In his "Three Books On The Soul," Aristotle discussed at length the question whether the human soul has five senses or one. The commentator, J. H. von Kirchmann, the publisher of the "Philosophical Library," remarks in his footnote 172 that man has six senses. He divides feeling into pure and active feeling. According to this, the phrase of the five senses belongs to the old iron the same as that of the four elements. Now neither you, nor I, nor any reader should worry about the question whether all sensation may be summed up in the one sense of feeling, whether there are five senses according to Aristotle, or six according to Kirchmann, or whether there is even a seventh sense for the transcendental, the organ of which, as some optimists hope, will gradually be developed with the growing perfection of man. We are concerned in this matter only so far as it is connected with the cardinal question, whether the world is only one thing or a mere collection of an infinite number of disconnected things; whether the so-called things are independent subjects and objects, or whether they are only predicates of the one world subject.

Looking through the window I see the river, the street, the bridge, houses, and trees. Everything is a thing in itself and yet is connected inseparably with all others. The qualities of the world are regarded by the intellect as subjects; but the intelligent subject should also know that its actions, its distinguishing and understanding, are formalities, a formal dismemberment of the absolute, which in spite of all division always remains the undivided whole.

In order to master this method of thought, you must understand above all that the things are only so-called things, but are in reality qualities of the universe, in other words, relative things or predicates of the absolute. You will then understand, that our thought has a right to make one thing as well as six of a chair, its back, its seat, and its four legs. You will recognize that the five senses of Aristotle are not an eternal truth, but a classification, which is eternally variable. Distinguishing means classifying.

I know very well that I am making a bold statement here, and that it is not easy to justify it. For this reason you must not expect that I can make my meaning clear in a few sentences. It is not only the general prejudice which prevents this by making a most mysterious and miraculous thing of the intellectual function, but also the fact that this thing is still very obscure, although it has become clearer and clearer in the course of time.

The freethinking pastor Hironymi writes on this point: "The most prominent naturalists of the present, such as Dubois-Reymond, who are at the same time thinkers, admit that they do not know what feeling, life, consciousness, are, and how they arise. And this ignorance is far more valuable for truth and religion than the alleged knowledge. Let us, therefore, continue in the devotion with which we have hitherto admired the universe without understanding it. The higher existence, the consciousness, has not been explained, it has remained a miracle, the only lasting, absolute, miracle."

Thus speaks the preacher who is a know-nothing by nature and makes a business of admiring and wondering, while we are interested in understanding and knowing. We wish to fathom the mystery, and hence I may write still more letters on logic and you may study some more.

I shall try to demonstrate by a trivial example, how it is that understanding or distinguishing is based on classification.

Take it that you awake at early dawn and notice in a corner of your bed room something uncouth and moving which you cannot clearly distinguish. To know that a phenomenon appears is not enough because the term phenomenon applies to everything, natural and unnatural things, good and evil spirits. Even if you are sufficiently enlightened to know that the thing in question must be something natural, still this explains very little, for the term "nature" again means everything. But you understand or recognize more when you ascertain that the uncouth thing is dead or alive, wall paper or garment, man or animal. You will notice that in this intellectual enlightenment it is simply a matter of classification, of the head under which the mystery should be classed. To classify the phenomena of truth and life, means to understand, to use the intellect, to enlighten the brain.

But we must well consider how far we shall have to go in our classification in order to find the place in the system which will fully clarify and determine understanding. Suppose that in the above mentioned case you have ascertained that the motion is due to a cat, then the inquiring faculty of understanding has not yet reached the end of its tether. The next question is then, whether it is your cat or that of your neighbor, whether it is black, white, or grey, young or old. And when you finally recognize that it is your tomcat Peter, you must remember that the subject which understands as well as the object to be recognized, being parts of the absolute, are absolutely and infinitely divisible parts, which are never fully understood and never fully exhausted.

Please remember that in speaking of something uncouth, we are not so much concerned in Peter or Tabby, but in the intellect which we desire to understand so that we may make a correct use of it. And I refer to it as uncouth merely because its understanding is beset with so many difficulties. When I compared it in the preceding letter with a photographic apparatus which should furnish us with pictures, and in likening it now to an instrument designed to distinguish things by classification, I warn you not to be confused thereby. Classification is most essential as a means of producing intellectual pictures. In this connection I emphasize once more that the faculty of understanding, the same as other things, is not independent by itself, but can accomplish something only in the universal interconnection. The understanding that the phenomenon quoted above belongs to the category of tomcats, and more especially into the column labeled Peter, would not be any understanding at all, if you had not become previously acquainted with the mouse-devouring race and individual in question. Only in connection with your previous experience is the understanding that this tomcat and the uncouth motion are one and the same thing, or belong to the same category, a true understanding.

Ludwig Feuerbach says: A talented writer is recognized by the fact that he assumes talent on the part of the reader also and does not chew up his subject into minute parts like a petty schoolmaster. On the other hand, it seems to me that it is possible to assume too much, and I pursued a schoolmasterly course in this case, because the subject is new to you and still leaves plenty of room for reflection.

I wanted to show by a commonplace example what I mean by insight and understanding and how by means of it the unknown and uncouth becomes known and familiar. True, the understanding in this case was illumined by previous experience, while you are after new knowledge. You want to know how enlightenment arises in order to acquire new insight. Now, all novelty has the dialectic quality of being at the same time something antiquated. New understanding can be acquired only by the help of old understanding. In other words, old and new understanding, which I define here as the faculty of classification, have their existence only in the total interdependence of the universal existence.

You must discard the old prejudice that knowledge can be collected like cents. Although this is well enough, it does not suffice for the purpose of logical thinking. One science belongs to another, and all of them together belong to one class with the entire universe. It will be apparent to you, then, that at the beginning of your young days your knowledge has not sprouted all at once, but has come out of the unknown. And what is true of you, is true of the whole human race. In its cradle it was without intellect. It had, indeed, the germ. But do not beasts, worms, and sensitive plants have that also? In short, the light of perception and understanding is nothing new in the radical sense of the word, but connected with the old and with the world in general, and of the same kind. All our knowledge must be connected and combined into one understanding, one system, one realm, and this is the realm of reality, of truth, of life.

Systematic classification is the task of logic. The first requirement for this purpose is the awakened consciousness of the indivisibility of the universe, of its universal unity. This consciousness is, in other words, at the same time the recognition of the merely formal significance of all scientific classification.

The unity of the universe is true, and is the sole and innate truth. That this sole world truth is full of differences, is just as absolutely different as absolutely the same, does no more contradict a reasonable unity and equality than there is any contradiction in the fact that the various owls have different faces and still the same owl face.

Aristotle divided the sense into five parts, anthropologists the race of man into five races, natural philosophers the space into three dimensions. It is now a question of showing to you that such a division, however true and just, is nevertheless far from being truth and justice, but is merely classification. The fundamental requirement of logic is to designate scientific classifications as that which they are, viz., mental operations. It is the business of the intellect to make classifications. That is its characteristic quality and does not contradict the indivisible truth in the least.

Old wiseacres teach that a reasonable man must not contradict himself, and this is a wise, though very narrow, lesson. Hegel maintains that everything in the world is reasonable, hence the contradictions are also. Under this conservative exterior there is hidden a very revolutionary perception of which the "destructive" minds take advantage in order to flatly contradict the wiseacres and their stable, dead, disordered order which cannot stand any contradiction.

Reason dissolves all contradictions and opposition into harmony by logical classification. "Everything in its own time and place." If it does not wish to be called unreason, reason must rise to the understanding that its opposite is only a formal antagonism. It must know that God and the world, body and soul, life and death, motion and rest, and whatever else the dualists may distinguish, are two and yet one. Then it becomes clear that the conservatives are the real revolutionaries, because by their senseless adherence to the "good old order" they drive the proletariat to desperation, until it upsets that order. On the other hand, the maligned revolutionaries are conservative, because they subordinate themselves to the world's evolutionary process which was, is, and will be eternal.

The red thread winding through all these letters deals with the following points: The instrument of thought is a thing like all other common things, a part or attribute of the universe. It belongs particularly to the general category of being and is an apparatus which produces a detailed picture of human experience by categorical classification or distinction. In order to use this apparatus correctly, one must fully grasp the fact that the world unit is multiform and that all multiformity is a unit.

It is the solution of the riddle of the ancient Eleatic philosophy: How can the one be contained in the many, and the many in one?