“Love”--thus Carpenter concludes his dissertation on marriage in the future--“is doubtless the last and most difficult lesson that humanity has to learn; in a sense, it underlies all the others. Perhaps the time has come for the modern nations when, ceasing to be children, they may even try to learn it” (_op. cit._, p. 113). A greater vogue even than Carpenter’s book had was obtained by the essays of the Swedish writer Ellen Key, “Love and Marriage,” which in 1894 appeared in a German translation,[203] and had an unusual success in the book-market. It is without exception the most interesting and pregnant work on the sexual question which has ever appeared. Written from the heart, and inspired by the observations of a free and lofty spirit, it avoids none of the numerous difficulties and by-paths in this department of thought; and the reproach of libertinism which has been cast at the author must be emphatically rejected. Ellen Key is the most outspoken realist of all the writers on the subject of free love. She takes her arguments from actual life; she associates her ideas of reform always with the real; she writes as an earnest evolutionist. Thus, in her book, her first aim is to establish “the course of the evolution of sexual morality” and the “evolution of love.” Ellen Key starts from the fact that no one has ever offered any proof that monogamy is that form of the sexual life which is =indispensable= to the vital force and civilization of the nations. Even among the Christian nations =it has never yet really existed=, and its legalization as the only permissible form of sexual morality has hitherto been rather harmful than helpful to general morality. The writer then develops the idea, no less beautiful than true, that the genuine character of love can be proved only by the lovers actually living together for a considerable time; only thus is it possible to demonstrate that it is moral for them to live together, and that their union will have an elevating influence on themselves and their generation. Consequently, of no conjugal relationship can we =beforehand= affirm or deny its success. Every new pair, whatever form they may have chosen for their common life, =must first of all prove for themselves that they are morally justified in living together=. Ellen Key then proceeds to maintain a view, which I myself also regard as an integral constituent of the programme of the love of the future, and one which I have advanced in earlier writings: that love is not merely, as Schopenhauer thought, an affair of the =species=, but is, at least in equal degree, the concern of the loving =individuals=. This is the result and the meaning of civilization, which, as I have proved in earlier chapters, exhibits a =progressive= individualization and an increasing spiritual enrichment of love (the “spiritualized sensuality” of Ellen Key), and thus gives to love a thoroughly independent importance for each individual.