Full Idea
Although Moore was reluctant to adopt it, the epistemology the non-naturalists tended to favour was intuitionism.
Gist of Idea
Despite Moore's caution, non-naturalists incline towards intuitionism
Source
report of G.E. Moore (Principia Ethica [1903]) by Michael Smith - The Moral Problem 2.2
Book Reference
Smith,Michael: 'The Moral Problem' [Blackwell 1994], p.19
A Reaction
Moore was presumably reluctant because intuitionism had been heavily criticised in the past for its inability to settle moral disputes. But if you insist that goodness is outside nature, what other means of knowing it is available? Reason?