As far as learning was concerned, Marx was, and still is incomparably more advanced than I. I knew nothing at that time of political economy, I had not yet rid myself of my metaphysical aberrations, and my socialism was only instinctive. Although younger than I, he was already an atheist, a conscious materialist, and an informed socialist. It was precisely at this time that he was elaborating the foundations of his system as it stands today. We saw each other often. I greatly respected him for his learning and for his passionate devotion- thought it was always mingled with vanity- to the cause of the proletariat. I eagerly sought his conversation, which was always instructive and witty when it was not inspired by petty hate, which alas! was only too often the case. There was never any frank intimacy between us- our temperaments did not permit it. He called me a sentimental idealist, and he was right; I called him vain, perfidious, and cunning, and I also was right.

In 1845 Marx was the leader of the German communists. While his devoted friend Engels was just as intelligent as he, he was not as erudite. Nevertheless, Engels was more practical, and no less adept at political calumny, lying, and intrigue. Together they founded a secret society of Germany communists or authoritarian socialists.

As I told him a few months before his death, Proudhon, in spite of all his efforts to shake off the tradition of classical idealism, remained all his life an incorrigible idealist, immersed in the Bible, in Roman law and metaphysics. His great misfortune was that he had never studied the natural sciences or appropriated their method. He had the instincts of a genius and he glimpsed the right road, but hindered by his idealistic thinking patterns, he fell always into the old errors. Proudhon was a perpetual contradiction: a vigorous genius, a revolutionary thinker arguing against idealistic phantoms, and yet never able to surmount them himself.... Marx as a thinker is on the right path. He has established the principle that juridical evolution in history is not the cause but the effect of economic development, and this is a great and fruitful concept. Thought he did not originate it- it was to a greater or lesser extent formulated before him by many others- to Marx belongs the credit for solidly establishing it as the basis for an economic system. On the other hand, Proudhon understood and felt liberty much better than he. Proudhon, when not obsessed with metaphysical doctrine, was a revolutionary by instinct; he adored Satan and proclaimed Anarchy. Quite possibly Marx could construct a still more rational system of liberty, but he lacks the instinct of liberty- he remains from head to foot an authoritarian.

Das Kapital, Kritik der politischen Oekonomie, by Karl Marx; Erster Band. This work will need to be translated into French, because nothing, that I know of, contains an analysis so profound, so luminous, so scientific, so decisive, and if I can express it thus, so merciless an expose of the formation of bourgeois capital and the systematic and cruel exploitation that capital continues exercising over the work of the proletariat. The only defect of this work... positivist in direction, based on a profound study of economic works, without admitting any logic other than the logic of the facts - the only defect, say, is that it has been written, in part, but only in part, in a style excessively metaphysical and abstract... which makes it difficult to explain and nearly unapproachable for the majority of workers, and it is principally the workers who must read it nevertheless. The bourgeois will never read it or, if they read it, they will never want to comprehend it, and if they comprehend it they will never say anything about it; this work being nothing other than a sentence of death, scientifically motivated and irrevocably pronounced, not against them as individuals, but against their class.