As I have said several times, ideas do not fall from heaven, and even those which, at a given moment arise from definite situations with the impetuosity of faith and with a metaphysical garb, carry always within themselves the index of their correspondence with the order of the facts, of which the explanation is sought or attempted. The idea of progress, as the unifier of history, appears with violence and becomes a giant in the eighteenth century, that is to say, in the heroic period of the intellectual and political life of the revolutionary bourgeoisie. Just as this engendered, in the order of its works, the most intensive period of history that is known, it also produced its own ideology in the notion of progress. This ideology in its substance means that capitalism is the only form of production which is capable of extending all over the earth and of reducing the whole human race to conditions which resemble each other everywhere. If modern technique can be transported everywhere, if all the human race appear on a single field of competition and all the world as a single market, what is there astonishing in the ideology which, reflecting intellectually these conditions of fact, reaches the affirmation that the present historical unity has been prepared by everything which precedes it? Translating this concept of pretended _preparation_ into the altogether natural concept of _successive condition_, and there is opened before us the road by which the passage is made from the ideology of progress to historical materialism; and now we arrive at the affirmation of Marx, that this form of bourgeois production is the last antagonistic form of the _processus_ of society.