" Thirdly and most important, the psychical energy model is logically unrelated to the concepts that Freud, and everyone since, regards as truly central to psychoanalysis—the role of unconscious mental processes, repression as a process actively keeping them unconscious, transference as a main determinant of behaviour, the origin of neurosis in childhood trauma. Not one of these concepts bears any intrinsic relation to a psychical energy model; and when this model is discarded all four remain intact and unchanged. The psychical energy model is a possible model for explaining the data to which Freud drew attention: it is certainly not a necessary one. "

― John Bowlby , Attachment