The study of the psycho-physical unity in the hope of finding a solution to the problem of the measurability of psychical phenomena (as done in the previous chapter) has led us nowhere. We shall now turn our attention to the manifestations of psychical phenomena by means other than those we have so far considered. This has also been done by experimental psychologists, for instance in the study of intelligence. We shall concentrate here on another line of approach and on another subject, which seems more pertinent to the study of unconscious processes.