Full Idea
Moral functionalism is the view that the meanings of moral terms are given by their place in the network of input, internal clauses, and output that makes up folk psychology.
Gist of Idea
Moral functionalism says moral terms get their meaning from their role in folk morality
Source
Frank Jackson (From Metaphysics to Ethics [1998], Ch.5)
Book Reference
Jackson,Frank: 'From Metaphysics to Ethics' [OUP 2000], p.131
A Reaction
Jackson considers this enough to support a cognitivist view of morality. In assuming that there is something stable called 'folk morality' he seems to be ignoring questions about cultural relativism.