I emphasize the inadequacy of all modes of thought and of all understanding in opposition to those who make an idol of science. I emphasize the truth of all perceptions in opposition to those knownothings who claim that truth cannot be understood, but can only be admired and worshipped. Hence it follows for our theory of understanding that intellect and reason and the art of thought are no independent treasure boxes which make any revelations to us. They are theoretical classifications which in practice are operative only in the universal interconnection of things. Understanding, perceiving, judging, distinguishing and concluding, etc., are unable to produce any truths. They can only enlighten and clarify experience by logical classification and distinction. Because man produces works which are preceded by planning, therefore the philosophical mode of research has "assumed that the whole is descended from a thought." But this is an assumption of human origin, which is shown to be without foundation on closer analysis. The plans of our works are copies of natural originals and are "free creations of the mind" only in a limited sense. The artists are well aware of the natural descent of their thoughts and fictions. To regard the world as the outcome of thought is a perverse logic. It is the first condition of rational, proletarian, thought to recognize the intellect and its products as attributes of the world subject.
EIGHTEENTH LETTER
Just as in political history action and reaction follow one another, just as periods of economic prosperity are alternated by periods of depression, so we find in literature a periodical fluctuation between philosophical and anti-philosophical tendencies.
After Hegel had for a time thoroughly aroused the spirits, a time of apathy followed, so that this hero of thought who shortly before had been almost idolized could be attacked and reviled. For about a decade, a philosophical breeze has now once more been blowing. The subject of logic, the theory of understanding, is again the object of universal attention. This movement is stimulated by important discoveries in science, such as the heat equivalent of Robert Mayer, the origin of species by Darwin, etc., and natural science and philosophy may be compared to two miners who are digging a tunnel, so that sharp ears on both sides can hear the blows of the hammers and the clanging of the tools.
There is much truth in this picture, but it may also lead to misunderstandings. By the vivisection of frogs and rabbits, by boring into the brain, physiology will not discover the mind. No microscope, no telescope, will reveal the nature of reason and truth or the art of logical discernment.
Neither will Lazarre Geiger, Max Müller, Steinthal, and Noiré succeed in philology in solving the "last questions of all knowledge" by the help of any primitive arch-language.
At the same time, the value of the co-operation of these gentlemen is not denied, only I desire to point out that the comparison with the tunnel is not quite accurate. What Marx said of economic formulas, is true of logical formulas: "In their analysis neither the microscope nor chemical reagents are of any service. The power of abstraction must replace them both."
The two sciences will finally meet, not because each one of them digs away in its own one-sided fashion, but because the miners meet after working hours and exchange their experiences. And the philosophers may be the dominant party, because they are specialists in logic and therefore prepared to utilize anything which may serve their purpose, no matter from what side it comes. The other party, on the other hand, has its own specialties and promotes the cause of logic in a secondary and involuntary fashion.
Natural science has its own monism which is distinguished from philosophical proletarian monism in that it does not appreciate the historical outcome of philosophical research. One of the most prominent representatives of the former is Noiré. He entitles one of his little works "Monistic Thought," but shows himself on its pages as a very unclear dualist. He speaks of the "dual nature of causality" and relates that the mind operates with a different causality than the mere mechanical one. He calls this other "sensory causality."