The softest, freest, most pliable and changeful living substance is the brain--the hardest and most iron-bound as well. Given a sufficiently deep conviction, and facts are but as dreams before its huge reality. Our convictions about the home go down to the uttermost depths, and have changed less under the tooth of time than any others, yet the facts involved have altered most radically. The structure of the home has changed from cave to tent, from tent to hut, from hut to house, from house to block or towering pile of "flats"; the functions of the home have changed from every incipient industry known to past times, to our remaining few; the inmates of the home have changed, from the polygamous group and its crowd of slaves, to the one basic family relation of father, mother, and child; but our feelings have remained the same. The progress of society we have seen to be hindered by many evils in the world about us and in our own characters; we have sought to oppose them as best we might, and even in some degree to study them for wiser opposition. Certain diseases we have traced to their cause, removed the cause, and so avoided the disease; others we are just beginning to trace, as in our present warfare with "the white plague," tuberculosis. Certain forms of vice we are beginning to examine similarly, and certain defects of character; we are learning that society is part of the living world and comes under the action of natural law as much as any other form of life. But in all this study of social factors affecting disease and vice and character, we have still held that the home--our most universal environment--was perfect and quite above suspicion. We were right at bottom. The home _in its essential nature_ is pure good, and in its due development is progressively good; but it must change with society's advance; and the kind of home that was wholly beneficial in one century may be largely evil in another. We must forcibly bear in mind, in any honest study of a long-accustomed environment, that our own comfort, or even happiness, in a given condition does not prove it to be good. Comfort and happiness are very largely a matter of prolonged adjustment. We like what we are used to. When we get used to something else we like that too--and if the something else is really better, we profit by the change. To the tired farmer it is comfort to take off his coat, put up his yarn-stockinged feet on a chair, and have his wife serve him the supper she has cooked. The tired banker prefers a dressing gown or lounging jacket, slippers, a well-dressed, white-handed wife, and a neat maid or stately butler to wait on the table. The domestic Roman preferred a luxurious bath at the hands of his slaves. All these types find comfort in certain surroundings--yet the surroundings differ.