Auto-suggestion is disconcerting in its simplicity. To the uninitiated, auto-suggestion or self-mastery is likely to appear disconcerting in its simplicity. But does not every discovery, every invention, seem simple and ordinary once it has become vulgarized and the details or mechanism of it known to the man in the street? Think of all the forces of the Universe ready to serve us. Yet centuries elapsed before man penetrated their secret and discovered the means of utilizing them. It is the same in the domain of thought and mind: we have at our service forces of transcendent value of which we are either completely ignorant or else only vaguely conscious.Power of auto-suggestion known in the Middle Ages. The power of thought, of idea, is incommensurable, is immeasurable. The world is dominated by thought. The human being individually is also entirely governed by his own thoughts, good or bad. The powerful action of the mind over the body, which explains the effects of suggestion, was well known to the great thinkers of the Middle Ages, whose vigorous intelligence embraced the sum of human knowledge.Every idea conceived by the mind, says Saint Thomas, is an order which the organism obeys. It can also, he adds, engender a disease or cure it.The efficaciousness of auto-suggestion could not be more plainly stated.Pythagoras and Aristotle taught auto-suggestion. We know, indeed, that the whole human organism is governed by the nervous system, the centre of which is the brain¬ the seat of thought. In other words, the brain, or mind, controls every cell, every organ, and every function of the body. That being so, is it not clear that by means of thought we are the absolute masters of our physical organism and that, as the Ancients showed centuries ago, thought-or suggestion-can and does produce disease or cure it? Pythagoras taught the principles of auto-suggestion to his disciples. He wrote: "God the Father, deliver them from their sufferings, and show them what supernatural power is at their call."Even more definite is the doctrine of Aristotle, which taught that "a vivid imagination compels the body to obey it, for it is a natural principle of movement. Imagination, indeed, governs all the forces of sensibility, while the latter, in its turn, controls the beating of the heart, and through it sets in motion all vital functions; thus the entire organism may be rapidly modified. Nevertheless, however vivid the imagination, it cannot change the form of a hand or foot or other member."I have particular satisfaction in recalling this element of Aristotle's teaching, because it contains two of the most important, nay, essential principles of my own method of auto-suggestion:1. The dominating role of the imagination.2. The results to be expected from the practice of auto-suggestion must necessarily be limited to those coming within the bounds of physical possibility.Unfortunately, all these great truths, handed down from antiquity, have been transmitted in the cloudy garb of abstract notions, or shrouded in the mystery of esoteric secrecy, and thus have appeared inaccessible to the ordinary mortal. If I have had the privilege of discerning the hidden meaning of the old philosophers, or extracting the essence of a vital principle, and of formulating it in a manner extremely simple and comprehensible to modern humanity, I have also had the joy of seeing it practiced with success by thousands of sufferers for more than a score of years.I hope to show, moreover, that the domain of application of auto-suggestion is practically unlimited. Not only are we able to control and modify our physical functions, but we can develop in any desired direction our moral and mental faculties merely by the proper exercise of suggestion: in the field of education there is vast scope for suggestion. Nothing is impossible to us, except, of course, that which is contrary to the laws of Nature and the Universe.