The less you go into the detailed study of physiology, the better for you. Our knowledge of this science is very imperfect, and leads to imperfect thought. Imperfect thought causes imperfect functioning, which is disease. Let me illustrate: Until quite recently, physiology fixed ten days as the extreme limit of man's endurance without food; it was considered that only in exceptional cases could he survive a longer fast. So the impression became universally disseminated that one who was deprived of food must die in from five to ten days; and numbers of people, when cut off from food by shipwreck, accident, or famine, did die within this period. But the performances of Dr. Tanner, the forty-day faster, and the writings of Dr. Dewey and others on the fasting cure, together with the experiments of numberless people who have fasted from forty to sixty days, have shown that man's ability to live without food is vastly greater than had been supposed. Any person, properly educated, can fast from twenty to forty days with little loss in weight, and often with no apparent loss of strength at all. The people who starved to death in ten days or less did so because they believed that death was inevitable; an erroneous physiology had given them a wrong thought about themselves. When a man is deprived of food he will die in from ten to fifty days, according to the way he has been taught; or, in other words, according to the way he thinks about it. So you see that an erroneous physiology can work very mischievous results.
No Science of Being Well can be founded on current physiology; it is not sufficiently exact in its knowledge. With all its pretensions, comparatively little is really known as to the interior workings and processes of the body. It is not known just how food is digested; it is not known just what part food plays, if any, in the generation of force. It is not known exactly what the liver, spleen, and pancreas are for, or what part their secretions play in the chemistry of assimilation. On all these and most other points we theorize, but we do not really know. When man begins to study physiology, he enters the domain of theory and disputation; he comes among conflicting opinions, and he is bound to form mistaken ideas concerning himself. These mistaken ideas lead to the thinking of wrong thoughts, and this leads to perverted functioning and disease. All that the most perfect knowledge of physiology could do for man would be to enable him to think only thoughts of perfect health, and to eat, drink, breathe, and sleep in a perfectly healthy way; and this, as we shall show, he can do without studying physiology at all.
