Dream hallucination arises when the countercathexes of the ego are diminished during sleep and can no longer control the repressed psychic contents which give rise to dreams. Contrary to Freud's theory of reality-testing, the uncontrollable psychic contents seem to convince the sleeping ego that they are real (external) because in the ego's waking experience it is less able to control psychic contents which originate in actual external reality, than psychic contents which arise spontaneously. The dream screen is a luminous surface on to which the dream contents are projected. Its light is a primordial hallucination, present in every dream. This primordial hallucination comes from a reactivation of the repressed memory of the dazzling vision of light which was received at the moment of birth.