Sight and hearing do not depend upon the eyes and ears. The nervous system can really cause no suffering. "Nerves are not the source of pain or pleasure." "Nerves have no more sensation, apart from what belief bestows upon them, than the fibre of a plant." What really suffers is mind, or belief; and, if we change that belief, the pain will disappear. "You say a boil is painful," says Mrs. Eddy, "but that is impossible, for matter without mind is not painful. The boil simply manifests your belief in pain, through inflammation and swelling; and you call this belief a boil." Mrs. Eddy even argues against spanking children because "the use of the rod is virtually a declaration to the child's mind that sensation belongs to matter."[11] Mrs. Eddy's idea is that our lungs are necessary to us because we think they are, just as we think heavy underwear is necessary in winter. Horses and cows, certainly, do not think much about their lungs, but Mrs. Eddy says that domestic animals are controlled by the beliefs of their human masters, and that we have corrupted the horse and have taught him to have epizooetic and colic. "What," says Mrs. Eddy, "if the lungs are ulcerated? God is more to a man than his lungs." "Have no fears that matter can ache, swell, and be inflamed.... Your body would suffer no more from tension or wounds than would the trunk of a tree which you gash, were it not for mortal mind." All functional and organic diseases are produced by a popular belief in their reality. "No gastric juice accumulates ... apart from the action of mortal thought." "Inflammation, hemorrhages, tubercles, decompositions are all dream shadows," "Man is the same after, as before, a bone is broken or a head chopped off." But as to who invented the idea of pain and whence came the superstition that we must have lungs to breathe and that the heart is necessary to life, Mrs. Eddy maintains a discreet silence. Sin, sickness, and death, she says, are beliefs which originated in mortal mind. And how and when did mortal mind originate? Mortal mind does not exist, she answers, therefore it had no origin. This reasoning satisfies her; she believes it perfectly adequate. It is not only the diseased body which is to be disregarded and put out of mind, but all hygienic precautions. Mrs. Eddy particularly objects to diets, and she says that one food is as good as another. God gave man "dominion not only over the fish in the sea, but over the fish in the stomach also," she once said. There is no such thing as fatigue: "You would not say that a wheel is fatigued; and yet the body is just as material as the wheel. If it were not for what the human mind says of the body, the body would never be weary, any more than the inanimate wheel."