The placebo effect refers to the process whereby the expectation that a treatment will help relieves symptoms, regardless of the actual substance of the treatment itself. The nocebo effect is similar, but causes, rather than relieves, symptoms.
- No one doubts—certainly not I—that the mind exercises a powerful influence over the body. From the beginning of time, the sorcerer, the interpreter of dreams, the fortune-teller, the charlatan, the quack, the wild medicine-man, the educated physician, the mesmerist, and the hypnotist have made use of the client's imagination to help them in their work. They have all recognized the potency and availability of that force. Physicians cure many patients with a bread pill; they know that where the disease is only a fancy, the patient's confidence in the doctor will make the bread pill effective.
- When I was a boy a farmer's wife who lived five miles from our village had great fame as a faith-doctor—that was what she called herself. Sufferers came to her from all around, and she laid her hand upon them and said, "Have faith—it is all that is necessary," and they went away well of their ailments. She was not a religious woman, and pretended to no occult powers. She said that the patient's faith in her did the work. Several times I saw her make immediate cures of severe toothaches. My mother was the patient. In Austria there is a peasant who drives a great trade in this sort of industry, and has both the high and the low for patients. He gets into prison every now and then for practising without a diploma, but his business is as brisk as ever when he gets out, for his work is unquestionably successful and keeps his reputation high. In Bavaria there is a man who performed so many great cures that he had to retire from his profession of stage-carpentering in order to meet the demand of his constantly increasing body of customers. He goes on from year to year doing his miracles, and has become very rich. He pretends to no religious helps, no supernatural aids, but thinks there is something in his make-up which inspires the confidence of his patients, and that it is this confidence which does the work, and not some mysterious power issuing from himself.
- Mark Twain, Christian Science (1907), Chapter IV.
- So long as the body is affected through the mind, no audacious device, even of the most manifestly dishonest character, can fail of producing occasional good to those who yield it an implicit or even a partial faith. The argument founded on this occasional good would be as applicable in justifying the counterfeiter and giving circulation to his base coin, on the ground that a spurious dollar had often relieved a poor man's necessities.
- The powers of the placebo are so strong that it may be morally wrong to call homeopathy a lie because the moment you say it then a placebo falls to pieces and loses its power.
- Sublime is the dominion of the mind over the body, that, for a time, can make flesh and nerve impregnable, and string the sinews like steel, so that the weak become so mighty.
- The wonderful influence of imagination in the cure of diseases is well known. A motion of the hand, or a glance of the eye, will throw a weak and credulous patient into a fit; and a pill made of bread, if taken with sufficient faith, will operate a cure better than all the drugs in the pharmacopœia. [...] Many hundreds of instances [...] might be related, especially from the history of witchcraft. The mummeries, strange gesticulations, and barbarous jargon of witches and sorcerers, which frightened credulous and nervous women, brought on all those symptoms of hysteria and other similar diseases, so well understood now, but which were then supposed to be the work of the Devil, not only by the victims and the public in general, but by the operators themselves.
- There is a case cited by Korzybski in Science and Sanity of a man who suffered from hay fever whenever there were roses in the room. In an experiment, a bunch of roses was produced unexpectedly in front of him, and he immediately had a violent attack of hay fever, despite the fact that the "roses" in this case were made of paper.
- The power which a man's imagination has over his body to heal it or make it sick is a force which none of us is born without. The first man had it, the last one will possess it. If left to himself, a man is most likely to use only the mischievous half of the force—the half which invents imaginary ailments for him and cultivates them; and if he is one of these—very wise people, he is quite likely to scoff at the beneficent half of the force and deny its existence. And so, to heal or help that man, two imaginations are required: his own and some outsider's. The outsider, B, must imagine that his incantations are the healing-power that is curing A, and A must imagine that this is so. I think it is not so, at all; but no matter, the cure is effected, and that is the main thing. The outsider's work is unquestionably valuable; so valuable that it may fairly be likened to the essential work performed by the engineer when he handles the throttle and turns on the steam; the actual power is lodged exclusively in the engine, but if the engine were left alone it would never start of itself. Whether the engineer be named Jim, or Bob, or Tom, it is all one—his services are necessary, and he is entitled to such wage as he can get you to pay. Whether he be named Christian Scientist, or Mental Scientist, or Mind Curist, or King's-Evil Expert, or Hypnotist, it is all one; he is merely the Engineer; he simply turns on the same old steam and the engine does the whole work.
- Mark Twain, Christian Science (1907), Chapter VIII.