Max Velmans, Understanding Consciousness
p. 300 “To make matters worse, there are four distinct ways in which body/brain and mind/consciousness might in principle, enter into casual relationship. There might be physical causes of physical states, physical causes of mental states, mental causes of mental states, and mental causes of physical states. Establishing which forms of causation are effective in practice has clear implication for understanding the aetiology and proper treatment of illness and disease.
Within conventional medicine, physical -> physical is taken for granted. Consequently, the proper treatment for physical disorders is assumed to be some from of physical intervention. Psychiatry takes the efficacy of physical -> mental causation for granted, along with the assumption that the proper treatment for psychological disorders may involve psychoactive drugs, neurosurgery and so on. Many forms of psychotherapy take mental -> mental causation for granted, and assume that psychological disorders can be alleviated by means of ‘talking cures’, guided imagery, hypnosis and other form of mental intervention. Psychosomatic medicine assumes that mental -> physical causation can be effective (‘psychogenesis’). Consequently, under some circumstances, a physical disorder (for example, hysterical paralysis) may require a mental (psychotherapeutic) intervention. Given the extensive evidence for all these causal interactions (cf. Velmans, 1996a), how we to make sense of them?”
Velmans, M. 1996a: The Science of Consciousness: Psychological, Neuropsychological and Clinical Reviews, London: Routledge.