Pascal's Wager

Pascal's Wager is Blaise Pascal's famous philosophical argument that belief in God is justified as a "good bet", regardless of any metaphysical uncertainty, because disbelief has great cost if wrong, while belief if wrong costs nothing.

It states that if you were to analyse your options of religion carefully, you would come out with the following possibilities:

You may believe in God, and God exists, in which case you go to heaven.
You may believe in God, and God doesn't exist, in which case you gain nothing.
You may not believe in God, and God doesn't exist, in which you gain nothing again.
You may not believe in God, and God may exist, in which case you will be punished.

Pascal deduced statistically, that it would be better to believe in God unconditionally. Pascal's Wager is also known as "Pascal's Gambit". It is a classic application of game theory to itemize options and payoffs and is valid within its assumptions.

Pascal's wager suffers from the logical fallacy of False dilemma, relying on the assumption that the only possibilities are:

the Christian God exists and punishes or rewards as stated in the Bible, or
no God exists.

The wager cannot rule out the possibility that there is a God who instead rewards skepticism and punishes blind faith, or rewards honest reasoning and punishes feigned faith. In societies where faith is often rewarded by economic and social benefit, its potential moral significance is dubious. It also assumes faith costs nothing, but there may be both direct (time, health, wealth) costs and opportunity costs: those who choose to believe in, say, scientific theories that may contradict scripture may be able to discover things and accomplish things the believer could not.

Variations of this argument can be found in other religious philosophies, such as Hinduism. In his own time, Pascal was severely criticized by Voltaire.