Note 50 — Chapter VII · The Marriage of the Positive Girl and the Positive Man
Reading edition
When I use the word “unnatural” here, I should like it to be understood as meaning “unnatural to human beings,” for, as we know, “nearly all rapacious animals, even the stupid vultures, are monogamous,” certain monkeys are so too; but no anthropologist would argue that monogamic marriage was natural to man.