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.

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.

There is nothing that war has ever achieved that we could not better achieve without it.

There is nothing more fragile than civilization.

All civilization has from time to time become a thin crust over a volcano of revolution.

The world's greatest thinkers have often been amateurs; for high thinking is the outcome of fine and independent living, and for that a professional chair offers no special opportunities.