I posted this last January, but, since the topic is coming up in my classes again this week I thought it'd be appropriate to post it again:
Here's the background. A professor has given a lecture this evening in which he claims that our behavior is the product of our genetic make-up. We don't really have free will. We're pretty much at the mercy of our genes which means that we're not really responsible for what we choose to do.
A psychopath has managed to kidnap the professor and challenges him to defend this thesis in the real world. The video, titled Cruel Logic, is pretty grim but as you watch it ask yourself, given the assumptions of the professor, what answer could he make to the psychopath's challenge.
If you were in the professor's position what could you say to save your life? Does the psychopath's behavior make sense if the professor is correct? If man truly is morally autonomous, if there is no objective standard of right and wrong, then what's actually wrong with the psychopath's behavior, beyond the fact that we're repelled by it? Does being repelled by something make it morally wrong?
The only way to resist the conclusion that there's really nothing wrong with what he's doing is to deny the premise that morality is a completely subjective phenomenon. But, in the absence of an objective, transcendent ground for moral behavior, there is no way to judge the psychopath's behavior as being wrong.
As philosopher Richard Rorty once said, the secular man has no answer to the question, why not be cruel. Ideas do indeed have consequences. If you believe that gratuitous cruelty is in fact wrong then you have to acknowledge that there's an objective standard of morality, but once you've taken that step, it's very hard to avoid the conclusion that there's a transcendent, personal, moral authority that has established that objective standard.
In other words, it's very hard to see how one can be a naturalist (i.e. an atheist) and also believe that what the psychopath in this video is doing is wrong.