[5] By 'civilized' societies the book refers specifically to the following sixteen historical peoples: Sumerians, Babylonians, Egyptians, Assyrians, Hellenes, Persians, Hindus, Chinese, Japanese, Sassanids, Arabs (Moors), Romans, Teutons, and Anglo-Saxons.

Unwin bases his categories on certain social phenomena that he observed in his study of the 86 world cultures, phenomena that he found coincided with varying levels of prenuptial chastity: The book concludes with the assertion that, in order to maintain a rationalistic society, sexual drive should be controlled and shifted to more productive work.

Unwin notes that women should enjoy the same legal rights as men and that the condition for a high level of cultural achievement lies in restricting prenuptial sexual opportunity rather than a state of patriarchy, although the two have historically coincided.

The book states that the effect of sexual constraints, either pre or post-nuptial, has always led to increased flourishing of a culture.

It is historically true to say that in the past social energy has been purchased at the price of individual freedom, for it has never been displayed unless the female of the species has sacrificed her rights as an individual and unless children have been treated as mere appendages to the estate of the male parent; but it would be rash to conclude that sexual opportunity cannot be reduced to a minimum under any other conditions.