Who is right, the idealists or the materialists? The question, once stated in this way, hesitation becomes impossible. Undoubtedly the idealists are wrong and the materialists right. Yes, facts are before ideas; yes, the ideal, as Proudhon said, is but a flower, whose root lies in the material conditions of existence. Yes, the whole history of humanity, intellectual and moral, political and social, is but a reflection of its economic history.