Without God, all things are permissible.
This is a recurring idea in Dostoevsky’s Brothers Karamazov and it gets a lot of airplay today in social media and popular culture. The problem with this supposed argument for Christianity is that it seems uniquely designed to make the humanist look better than the Christian. If you tell me that without God we would have no reason to behave morally, aren’t you telling me that in your heart you would just as soon screw me but refrain only out of fear of God? Doesn’t this make the humanist — who is nice to others because of a heartfelt recognition of the intrinsic value of being nice — more admirable, more noble, more trustworthy in a pinch? (This is not an attack on Christianity en masse, just on a troubling line of reasoning employed by some Christians.)
Interestingly, Nietzsche may make an equal and opposite mistake. (Perhaps my readers who are more up on Nietzsche can affirm or deny or elaborate.) Nietzsche also suggests that God’s demise puts us “beyond good and evil,” but unlike our Christian interlocutor, he sees this as a good thing, a liberation of the human spirit from dogmatic ethical constraints (at least for those who are strong enough to handle the implications). The problem is that Nietzsche’s conclusion, like the Christian’s, rests on the premise that morality (or systems of good and evil) founder, or devolve into purely personal prejudices, in the absence of God.
Our humanist combatant of the first paragraph disputes this premise, arguing that rational principles and intuitive sympathies can provide a basis for ethics equal or stronger than any God-based ethic. I can’t say for sure that our humanist is correct, but I can say that in times of moral crisis I’d rather have her at my side than Nietzsche or the Christian of our example (although I might opt for Nietzsche when a crisis of wit is at hand).