Chapter I: Part 1

GESTALT
PSYCHOLOGY

BY
DR. WOLFGANG KÖHLER

NEW YORK
HORACE LIVERIGHT
1929

Copyright, 1929, by
Horace Liveright, Inc.

First printing, April, 1929
Second printing, April, 1929
Third printing, August, 1929
Fourth printing, October, 1929

PRINTED IN THE U. S. A. BY
QUINN & BODEN COMPANY. INC.
RAHWAY, N. J.

_To_
MAX WERTHEIMER

_Preface_

I OFFER this book to the patient reader, feeling more than ever how much I have been inferior to my task. Nothing is easier than to criticize it. _Gestalt_ psychology, the subject matter I have tried to present, resembles in 1928 a promising start more than a complete achievement. At all events it would have been difficult to introduce it adequately. To present it skillfully in a foreign language was far beyond my linguistic ability. I have done all that I possibly could. The greatest difficulty, however, is that only certain simple and almost crude concepts of _gestalt_ psychology would yield to my painful efforts to convey them through the medium of English. Under these circumstances the optimism of my excellent publisher is responsible if the incomplete portrait of an incomplete thing is here recommended to public consideration.

Certain other trends in contemporary psychology are discussed in connection with _gestalt_ psychology. The first question a foreign psychologist has to answer in America is, of course: How do you like behaviorism? This vigorous school has energetically drawn certain lines beyond which a psychologist should never go. And, then, indicating the only direction that all psychologists must take, it has left little place open for free discussion of theory and research; in other words, it has developed into such a fundamentalism that I felt myself forced to clear my way for a certain liberalism to which I am accustomed in science.

With introspectionism things are not entirely different. In this psychological school a scheme of procedure, which is just the opposite to my own, has become dominant. This is unfortunate. If behaviorists should refuse to take account of this book because in it _direct experience_ is employed and referred to without apology, introspectionists would not treat it any better, since my use of experience, from their point of view, is not of the right sort. I have had to explain, then, not only how I could eat the forbidden fruit in spite of all commandments, but also why I took the common ware from the street and from the market-place instead of buying the standardized and sterilized products which introspection would furnish from its cultivated orchard. It was my aim, however, to make this discussion productive and, in addition to criticism, the reader will find some of our own rules of procedure expressed in these first chapters. If the fighting spirit should be found to prevail in some paragraphs, I beg you to remember that, as in politics, we sometimes strike at a system though we are fond of its defenders.

Certain psychologists, both in the United States and in England, will recognize their own ideas or, at least, find some similarities to them, in these chapters. Instead of treating all the instances of this convergence and agreement in detail, I only mention the theory of “emergent evolution” and the doctrine of Professor Whitehead’s imposing work, with all the respect which is due them both. Perhaps Professor R. M. Ogden will allow me to call him a _gestalt_ psychologist. I have not been able to see quite clearly to what degree there is agreement with certain other eminent psychologists. In Professor Bentley’s well-known book, for example, his term “organization” sometimes seems to come very near the concept of _gestalt_. But there must be some difference, since on the other hand, the basic doctrine of introspective psychology seems to be preserved in a manner incompatible with _gestalt_ psychology. Future development will undoubtedly show whether or not our views can be brought to a full congruence.

Dr. Mortimer Adler deserves the reader’s thanks as well as my own for the skill and tact which he displayed in the correction of my text, which was finally revised by K. Koffka.

My thanks are due to Mrs. L. Köhler, without whose help my work would have been all but impossible.

To Max Wertheimer I should like to dedicate something of which I could be prouder than these ten chapters. I hope he will accept them, however, as a testimony of my good will and of our friendship.

W. K.

Ormor, Sweden,
August 12, 1928.

_Contents_

CHAPTER PAGE

PREFACE vii

I. THE VIEWPOINT OF BEHAVIORISM 3

II. PSYCHOLOGY AS A YOUNG SCIENCE 35

III. THE VIEWPOINT OF INTROSPECTION 70

IV. DYNAMICS AS OPPOSED TO MACHINE THEORY 103

V. SENSORY ORGANIZATION 148

VI. THE PROPERTIES OF ORGANIZED WHOLES 187

VII. BEHAVIOR 224

VIII. ASSOCIATION 269

IX. REPRODUCTION 301

X. INSIGHT 349

INDEX 395

GESTALT PSYCHOLOGY

I

_The Viewpoint of Behaviorism_

THERE seems to be a single starting point for psychology, exactly as for all the other sciences: the world as I find it, naïvely and uncritically. The naïveté may be lost as we proceed. Problems may be found, which were completely hidden from our eyes at first, and for their solution it may be necessary to devise concepts which seem to have little contact with uncritical experience; nevertheless the whole development should begin with a naïve picture of the world. This origin is necessary because there is no other basis from which a science can arise. In my case, which may be taken as representative of many others essentially similar to it, that naïve picture consists, at this moment, of a blue lake with dark forests around it, a big, gray stone, hard and cool, which I have chosen as a chair, a paper on which I write, a faint noise of the wind which hardly moves the trees, and a strong odor characteristic of boats and fishing. But there is more in this world: somehow I now behold, though it does not become fused with the blue lake of the present, another lake of a milder blue, and I find myself, some years ago, looking at it from its shore in Illinois. I am perfectly accustomed to beholding thousands of pictures of this kind which arise some way or other when I am alone. And there is still more in this world: my hand and fingers moving lightly over the smooth surface of the paper; now, when I stop writing and look around again, there is a feeling of health and vigor, but in the next moment I feel something like a dark pressure somewhere in my interior which tends to develop into a feeling of being hunted--I have promised to have this manuscript ready within a few months.

Most people live in such a world permanently, which is _the world_ for them, and hardly ever find problems or difficulties in its properties. Crowded streets may take the place of the lake, a cushion in a sedan that of my stone, some serious words of a business transaction may be remembered instead of Lake Michigan, and the dark pressure may have to do with tax-paying instead of book-writing. All these are minor differences so long as one takes the world at its face-value, as we all do except in those hours when science disturbs our natural attitude. There are problems, of course, even for the most uncritical citizen of this first-hand world. But, for the most part, they do not refer to the nature of it; they are of a practical or an emotional sort and they usually mean that, this world being taken for granted, we do not know how to judge or how to behave in that actual part of it which we face as our present situation.

Various sciences, most of all physics and biology, began centuries ago to destroy the simple confidence with which human beings take that naïve world as _the reality_. Though hundreds of millions still remain undisturbed, the scientist has found it, in some respects, full of almost contradictory properties. Fortunately he has been able to discover another world, as it were, behind it, whose properties, highly different from those of the everyday world of naïve people, do not seem to be contradictory at all. No wonder therefore that now, as psychology begins to be a science, some of its most energetic students should wish to make it go the way of the exact sciences at once. Indeed, if other sciences have found the naïve world of everyday reality impervious to and unavailable for scientific method, what hope of better success can we as psychologists have? And if the enormous and almost impossible feat of jumping out of the world of direct, but confused, experience into a world of clear and hard reality, has already been achieved by physical science, it would seem wise for the psychologist to take advantage of that great event in the history of science and begin to construct psychology on the solid basis laid down by the physicist and the physiologist outside the field of uncritical experience.

A few words about the history of scientific criticism will help to define better the material or field to be given up by psychological investigation and to indicate what shall be taken as a better object of research. Our naïve experience consists of objects, their properties and changes, existing quite independently of us. It does not matter to them and their existence whether or not we see and feel and hear them; they remain exactly as they are when we state their properties, when we are not present or are occupied in other matters. It was a great step when men began to ask how seeing and feeling and hearing occur, and it was a revolution when they found that colors and noises and smells, etc., were merely products of some of the influences exerted on man by his surroundings. Still these surroundings seemed to subsist in their primary characteristics and to remain “the real world,” if only you subtracted those “secondary qualities” as purely subjective ingredients. But finally even the “primary qualities” of naïve realism were assimilated to the secondary as subjective. The form, weight and movement of the objects of immediate experience were treated as colors and sounds, i.e., as functions of the experiencing organism, as end results of its complicated processes. And therefore we cannot hold that these objects excite the processes, since, according to this point of view, their very existence as parts of immediate experience is only a consequence of these processes. So the picture of the objective and independent _physical world_ of physical things, of physical time, of physical movement and physical space, has to be constructed as something different from the world-picture of direct experience.

Physical objects, which _as such_ we can neither see nor feel, exert upon each other a great variety of physical influences, which _as such_ similarly do not occur in the world of immediate experience. There is one physical object more interesting than all the others but in every way as foreign to naïve experience as they are: that is my physical body, an astounding system of electromagnetic entities. If the right influences be exerted upon this system by other physical objects, those processes will occur in it, the consequences of which I know as the exterior part of the world of naïve experience, the so-called external sensory world. But an enormous amount of physical activity is constantly going on inside my body. We have sufficient grounds, therefore, to assume that there are still other processes with the occurrence of which the _inner_ side of our immediate experience is connected: such are the feeling of strain, when I contract the muscles of my arm, also that of hunger and fatigue, my “memory image” of Lake Michigan, fear and hope and so on, almost _ad infinitum_.

At present we shall not consider _how_ the physicist accomplishes the gigantic task of investigating the properties of a world which does not appear directly in any part of immediate experience. But there can be no doubt concerning the remarkable success of his procedure. Whereas the world of naïve man is somewhat confused, revealing its subjective character in any critical discussion of its properties, the world of the physicist gives short shrift to confusion and contradiction. And though we find ourselves surprised by the rapid changes which physical theory undergoes in our times, we still have the feeling that progress is made with most of these changes. Eventually there will be agreement about all the more important properties of the physical world.

For a while psychology was supposed to be the science of the events of direct experience, both in its external and its internal aspects, as contrasted to physical objects and occurrences.[1] By description of direct experience the psychologist hoped to get not only an orderly registration of all the possible varieties of such experience, but also a great deal of information about the functional relations among these events. He even aimed at formulating laws governing the flow of direct experience.

The well-known psychological school of behaviorism has leveled against the older psychology the criticism that it was misguided both with respect to its subject-matter and its aim. It has not been possible, according to the behaviorist, to register the varieties of direct experience in a convincing manner, nor has anything come of the attempt to describe their functional relationships or to formulate the laws of so-called “mental life.” In no respect, the behaviorist holds, do we have the impression that there exists a real and progressive science of direct experience, clear in its methods and results. On the contrary, we find endless discussions of minor and, less frequently, major items, different psychologists giving quite different descriptions of “facts” which are supposed to be more or less the same for both of them. Take the example of “images”! One psychologist claims to have them in numbers, many of them almost as lively and concrete as perceptions. Others tell us that there are no real images at all in direct experience and that probably the first man was deceived by words or other motor phenomena which correspond to objects and facts not actually present in experience. If the famous method of “introspection,” i.e., observation of direct experience,[2] cannot give better results in such a gross investigation, what shall we expect from it when we are confronted by questions of equal or even greater importance which are also more subtle and intrinsically more difficult? Unfortunately, the adherents of introspection do not seem to trust their own procedure. At least they must have agreed upon facing important problems as seldom as possible, since they are occupied mainly with describing the more remote and less exciting corners of experience, as e.g., minor nuances of sensations, or the “glassy” appearance of certain parts of space, and so forth. If all I have to do to develop the science of direct experience is to describe it, why then not attack the central facts of “mental life” at once, instead of scratching a little at the surface, or periphery, of it? There was a time in Germany, not very long ago, when people began to joke about psychology’s ponderous discussion of trifles. And, indeed, it was strange to see how the description of a direct experience, what happens, for instance, during a single comparison of two tones or colors, could fill hundreds of pages without giving us the slightest positive idea about how the occurrence and accuracy of such a comparison might be explained. Even in a state of perplexity a science can be highly interesting. But psychology, so far as it deals with direct experience by the method of introspection, has not only been a complete failure; it has also become boresome for all those who are not professionally connected with it.

And the behaviorist is not slow in giving us reasons why this must be so. The meaning of “direct experience,” through opposition to the world of physics, becomes associated with concepts like “the mental,” “mind” and “soul,” almost without our being aware of this association. Thus gradually this term becomes the expression for “spiritual life” or the name for the effects of a special mental substance, existing independently of the facts of physics and biology. Consequently, all the old prejudices and superstitions of religious or metaphysical extraction slip into the concept and into the treatment of direct experience. The psychologist loses his impartial judgment; what he has heard about “mind,” or “soul,” and their miraculous properties since the early days of his childhood, creeps into his statements and makes “introspection” an ill disguised rhetoric in favor of prescientific mythology and medieval darkness.

However, if this were the only argument against introspection, the introspectionist might answer that if the behaviorist were right in this point, his criticism would not apply to the description of direct experience itself, but rather would indicate an accidental source of defect in the method. Then, some increase of self-criticism and a careful elimination of religious or metaphysical interests in students of psychology might be a remedy for these defects, and a very welcome gesture towards sober behaviorism at the same time.

But the behaviorist has other reasons for not accepting direct experience as a field of scientific research. First of all, as a procedure, introspection lacks the chief methodological virtue of physical research, a position of observation external to the system under observation; on the contrary, it is a special process _in_ this system itself, and all chances are against its leaving the “observed” parts of the system undisturbed. _Hinc illæ lacrimæ!_ An example of this is the attempt to study introspectively the direct experience of sorrow and joy; they do not remain the same, but rather tend to disappear when the selfsame person who has or had the sorrow and the joy must assume the attitude of introspection.

But even supposing that this difficulty might be overcome by some scarcely imaginable improvement of the method, we still should find it useless, the behaviorist argues, because of its miserable and inevitable subjectivity. What is the first characteristic of an objective statement as the result of an objective scientific procedure? That whoever happens to be interested in it can be obliged to understand it in one determinate meaning, if only you give him exact definitions of the terms you are using in your statement. So we define the atomic weight or the atomic number of an element, so analogy and homology of morphological structures, and there is no physicist or biologist who does not know the exact significance of those words. If now you listen to psychologists talking, let us say, about the “confusion” which they observe in peripheral vision, what exact meaning can be conveyed by this word so long as it is not fixed by definition? A real definition, however, seems to be impossible wherever one has to do with the ultimate data of direct experience. If you are asked for the definition of “confusion,” you may attempt to define it negatively, say in terms of “lack of clearness.” But that does not help you very much, since your friend will then ask what you mean by “clearness.” You may tell him that a rather high degree of clearness is a normal property of the central parts of a simple and orderly visual field. But such a field might have more than one normal property and you did not give a _differentia specifica_ in your pseudo definition, in addition to which the words “simple” and “orderly” need definition as badly as did “confusion” and “clearness.” In any case, you have now resorted to the only thing which seems feasible where, as in this field of direct experience, a true definition cannot be achieved, viz., a kind of _demonstration_. You do not define your term, but you give your friend a hint about what conditions are necessary in order to have the specific kind of direct experience about which you are talking. Supposing that he understands the words by which you describe those conditions, there is some chance now that he may attach your undefined term to the precise phase of his actual direct experience that your use of the term intended. But what a crude and altogether vague procedure this is, if you compare it with the elegant definitions of the exact sciences!

And still we have supposed that, given the same conditions, your friend, who cannot make statements about any direct experience except _his own_, must find in it the same properties, objects and occurrences, which you have found in _your_ direct experience. You cannot, as the physicists seem to do, make your two statements about one and the same event, neither do you make readings from one and the same apparatus or scale. You have _two_ events in _two_ experiences. What is your evidence for assuming that under the same conditions the ultimate data of experience are the same for both of you? Unfortunately you shall never know whether this is the case or not. On one hand, color blindness and similar phenomena show conclusively that such an identity does not exist; on the other, you have no proof of that identity even in those cases where all the tests you might imagine give the same description, i.e., the verbal report you both make. Your friend may report “red” where you say “red.” Still you do not know more than that your friend always has the _same_ quality wherever and whenever you have your “red,” without knowing at all that he has _just that_ quality which you call “red.” Neither does it help you to a real identification of qualities in the two direct experiences that what he calls “red” seems to have (more or less) the same “stimulating” value as you find verified in your own description, because you will see at once that he may use the same term “stimulating” in quite a different meaning, so that he does not have the same kind of experience when he uses it.

This is subjectivity in its extreme form. If every one has his own direct experience and if he is forever excluded from that of all other persons, direct experience is the private affair of each of us, and with respect to it a common science cannot possibly be achieved. Indeed, so little can be derived from the direct experience of one man, concerning similar experiences in others, that, in epistemology, it has become a truism that I shall never know whether or not there exists any “direct experience” at all even in my best friend. Whatever I see or hear when we talk together is a part of _my_ experience. Certainly, what I call his attitude, or his voice, in my experience, is determined by physical events in the muscles and in the nervous system, etc., of his physical body. It is not only possible but even necessary to understand these physical events from the viewpoint of pure physics or physiology. Consequently, there is no proof that some of these processes in my friend are accompanied by “direct experience” in him.

The behaviorist might add to this criticism that he does not deny the great contributions which, before his time, the older forms of psychology have made to the advancement of this science. But he will say that, looking upon those achievements from the present point of view, one will easily discover a simple fact: viz., that nearly all of them are to the credit not of introspection and description but of the “objective experiment.” The meaning of this word may be explained as follows: Instead of making a subject observe and describe his direct experience in a given case, we place him in a well-defined situation to which he has to react by certain performances. These we can state and measure without his giving us any description of his experience. So Weber’s law was discovered; this was the kind of experiment by which Fechner made psychology an experimental science; memory and the formation of habits were investigated by research of this type with almost no introspection; and since Binet and Simon we have learned to treat intelligence in the same manner. If we are not mistaken, even the introspectionist gives us “descriptions” of colors and tones, pleasure and volition, only so long as he has not found a method by which he might transform them through objective experiments into measurable achievements or reactions. The introspectionist himself seems to accept the “descriptive” observation of a fellow introspectionist, according to the measure in which the other has been able to give objective experiments as a verification and corroboration of his descriptions. What, then, is the use of “direct experience” and its description?

From their common criticism all behaviorists do not draw quite the same conclusions about “direct experience.” None of them, it is true, find direct experience a matter of interest for science, since as the private affair of those who have such experience it is not accessible to the objective observation undertaken by others, as it ought to be were it a proper object of scientific research. A few members of the school seem to go so far as to deny the existence of direct experience altogether; they simply abominate the notion. But these minor differences of opinion are of no importance for us, because in the question of _method_ all behaviorists have not only the same negative but also the same positive opinion. Their program is a simple consequence of the foregoing argument. In his objective experiment the psychologist has tacitly accepted the procedure of the exact sciences, even if he has not become fully aware of the difference in principle which separates this attitude from that of introspection. Both the physicist and the chemist are interested in knowing how a system which they are investigating will react when exposed to a certain set of conditions; they also ask how the reaction will change with a variation of those conditions. Both questions are answered by objective observation, registration and measurement. This is exactly the form of real experimentation in psychology, too: a subject of a certain type (child, adult, man, woman, animal) is the system to be investigated; certain conditions are given and objectively controlled; the most important of these we call “the stimuli”; and a reaction occurs which is observed quite objectively.

The only thing which psychologists need, then, is to recognize, generally and in principle, that this form of procedure is the only possible one, and also that it is precisely the same as that of all other exact sciences. Behavior, i.e., the reaction of a living system, is its only subject-matter, and behavior in no way includes any direct experience. In the experimental work of the future, even the highest forms of behavior will be studied and described in purely objective terms. They _must_ be, since personal, direct experience does not occur at a single point in the whole experiment. For some this truth is somewhat hidden by the fact that in most of our experiments language reactions are of a special importance. If the experimenter himself enjoys what he calls direct experience and if this experience includes a great many things associated with words, he will be inclined to take the words of his subject as signs of similar direct experience on his part. Nevertheless, the words are registered as responses of the subject, and as such are purely objective, physical facts, produced by certain processes in the larynx and the mouth of the subject. Though the experimenter knows that other objective processes (of innervation, inhibition, and so forth) will have occurred before these sound waves are produced by the action of muscles, he will never be able to decide, according to our analysis, whether there was any direct experience accompanying those inner processes. Perhaps we should discipline ourselves to a less frequent use of language reactions in our experiments, until finally we overcome the danger of associating language with direct experience, and introspection will have disappeared from psychology as an exact science.

Of course, not all the reactions of the subject are observed with equal facility in the objective manner. Sometimes even strong stimulation will not produce any overt behavior which can be registered externally with our present methods. But in the majority of these cases the physiologist can give us highly valuable information about the functioning of the autonomic part of the nervous system and about the subsequent reactions which occur in the most important visceral organs, including the endocrine glands. One of the main tasks of psychology will be to develop and to adapt the physiological techniques until these visceral reactions can be registered with perfect ease under the conditions of behavioristic experimentation. We also have some evidence for assuming that, in addition to the reactions just mentioned, so-called “thinking” consists in slight innervations of the muscles concerned in speech reactions.

* * * * *

So far I hope that I have given a fair statement of the opinions which prevail among behaviorists. It ought to be the more correct, since I sympathize with these opinions in several points, most of all in the criticism of “introspection.” Indeed, much of current introspection seems to be rather sterile and, in an odd contrast to its ambitions, to lead research away from the more urgent problems. Whether this be an intrinsic property of introspection or merely a consequence of some accidental mistake usually associated with it, we shall discuss later on.

At present, we have a simpler problem before us. In the natural sciences, so the behaviorist tells us, methods deal with objective reality, whereas in the treatment of direct experience--if there is such a thing--they deal with something entirely subjective. Is that true? Is that the real reason why natural science has won the admiration of the world and psychology is still in an embryonic state? I cannot admit it. It seems to me that, starting with an admirable enthusiasm for exactness, behaviorism has been misled completely at this point and that, consequently, the energy spent by behaviorism in its fight against “direct experience” and “consciousness” has been spent in the wrong direction. So, at least, the situation appears to me because, whatever may have happened to the keen leaders of behaviorism in their individual development, I must give the following report about myself. It is a well-known story, but some psychologists seem to have forgotten it.

There cannot be the slightest doubt for me that, as a child, I had “direct experience” before I even dreamed of a world like that of physics. Of course, I did not know that term then, which could acquire its meaning later on only by the very fact that the world of physics became opposed to it. There were innumerable varieties of experiences appearing as “objective,” i.e., as existing or occurring independently and externally. There were other experiences which belonged to me personally and privately, and insofar were “subjective,” such as, among others, dreadful fear upon certain occasions, and an overwhelming, warm happiness at Christmas.

In the following chapters we shall be occupied mainly with “objective experience.” This term, however, may be misinterpreted rather easily. So I shall try to specify its meaning a little more. Doing so, I shall even run the risk of repeating some arguments several times, because this is the point where most of our difficulties arise.

The name “experience” seems to indicate that, though appearing as “objective,” those things and events were felt by me as “being given in my perception” and therefore as “subjective.” Certainly, they were not. They simply _were there outside_, and at that time I had no suspicion whatever of their being the effects of something else upon “me.” I must go further. There was not even a question of their depending upon my presence; upon my keeping my eyes open, and so forth. When I went around an object it remained the same identical thing. So absolutely “objective” were those objects and events, that there was no place left for a more objective world. Even now, this “objectivity” is still so strong and natural, that I am constantly tempted to attribute to the interior of these self-same “things” all those properties which, in the meantime, physics has taught me to attribute to objects of the physical world. When, in these pages, I talk about “direct experience” of the “objective” type, the word is always used in this meaning: e.g., a chair as something there outside, hard, stable, brown, generally without any taint of “being perceived” by me, of being “a subjective phenomenon.”

In some cases, it is true, the discrimination between the
“objective” and the “subjective” side of direct experience may
become dubious: as with after-images or with the prick of a needle
in my finger. That does not make the discrimination less important
in itself. In physics the discrimination of the conducting
substances from insulators remains of high value, though between
the extremes we find a great many intermediate cases. For us, the
main point is the fact that in “things” and their “movements,”
etc., an almost unsurpassable degree of “objectivity” is reached.

At the time when I began to understand physics I did not learn only about the physical world. Another lesson was necessarily connected with studying physics, and it was this lesson that gave the term “direct experience” its connotation or, better, which introduced me to a manner of thinking that made the meaning of “direct experience” clear. The physical world could not be the same as that “objective” world which I had had around me the whole time. Certain physical objects were found to influence a particularly interesting physical body, viz., my physical organism, and what has been called “objective” experience here, was shown to depend upon subsequent and very complicated processes in that physical organism. Though that influence, exerted by other physical objects, starts these processes in the organism, there is no possibility of identifying the final product, “things” and their “changes” as I have them in immediate experience, with those physical objects from which the influences came. If a wound is not the gun which emitted the projectile, then the “thing” which I have before me, which I see and feel, cannot be identical with the corresponding physical object. This object, influencing my physical organism, produces certain disturbances in it, _the final outcome_ of which is the “thing” before me in direct experience.[3]

Such “things,” however, were the first items _I knew_. Therefore, a picture of the physical world had to be _constructed_ after I once appreciated the necessity of it. Hence it is built up by inference as something found indirectly or mediately; and, _in contrast to it_, the world around me, as I had it before and still have it, quite apart from the physicist’s construction, is now called the world of direct, or immediate, experience.

But how can I say that a “chair,” for example, is an “objective experience” if I must admit that it depends upon certain processes in my organism? Does not the chair become “subjective” then? It does and it does not. At this very moment the meaning of our terms has changed. In the last paragraphs “objective” has denoted a certain experienced property which some parts of my direct experience, in contrast to other experiences, possess _as such_ (exactly as they have size, color, hardness and so forth); the term “subjective” in _this_ paragraph means their genetic dependence upon my physical organism. “Subjectivity,” in this latter meaning, is not itself a directly experienced property, but a relationship which we ascribe to “objective” experiences after we have learnt to regard them as the outcome of organic processes and, therefore, as distinct from the physical reality external to the physical organism. Sometimes the two connotations of the term are confused in the most deplorable manner as though what is “subjective” genetically ought also to be “subjective” in experience. So most introspectionists seem to think that, properly speaking, the chair before me must be a subjective phenomenon _in experience_, appearing “before me” only in consequence of some illusion. And since there is no “subjective” chair to be discovered, the behaviorist derides the introspectionist for dwelling in a world of imaginary ghosts. The simple truth is that some of the experiences depending upon processes in my physical organism have the character of “objectivity,” whereas others, depending upon other processes in the same organism, have a “subjective” character, this contrast being something altogether indifferent to the _genetic_ “subjectivity” of _both_ types of processes and experiences, as depending upon the physical organism. After this, I hope that no misunderstanding of the term “objective experience” will be possible. When I talk about “a chair,” the chair of my everyday life is meant and not some “subjective phenomenon” to be observed perhaps by highly trained introspectionists, but utterly unknown to me.

On the other hand, we have seen that we cannot identify the chair of “objective experience” with the chair as a part of the physicist’s world. Under these circumstances, the world of direct experience being the first I had, and since all that I know about the physical world being inferred later on from the properties of the experienced world, how can I deny this experienced world which, for me, is the only basis upon which I can continue to guess about physical realities? No one can prevent me from thinking, if I choose, that after all the physical world may be the more important and more essential one. But even then I must confess that the other world has existed first and always _for me_, and that I still can see no other way of discovering the properties of physical reality but by observing “objective experiences” and drawing my conclusions about the physical world from them. With future progress of physiology I may become able to discover even the nervous processes underlying my “observing” and “guessing” and so be able to give a physical theory of these events. But even then, since the world of physiology is part of the physical world and _as such_ is not directly accessible to me, any progress whatever along this line will depend upon my observing what I call a body or a nervous system as parts of “direct experience.” It may be otherwise for behaviorists, so that the physical (and physiological) world _as such_ is directly known to them, and that for them the term “known” has nothing to do with direct experience. But that cannot change my report about my own case in which affairs are as I have described them. It is in the terms of this description that I must decide whether I shall become a behaviorist or not.

What then about the behaviorist’s statement that observation in physics deals with objective reality whereas, in the treatment of direct experience, it deals with something subjective?

Let me describe my own procedure when I investigate the physical properties of a physical object. Is there any considerable amount of H_{4}C_{2}O_{2} in a given mixture of chemical substances? I know about these substances by the corresponding “objective experience” before me, and I find the positive answer to the question by smelling, i.e., in direct experience. This being a rather crude procedure, let us consider a case of fine measurement. What is the intensity of an electric current which, under certain conditions, must exist in a given wire? The position of a needle on the scale of a definite apparatus will tell me, but it will tell me in direct optical experience, the whole apparatus being an “objective” part of my actual experience, exactly as the wire and the given set of conditions must manifest themselves either as parts of direct experience or by a sufficient testimony of their existence in some part of experience which I have learnt to regard as a sign for them. And this is true of all possible objective statements or measurements which I shall ever be able to make in physics. They are statements about my actual objective experiences in these different cases. I shall never be able to make a direct statement about a physical event _as such_. Therefore my observation of physical facts will always remain of the same kind in principle as that of an after-image, or of the “confusion” which I find so characteristic of peripheral vision, or of my feeling healthy. Therefore, the exactness of my physical observation cannot depend upon my avoidance of “direct experience” in physics. I do not avoid it, for I cannot avoid it. Yet the procedure _works_. _Some_ observations of direct experience must then be an adequate basis for science.

If all the concrete statements which I can make in physical research are observations of direct experience, there are some inevitable consequences. How do I define my terms as a physicist? Since my knowledge of physics consists entirely of concepts and observations derived from or contained in direct experience, all the terms which I use in discussing physical problems must refer either to concepts or observations or, more probably, complicated combinations of the two--in any case, products of my direct experience. If I try to define them, my definitions must refer to other concepts or observations, and so forth. A gestural denotation toward the locus of the phenomena about which I am talking, as, for instance, a hint where to make certain observations or have certain direct experiences, will be the ultimate step in any process of definition I may attempt. Even the most abstract concepts of physics, as, for example, that of entropy, can have no meaning without a reference, indirect though it may be, to truly direct experiences. I shall never be able to give a definition of my terms in physics or to understand a definition given by others, which, in this respect, differs in principle from what I may use as a definition in psychology. Nevertheless the method of physics is successful. I never have difficulty with definitions when I talk with physicists about their science. Hence some definitions, or hints about cases of direct experience, must be sufficiently safe for exact science. Therefore the exactness of my definitions in physics cannot be the result of their being independent of “direct experience,” for they are not independent.

But the behaviorist tells me that observation of my direct experience is a private affair of mine, whereas in physics, two physicists can make the same observation on the same galvanometer. I deny the truth of this statement. If another man observes the galvanometer, he observes something other than the galvanometer as a physical object, since the object of his observation is the result of certain organic processes, determined by the physical galvanometer. Again, the galvanometer I am observing is the final result of a different series of processes occurring in _my_ physical organism. By no means do we “observe the same instrument” then, though physically both series of processes are started by the same physical object. Still, our statements about our observations seem to agree so well in a great many cases, that we do not discuss the question very much, whether there is an absolute philosophical proof for sufficient similarity between my galvanometer and his. Again the procedure works. Since I, at least, do not know about a galvanometer except through “objective experience,” and yet almost all the statements which the other man makes agree with my statements, the privacy of direct experience does not disturb us at all--in physics. Again, in principle, there is no difference here between physics and psychology. All physicists, when working with others in such a case, are convinced naïvely that their fellow-physicists “have a galvanometer before them,” and that their observations refer to it. In this sense they assume that their fellow-workers have a very definite “objective experience,” highly similar to their own experience, and they quite naïvely understand the words of their colleagues as statements about that experience. That, however, is allowing private affairs in exact science. It does not seem to disturb scientific procedure, as it does not disturb the affairs of everyday life, wherein it is the most general and natural occurrence. In certain cases, therefore, belief in the “direct experience” of others must be innocent and is not a hindrance to scientific progress. If psychology does not make rapid advancement, the reason for it cannot be that belief as such.

There remains one consequence of the elementary fact that observation in physics involves observation of direct experience. As a physicist, observing my apparatus, I do not fear that my activity as an observer has any serious or distorting influence upon the essential properties of what I observe, if only I keep myself, as a physical system, at a certain distance from the apparatus, as another physical system. Now, as direct experiences both the apparatus to be observed and my “activity” of observing depend upon processes in the same system, viz., my physical organism. Again the behaviorist must be wrong when he declares that, because of the fact just mentioned, direct experience can not be observed scientifically, since in this case of observation in physics, the situation is similar: the material to be observed and the process of observing belong to the same system. Thus we see that the physicist and the psychologist are in exactly the same situation in this respect. It does not matter at all whether I call myself a physicist or a psychologist in observing a galvanometer. In both cases my observation is directed towards the same “objective experience.” The procedure works in physics. Why not in psychology? There must be some cases in which my observation of direct experience does not disturb the observed facts seriously.

This argument contains in itself a most remarkable limitation of the range of its own application. It does not mean at all, that all forms of so-called introspection are justified, even less does it mean that _generally_ the products of so-called introspection are independent of introspection. Here the critical position of behaviorism has exaggerated the scope of a fair argument and unjustly applied it to _all_ statements about direct experience, although the critical point is thoroughly justified in a great many cases.

I have described how, as a physicist, I must deal with direct experience. Evidently some epistemological difficulties with respect to the objectivity of procedure in that science may be derived from that description by a very extreme purist, as the behaviorist seems to be. But, fortunately, those dilemmas had not yet been discovered, when in the time of Galileo, Newton and Huyghens the first really important steps were made in physics. Those great investigators carried on, pragmatically naïve and happily undisturbed by a “behaviorism” of physics which might have impeded or blocked the whole development for the sake of “epistemological purity.” Somehow the procedure has worked in spite of the fact that logically, perhaps, it is not possible to certify it as absolutely objective. Sciences which wish to carry on their researches and be productive often show a certain healthy disdain of such scruples. It might be better for psychology, too, if, after listening to a very wholesome critical lesson from behaviorism, it returns to undertaking productive work with some naïveté, using all possible means which yield results.

As a scientific attitude the Homeric assault of behaviorists against “direct experience,” “consciousness” and so forth, appears very strange to me. They do not generally show an undue interest in epistemological considerations. It is just _one_ question which suddenly arouses their interest: How can I know about the direct experience of others? I shall never have a definite proof of the validity of such knowledge. But physics, that is another matter! There we are safe! The behaviorist, however, forgets that it is a truism in epistemology that I shall never be able to “prove” conclusively the existence of an independent physical world. As an extreme purist I might argue this point exactly as the behaviorist disputes the assumption of direct experience in others. Somehow it does not occur to the behaviorist to apply his epistemological criticism to the assumption of the physical world. He does not say: Thou shalt not work upon a physical world, the existence of which will always remain a mere assumption. On the contrary, he assumes its reality with all the healthy naïveté which he lacks in psychology. The reason is, perhaps, that the achievements of physical science are imposing and have become the ideal of behaviorism. But to the mind of a methodological purist that cannot be taken as a satisfactory proof of the existence of the physical world. Of course, personally and practically I am as convinced of its existence as any behaviorist has ever been, and I am fully aware of the fact that sciences may and must believe and postulate, where the epistemologist, if he likes, may doubt. But then I shall believe and postulate the direct experience of others, as well as the existence of physical entities, if this makes my procedure simpler and more productive. And I feel the more justified in this attitude, since I have seen that all work I may do in physics is founded on direct experience and that, therefore, the enormous superiority of physics over psychology in accomplishment, cannot follow from any differences in this respect.

At this moment I see the behaviorist smiling ironically: With all his medieval philosophy Mr. Köhler will never make any progress against the sound scientific basis of behaviorism. I answer that this basis of behaviorism is as philosophical as anything could be: it is purely epistemological. In this connection the only difference between the behaviorist and me is one of completeness: the behaviorist sees a single theorem of epistemology and, as an extreme purist, he dwells exclusively on this one point, ignoring the context from which it has been taken. I am aware of this context; it is stated in the foregoing argument; and I find myself therefore opposed to behaviorism, or any other one-sided and impractical purism in science.

BIBLIOGRAPHY

W. S. Hunter: _Human Behavior_. 1928.

K. Koffka: _The Growth of the Mind_. 1924. 2nd edition, 1928.

J. B. Watson: in _Psychologies of 1925_ (ed. by C. Murchison).

A. P. Weiss: _A Theoretical Basis of Human Behavior_. 1925.

II

_Psychology as a Young Science_

IN the first chapter I became slightly autobiographical in order to show why I have found it impossible to become a behaviorist. If I am ever to become one, some adherent of that school will have to effect the conversion. I do not myself see the way.

So far direct experience has been shown to be the raw material of both physics and psychology. If despite this fact the physical sciences are so far ahead of psychology in their development, what shall be our method of imitating their achievements?

Contemporary physics has a real advantage in the careful selection of the experiences which play a decisive rôle in the crucial moments of physical research. Of course, the physicist ignores all “_subjective_ experience,” as defined in the previous chapter, as far as possible, because apparently it has nothing to do with the properties of the physical world. All the difficulties of psychologists who try to observe and describe subjective experience are simply avoided by the physical sciences.

But the selection and exclusion does not stop there. If most “objective experience” was taken as evidence of physical existences and physical events in early investigations, a more critical view of the situation tended to eliminate large parts of this material as well. The process of selection has become particularly severe, since the advancement of science has made it possible almost everywhere to transform qualitative observation into quantitative measurement. At the present time almost all physical measurements are made in an extremely indirect way. We do not observe an experienced counterpart of the physical variable in question; we observe a related but different object the virtue of which is that it lends itself to more exact statement and is shown, or supposed, to be in a well-known functional relationship to the physical variable. Of all possible objective experience nothing seems better to fulfill the requirements of the physicist than the localization of a single line (a needle) on a scale of other lines, especially if this localization becomes the coincidence of the first line (needle) with one of the others (or inclusion between two which are near to each other). The range of direct experiences used in measurement has now reached a minimum value, indeed. It almost seems as if the same scale and the same needle were used universally; it tells a hundred altogether different stories about the physical world. It means “atmospheres” or “volts,” or “ampères” or “temperature” and so forth, as the case may be. In addition to observing a definite coincidence, and controlling the connection of the apparatus with the system to be investigated, the physicist has only to recognize certain words and figures on the scale. That is all the direct experience which enters into the procedure. There is not much opportunity for serious blundering. Even so simple a property as physical size is not measured directly. No physicist measures the length of an object by comparing it with the experienced length of a standard object directly. That would not be accurate enough. Rather he prefers the method of coinciding lines or points. Defining physical length by this method, he measures the length of a line by observing the coincidence of its ends with certain points on a scale.