Pascal's Wager (or Pascal's Gambit) is a suggestion posed by the French philosopher, mathematician and physicist Blaise Pascal that, even though the existence of god cannot be determined through reason, a person should wager as though god exists, because living life accordingly has everything to gain, and nothing to lose.
Pascal states, however, that some do not have the ability to believe. In this case, he directs them to live as though they had faith, which may lead them to belief. The Wager was set out in note 233 of his Pensées, a posthumously published collection of notes made by Pascal in his last years as he worked on a treatise on Christian apologetics.
Historically, Pascal's Wager was groundbreaking as it had charted new territory in probability theory, was one of the first attempts to make use of the concept of infinity, marked the first formal use of decision theory, and anticipated the future philosophies of pragmatism and voluntarism
Richard Dawkins suggests that instead of the deity Pascal assumed, god might reward honest attempted reasoning and punish blind or feigned faith.
Richard Carrier expands this argument as such:
Suppose there is a god who is watching us and choosing which souls of the deceased to bring to heaven, and this god really does want only the morally good to populate heaven. He will probably select from only those who made a significant and responsible effort to discover the truth. For all others are untrustworthy, being cognitively or morally inferior, or both. They will also be less likely ever to discover and commit to true beliefs about right and wrong. That is, if they have a significant and trustworthy concern for doing right and avoiding wrong, it follows necessarily that they must have a significant and trustworthy concern for knowing right and wrong. Since this knowledge requires knowledge about many fundamental facts of the universe (such as whether there is a god), it follows necessarily that such people must have a significant and trustworthy concern for always seeking out, testing, and confirming that their beliefs about such things are probably correct. Therefore, only such people can be sufficiently moral and trustworthy to deserve a place in heaven — unless god wishes to fill heaven with the morally lazy, irresponsible, or untrustworthy