Pascal's wager is well known. It assumes everyone is betting on whether God exists by how they are living. But since there are good arguments either way, nobody generally decides which way to wager based on the arguments, but on personal desires. So is there any prudent way of deciding which way to wager? Pascal basically says that if you place your bet on the truth of Christianity and it turns out to be untrue, you end up the same as the atheist: dead. But if you bet on the truth of atheism and it turns out to be false (and Christianity true), you have all eternity to think about what you missed out on.
People often find this wager silly, or just plain stupid. On one level, I would agree that it seems so-- at least IF you take it as an argument intended to persuade anyone to change their views about God. Even if it only convinced you that you had a vested interest in believing that God exists and that you had good reason to submit to Him, it couldn't achieve the goal of getting you to change your beliefs. Pascal knew that our beliefs are, on some level, beyond our volitional control. I can't get you to believe the moon is made of blue cheese by offering you a $1000 to believe it, even if you'd like to. Pascal understood all this.
He also understood that the traditional metaphysical proofs, though valid as arguments, were generally ineffective except for the most exceptional philosopher-types, since they are far too abstract and complicated for most people, and even if it were effective for them, it would be only during the demonstration, because the moment it was completed, they would wonder whether a mistake could have been made somewhere and they were just being credulous.
So Pascal took a different approach, which his gambling and skeptical friends couldn't wriggle out of--an approach which couldn't help engage their wills: he pointed out to them by his "wager" that they were involved in gambling with their lives and eternal destinies by the little decisions they were already making every day-- whether or not to take prayer and moral integrity seriously, whether or not to take truth seriously and respond honestly to the light that each of them already had, and so forth. In other words, he put the onus on THEM by showing that some of the most important kinds of knowledge in the world (including religious knowledge) has attitudinal, moral, and dispositional prerequisites, and that if they hadn't already engaged in a serious and sincere investigation of the claims of religion, their dismissal of things religious couldn't be taken seriously as having any intellectual or moral integrity.
Hence, the wager wasn't intended to get anyone to directly change their beliefs. Pascal knew he couldn't achieve that. He also knew that if people chose to "become religious" simply on the basis of "fire insurance," this would be one of the most self-centered and unworthy motives in the world. Rather, his wager was intended to get people to consider how they were in fact already wagering their lives, and to consider those areas which, unlike their beliefs, are under their volitional control: their decisions about how to live, whether to take their moral lives seriously, along with things like prayer and search after truth, etc. The wager, thus, was intended to launch people in a new direction in their lives, by beginning to change those areas of their lives where they could do so-- their actions: keeping their promises, treating their neighbors with respect, caring about moral integrity, caring about truth where they could see it. I'm guessing that Pascal calculated that this would lead people eventually see things as "evident" to which they had previously been blinded, much as Max Scheler says (in The Nature of Sympathy) that love, far from being blind, opens the eyes of the lover to qualities in the beloved that others are blind to. Eventually, then, the person to whom the world looked devoid of any ultimate purpose or meaning might come to view the same data as replete with the handiwork of God and as saturated with His presence.
Something like that.