I've been thinking a lot about morality lately and how it fits into naturalistic versus supernaturalistic world-views. I've listened to a lot of debates and many different perspectives and I think I've come to some pretty solid conclusions. But there is still one area where I don't have a good answer. That is: how can the idea of moral obligation fit into a naturalistic (and therefore deterministic) world-view?
It seems to me that naturalists can make a good case that human morality is objective and that it is based on the concept of well-being versus suffering of sentient creatures. Therefore, using a well thought out and well tested ethical system like "rule-utilitarianism" that takes well-being and suffering into account to decide on the right action in any given situation, the naturalist can justifiably discern the moral from the immoral. Where the naturalist's system of morality breaks down is trying to justify the existence of objective moral obligations.
I have come to believe that in order to argue that moral obligations exist there must be an inherent purpose to human life, a purpose that cannot be supplied by the naturalistic world view (as argued very ably by this panel of atheist and Christian all-stars [this debate is certainly worth watching if you've got the time, I think I agree most strongly with Michio Kaku, but he doesn't get to talk until the end]). Now I'm not saying that naturalists lives are purposeless, but they create those purposes for themselves in order to live fulfilling lives. There can be no inherent objective purpose to life in naturalism as there is in the theistic world view.
From the theistic perspective it is simple. Every person is created by God with the inherent purpose of coming to know God and engage in a loving relationship with Him. God is the perfection of morality, so those characteristics which he possesses are moral, anything opposing the moral is immoral. And since the inherent purpose of our life is to have a relationship with God, we therefore have an obligation to act morally.
But since the only purposes we can have in the naturalistic universe are those subjective purposes that we create for ourselves, there can be no true obligation to act morally.
The only arguments I can foresee against this conclusion are:
1) The argument from evolution: we have a natural obligation to propagate our genes & since morality is an adaptive strategy we have an obligation to engage in it.
-But it seems to me that same line of reasoning could be used to argue we have an obligation to engage in social Darwinism and/or eugenics.
2) When a rational mind realizes that there are moral truths, reason obligates him to act morally.
Really the big problem I see with any conceivable argument for the existence of moral obligation in the naturalistic world view is this: Someone once said "Ethics is what we do when nobody is looking." And within the naturalistic universe I can't think of anything that obligates a person to act morally even when nobody is looking or when nobody will ever know whether you acted morally or not.