What Freud called “the reality principle,” or judgment, presumes on the part of the child who has arrived at judgment the implicit grasp of a complex of concepts: truth and falsity, belief, subjective and objective, the objectively real, my perspective and yours. Work in both philosophy and infant research points to the essential importance in the development of judgment of a triangulating situation that involves particular sorts of communications between two creatures and an external object that interests them both. In this light Bion's theory of thinking is critically examined and the meaning of primary process and fantasy is discussed.