Pascal's Wager
Pascal's Wager is an argument, presented by Blaise Pascal, that it is in one's best interest to believe in God and to lead a Christian life, even if one is not convinced of his existence.
Blaise Pascal
Blaise Pascal was a French mathematician, philosopher and theologian, who lived from 1623 to 1662.
The Wager
Pascal came up with Pascal's Wager, an argument which goes along these lines.
We cannot know for certain whether God exists. If he does, then heaven awaits believers, hell awaits non-believers. If he doesn't, oblivion awaits us all.
Suppose you believe and live a Christian life.
If you are right, then you gain an infinite number of years of total pleasure; if you are wrong, you miss out on a few pleasures for the few years of this life.
Suppose you don't believe.
If you are right you can do a few things in this life that you shouldn't do as a Christian. If you are wrong, you will be subject to an infinite number of years of total pain.
The range of possible outcomes is clearly better if you believe.
It is therefore in everyone's interest to believe and be Christian.
The Fallacy
If the probability of the existence of God is say 10%, then the wager assumes that not believing gives us a 10% chance of hell and infinite pain; believing gives us a 0% chance.
However, in reality, believing doesn't guarantee not going to hell, for three reasons:
1. The Muslims might be right rather than the Christians, or any of the other thousands of religions, in which case Christians could still go to hell.
2. Christian salvation is based on faith and Hebrews 11:1 indicated that faith requires assurance or certainty. A 10% belief probably wouldn't cut it.
3. Many Christians have a Calvinist belief that God decides who is to be saved and that we have no say in it. If this is the case, then choosing to be a Christian makes no difference anyway.
All we can say is that, if we decide to live a Christian life, the chance of hell and infinite pain reduces slightly from 10%, maybe to 9.9%. This difference might not worth sacrificing the pleasures of this life for.