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."

According to him the world has only two attributes: "Motion and sensation are the only true and objective qualities of the world.... Motion is the truly objective ... though it is admitted that it gives us only the phenomenon.... Sensation makes up the internal nature of things. Every subject, whether man or atom, is endowed with the two qualities of all beings, viz., motion and sensation."

Thereupon I have carefully looked for an explanation in NoirÉ's works, why he regards the nature of things as composed of an external and an internal quality, and why sensation should not be regarded as a sort of motion, but the only reason I could find was the dualistic nature of his "monistic" reasoning.

As Schopenhauer provided the whole world with a "will," so NoirÉ provides it with "sensation."

Kant and his "Critical Philosophy" held in their time that our intellect perceives only the phenomena of nature, while the mystic law of causality, according to him, points to a hidden being, which cannot be perceived but must be believed, which we may venerate but must leave undisturbed by science. Schopenhauer, his brilliant successor, who in spite of his brilliancy did not materially advance the cause of philosophy, mystified the problem of causality by his discovery that the nature of the world is will power. These teachings of Kant and Schopenhauer are dressed up anew and mixed with the recent discoveries of science by NoirÉ. But he entirely ignores the work of Schelling and Hegel, who by their criticisms have made evident the lack of logic in the Kantian separation of phenomenon (apparition) from noumenon (essence), of cause from effect.

You are familiar with the silly question whether Goethe or Schiller, Shakespeare or Byron, is the greater poet, and you will not think that I am trying to elevate Hegel above Kant or Kant above Hegel. They are just two cogs on the spinning wheel of history. If the second crushes what the first has cracked, such is the result of their succession.

Natural science is also a valuable co-operator in the solution of the world problem, not so much by digging in the logical tunnel itself, or making amateur excursions into the fields of philosophy or metaphysics, but because it elucidates and renders tangible the special object of logic in such far-embracing objects as the unity of natural forces or of animal species. The scientific presentation of this special object, however, requires a brain armed with the full equipment of the historical outcome of philosophy.

Now you must not believe that I am conceited enough to place my own little personality on the pedestal as the only true philosopher. I am too well aware of my shortcomings as a self-educated man. But seeing that I have striven earnestly and without prejudice since my young days to understand the high object of my studies, I feel in my heart a certain confidence in my qualification to deal with it. On the other hand, I know my lack of that sort of learning which is required in order to be able to present the scientifically much-courted nature of the human mind in such a form and with such emphasis as its sublime character deserves. And if I, nevertheless, come before the public on various occasions with my tentative works, I offer as an excuse that hitherto the Messiah has not appeared who will come after me and whose John the Baptist I should like to be.

You, my dear Eugene, will take me soberly and reduce my resounding words to their proper measure, when I, in the intoxication of enthusiasm, flow over like that now and then. You know that I am no hero worshipper. Though all research is but the product of individual minds, the mind of each man is a part of the universal mind which produces science. Now follows the point which forms the conclusion of all my letters: The intellect which produces science is indeed a part of man, but still more a part of the world, it is the universal world intellect, the reason of the absolute, the absolute reason.

The study of this intellect at work, not merely in shoemaking, in anatomy, or in astronomy, but in all fields, in the infinite, of its life in the absolute, is the means by which the art of logic is acquired. It is true that the infinite exists only in finite parts, and you cannot conceive of the infinite directly, you can perceive it only in its parts. And in perceiving them you must always remember that every part is an infinite piece of the infinite universe.

In his "Introduction and Proofs of a Monistic Theory of Understanding," NoirÉ, after enumerating the new points contained in his work, adds sneeringly that he is "not in a position to give any new clews as to the nature of the absolute." For this very reason I want to denounce his "Monism" as a shallow piece of work, which offers only the name instead of the essence.

The well-known Ernst HÆckel knows a great deal more about this subject. In a lecture given at the twenty-fifth convention of natural scientists in Eisenach, he calls the monistic view of nature "a grand pantheistic one." The essence of all religion, according to him, consists in the "conviction of a final and unmistakably common cause of all things." And he continues: "In the admission that with the present day organization of our brain, we are unable to penetrate to the final cause of all things, the critical natural philosophy and dogmatic religion agree." Whether the professor is one of those natural philosophers who regard the human mind as too narrow for the understanding of the "unmistakably (hence somewhat understood) common cause of all things," is not quite clear to me, nor probably to the famous scientist himself. For he adds: "The more we progress in the understanding of nature, the more we approach that unattainable final cause." And further on: "The purest form of monistic faith culminates in the conviction of the unity of God and nature."

Now I ask: If nature, God, and absolute truth are one and the same thing, have we not learned something about the "final cause of all things?" What necessity is there in that case for speaking in such an abjectedly humble tone of human understanding, or to assign nothing but straw and husks to it, in the language of Hegel?

You see, then, that HÆckel has a higher estimate of absolute nature than NoirÉ who does not care to have anything to do with the nature of the absolute. But my object at this moment is to convince you that neither the one nor the other of these two, nor natural science, so-called, is directly digging in the tunnel which will give us light on the question of the limits of our understanding and the final cause of things. Our logic, on the other hand, which treats the intellect as a part of nature, cultivates a natural science that includes the mere empirical natural science in the same way in which the day of twenty-four hours includes the day of twelve hours and the night.

Natural science proper deals mainly with tangible things. Light and sound, the objects of eye and ear, are still included in its studies. The objects of smell and taste stand on the dividing line. But the socalled sciences of the mind, such as grammar and politics, political economy and history, morals and law, and most decidedly logic, are entirely excluded.

Such a limitation is well enough, if we remember that it is purely formal. However, it must not overlook the bridge which leads from limited nature to universal, infinite, nature.

The monism of natural science has a far too narrow view of the universe. When it says that "all is motion," it says just as little or as much as Solomon with his "all is vain." Everything is crooked and straight, everything great and small, everything temporal and eternal, everything truth and life. But nothing is thus said to show the meaning of distinction in this world, to explain how rest exists in motion, and sense in nonsense.

In order to differentiate logically we must know that everything is everything, that the universe or absolute is its own cause and the final cause of all things, which embraces all distinctions, even that of causality and that between matter and mind.