There is certainly evidence to indicate that man is dependent on his physical nature. There is also metaphysical evidence which reveals that the body is strongly influenced by the psyche. Materialist medicos are right so far as they go, but they cannot explain why such-and-such a person has a particular kind of physique, for example, which metaphysics can and does. That reason lies in former incarnations where concentration upon the present form took place. The quality of thought, plus the capacity to rise above it, are special keys to this problem.
-- Notebooks Category 10: Healing of the Self > Chapter 3: The Origins of Illness > # 1