Just as it is possible for the dream-mind to assume different personalities, each speaking and behaving according to type, so it is possible for other hidden layers of the mind to dramatize themselves and speak as they might be expected to in their respective capacities. We are only on the fringe of discovering what latent powers the human mind possesses. The entity which controls can quite well be himself in another guise, not only because of the foregoing but also because of characteristics developed in former births and still lying beneath the surface of this birth. On the other hand, there is a less likely possibility of genuine spirit-control. This is true even if, during the delivery of trance addresses, the medium himself is quite unconscious of them and of everything that is happening at the time.
-- Notebooks Category 16: The Sensitives > Chapter 13 : The Occult > # 134
