Part 18 (1/2)

have a sensation of the external world when something appears to us as light. What we then really have is a state of our optic nerve. Whatever may happen outside, the optic nerve translates this external event into the sensation of light.

”The sensation is not a process that transmits a quality or a state of an external object to our consciousness but one that transmits a quality, a state of our nerves caused by an external event, to our consciousness. This Johannes Mueller called ”the law of specific sense energies.” If that is correct, then our observations contain nothing of the external world but only the sum of our own inner conditions. What we perceive has nothing to do with the external world; it is a product of our own organization. We really perceive only what is in us.

Natural scientists of great renown regarded this thought as an irrefutable basis of their world conception. Hermann Helmholtz (1821 94) considered it as the Kantian thought - that all our knowledge had reference only to processes within ourselves, not to things in themselves - translated into the language of natural science (compare Vol. I of this book).

Helmholtz was of the opinion that the world of our sensations supplies us merely with the signs of the physical processes in the world outside.

I have been convinced that it is necessary to formulate the relation between the sensation and its object by declaring the sensation to be merely the sign of the effect of the object. The nature of the sign demands only that the same sign be always given to the same object. Beyond this requirement there is no more similarity necessary between the sensation and its object than between the spoken word and the object that we denote with it. We cannot even call our sense impression pictures, for a picture depicts the same by the same. In a statue we represent one bodily form through another bodily form; in a drawing we express the perspective view of an object by the same perspective in the picture; in a painting we depict color

through color.

Our sensations, therefore, must differ more from the events they represent than pictures differ from the objects they depict. In our sensual world picture we have nothing objective but a completely subjective element, which we ourselves produce under the stimulation of the effects of an external world that never penetrates into us. This mode of conception is supported from another side by the physicist's view of the phenomena of sensation. A sound that we hear draws our attention to a body in the external world, the parts of which are in a certain state of motion. A stretched string vibrates and we hear a tone. The string transmits the vibrations to the air.

They spread and reach our ear; a tone sensation is transmitted to us. The physicist investigates the laws according to which the physical particles outside move while we hear these tones.

He finds that the subjective tone sensation is based on the objective motion of the physical particles. Similar relations are observed by the physicist with respect to the sensations of light. Light is also based on motion, only this motion is not transmitted by the vibrating particles of the air, but by the vibrations of the ether, the thinnest matter that fills the whole s.p.a.ce of the universe. By every light-emitting body, the ether is put into the state of undulatory vibrations that spread and meet the retina of our eye and excite the optic nerve, which then produces the sensation of light within us. What in our world picture appears as light and color is motion outside in s.p.a.ce. Schleiden expresses this view in the following words: The light outside ourselves in nature is motion of the ether. A motion can be slow and fast; it can have this or that direction, but there is obviously no sense in speaking of light or dark, of green or red motion. In short, outside ourselves, outside the beings who have the sensation, there is no such thing as bright and dark, nor are there any colors.

The physicist expels colors and light from the external world because he finds only motion in it. The physiologist feels that he is forced to withdraw them into the soul because he is of the opinion that the nerve indicates only its own state of irritation no matter what might have excited it. The view that is given with these presuppositions is sharply delineated by Hippolyte Taine (1828 93) in his book, Reason. The external perception is, according to his opinion, nothing but hallucination. A person who, under the influence of hallucination, perceives a death skull three steps in front of him, has exactly the same perception as someone who receives the light rays sent out by a real skull. It is the same inner phantom that exists within us no matter whether we are confronted with a real skull or whether we have a hallucination. The only difference between the one perception and the other is that in one case the hand stretched out toward the object will grasp empty air, whereas in the other case it will meet some solid resistance. The sense of touch then supports the sense of sight. But does this support really represent an irrefutable testimony? What is correct for one sense is also valid for the other. The sensations of touch can also turn out to be hallucinations.

The anatomist Henle expresses the same view in his Anthropological Lectures (1876) in the following way: Everything through which we believe to be informed about an external world consists merely of forms of our consciousness for which the external world supplies merely the exciting cause, the stimulus, in the language of the physiologists. The external world has no colors, tones and tastes. What it really contains we learn only indirectly or not at all. How the external world affects a sense, we merely conclude from its behavior toward the other senses. We can, for instance, in the case of a tone, see the vibrations of the tuning fork with our eyes and feel it with our fingers. The nature of certain stimuli,

which reveal themselves only to the one sense, as, for instance, the stimuli of the sense of smell, is still inaccessible to us. The number of the properties of matter depends on the number and on the keenness of the senses. Whoever lacks a sense loses a group of properties without a chance of regaining them. A person who would have an extra sense would have an organ to grasp qualities of which we have no other inkling than the blind man has of color.

If one glances over the physiological literature from the second half of the nineteenth century, one sees that this view of the subjective nature of the world picture of our perceptions has gained increasing acceptance. Time and again one comes across variations of the thought that is expressed by J.

Rosenthal in his General Physiology of Muscles and Nerves (1877). ”The sensations that we receive through external impressions are not dependent on the nature of these impressions but on the nature of our nerve cells. We have no sensation of what exerts its effect on our body but only of the processes in our brain.”

To what extent our subjective world picture can be said to give us an indication of the objective external world, is expressed by Helmholtz in his Physiological Optics: To ask the question if cinnabar is really red as we see it or if this is only a sense deception is meaningless. A red-blind person will see cinnabar as black or in a dark yellow-gray shade; this is also a correct reaction for the special nature of his eye. He must only know that his eye happens to be different from that of other people. In itself one sensation is neither more nor less correct or incorrect than the other, even if the people who see the red have the great majority on their side. The red color of cinnabar exists only insofar as the majority of men have eyes that are of a similar nature. One can say with exactly the same right that it is a quality of

cinnabar to be black for red-blind people. It is a different question, however, if we maintain that the wave length of light that is reflected by cinnabar has a certain length. This statement, which we can make without reference to the special nature of our eye, is only concerned with the relations of the substance and the various systems of ether waves.

It is apparent that for such a conception all phenomena of the world are divided into two completely separated parts, into a world of motions that is independent of the special nature of our faculty of perception, and a world of subjective states that are there only within the perceiving subjects. This view has been expressed sharply and pointedly by the physiologist, Du Bois-Reymond (1818 96), in his lecture, On the Limits of Natural Science, which he gave at the forty-fifth a.s.sembly of German naturalists and physicians on August 14, 1872 in Leipzig. Natural science is the reduction of processes we perceive in the world to motions of the smallest physical particles of a ”dissolution of natural processes into mechanics of atoms,” for it is a ”psychological fact of experience that, wherever such a dissolution is successful” our need for explanation is for the time being satisfied. Moreover, it is a known fact that our nervous system and our brain are of a material nature. The processes that take place within them can also be only processes of motion. When sound or light waves are transmitted to my sense organs and from there to my brain, they can here also be nothing but motions. I can only say that in my brain a certain process of motion goes on, and I have simultaneously the sensation ”red.” For if it is meaningless to say of cinnabar that it is red, it is not less meaningless to say of a motion of the brain particles that it is bright or dark, green or red. ”Mute and dark in itself, that is to say, without qualities,” such is the world according to the view that has been obtained through the natural scientific conception, which . . . knows instead of sound and light only

vibrations of a property-free fundamental matter that now can be weighed and then again is imponderable. . . . The Mosaic word, ”And there was light,” is physiologically incorrect. Light came into being only when the first red eye spot of the infusoria differentiated for the first time between light and darkness. Without the substance of the optic and auditory sense this world, glowing in colors and resounding around us, would be dark and silent. (Limits of Natural Science.) Through the processes in the substance of our optic and auditory senses a resounding and colorful world is, according to this view, magically called into existence. The dark and silent world is physical; the sounding and colorful one is psychic. Whereby does the latter arise out of the former; how does motion change into sensation? This is where we meet, according to Du Bois-Reymond, one of the ”limits of natural science.” In our brain and in the external world there are only motions; in our soul, sensations appear. We shall never be able to understand how the one can arise out of the other.

At first sight it appears is if, through the knowledge of material processes in the brain, certain processes and latent abilities can become understandable. I am thinking of our memory, the stream of the a.s.sociation of our thought pictures, the effect of exercise, specific talents and so forth. But a little concentration at this point tells us that this view is an error.

We would only learn something concerning the inner conditions of our mental life that are approximately of the same nature as our sense impressions, but we should learn nothing that would explain how the mental life comes into existence through these conditions. What possible connections can there be between certain motions of certain atoms in my brain, on the one hand, and, on the other, such undeniable and undefinable facts expressed by the words: I feel pain; I am delighted; I taste something sweet, smell the scent of roses, hear the sound of an organ, see red, and also

the certainty that immediately follows from all this, Therefore I am. It is altogether incomprehensible that it should not be a matter of perfect indifference to a number of atoms of carbon, hydrogen, nitrogen, oxygen, etc., what their position is and how they move, how this has been and how it will be.

There is no bridge for our knowledge that leads from motion to sensation. This is the credo of Du Bois-Reymond. From motion in the material world we cannot come into the psychical world of sensations. We know that sensation arises from matter in motion, but we do not know how this is possible. Also, in the world of motion we cannot go beyond motion. For our subjective perceptions we can point at certain forms of motions because we can infer the course of these motions from the process of our perceptions, but we have no conception of what it is that is moving outside in s.p.a.ce. We say that matter moves. We follow its motions as we watch the reactions of our sensations, but as we do not observe the object in motion but only a subjective sign of it, we can never know what matter is. Du Bois-Reymond is of the opinion that we might be able to solve the riddle of sensation if the riddle of matter were disclosed. If we knew what matter is, we should probably also know how it produces sensations, but both riddles are inaccessible to our knowledge. Du Bois- Reymond meant to check those who wanted to go beyond this limit with the words, ”Just let them try the only alternative that is left, namely, supra-naturalism, but be sure that science ends where supra-naturalism begins.”

The results of modern natural science are two sharply marked opposites. One of them is the current of monism. It gives the impression of penetrating directly from natural science to the most significant problems of world conception. The other declares itself incapable of proceeding any further with the means of natural science than to the insight that to a certain subjective state there is a certain corresponding process of

motion. The representatives of the two currents vehemently oppose each other. Du Bois-Reymond rejected Haeckel's History of Creation as fiction (compare Du Bois-Reymond's speech, Darwin versus Galiani). The ancestral trees that Haeckel constructs on the basis of comparative anatomy, ontogeny and paleontology appear to Du Bois-Reymond to be of ”approximately the same value as are the ancestral trees of the Homeric heroes in the eyes of historical criticism.”

Haeckel, on the other hand, considers the view of Du Bois- Reymond to be an unscientific dilettantism that must naturally give support to the reactionary world conceptions.

The jubilation of the spiritualists over Du Bois-Reymond's ”Limitation Speech” was so much the more resonant and justified, as Du Bois-Reymond had, up to that time, been considered an important representative of the principle of scientific materialism.

What captivates many people in the idea of dividing the world dualistically into external processes of motion and inner, subjective processes of sensation and perception is the possibility of an application of mathematics to the external processes. If one a.s.sumes material particles (atoms) with energies to exist, one can calculate in which way such atoms have to move under the influence of these energies. What is so attractive in astronomy with its methods of strict calculations is carried into the smallest elements. The astronomer determines the motion of the celestial bodies by calculating the laws of the mechanics of the heavens. In the discovery of the planet Neptune we experienced a triumph of the mechanism of the heavens. One can also reduce the motions that take place in the external world when we hear a tone and see a color to laws that govern the motions of the celestial bodies. Possibly one will be able in the future to calculate the motion that goes on in our brain while we form the judgment, two times two is four. The moment when everything that can

be expressed in mathematical formulas has been calculated will be the one in which the world has been explained mathematically. Laplace has given a captivating description of the ideal of such an explanation of the world in his Essai Philosophique sur les Probabilites (1814): A mind that would know for a given moment all forces that activate nature as well as the mutual position of the ent.i.ties of which nature consists would, if its power of comprehension were otherwise sufficient, comprehend in the same formula the motions of the largest celestial body and of the lightest atom.

Nothing would be uncertain for such a mind, and the future as well as the past would be within the scope of its perfect and immediate knowledge. Man's power of reasoning offers, with the perfection that it has given to astronomy, a feeble imitation of such a mind.

Du Bois-Reymond says in connection with these words: As the astronomer predicts the day on which a comet reemerges from the depth of world s.p.a.ce after years in the firmament of heaven, so would this mind read in its calculation the day when the Greek cross will s.h.i.+ne from the mosque of the Hagia Sophia and when England will burn its last coal.

There can be no doubt that even the most perfect mathematical knowledge of a process of motion would not enlighten me with regard to the question of why this motion appears to me as a red color. When one ball hits another, we can explain the direction of the second ball but we cannot in this way determine how a certain motion produces the red color. All we can say is that when a certain motion is given, a certain color is also given. While we can explain, apparently,

as opposed to merely describe, what can be determined through calculation, we cannot go beyond a mere description in anything that defies calculation.

A significant confession was made by Gustav Robert Kirchhoff (1824 87) when, in 1874, he defined the task of mechanics: ”It is to describe the motions occurring in nature in the most complete and simple way.” Mechanics applies mathematics. Kirchhoff confesses that with the help of mathematics no more can be obtained than a complete and simple description of the processes in nature.

To those personalities who demand of an explanation something essentially more than just a description according to certain points of view, the confession of Kirchhoff could serve as a confirmation of their belief that there are ”limits to our knowledge of nature.” Referring to Kirchhoff, Du Bois- Reymond praises the wise reserve of the master, who characterizes the task of mechanics as that of describing the motions of the bodies, and places this in contrast to Ernst Haeckel, who ”speaks of atom souls.”

An important attempt to base his world conception on the idea that all our perceptions are merely the result of our own organization has been made by Friedrich Albert Lange (1828 73) with his History of Materialism (1864). He had the boldness and consistency of thought that does not allow itself to be blocked by any obstacle but follows its fundamental conception to its last conclusion. Lange's strength lay in a forceful character that was expressed in many directions. His was a personality able to take up many things, and he had sufficient ability to carry them out.

One important enterprise was his renewal of Kant's conception that, with the support of modern natural science, we perceive things not as they require it, but as our organization demands it. Lange did not really produce any new conceptions, but he did throw light into given thought worlds that is rare in its brightness. Our organization, our brain, in connection with our senses, produces the world of sensation. I see ”blue,” or I feel ”hardness,” because I am organized in this particular way. I combine the sensations into objects. By combining the sensations of ”white” and ”soft,”

etc., I produce, for instance, the conception of wax. When I follow my sensation with my thoughts, I do not move in the external world. My intellect produces connections within the world of my sensations according to the laws of my reason.

When I saw that the qualities I perceive in a body presuppose a matter with laws of motion, I also do not go outside of myself. I find that I am forced through my organization to add the thoughts of processes of motion to my sensations.

The same mechanism that produces our sensations also produces our conception of matter. Matter, equally, is only a product of my organization, just as color and tone. Even when we speak of things in themselves, we must be clearly aware of the fact that we cannot go beyond our own realm. We are so organized that we cannot possibly go beyond ourselves. Even what lies beyond our realm can be represented to ourselves only through our conception. We become aware of a limit to our world. We argue that there must be something beyond the limit that causes sensations in us. But we can only go as far as to that limit, even the limit we set ourselves because we can go no further. ”A fish can swim in water in the pond, not in the earth, but it can hit its head against the bottom and the walls.”