There is this big shot, Blaise Pascal, who was supposed to be the créme de la créme in French intellectual circles in the mid-1600s. He had this argument, this "wager", which is not about whether god exists, but whether it might be profitable to believe she does.
So it went like this: even if there was one chance in a million god exists, but you would spend an eternity in hell if you didn't believe in her, then you ought to believe in god just to avoid this one in a million chance of having an infinitely negative payoff.
I mean... really... "payoff". This is the way Blaise would go about it... You multiply 1/(1 million) by (-infinity), and you get (-infinity).
I won't spend too much time on picking out the many holes in this argument, like assuming that a god that would punish you for not believing in her is actually worth believing in, or would have a paradise that is worth working for. Or whether such a god would admit you in paradise when you bet on her existence, rather than have faith. I mean, frankly, Blais's argument was very much that of a banker, a merchant or a casino addict. And those people are a big no no in paradise, from what I gather.
Nah, the main issue I have with this half-clever argument is that it can be used to support any kind of superstition. Suppose for example I am told that eating dog will get me in hell, and then, according to the argument, and even though I am pretty sure eating dogs is perfectly fine, I should go, "hey, maybe, just maybe you are right", and therefore, based on this one in a million chance, would not want to risk it. OK, you could go, "only god can get you in hell", but then suppose I am told: "Eating dog will make you so sick for the rest of your life that you will regret ever having been born", and then, according to the argument, and even if everybody around me eats dog and is fine, I would not eat dog just so as not to risk a lifetime of pain. OK, so again, you could say that a lifetime of pain may not be as bad as an eternity of pain, but as I will argue later, it is quite well proven people discount the future, so the difference is minor.
Just to summarize before going on, I think poor Blaise really stretched his concepts from probability theory a little wee bit too far by applying them to the religious setting. The sad thing is that he ended up believing his own half-baked arguments and relegated himself to some sort of monastery, Port Royal. Personally, I think he had a nervous breakdown, and from that point on everything went pear shaped.
Anyway, here is now my modified Pascal's wager. In all the following, I will assume that only a firm belief in god will save you from hell, i.e. you must believe with 100% certainty that god exists. Any deviation is fatal.
Let's normalize the disutility you incur from spending one year of hell (i.e. pain, suffering and all the tra-la-la) to 1. This is the measure that we will use as the benchmark for everything, so let's call it a one-year hell-equivalent ("OYHE"). Let's also assume that you discount each year in hell by 0.9, which means the prospect of an eternity in hell is viewed as only 1/(1-0.9)=10 times more painful than 1 year in hell; even "infinity" gets discounted to something that can be grabbed within human understanding.
This means that, defining p as your own subjective (or maybe objective, tell me then!) probability that god exists, and assuming that your p=10%, then not believing in god exposes you to an expected 10%*10=1 OYHE.
Given this p of yours (10%), and your discount factor (0.9), you should believe in god (i.e. jump your existence probability p from 10% to 100%) as long as your disutility in doing so does not exceed 1 OYHE.
Now, be careful! What will that disutility be? This depends of course on what a firm belief in god might entail. Consider that your disutility from not believing would increase suddenly from 1 OYHE to 10 OYHE as your p increased from 10% to 100%. You will thus become very afraid of anything that might induce you to doubt your religion, since that would immediately condemns you to 10 OYHE. Once you are locked in, there is almost no limit to what you might do to ensure your faith is not shakenÉ
You should thus not be so naive as to think that believing in god would be a benign matter. It is not just some sort of abstract adherence to the idea that god exists. Protecting this belief of yours might involve much more than going to church every Sunday to strengthen your faith. This fear of entertaining any doubt might turn into paranoia as you try to ensure the certainty of your belief that god exists. Your will be ready to do almost anything to anyone whom you might perceive as a threat to your certainty that god exists.
Moreover, and this is the dark part of Pascal's try, it has suddenly become much easier to convince you of further superstitions that often go with religion, like you have to stop any drinking, any sex, any consumption of forbidden food, deny your sexual inclinations, etc... It will be much easier to convince you to adopt those new beliefs because now you believe in god, the consequences of not adopting them is 10 OYHE, not the 1 OYHE that convinced you to bet on god. You should therefore be very careful before making a bet on god; this is often the first step towards adopting even sillier beliefs.
Sadly enough, human limitations are such that most don't anticipate what this first bet will lead them to do. This means that people, even with the best of intentions, might become trapped into religion. Furthermore, while a skeptical person was less likely to adopt a belief in god, her behavior after conversion will be the same as that of a gullible one, since they both have the same p now. This explains why the sudden and horrible changes that occur once one starts believing in god are all the more sudden, unpredictable and violent when one previously entertained strong doubts about the existence of god.
Conclusion: Be very careful with sudden converts, like Paul, or "born again" Christians, like Bush. Be also very careful not to fall into the religion trap, because there is no way out. Finally, don't believe in any religion that requires full adherence to its requirements, even when it masks those requirements by presenting them as ideals. Prefer religions that admit doubts, that reject sudden convert (or don't believe in sudden conversion), and that have no concept of hell or of infinity. This includes having no concept of reincarnation or of a permanent soul, since this means one's existence is forever. This also includes having no concept of paradise or of the end of suffering, since those are merely mirror images of hell.
Those requirements of mine are aimed at ensuring that adherence to religion is a fully reasoned act that takes account of human limitations. However, to my knowledge, no religion fits this bill, and I don't think any will probably ever do.