it would be irresponsible of you to make the bet.
If we atheists are right, this is the only life you have. Using it to place a risky bet is irresponsible.
Reverend James's Wager
Let's end our discussion with an "intuition pump." Reverend James's Wager is a not-so-famous argument to send me a five-dollar (US) donation via PayPal.
If you send the money you will go to Heaven when you die. If you don't, you will go to Hell. You may question my ability to actually pay off, especially the part about sending you to hell. Gotcha! The "Trinity Knot" near the top of this page is actually a soul-trap; a little something I ran across in my occult studies. This altered version should make its nature clear:
Three interlocked sixes, the mark of the beast. Actually, just a mark of the beast. There are dozens. But I digress. The inscription is ancient Greek and says, in essence, "I freely accept this mark by tracing it." More or less the metaphysical equivalent of a shrink-wrap license. It counts, even though most of you can't read it, because much of the New Testament was also written in ancient Greek, making it a de facto official language for this sort of thing.
If you traced it with your eyes (which is almost impossible not to do, at least subconsciously) you "bear the mark" on your forehead. If you actually traced it with a finger or with a pointing device you manipulated with your hand (like a mouse), then you "bear the mark" on your hand. Since you took it of your own free will (even if you didn't know what you were doing) there is no way for you to get rid of it. Jesus won't even look at you if you have the mark. I can, however, refuse to let you have it. I will do this if you send me the five-dollar donation I mentioned earlier.
Still skeptical? Remember that this is not a normal betting situation. The payoff is infinite and the cost is finite. If there is any chance, no matter how small, that I can damn you then it's a good bet to send me the money. You have so little to lose, and infinitely much to gain. Besides which, what's five dollars compared with spending even one Sunday in church?
Perhaps you'd rather bet that the whole trinity knot / soul trap / mark of the beast is something I just made up to encourage your generosity. Perhaps you also think that the ancient Greek inscription is nonsense. Considering what's at stake, Can you really take that chance?
Here's that link again. What's $5 compared to even a tiny chance of eternal damnation?