The key to the knowledge of the nature of the soul’s conscious life lies in the realm of the unconscious. This explains the difficulty, if not the impossibility, of getting a real comprehension of the soul’s secret … But if this impossibility is only apparent, then the first task of a science of the soul is to state how the spirit of Man is able to descend into these depths. (Carus 1846, quoted in Ellenberger 1994: 207)
