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The Tacit Dimension [Excerpt]


Michael Polanyi

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The book “The Tacit Dimension” by Michael Polanyi was published firstly in 1966 at The University of Chicago Press. The following is an excerpt from the chapter “Tacit Knowing” (p. 4-13). 

I shall reconsider human knowledge by starting from the fact that we can know more than we can tell. This fact seems obvious enough; but it is not easy to say exactly what it means. Take an example. We know a person’s face, and can recognize it among a thousand, indeed among a million. Yet we usually cannot tell how we recognize a face we know. So most of this knowledge cannot be put into words. But the police have recently introduced a method by which we can communicate much of this knowledge. They have made a large collection of pictures showing a variety of noses, mouths, and other features. From these the witness selects the particulars of the face he knows, and the pieces can then be put together to form a reasonably good likeness of the face. This may suggest that we can communicate, after all, our knowledge of a physiognomy, provided we are given adequate means for expressing ourselves. But the application of the police method does not change the fact that previous to it we did know more than we could tell at the time. Moreover, we can use the police method only by knowing how to match the features we remember with those in the collection, and we cannot tell how we do this. This very act of communication displays a knowledge that we cannot tell.

There are many other instances of the recognition of a characteristic physiognomy-some commonplace, others more technical-which have the same structure as the identification of a person. We recognize the moods of the human face, without being able to tell, except quite vaguely, by what signs we know it. At the universities great efforts are spent in practical classes to teach students to identify cases of diseases and specimens of rocks, of plants and animals. All descriptive sciences study physiognomies that cannot be fully described in words, nor even by pictures.

But can it not be argued, once more, that the possibility of teaching these appearances by practical exercises proves that we can tell our knowledge of them? The answer is that we can do so only by relying on the pupil’s intelligent co-operation for catching the meaning of the demonstration. Indeed, any definition of a word denoting an external thing must ultimately rely on pointing at such a thing. This naming-cum-pointing is called “an ostensive definition”; and this philosophic expression conceals a gap to be bridged by an intelligent effort on the part of the person to whom we want to tell what the word means. Our message had left something behind that we could not tell, and its reception must rely on it that the person addressed will discover that which we have not been able to communicate.

Gestalt psychology has demonstrated that we may know a physiognomy by integrating our awareness of its particulars without being able to identify these particulars, and my analysis of knowledge is closely linked to this discovery of Gestalt psychology. But I shall attend to aspects of Gestalt which have been hitherto neglected. Gestalt psychology has assumed that perception of a physiognomy takes place through the spontaneous equilibration of its particulars impressed on the retina or on the brain. However, I am looking at Gestalt, on the contrary, as the outcome of an active shaping of experience performed in the pursuit of knowledge. This shaping or integrating I hold to be the great and indispensable tacit power by which all knowledge is discovered and, once discovered, is held to be true.

The structure of Gestalt is then recast into a logic of tacit thought, and this changes the range and perspective of the whole subject. The highest forms of integration loom largest now. These are manifested in the tacit power of scientific and artistic genius. The art of the expert diagnostician may be listed next, as a somewhat impoverished form of discovery, and we may put in the same class the performance of skills, whether artistic, athletic, or technical. We have here examples of knowing, both of a more Intellectual and more practical kind; both the “wissen” and “können” of the Germans, or the “knowing what” and the “knowing how” of Gilbert Ryle. These two aspects of knowing have a similar structure and neither is ever present without the other. This is particularly clear in the art of diagnosing, which intimately combines skillful testing with expert observation. I shall always speak of “knowing,” therefore, to cover both practical and theoretical knowledge. We can, accordingly, interpret the use of tools, of probes, and of pointers as further instances of the art of knowing, and may add to our list also the denotative use of language, as a kind of verbal pointing.

Perception, on which Gestalt psychology centered its attention, now appears as the most impoverished form of tacit knowing. As such it will be shown to form the bridge between the higher creative powers of man and the bodily processes which are prominent in the operations of perception.

Some recent psychological experiments have shown in isolation the principal mechanism by which knowledge is tacitly acquired. Many of you have heard of these experiments as revealing the diabolical machinery of hidden persuasion. Actually, they are but elementary demonstrations of the faculty by which we apprehend the relation between two events, both of which we know, but only one of which we can tell.

Following the example set by Lazarus and McCleary in 1949, psychologists call the exercise of this faculty a process of “subception.” 1 Lazarus, R. S., and McCleary, R. A., Journal of Personality (Vol. 18, 1949), p. 191, and Psychological Review (Vol. 58, 1951), p. 113. These results were called in question by Eriksen, C. W., Psychological Review (Vol. 63, 1956), p. 74 and defended by Lazarus, Psychological Review (Vol. 63, 1956), p. 343. But in a later paper surveying the whole field-Psychological Review (Vol. 67, 1960), p. 279-Eriksen confinned the experiments of Lazarus and McCleary, and accepted them as evidence of subception.

I am relying on subception only as a confirmation of tacit knowing in an elementary form, capable of quantitative experimental demonstration. For me it is the mechanism underlying the formation of Gestalt, from which I first derived my conception of tacit knowing in Personal Knowledge. Strangely enough, the connection of subception with Gestalt has been hardly noticed by psychologists in the course of their controversies on the validity of subception. I could find only one place alluding to it, in a paper by Klein, George S., “On Subliminal Activation,” Journal of Nervous Mental Disorders (Vol. 128, 1959), pp. 293-301. He observes: “It requires no experimental demonstration to say confidently that we are not aware of all the stimuli which we use in behavior.”

I have said already basically in Personal Knowledge and have continued to emphasize since then, that it is a mistake to identify subsidiary awareness with unconscious or preconscious awareness, or with the Jamesian fringe of awareness. What makes an awareness subsidiary is the function it fulfolls; it can have any degree of consciousness, so long as it functions as a clue to the object of our focal attention. Klein supports this by saying that subliminal activation is but a special case of transient or incidental stimuli of all kinds. It is not the subliminal status that matters but “the meanings and properties [a stimulus] acquires at the periphery of thought and action.”

Eriksen and Kuethe, whose observation of not consciously identified avoidance I have quoted as a kind of subception, have called this avoidance a defense mechanism, thus affiliating it to Freudian conceptions. This practice is widespread and has caused Psychological Abstracts to divide the subject matter into subception and defense mechanism.

Yet another fragmentation of this matter occurred by taking due notice of Otto Potzl’s observations going back to 1917. A survey of his work and of that of his direct successors has appeared in Psychological Issues (Vol. II, No. 3, 1960) under the title “Preconscious Stimulation in Dreams, Associations, and Images” by Otto Potzl, Rudolf Allers, and Jacob Teler, International Universities Press, New York 11, N.Y. An introduction to this monograph by Charles Fisher links these observations to recent studies and notes. the present uncertainty about the status of stimuli of which we become conscious only in terms of their contribution to subsequent experience. “The matter needs to be settled,” writes Fisher on p. 33, “because the issue of subliminality has important implications for theories of perception.”

I believe that this matter has actually much wider implications and must be generally subsumed under the logical categories of tacit knowing.]]] These authors presented a person with a large number of nonsense syllables, and after showing certain of the syllables, they administered an electric shock. Presently the person showed symptoms of anticipating the shock at the sight of “shock syllables”; yet, on questioning, he could not identify them. He had come to know when to expect a shock, but he could not tell what made him expect it. He had acquired a knowledge similar to that which we have when we know a person by signs which we cannot tell.

Another variant of this phenomenon was demonstrated by Eriksen and Kuethe in 1958. 2 Eriksen, C. W., and Kuethe, J. L., “Avoidance Conditioning of Verbal Behavior Without Awareness: A Paradigm of Repression,” Journal of Abnormal and Social Psychology (Vol. 53, 1956), pp. 203-09. They exposed a person to a shock whenever he happened to utter associations to certain “shock words.” Presently, the person learned to forestall the shock by avoiding the utterance of such associations, but, on questioning, it appeared that he did not know he was doing this. Here the subject got to know a practical operation, but could not tell how he worked it. This kind of subception has the structure of a skill, for a skill combines elementary muscular acts which are not identifiable, according to relations that we cannot define.

These experiments show most clearly what is meant by saying that one can know more than one can tell. For the experimental arrangement wards off the suspicion of self-contradiction, which is not easy to dispel when anyone speaks of things he knows and cannot tell. This is prevented here by the division of roles between the subject and the observer. The experimenter observes that another person has a certain knowledge that he cannot tell, and so no one speaks of a knowledge he himself has and cannot tell.

We may carry forward, then, the following result. In both experiments that I have cited, subception was induced by electric shock. In the first series the subject was shocked after being shown certain nonsense syllables, and he learned to expect this event. In the second series he learned to suppress the uttering of certain associations, which would evoke the shock. In both cases the shock-producing particulars remained tacit. The subject could not identify them, yet he relied on his awareness of them for anticipating the electric shock.

Here we see the basic structure of tacit knowing. It always involves two things, or two kinds of things. We may call them the two terms of tacit knowing. In the experiments the shock syllables and shock associations formed the first term, and the electric shock which followed them was the second term. After the subject had learned to connect these two terms, the sight of the shock syllables evoked the expectation of a shock and the utterance of the shock associations was suppressed in order to avoid shock. Why did this connection remain tacit? It would seem that this was due to the fact that the subject was riveting his attention on the electric shock. He was relying on his awareness of the shock producing particulars only in their bearing on the electric shock. We may say that he learned to rely on his awareness of these particulars for the purpose of attending to the electric shock.

Here we have the basic definition of the logical relation between the first and second term of a tacit knowledge. It combines two kinds of knowing. We know the electric shock, forming the second term, by attending to it, and hence the subject is specifiably known. But we know the shock-producing particulars only by relying on our own awareness of them for attending to something else, namely the electric shock, and hence our knowledge of them remains tacit. This is how we come to know these particulars, without becoming able to identify them. Such is the functional relation between the two terms of tacit knowing: we know the first term only by relying on our awareness of it for attending to the second.

In his book on freedom of the will, Austin Farrar has spoken at one point of disattending from certain things for attending to others. I shall adopt a variant of this usage by saying that in an act of tacit knowing we attend from something for attending to something else; namely, from the first term to the second term of the tacit relation. In many ways the first term of this relation will prove to be nearer to us, the second further away from us. Using the language of anatomy, we may call the first term proximal, and the second term distal. It is the proximal term, then, of which we have a knowledge that we may not be able to tell.

In the case of a human physiognomy, I would now say that we rely on our awareness of its features for attending to the characteristic appearance of a face. We are attending from the features to the face, and thus may be unable to specify the features. And I would say, likewise, that we are relying on our awareness of a combination of muscular acts for attending to the performance of a skill. We are attending from these elementary movements to the achievement of their joint purpose, and hence are usually unable to specify these elementary acts. We may call this the functional structure of tacit knowing.

But we may ask: does not the appearance of the experimental setting-composed of the nonsense syllables and the electric shocks-undergo some change when we learn to anticipate a shock at the sight of certain syllables? It does, and in a very subtle way. The expectation of a shock, which at first had been vague and unceasing, now becomes sharply fluctuating; it suddenly rises at some moments and drops between them. So we may say that even though we do not learn to recognize the shock syllables as distinct from other syllables, we do become aware of facing a shock syllable in terms of the apprehension it evokes in us. In other words, we are aware of seeing these syllables in terms of that on which we are focusing our attention, which is the probability of an electric shock. Applying this to the case of a physiognomy, we may say that we are aware of its features in terms of the physiognomy to which we are attending. In the exercise of a skill, we are aware of its several muscular moves in terms of the performance to which our attention is directed. We may say, in general, that we are aware of the proximal term of an act of tacit knowing in the appearance of its distal term; we are aware of that from which we are attending to another thing, in the appearance of that thing. We may call this the phenomenal structure of tacit knowing.

But there is a significance in the relation of the two terms of tacit knowing which combines its functional and phenomenal aspects. When the sight of certain syllables makes us expect an electric shock, we may say that they signify the approach of a shock. This is their meaning to us. We could say, therefore, that when shock syllables arouse an apprehension in us, without our being able to identify the syllables which arouse it, we know these syllables only in terms of their meaning. It is their meaning to which our attention is directed. It is in terms of their meaning that they enter into the appearance of that to which we are attending from them.

We could say, in this sense, that a characteristic physiognomy is the meaning of its features; which is, in fact, what we do say when a physiognomy expresses a particular mood. To identify a physiognomy would then amount to relying on our awareness of its features for attending to their joint meaning. This may sound far-fetched, because the meaning of the features is observed at the same spot where the features are situated, and hence it is difficult to separate mentally the features from their meaning. Yet, the fact remains that the two are distinct, since we may know a physiognomy without being able to specify its particulars.

To see more clearly the separation of a meaning from that which has this meaning, we may take the example of the use of a probe to explore a cavern, or the way a blind man feels his way by tapping with a stick. For here the separation of the two is wide, and we can also observe here the process by which this separation gradually takes place. Anyone using a probe for the first time will feel its impact against his fingers and palm. But as we learn to use a probe, or to use a stick for feeling our way, our awareness of its impact on our hand is transformed into a sense of its point touching the objects we are exploring. This is how an interpretative effort transposes meaningless feelings into meaningful ones, and places these at some distance from the original feeling. We become aware of the feelings in our hand in terms of their meaning located at the tip of the probe or stick to which we are attending. This is so also when we use a tool. We are attending to the meaning of its impact on our hands in terms of its effect on the things to which we are applying it. We may call this the semantic aspect of tacit knowing. All meaning tends to be displaced away from ourselves, and that is in fact my justification for using the terms “proximal” and “distal” to describe the first and second terms of tacit knowing.

From the three aspects of tacit knowing that I have defined so far -the functional, the phenomenal, and the semantic – we can deduce a fourth aspect, which tells us what tacit knowing is a knowledge of. This will represent its ontological aspect.

Since tacit knowing establishes a meaningful relation between two terms, we may identify it with the understanding of the comprehensive entity which these two terms jointly constitute. Thus the proximal term represents the particulars of this entity, and we can say, accordingly, that we comprehend the entity by relying on our awareness of its particulars for attending to their joint meaning.


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  1. Lazarus, R. S., and McCleary, R. A., Journal of Personality (Vol. 18, 1949), p. 191, and Psychological Review (Vol. 58, 1951), p. 113.
  2. Eriksen, C. W., and Kuethe, J. L., “Avoidance Conditioning of Verbal Behavior Without Awareness: A Paradigm of Repression,” Journal of Abnormal and Social Psychology (Vol. 53, 1956), pp. 203-09.