I regard sex as the central problem of life. And now that the problem of religion has practically been settled, and that the problem of labor has at least been placed on a practical foundation, the question of sex—with the racial questions that rest on it—stands before the coming generations as the chief problem for solution. Sex lies at the root of life, and we can never learn to reverence life until we know how to understand sex.

The family only represents one aspect, however important an aspect, of a human being's functions and activities. A life is beautiful and ideal or the reverse, only when we have taken into our consideration the social as well as the family relationship.

The greatest task before civilization at present is to make machines what they ought to be, the slaves, instead of the masters of men.

The sexual regions constitute a particularly vulnerable spot, and remain so even in man, and the need for their protection which thus exists conflicts with the prominent display required for sexual allurement. This end is far more effectively attained, with greater advantage and less disadvantage, by concentrating the chief ensigns of sexual attractiveness on the upper and more conspicuous parts of the body. This method is well-nigh universal among animals as well as in man.

Here, where we reach the sphere of mathematics, we are among processes which seem to some the most inhuman of all human activities and the most remote from poetry. Yet it is here that the artist has the fullest scope of his imagination.

To live remains an art which everyone must learn, and which no one can teach.

Reproduction is so primitive and fundamental a function of vital organisms that the mechanism by which it is assured is highly complex and not yet clearly understood. It is not necessarily connected with sex, nor is sex necessarily connected with reproduction.