Blaise Pascal On Man's Ability to do Evil in the Name of Faith

'Men never do evil so completely and cheerfully as when they do it from a religious conviction'.

Blaise Pascal
French mathematician, physicist (1623 - 1662)

My namesake is also known for Pascal's wager, a pragmatic or decision theory-based approach to faith-- resolving that it is better to have faith in God because if you don't and God does, indeed, exist, you would have considerable downside in being wrong.

From the Stanford Encyclopedia of Philosophy:

“Pascal's Wager” is the name given to an argument due to Blaise Pascal for believing, or for at least taking steps to believe, in God. The name is somewhat misleading, for in a single paragraph of his Pensées, Pascal apparently presents at least three such arguments, each of which might be called a ‘wager’ — it is only the final of these that is traditionally referred to as "Pascal's Wager". We find in it the extraordinary confluence of several important strands of thought: the justification of theism; probability theory and decision theory, used here for almost the first time in history; pragmatism; voluntarism (the thesis that belief is a matter of the will); and the use of the concept of infinity.