We have attempted to conceptualize the relationship between a conscious desire expressed by a patient during a therapy session, a remembered latency period fantasy and a delusion experienced during a psychotic period. Based on our clinical material, we have offered a reappraisal of the function, structure, and genesis of delusion, fantasy and desire as metapsychological entities. A delusion, we suggest, forms during the period of childhood to give representation to significant traumata affecting the separation-individuation tasks. It functions to restore a basic sense of safety. Fantasying is a mental activity which provides a key to the understanding of the other contents. While fantasy is the testing ground wherein modes of satisfaction are tried out for their personal appeal, desire is the testing ground wherein concrete reality satisfactions are tried out for their attainability. Without fantasy, mental functioning would be mechanical and uncreative. Without conscious and preconscious desire, the full awareness of the self would not develop.