Full Idea
Moral Philosophy rests on the mistake of supposing the possibility of proving what can only be apprehended directly by an act of moral thinking.
Gist of Idea
The mistake is to think we can prove what can only be seen directly in moral thinking
Source
H.A. Prichard (Does moral phil rest on a mistake? [1912])
Book Reference
Prichard,H.A.: 'Moral Writings' [OUP 2002], p.19
A Reaction
This is a beginning of the rebellion against the Enlightenment Project in ethics, which is why Prichard has become popular. At bottom he is offering intuition ('direct moral thinking'), which is a frustratingly thin concept.