One common argument that Christians use to persuade atheists to risk a belief in God runs like so:
God is or He is not... Let us weigh the gain and the loss in wagering that God is. Let us estimate these two chances. If you gain, you gain all; if you lose, you lose nothing. Wager, then, without hesitation that He is.
Of course, it typically comes out these days sounding a touch more linguistically modern: "If God exists and you believe in Him, you win big; if God exists and you don't believe in Him, you lose really big; and if God doesn't exist, it doesn't matter what you think. But why risk it?" The original quote sounds old because it is — it comes from 17th century mathematician Blaise Pascal, and is commonly referred to as Pascal's Wager
I grew up hearing this sort of argument all the time. All the time. It wasn't until much later in life that I learned of its origins. And of its shortcomings. Namely, that the whole thing depends on God necessarily rewarding folks for believing in Him. Christians, of course, think that dependency is met by simple evaluation of the nature and recorded words of God — of course God wants us to believe in Him. But you can't play those cards with an atheist, since you have yet to establish that the God with said nature exists.
Now, if you're reading this and expect my next paragraph to be a newly revised wager that's logically solid, I'm sorry to disappoint you. I'm only here to say to that in my Bible reading for today, I came across a verse that — perhaps loosely interpreted — pretty much shoots Pascal's wager in the foot on the same grounds. Hebrews 11:6 says:
And without faith it is impossible to please God, because anyone who comes to him must believe that he exists and that he rewards those who earnestly seek him.
Did you catch that? Not only does the author of Hebrews state up front that belief in God's existence requires faith — that is, cannot be proven empirically — but then he says that even if you get that far, you need still more faith to believe that God actually wants you to seek Him. This pretty much buries Pascal's Wager. But at least atheism can't say it was first to bury it.