Blaise Pascal was a philosopher and mathematician in the 17th century. Pascal's wager, in a nutshell, is this: No one knows for certain whether God exists. Maybe he does, maybe he doesn't. It's a gamble whether you believe in him or not. So let's treat it like a gamble, says Pascal, and look at the odds.
He described the payoff of this gamble as follows. If you choose to believe in God, and you happen to be right, then the reward is infinity. Eternal bliss in heaven. However, if you are wrong, then you lose nothing at all. On the other hand, if you choose not to believe in God, and you're right, you gain nothing (in either of the previous two cases, you just die and that's the end). But if you are wrong, your payoff is negative infinity. Eternal suffering in hell.
Since the chance of God existing is unknown, but the payoff/punishment scheme is infinitely in favor of believing in God, just on the small chance that he might exist, you had better believe. It seems to be the only wager that makes sense. But wait a minute...
Problems with Pascal's Wager
1. In the case where God does not exist, there is a clear advantage to not believing. In other words, the payoff is not zero. For one thing, if you go through life believing a lie, that is a bad thing in itself.
2. Besides that, there is more to being a believer than just saying "Okay, I believe now" and getting on with your life. Serious believers spend a lot of their time in church, and contribute a lot of money as well. There's a reason why some towns have very affluent looking buildings for churches, and why large and elaborate cathedrals are possible: they're funded by folks who donate a tenth of their income throughout their lives to tithing. This is surely most foolish if the object of worship isn't real and much of the money is being spent on the building. If you want to help poor people we suggest that you donate directly to charities that help the poor and don't waste anything on church buildings or misguided missionary word that damages the culture of indigenous people in an effort to save their imaginary souls. Far too often missionaries put the fear of hell into people who were happy without that before.
3. Even if you buy into Pascal's wager and decide you should believe, that doesn't give any basis for choosing which religion to believe in. Fundamentalists often use the wager to prove that you should be a Fundamentalist, but of course, Pascal was Catholic and was using it to prove you should be a Catholic! This just highlights the whole problem of which religion is the right one. Since many Fundamentalists believe that Catholics are going to go to hell, Pascal's not much better off than an unbeliever. We don't know if the Jews are correct, or if reincarnation is right, or worse, if there's a perverse God who only lets atheists into heaven! It's not impossible, right? For all we know, maybe God exists but he doesn't care at all whether people believe in him, however unlikely such a god may be.
4. If you can accept Pascal's wager as a realistic reason to believe, that leads you to a point where you have no choice but to believe just about everything on the same grounds, even if every religion DOES say that every other belief is wrong. Maybe if you don't register with Wikia.com, you'll go to hell! Why not? You don't know. Maybe you have to send Jason Wales $10 a week for life. Hey, what's a measly ten bucks if it will save you from eternal hellfire? Or maybe God really likes nude mud wrestling and he will punish those who do not partake of his gift. Perhaps god is not jealous as the Bible says but enjoys extreme irony and in fact punishes believers and rewards atheists to satisfy his need for it. But we're just throwing ridiculous speculations out there that we really have no basis for at all since we didn't actually bother researching anything except what we like to hear.
If all of this sounds utterly silly to you, good! That's probably because you know that you should only believe things which have some sort of clear evidence favoring them. You don't believe just any old preposterous claim about UFO's, pyramid shaped get-rich-quick schemes, or magic pixies just because somebody tells you they're true and because there's a chance you might be wrong. You have a brain — use it and go find out if it's true yourself! But be careful- too much research into what's true and what's not and you might wind up like Josh McDowell!
A More Formal Analysis
Pascal's wager in modern form goes something like this:
- A1 Either god exists or not, and we can wager on that and may be rewarded or punished for our wager if he does. The various rewards can be summed up in the following table (a "decision matrix"; r1, r2 and r3 are some finite numbers, perhaps negative to indicate punishment):
|God Exists||God Doesn't Exist|
|Wager for God||R||r1|
|Wager against God||r2||r3|
- A2 Rationality requires that the probability you assign to the existence of god to be finite and greater than zero
- A3 Rationality requires that you act to maximize the expected utility
If one assumes that R is inifinite, the conclusion that you should wager for god follows, regardless of how small the probability (p) you assign to it. This is because a small number times infinity is infinity, so that the wager for god has the utility p*R + (1-p)*r1 = ∞, which is (infinitely) larger than the utility for wagering against god p*r2+(1-p)*r3.
The counter-points above show that the argument is mistaken. The resulting guillibility to any claim is especially worriesome from the point of view of deision theory. Clearly, there is something very wrong with the argument, but it is actually not easy to see what it is. We shall argue here that the core problem is, of all things, (A3).
Infinities and Gods: Unsatisfactory Counterarguments
While all the above counterarguments are true, they are unsatisfactory in the sense that they only demonstrate that the argument is invalid, they don't show why it is so.
It is true that in the original formulation Problem 1 was correct: the argument assumed that a payoff of zero for not believing. But the modern formulation states above, the pay-off in this case is any finite quantity. So this objection doesn't cut to the heart of the problem. (If there is a god who rewards those who use their critical faculty and punishes those with blind faith not believing brings infinite reward.)
It is also true that one cannot simply decide to believe (Problem 2). Indeed, as noted above, a rational person should believe what is most likely, not what is most lucrative. However, there are certain religions that do not require belief, merely action. Certain strands of Judaism follow this vein, for example. Should we all convert to Judaism? Of course not. So what is wrong with the argument, beyond this point?
Problem 3 raises the point that there is an infinity of possibilities neglected by the argument. For every god with the above rewards, there may be a god with an opposing one. This is the 'many gods' objection. This objection is problematic, since a theist might well argue that such gods are less likely, and we'd like the argument to falter even assuming - for the sake of argument - that he is right. (We find nearly all gods equiprobable, but still.) Even more importantly, the core reason the argument fails is not that there are other unlikely possibilities - the analysis of this possibility alone should reject it, without any need to introduce other options.
A related issue is the "Greater God" problem - assuming infinities are banned, you should rationally choose some other god whose R is bigger than the current one and so on ad infinitum - so you're paralyzed without an ability to choose. This applies even to infinite R, using certain extensions such as surreal numbers.
Problem 4 highlights this point - there is just something fundamentally wrong with decision theory as it is applied here. If the argument was valid, it would lead to all sorts of guillibility, making the rational agent purchase indulgences and pay for Jason Wales's pension. Clearly, something is deeply wrong here.
Some maintain that, formally, decision theory cannot handle an infinite R. But this objection is not too relevant, since the argument works with merely a very-very big R. Likewise, maintaining that the probability for god's existence is infinitesimal may be valid for an atheist, but the argument should fail even for someone less extreme.
While they demonish the argument, these objections are not satisfying. There is still something very wrong at the heart of the argument.
Against Maximizing Utility (A3)
Why should a rational agent maximize utility? The idea is that this would mean that on average he will gain the most. But it turns out averages aren't meaningful here. We are usually faced with situations where the possibilities are fairly limited, so that the average is a good representation of what is likely to happen. But when the probability distribution is too broad, the typical is no longer the average. In this case, most cases will turn out to be very far from the average, and we suggest that in such cases it is better to stick to the typical than to the average as your guide to rational behavior.
Let us consider, for simplicity, the case where r1=0. In this case the average utility for wagering for god is p*R. But the standard deviation of the utility is (p(p-1))1/2R, which is larger than the utility when p<0.5. So the average loses its usual intuitive meaning when p<0.5; in these cases a typical result will be that the agent gets 0 as its reward. This gets a bit more complicated with finite r1, but the principle stands - for sufficiently small p's, the typical case would be that you will get r1 as the reward. In this case, wagering on God on the off-chance that you will get R is not rational; most rational agents will fail if they pursue this line of reasoning. Assuming the other elements in the decision matrix are appropriate (e.g. r3 is far larger than any other element), choosing atheism becomes the rational choice. Even if they aren't, the choice at least returns to rationality - the rational agent isn't lured away by astronomically unlikely options.
There is also an argument to be made against following arbitrarily low probabilities in general. A probability of 10-57 for example is zero for all intents and purposes - no matter how often it is checked, it is extremely unlikely to be realized within the lifetime of the universe. Since it may still grossly affect the average, this is a further indication that it is just not rational to follow the average utility. Following the typical utility is far more sensible when the standard deviation of the utility is larger than its avergae.
References and Notes
- See the Standford Encyclopedia of Philosophy
- For a clear discussion of infinities in relation to Pascal's Wager, see Alan Hajek's Waging War on Pascal's Wager, The Philosophical Review, Vol. 112, No. 1 (January 2003). Hajek argues all wager arguments are doomed to failure due to either the greater god problem, or to the ability to wager on god by non-commiting strategies - a point not covered on this site.
- The objections are briefly, but well, considered in the Internet Encyclopedia of Philosophy 
- The standard deviation of a random variable is a measure of how much it varies around the average - how far will typical results be from the average. See Wikipedia,