Ed Simon in Nautilus:
Pascal’s theological masterpiece Pensees (or “Thoughts”) was where he elaborated on one of his most famous concepts, born out of an obsession with gambling inculcated during his libertine years, between his father’s death and his conversion. (Pascal was the inventor of a type of early roulette.) From this strange union of luck and theology Pascal conceived his infamous and celebrated “wager,” the argument not for the rationality of God, but for the rationality of belief in God. Reflecting the skepticism of the age, Pascal affirmed that we are “incapable of knowing either what He is or if He is.” The patristic churchmen and medieval scholastics had used gallons of ink and yards of vellum to rationally prove the existence of God, but prefiguring Immanuel Kant’s Critique of Pure Reason a century later, Pascal claimed that such proofs were for naught. Between humankind’s apprehension and the true nature of reality, there is, he said, “an infinite chaos which separate[s] us.” But the mechanism for one’s own personal faith can be supremely rational, and to make his case, Pascal returned us to the smoky gambling dens of his youthful indiscretions.
Pascal reasoned that life is a sort of “game,” and that our faith in God, or lack-there-of, is our wager as to the ultimate nature of reality—and what we stand to win (or lose) is nothing less than eternal life. Imagine that all of reality rides on a coin-toss, with one side of the coin affixed with the phrase “God Exists” and the other “God Does Not Exist.” The question that Pascal asked is, “What will you wager?” The essence of his thought experiment was that if one wagers that God does exist, and He does not, the gambler loses comparatively little (perhaps a bit of wine, women, and song, as Pascal may have enjoyed during his wild years). However, if one makes the bet that God does exist, and that coin lands heads-up, then the gambler is rewarded with an eternity in paradise. On the other hand, bet rightly that God does not exist, and you’ve gained very little (again, a life of finite pleasures). Bet wrongly that God does not exist, then you are punished with eternal damnation.