It’s nearly as predictable as if it were a law of nature: Every few years, someone argues with me online that Hume’s Law (that one cannot derive an “ought” from an “is”) is wrong. And usually, the challenge comes from an atheist who is convinced that they must set this law aside in order to defend moral realism — and thus answer critics who say that atheism cannot justify morality.
There are two basic points such people should learn about this. First, that Hume’s Law is a simple matter of logic; in the sense Hume was talking about, an “ought” cannot be derived from an “is,” period. Second, that in itself this does not show there are no moral truths. It doesn’t even show that ethical naturalism (the view that there are “natural” — and thus in principle scientifically discoverable — moral truths) is false. Anyone who wishes to maintain that there are moral facts discoverable by science is therefore welcome to attempt to do so some other way, in spite of Hume’s Law.























