Pascal's Wager Revised
Blaise Pascal famously argued that, as long as there was any probability that God existed, a rational gambler should worship him, since the cost if he did exist and you failed to worship him was enormously greater than the cost if it went the other way around.
A variety of objections can be made to this, most obviously that a just God would reject a worshiper who worshiped on that basis. But I have a variant on the argument that I find more persuasive.
The issue is not God but morality. Most human beings have a strong intuition that some acts are good and some bad--that one ought not to steal, murder, lie, bully, torture, and the like. Details of what is covered and how it is defined vary a good deal, but the underlying idea that right and wrong are real categories and one should do right and not wrong is common to most of us.
There are two categories of explanation for this intuition. One is that it is a perception--that right and wrong are real, that we somehow perceive that, and that our feel for what is right and what is wrong is at least very roughly correct. The other is that morality is a mistake. We have been brainwashed by our culture, or perhaps our genes, into feeling the way we do, but there is really no good reason why one ought to feed the hungry or ought not to torture small children.
Suppose you are uncertain which of the two explanations is correct. I argue that you ought to act as if the first is. If morality is real and you act as if it were not, you will do bad things--and the assumption that morality is real means that you ought not to do bad things. If morality is an illusion and you act as if it were not, you may miss the opportunity to commit a few pleasurable wrongs--but since morality correlates tolerably well, although not perfectly, with rational self interest, the cost is unlikely to be large.
I think this version avoids the problems with Pascal's. No god is required for the argument--merely the nature of right and wrong, good and evil, as most human beings intuit them. And, by the morality most of us hold, the fact that you are refraining from evil because of a probabilistic calculation does not negate the value of doing so--you still haven't stolen, lied, or whatever. One of the odd features of our intuitions of right and wrong is that they are not entirely, perhaps not chiefly, judgements about people but judgements about acts.