The brain is chemically controlled, and experience has shown that it can be made permeable to the (biologically speaking) superfluous aspects of Mind-at-Large by modifying the (biologically speaking) normal chemistry of the body. For almost half of every year our ancestors ate no fruit, no green vegetables, and (since it was impossible for them to feed more than a few oxen, cows, swine, and poultry during the winter months) very little butter or fresh meat, and very few eggs. By the beginning of each successive spring, most of them were suffering, mildly or acutely, from scurvy, due to lack of vitamin C, and pellagra, caused by a shortage in their diet of the B complex. The distressing physical symptoms of these diseases are associated with no less distressing psychological symptoms. The nervous system is more vulnerable than the other tissues of the body; consequently vitamin deficiencies tend to affect the state of mind before they affect, at least in any very obvious way, the skin, bones, mucous membranes, muscles, and viscera. The first result of an inadequate diet is a lowering of the efficiency of the brain as an instrument for biological survival. The undernourished person tends to be afflicted by anxiety, depression, hypochondria, and feelings of anxiety. He is also liable to see visions; for when the cerebral reducing valve has its efficiency reduced, much (biologically speaking) useless material flows into consciousness from 'out there', in Mind-at-Large. Much of what the earlier visionaries experienced was terrifying. To use the language of Christian theology, the Devil revealed himself in their visions and ecstasies a good deal more frequently than did God. In an age when vitamins were deficient and a belief in Satan universal, this was not surprising. The mental distress, associated with even mild cases of pellagra and scurvy, was deepened by fears of damnation and a conviction that the powers of evil were omnipresent. This distress was apt to tinge with its own dark colouring the visionary material, admitted to consciousness through a cerebral valve whose efficiency had been impaired by underfeeding. But in spite of their preoccupations with eternal punishment and in spite of their deficiency disease, spiritually minded ascetics often saw heaven and might even be aware, occasionally, of that divinely impartial One, in which the polar opposites are reconciled. For a glimpse of beatitude, for a foretaste of unitive knowledge, no price seemed too high. Mortification of the body may produce a host of undesirable mental symptoms; but it may also open a door into a transcendental world of Being, Knowledge, and Bliss. That is why, in spite of its obvious disadvantages, almost all aspirants to the spiritual life have, in the past, undertaken regular courses of bodily mortification. So far as vitamins were concerned, every medieval winter was a long involuntary fast, and this involuntary fast was followed, during Lent, by forty days of voluntary abstinence-Holy Week found the faithful marvellously well prepared, so far as their body chemistry was concerned, for its tremendous incitements to grief and joy, for seasonable remorse of conscience and a self-transcending identification with the risen Christ. At this season of the highest religious excitement and the lowest vitamin intake, ecstasies and visions were almost a commonplace. It was only to be expected.
