At the moment when the Manifesto was written the historic horizon did not go beyond the classic world, the scarcely studied German antiquities and the Biblical tradition which had only lately been reduced to the prosaic conditions of all profane history. Our historic horizon is now quite another thing, since it extends to the Aryan antiquities and to the ancient deposits of Egypt and Mesopotamia which precede all the Semitic traditions. And it extends still further back into prehistory, that is to say, into, unwritten history. Morgan has given us a knowledge of ancient society, that is to say a pre-political society, and the key to understand how from it came all the later forms marked by monogamy, the development of the paternal family, the appearance of property, first of the _gens_, then of the family, lastly individual, and by the successive establishment of the alliances between _gentes_ which are the origin of the State. All this is illustrated by the knowledge of the process of technique in the discovery and in the use of the means and instruments of labor and by the understanding of the effect of this process upon the social complexus, urging it in certain directions and making it traverse certain stages. These discoveries may still be corrected at certain points, notably by the study of the different specific fashions according to which in different parts of the world the passage from barbarism to civilization has been effected. But, henceforth, one fact is indisputable, namely, that we have before our eyes the general embryogenic record of human development from primitive communism to those complex formations as at Athens or at Rome with their constitutions of citizens arranged in classes according to census which not long ago constituted the columns of Hercules for research into written tradition. The classes which the Manifesto assumed have been later resolved into their process of formation and in this can already be recognized the plexus of reasons and of different economic causes for the categories of the economic science of our bourgeois epoch. The dream of Fourier to find a place for an epoch of civilization in the series of a long and vast process has been realized. A scientific solution has been found for the problem of the origin of inequality among men which Rousseau had tried to solve by arguments of an original dialectic, relying however upon too few real data.