Quoted from the author's "Introduction" in Chapter 1.
In the series of volumes which I now begin we detach these strands of particular interest from the broad tapestry of human development, and we study each of them thoroughly from beginning to end. The editor and I have had no hesitation in choosing the first three of these special themes. The first, the philosophy of sex and-love, pervades nearly the whole series of the forty volumes of the Key to Culture, yet we were able on the plan of that work to give only the few elementary facts about sex which every man and woman ought to know, not the full and clear understanding of them which the thoughtful man or woman desires. There is, it is
true, a very large literature about sex to meet this desire, but I will explain presently how this series of volumes will have a very distinctive character."
"It is obvious that the most conspicuous and most attractive element in the story of morals will be the relation of the sexes, and it is equally clear that a sound understanding of the relations of the sexes ought to precede such a study. Even in the legends of primitive
peoples, like those of the Hebrews, sex is from the first the outstanding fact of life, So completely does sex dominate the mind that even the gods and goddesses are credited with it in a superhuman degree. All early literature is very largely inspired by the sex-theme, from the love-stories of Egypt to the early poetry, the great tragedies, and the brilliant comedies of the Greeks. The legend of Isis and Osiris, probably one of the oldest we know, is as saturated
with sex as are the lyrics of the Greek poets or such literature as we have of the ancient Babylonians or the Old Testament or the oldest stories of Rome. History, although it is in the main the record of battles and dynastic revolutions, tells in every chapter of the intrusion of the sex-interest into the most momentous affairs of man. In every age the literary man has burst through the accepted tradition that sex is an impulse essentially belonging to what is called the lower nature of man and unfit for discussion and description; and in this age of ours, which is in emotional and intellectual development the highest yet known, there is an immensely larger and more serious literature about sex than was ever known before."