(Washington, DC) Moral propositions are true or false. For example, “Genocide is evil” is a true statement. If you disagree with it, you’re wrong. So I believe, and so do most moral philosophers. This assumption violates the fact/value distinction that we teach kids as early as elementary school. We teach them that values are opinions, in contrast to facts. But I as little doubt that genocide is wrong as I doubt Newton’s laws of motion or the existence of the chair on which I sit right now. If the chair turned out to be an illusion, I wouldn’t be thoroughly crazy. If I started to favor genocide, I would be.

So what leads people to the theoretical view that moral propositions are mere opinions, neither true nor false? The problem is one of method.

We believe in natural facts because from our earliest days, nature is obdurate. Fire burns, and we form a solid belief that the fire has caused our pain. The same sensory perceptions and logical premises that we use to reach such simple conclusions also underlie scientific method, which extends our knowledge vastly, pays practical dividends, and sometimes generates counter-intuitive findings that turn out to be correct. We are almost all naturalists now, believing that science (broadly defined) yields truth, and that what is true is what science yields.

With morality, we also draw firm impressions about vivid cases. Even if you are skeptical about moral truth (in theory), you will feel with virtual certainty that it is wrong to kill someone in cold blood for one’s own amusement. You may have convinced yourself that “wrong” is just an opinion, or just an instinct inbred by natural selection, but you will oppose cold-blooded murder with as much certainty as you believe in cause-and-effect or the persistence of objects in nature.

But many other cases are more ambiguous. We know that our moral knowledge is unreliable, because we disagree with one another and because our assumptions have changed over time. For many centuries, virtually everyone (female as well as male) believed that men were superior to women in many respects. Now I and many others are sure that was wrong. But if I had been born 200 years ago, I would have been mistaken about gender. If I had been born a gentile German around 1900, I assume that I would have supported Hitler in 1939, because almost everyone did.

When we study nature, we also face ambiguity and commit errors. Like moral views, scientific theories change. It’s just that with morality, we lack an agreed-upon method for addressing uncertainty and correcting error.

That is not to say that we lack methods altogether. Philosophers often propose them. For example, John Rawls proposed developing the rules of a just society while imagining that one does not know one’s own circumstances. Putting oneself behind an imaginary “veil of ignorance,” as Rawls suggested, is a method.

But the reception of Rawls is characteristic of philosophy. Critics quickly said that too many moral assumptions were built into his method. You had to be a liberal individualist, they said, to endorse the method that led Rawls to his liberal conclusions. Moral methodology doesn’t seem separable from substantive moral views.

I acknowledge that problem, and I don’t think we are likely to find a moral method that wins consensus and  solves one controversy after another. But it doesn’t follow that morality is mere opinion. Alas, moral propositions are true or false and yet we have no agreed-upon way to know which is which in a range of ambiguous situations.