The question is: Are moral obligations real? Perhaps what can be answered is: What are rational ways to justify belief or disbelief in the reality of moral obligations?
G. E. M. Anscombe, in her paper "Modern Moral Philosophy", provided three general perspectives from which one might rationally justify belief or disbelief in moral obligations.
First, Anscombe claimed that Aristotle's ethics did not have the idea of an obligation not to be unjust. Some may be blameworthy, but they are under no obligation not to make a mistake: (page 1 of the linked file)
Now has Aristotle got this idea of moral blame, as opposed to any other? If he has, why isn't it more central? There are some mistakes, he says, which are causes, not of involuntariness in actions but of scoundrelism, and for which a man is blamed. Does this mean that there is a moral obligation not to make certain intellectual mistakes? Why doesn't he discuss obligation in general, and this obligation in particular?
Regardless whether one accepts Anscombe's view of Aristotle, she raises the possibility with Aristotle of the existence of a rational ethics without moral obligation.
Second, Anscombe references a "law conception of ethics" which requires a divine law and legislator: (page 5)
Naturally it is not possible to have such a conception unless you believe in God as a law-giver; like Jews, Stoics, and Christians.
Given a law and a legislator, one can rationally justify the reality of moral obligations to obey that law.
Third, she mentions that with the Reformation the idea arose that, although there is a divine law, it is not something humans have the ability to obey although they may be obligated to do so. This over the centuries created the positions of modern moral philosophy where only the idea of moral obligation remained, but neither the divine law nor the legislator. She describes this situation as like the following: (page 5)
It is as if the notion of "criminal" were to remain when criminal law and criminal courts had been abolished and forgotten.
If she was right, this may be the situation we are be in today. Rather than a divine law, moral obligation comes from such psychological sources as conscience for Butler, legislating for oneself for Kant, pleasure for Bentham and Mill or consequences for Sidgwick. (pages 2-7)
From these three perspectives come three rational ways to justify belief or disbelief in moral obligations.
- From an Aristotelian perspective, moral obligations are not necessary for ethics.
- From a law conception of ethics, moral obligations are as real as the divine law and legislator.
- From a modern perspective, moral obligations are real, but they have a psychological rather than a divine ground.
Anscombe, G. E. M. (1958). Modern moral philosophy. Philosophy, 33(124), 1-19.