The discussion of the game of marbles seems to have led us into rather deep waters. But in the eyes of children the history of the game of marbles has quite as much importance as the history of religion or of forms of government. It Is a history, moreover, that is magnificently spontaneous; and it was therefore perhaps not entirely useless to seek to throw light on the child's judgment of moral value by a preliminary study of the social behaviour of children amongst themselves.

Ch. 2 : Adult Constraint and Moral Realism - The Moral Judgment of the Child (1932)