From this lowest depth of depravity it would be interesting, if space and the architectural plan of this volume permitted, to trace the growth of the sentiment which demands chastity; noting, in the first place, how married women were compelled, by the jealous fury of their masters, to practise continence; how, very much later, virginity began to be valued, not, indeed, at first, as a virtue having a value and charm of its own, but as a means of enhancing the market value of brides. Indifference to masculine chastity continued much longer still. The ancient civilized nations had advanced far enough to value purity in wives and maidens, but it hardly occurred to them that it was man's duty to cultivate the same virtue. Even so austere and eminent a moral philosopher as Cicero declared that one would have to be very severe indeed to ask young men to refrain from illicit relations. The mediaeval church fathers endeavored for centuries to enforce the doctrine that men should be as pure as women, with what success, every one knows. A more powerful agency in effecting a reform was the loathsome disease which in the fifteenth century began to sweep away millions of licentious men, and led to the survival of the fittest from the moral point of view. The masculine standard is still low, but immense progress has been made during the last hundred years. The number of prostitutes in Europe is still estimated at seven hundred thousand, yet that makes only seven to every thousand females, and though there are many other unchaste women, it is safe to say that in England and America, at any rate, more than nine hundred out of every thousand females are chaste, whereas among savages, as a rule, nearly all females are prostitutes (in the moral sense of the word), before they marry. In view of this astounding progress there is no reason to despair regarding man's future. It would be a great triumph of civilization if the average man could be made as pure as the average woman. At the same time, since the consequences of sin are infinitely more serious in women, it is eminently proper that they should be in the van of moral progress. Chastity, modesty, polygamy, murder, religion, and nature have now furnished us an abundance of illustrations showing the changeableness and former non-existence of sentiments which in us are so strong that we are inclined to fancy they must have been the same always and everywhere. Before proceeding to prove that romantic love is another sentiment of which the same may be said, let us pause a moment to discuss a sentiment which presents one of the most difficult problems in the psychology of love, the Horror of Incest. HORROR OF INCEST