One way to use Pascal’s Wager (the way I use it here) is to have four quadrants — what happens if you believe and God exists, what happens if you believe and He doesn’t exist, what happens if you don’t believe and He does exist, and what happens if you don’t believe and He doesn’t exist — and compare the four in deciding whether it is rational to cultivate belief or unbelief.
But here’s another way, which, while it ultimately reduces to the same thing, is perhaps more direct: Compare the lives of a believer and an unbeliever in a universe where God exists, and compare the two lives in a universe where God doesn’t exist.
In the afterlife, it’s an easy choice: If there’s no God, both are equally dead and literally oblivious forevermore; if God does exist, then the believer has infinite happiness and the unbeliever infinite unhappiness. So there’s no reason not to believe, and the reason to believe is overwhelming.
So, to make up for that, the wannabe unbeliever must demonstrate (1) that there is a negligible chance that there is an afterlife and (2) that the life of an unbeliever in this world is much happier than that of an unbeliever.
Now, I will just assert here that I don’t think that the first point can be proved. Think about it: How would you prove that there is no afterlife? You can’t. (And, by the way, you can prove that there is an afterlife, if you believe those who have died and then returned to life — or, of course, if you believe in the Resurrection and that the New Testament is not basically just an elaborate hoax.)
But what I really want to highlight, and this is with regard to the second point above, is that the believer is actually happier in this world than the unbeliever. Why would you choose to live an ephemeral and purposeless existence, and in a cold universe where there is no distinction between good and evil? The answer can only be, “Because a believer must, because of his belief, give up so much pleasure in which the unbeliever can happily indulge.” Really? Is worship and prayer that unpleasant? No? Then the claim is that extramarital sex and, I suppose, drugs are that pleasant.
I don’t believe that. And I would hope that anyone who does believe that will at least reconsider when, for whatever reason, the allure of extramarital sex wanes. Nor of course would I counsel waiting for that, since we never know when we’ll find ourselves in the afterlife.
I’ll also note that it is odd for the wannabe unbeliever to explain condescendingly that his happiness requires that he must follow no matter what the Truth. After all, he can’t really know with much confidence that there is no God and, besides, if there is no God then what does it matter if Truth is not followed?
Finally, remember that Pascal is right about which way to wager unless the unbeliever is not only happier but much happier in this world than the believer. If it’s anything else, then the overwhelming — indeed, infinite — advantage enjoyed by believers over unbelievers in their respective afterlives makes the believers the winners.