So we see that the "historical series" of Saint Simon really explained nothing at all; they themselves need explanation, and for this we have again to fall back upon this inevitable human nature. The French Revolution was directed along a certain line, because human nature was so and so. One of two things. Either human nature is, as Morelly thought, invariable, and then it explains nothing in history, which shows us constant variations in the relations of man to society; or it does vary according to the circumstances in which men live, and then, far from being the _cause_, it is itself the _effect_ of historical evolution. The French Materialists knew well enough that man is the product of his social surroundings. "Man is all education," said Helvétius. This would lead one to suppose that Helvétius must have abandoned the human nature point of view in order to study the laws of the evolution of the environment that fashion human nature, giving to socialised man such or such an "education." And indeed Helvétius did make some efforts in this direction. But not he, nor his contemporaries, nor the Socialists of the first half of our century, nor any representatives of science of the same period, succeeded in discovering a new point of view that should permit the study of the evolution of the social environment; the cause of the historical "education" of man, the cause of the changes which occur in his "nature." They were thus forced back upon the human nature point of view as the only one that seemed to supply them with a fairly solid basis for their scientific investigations. But since human nature in its turn varied, it became indispensable to make abstraction from its variations, and to seek in nature only stable properties, fundamental properties preserved in spite of all changes of its secondary properties. And in the end all that these speculations resulted in was a meagre abstraction, like that of the philosophers, _e.g._, "man is a sentient and reasonable being," which seemed all the more precious a discovery in that it left plenty of room for every gratuitous hypothesis, and every fantastical conclusion.