“According to the materialistic conception, the determining factor in history is, in the final instance, the production and reproduction of the immediate essentials of life. This, again, is of a twofold character. On the one side, the production of the means of existence, of articles of food and clothing, dwellings, and of the tools necessary for that production; on the other side, the production of human beings themselves, the propagation of the species. The social organization under which the people of a particular historical epoch and a particular country live is determined by both kinds of production: by the stage of development of labor on the one hand and of the family on the other.”

Most of the canonical works of Marxism, such as Capital or The Communist Manifesto, focus squarely on economic matters, which Marx and Engels saw as most important in the development of humanity. Marx and Engels drew strong criticism for suggesting that the onset of communism would destroy the family as it was understood. This book is Engels’s way of showing that the concept of the family has always evolved in accordance with economic forces, and so there is nothing surprising—or avoidable—about it doing so again.

“The science of history was still completely under the influence of the five books of Moses. The patriarchal form of the family, which was there described in greater detail than anywhere else, was not only assumed without question to be the oldest form, but it was also identified—minus its polygamy—with the bourgeois family of today, so that the family had really experienced no historical development at all.”

Capitalism represents itself as inevitable, and one of the ways it advances that claim is by treating the social arrangements that it produces as entirely natural, so that any deviation is a perversion. This argument is particularly effective when it comes to marriage and sexual arrangements, where standards of appropriateness are applied with particular rigor. To question the family unit is to open oneself to harsh criticism, and so it is preferable to remain silent and therefore perpetuate the supreme power of capital.

“The whole matter of the dispute [between matriarchy and patriarchy] is briefly summed up in the debate which now takes place between Orestes and the Furies. Orestes contends that Clytemnestra has committed a double crime; she has slain her husband and thus she has also slain his father. Why should the Furies pursue him, and not her, seeing that she is by far the more guilty? The answer is striking: ‘She was not kin by blood to the man she slew.’”

Engels's analysis of the Oresteia views the tragedy as representing the moment when ancient Greece shifted from matriarchy to patriarchy and thus set in motion the end of what he calls “the gentile constitution.