Under the influence of Weininger’s book, the attempt has recently been made to deny the existence of sexual differences in the psychical sphere, and especially to contest the origin of these differences from the fundamentally different nature of the masculine and feminine types. (Weininger himself not only went so far as to declare the obliteration and equalization of sexual differences, but he even asserted that all feminine nature was a personification of nothingness, of evil; he wished to annihilate femininity, in order to allow the existence of one sex only, the male, this being to him the embodiment of the objective and the good.) I recently read with great interest a most intelligent book, one full of new ideas, by Rosa Mayreder--“Zur Kritik der Weiblichkeit” (A Critique of Femininity), Jena, 1905--in which the author maintains what she calls the “primitively teleological character of sexuality”; that is, she considers the different sexual functions of man and woman to be comparatively unimportant for the determination of their spiritual nature, and regards the individual psychical differentiation as independent of sexuality and of the different sexual natures. In her opinion, sexual polarity does not extend to the “higher nature” of mankind, to the spiritual sphere. She offers as a proof of this, among other points, the fact that by crossed inheritance spiritual peculiarities of the father can be transmitted to the daughter. Very true. Moreover, no objective student of Nature will deny that a woman can attain the same degree of individual psychical differentiation as a man, or that she can bring her “higher nature” to an equally great development. But quite as incontestable is the fact which Rosa Mayreder keeps too much in the background: =that everything psychical, the entire emotional and voluntary life, receives from the particular sexual nature a peculiar characterization, a distinctive colouring, and a specific nuance=; and that these precisely constitute the heterogeneous and the incomparable in the masculine and the feminine natures. The attempts to annihilate sexual differences in theory are very old,[24] but they have always proved untenable in practice. They have invariably been shattered by contact with--sexual differences. _Naturam expellas furca, tamen usque recurret_ (You may drive out Nature with a pitchfork, but she will inevitably return). And this return of Nature is, in fact, a =step forward=, in advance of primitive hermaphroditic states. Sexual differences are ineradicable; civilization shows an unmistakable tendency to increase them. There is also an individual differentiation of sexual characters. It is proportional to the differentiation of the psychical characters of man and woman. And the problem is this: How is it possible for woman to ensure the development and perfectibility of her higher nature, without eliminating and obscuring her peculiar character as a sexual being?