This section is from the book "The Transmission Of Life. Counsels On The Nature And Hygiene Of The Masculine Function", by George H. Napheys. Also available from Amazon: The Transmission of Life.
We have confined ourselves so far in our considerations on the relations of the sexes to the physiological aspects of the question, its physical and, to some extent, its intellectual bearings. It seemed more appropriate to the nature of our 6tudies and to the character of our researches. Now, however, that we have brought our labors so nearly to a close, and have examined the peculiarities of sex in their various bearings upon the temporal welfare of the individual and the race, we may be permitted to step aside from our path and explain the influence which these powerful instincts have exerted and continue to exert on his actions and destiny as a moral being.
The historian or theologian who does not carefully estimate the strength and power of the sexual impulses will often fail to interpret the actions and the creed of past generations. He will attribute to motiveless caprice and to unmeaning malignity many actions which were merely the expression of an uncontrolled instinct.
So also in the lives of individuals, it is a matter of daily observation that in these respects it is next to impossible to understand the vagaries which govern otherwise prudent and cautious men.