Is Moral Nihilism a Morality?

[vulcanlogician]

What would be a non-natural fact? Does 2+2=4 need empirical evidence to be true? Is the sum of the square of a right triangle's two angles equal to the square of the hypotenuse only true if we can find an example of such a triangle in nature?

Does 2+2=4 require minds to be true? Does empiricism require subjective experience? Does subjective experience require a mind?

I think 2+2=4 even without minds. But I think the whole world is natural because nothing is supernatural.

But if non-natural just means non-empirical then I don't think that 2+2=4 is a natural fact because it's a priori.

But I don't think moral statements can be true without the existence of minds ... and minds are natural phenomena.

As I see it, you can go three ways with this argument. You could accept the conclusion and be an error theorist. You could disagree with the second premise and be a moral naturalist. -OR- You could disagree with the first premise (as I do) and be a non-naturalist like G.E. Moore or Plato (or maybe Spinoza and the Stoics too, among others). Notice that relativists have nowhere to go in the debate over this argument. Unlike you and GB, I find moral nihilism somewhat compelling. If you asked me what theories made no fucking sense whatsoever, I'd have to say all forms of moral relativism suffer from an irredeemable incoherence. Nihilism is crystal clear by comparison. It just so happens that I think non-naturalism is clearer.

I think the first premise is false unless science includes empiricism as a whole (science in a wide sense).

If the first premise is referring to empiricism as a whole then I think the second premise is false instead.

All a priori knowledge is non-natural. The point I was trying to make was that there is a such thing as non-natural knowledge. A priori knowledge is a perfect example.

But other than to demonstrate that non-natural knowledge is a thing, the a priori/a posteriori distinction is not identical with the natural/non-natural distinction. Non-naturalists consider empirical evidence all the time when formulating what is good and what is not.

A non-naturalist simply holds that moral facts aren't the same as natural facts. For example, a hedonist can say that the object of his morality is natural because it is (in principle) measurable by science. You could (in principle) measure via scientific investigation levels of happiness/suffering. Therefore, the level of happiness/suffering in the world is measurable by scientists. Ergo, moral facts are really natural facts.

A non-naturalist rejects that moral principles can be solely perceived by empirical investigation. In the simplest terms, the non-naturalist says (correctly, I think) that no amount of empirical investigation (by itself) will reveal a moral fact.