Pascal's Wager (or Pascal's Gambit) is a suggestion posed by the French philosopher, mathematician, and physicist Blaise Pascal that even if the existence of God could not be determined through reason, a rational person should wager as though God exists, because living life accordingly has everything to gain, and nothing to lose. Pascal formulated his suggestion uniquely on the God of Jesus Christ as implied by the greater context 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. The Wager was set out in note 233 of this work.
Following his argument establishing the Wager, Pascal addressed the possibility that some people may not be willing to sincerely believe in God even after acknowledging the enormous benefit of betting in favor of God's existence. In this case, he advises them to live as though they had faith, which may subvert their irrational passions and lead them to genuine belief.
Following the publication of Pascal's Wager, some have argued that the Wager may also apply to conceptions of God within different religious traditions or belief systems, and as such has been used in traditions other than Christianity, such as Islam. Historically, Pascal's Wager was groundbreaking because it 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 future philosophies such as existentialism, pragmatism, and voluntarism.