This section is from the book "Human Sexuality", by J. Richardson Parke. Also available from Amazon: Human Sexuality.
I shall not devote much space to the modern status of marriage. It would involve much speculation, is pretty fairly known, as far as it may be known with any degree of certainty, and its literature is already sufficiently voluminous to answer every end; but there is a form of marriage, influenced by equality of the sexes, which demands at least passing notice.
When so-called love, which, in its protean forms, I am far too wise to attempt to analyze, depends wholly upon external attractions,, it is necessarily both changeable and imperfect. It cannot help but be so; since the qualities which excite it are themselves both changeable and indefinite; but when it is founded on sympathy, arising out of similarity of the mental constitution, that peculiar sexual and psychological adaptability difficult to describe in brief terms, the union is apt to be both permanent and happy, and to continue long after both youth and beauty have disappeared. Along with love, which I might possibly better answer the present purpose by calling the "monogamous instinct," there is the great law of numerical equality between the sexes, as well as the implied New Testament teaching, to oppose the progress of polygyny.
 
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