The Naturalistic Fallacy

Wherever you look, G. E. Moore's Naturalistic Fallacy is not described very clearly.  Moore's own explanation is too-involved, and his illustrations of the idea are tiresome. When she explains it in her paper "Modern Moral Philosophy," Elizabeth Anscombe, for some reason, embarks upon a long-winded description of an idea from Hume that resembles the Naturalistic Fallacy. The Ethics textbooks are similarly confusing, or boring.

It is, however, a pretty easy idea. First, recall what we already know about propositions.  Next, consider how the Naturalistic Fallacy helps us to understand why (I believe) that Logic cannot prove--like a mathematical or geometric proof--a moral proposition.

Consider the following propositions:

1) Two and two is four.

2) Stealing is wrong.

In each of these two examples, is has a different kind of meaning.

In the first example, "Two and two is four", is means equivalence.  It is true in an analytic sense.  That is, it is logically true: 2 + 2 = 4.  We don't usually call mathematical equations "propositions," but note that the example here is a grammatical sentence, and it is proved by the relationship of (2 + 2) and (4). That is, two and two is four.

In the second example, "Stealing is wrong," is means "I think" or "some people think" stealing is wrong.  Although many people agree, and even though I (the consummate highbrow) and you (card-carrying members of the Highbrow Commonwealth) think (or believe) stealing is wrong, in this case, is is not the same as equivalence or conclusive proof.

Stealing is wrong because we say so.

George Edward Moore