It is thus an easy thing, especially in the way it has been done by certain shallow critics, to find precursors for Marx and Engels, who first defined this doctrine in its fundamental points. And when did it ever occur to any of their disciples, even of the strictest school, to represent these two thinkers as miracle-workers? What is more, if we wish to go on a search after the premises of the logical creation of Marx and Engels, it will not suffice to stop at those who are called the precursors of socialism, Saint-Simon for example, and his predecessors, or the philosophers, particularly Hegel, or the economists who had laid bare the anatomy of the society which produces commodities; we must go back to the very formation of modern society, and then at last declare triumphantly that the theory is a plagiarism from the things that it explains. The truth is that the real precursors of the new doctrine were the facts of modern history, which has become so transparent and so explanatory of itself since the accomplishment in England of the great industrial revolution at the end of the eighteenth century, and since the great social upheaval took place in France. These things, _mutatis mutandis_, have subsequently been reproduced, in various combinations and in milder forms, throughout the whole civilized world. And what else is our thought at bottom if not the conscious and systematic complement of experience, and what is this last if not the reflection and the mental elaboration of the things and the processes which arise and unfold either outside our volition, or through the work of our activity; and what is genius but the individualized, derived and acute form of thought, which arises through the suggestion of experience, in many men of the same epoch, but which remains in most of them fragmentary, incomplete, uncertain, wavering and partial? Ideas do not fall from heaven; and what is more, like the other products of human activity, they are formed in given circumstances, in the precise fullness of time, through the action of definite needs, thanks to the repeated attempts at their satisfaction, and by the discovery of such and such other means of proof which are, as it were, the instruments of their production and their elaboration. Even ideas involve a basis of social conditions; they have their technique; thought also is a form of work. To rob the one and the other, ideas and thought, of the conditions and environment of their birth and their development, is to disfigure their nature and their meaning.