Blaise Pascal was a C17th mathematician and philosopher most famous for his application of decision theory to the belief in God.
What Pascal said was, it makes logical sense to believe in God, in the absence of certainty, because it's a better bet to do so.
If God doesn't exist and you don't believe in him, you saved yourself a bit of bother: if he doesn't exist and you do believe, you spend a lot of your Sundays in church and there are some rules you are needlessly following.
If God does exist and you don't believe in him, you incur infinite loss: eternal damnation and hellfire and whatnot. If you do you incur infinite gain: eternal salvation and heaven and that.
Since you don't know whether he exists, the logical option is to believe: minor down side if you wrong, infinite upside. Whereas the alternative has minor upside and infinite burning and pitchforks in the bottom.
The smart chap in the video above, sent to me by the lovely Ed, has applied Pascal's Wager to global warming, and it's remarkably compelling.
It also ends with a different statement of belief, one of the foundations of the information age: that spreading information is action.