Friday, 20 April 2012

Clinical judgement, tacit knowledge and recognition in psychiatric diagnosis

This is a substantial reworking of a previous draft chapter for the Oxford Handbook of Philosophy and Psychiatry.
This chapter contrasts the recent emphasis on operationalism as the route to reliability in psychiatry with arguments for an ineliminable role for tacit knowledge. Although Michael Polanyi is widely credited with the most forceful arguments for the presence of a tacit dimension, I argue that two clues he offers as to its nature – that we know more than we can tell and that knowledge is an active comprehension of things known – are better interpreted through regress arguments set out both by Ryle and Wittgenstein. Those arguments, however, suggest that tacit knowledge is not inexpressible but merely inexpressible in context-free terms. Tacit knowledge is context-dependent practical knowledge. So understood, the regress arguments suggest that the operational approach to psychiatric diagnosis can never free itself from a tacit dimension. Given that claim then Parnas’ opposing view of diagnosis can be seen as a way to embrace, rather than deny, the importance of tacit knowledge and skilled clinical judgement for psychiatry.
In this chapter, I will examine the role of clinical judgement in the recognition of psychiatric symptoms via the idea that this involves an ineliminable tacit dimension. I will do this by examining three authors (Polanyi, Ryle and Wittgenstein) who offer support for the existence of some form of tacit knowledge. But I will place them in the context, in this section, of the dominant criteriological approach to psychiatric diagnosis and, in the final section, one reaction against it.
One reason for doubting, or playing down, a role for tacit knowledge in psychiatric diagnosis is the influence of operationalism in a quest for reliability for the last 50 years or so. There were two main factors which explain this.
Firstly, on its foundation in 1945, the World Health Organisation set about establishing an International Classification of Diseases (ICD). Whilst the chapters of the classification dealing with physical illnesses were well received, the psychiatric section was not widely adopted and so the British psychiatrist Erwin Stengel was asked to propose a basis for a more acceptable classification. Stengel chaired a session at an American Psychological Association conference of 1959 at which the philosopher Carl Hempel spoke. As a result of Hempel’s paper (and an intervention by the UK psychiatrist Sir Aubrey Lewis) Stengel proposed that attempts at a classification based on theories of the causes of mental disorder should be given up (because such theories were premature), and suggested that it should instead rely on what could be directly observed, that is, symptoms.
In fact, Hempel’s paper provided only partial support for the moral that was actually drawn for psychiatry. He argued that:
Broadly speaking, the vocabulary of science has two basic functions: first, to permit an adequate description of the things and events that are the objects of scientific investigation; second, to permit the establishment of general laws or theories by means of which particular events may be explained and predicted and thus scientifically understood; for to understand a phenomenon scientifically is to show that it occurs in accordance with general laws or theoretical principles. [Hempel 1994: 317]
These two requirements – that terms employed in classifications should have clear, public criteria of application and should lend themselves to the formulation of general laws – correspond to the aims of reliability and validity respectively. But it was the former that was adopted by psychiatry as the key aim at the time. With respect to it, Hempel claims that
Science aims at knowledge that is objective in the sense of being intersubjectively certifiable, independently of individual opinion or preference, on the basis of data obtainable by suitable experiments or observations. This requires that the terms used in formulating scientific statements have clearly specified meanings and be understood in the same sense by all those who use them. [ibid: 318]
He commends the use of operational definitions (following Bridgman’s book The Logic of Modern Physics [Bridgman 1927]), although he emphasises that in psychiatry the kind of measurement operations in terms of which concepts would be defined would have to be construed loosely. This view has been influential up to the present WHO psychiatric taxonomy in ICD-10.
The second reason for the emphasis on reliability and hence operationalism was a parallel influence from within American psychiatry that shaped the writing of DSM-III. Whilst DSM-I and DSM-II had drawn heavily on psychoanalytic theoretical terms, the committee charged with drawing up DSM-III drew on the work of a group of psychiatrists from Washington University of St Louis. Responding in part to research that had revealed significant differences in diagnostic practices between different psychiatrists, the ‘St Louis group’, led by John Feighner, published operationalised criteria for psychiatric diagnosis. The DSM-III task force replaced reference to Freudian aetiological theory with more observational criteria. The task force leader, Robert Spitzer, later reported: ‘With its intellectual roots in St. Louis instead of Vienna, and with its intellectual inspiration drawn from Kraepelin, not Freud, the task force was viewed from the outset as unsympathetic to the interests of those whose theory and practice derived from the psychoanalytic tradition.’ [Bayer and Spitzer 1985: 188 quoted in Shorter 1997: 301-2].
This stress on operationalism has had an effect on the way that criteriological diagnosis is codified in DSM and ICD manuals. Syndromes are described and characterised in terms of disjunctions and conjunctions of symptoms. The symptoms are described in ways influenced by operationalism and with as little aetiological theory as possible. (That they are neither strictly operationally defined nor strictly aetiologically theory free is not relevant here.) Thus one can think of such a manual as providing guidance for, or a justification of, a diagnosis offered by saying that a subject is suffering from a specific syndrome. Presented with an individual, the diagnosis of a specific syndrome is said to be justified because he or she has enough of the relevant symptoms which can be, as closely as possible, ‘read off’ from their presentation. Such an approach to psychiatric diagnosis plays down the role of individual judgement or tacit knowledge amongst clinicians.
Polanyi on tacit knowledge
Whilst the influence of operationalism deployed in the service of reliability aims to remove or reduce the presence of judgement and thus an uncodified tacit element in psychiatric diagnosis, there is a tradition in the history and philosophy of science (dating from about the same time) which stresses an ineliminable role for tacit knowledge in science. In this section, I will examine arguments offered by the chemist turned philosopher of science Michael Polanyi.
But first, what does Polanyi mean by ‘tacit’ knowing or knowledge? (Polanyi himself talks of tacit knowing rather than knowledge. I will, nevertheless, use ‘knowledge’ whilst talking about his views but will return to emphasise the practical dimension to what is tacit.) In this chapter, I will follow two clues. The first comes from the start of his book The Tacit Dimension.
I shall reconsider human knowledge by starting from the fact that we can know more than we can tell. [Polanyi 1967b: 4]
The second clue comes from his book Personal Knowledge in which he says:
I regard knowing as an active comprehension of things known, an action that requires skill. [Polanyi 1958: vii]
These passages suggest two features tacit knowledge might have: that it is not, or perhaps cannot be made, explicit and that it is connecte to action: the personal practical knowledge of a skilled agent. I will start with the first clue and, in later sections, return to the second. The first clue (that we can know more than we can tell) continues:
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. [Polanyi 1967b: 4]
The suggestion is that tacit knowledge is tacit because it is ‘more than we can tell’. We cannot tell how we know things that we know tacitly. But what argument does he give for this? What are the limits on what can be said still leaving something that can be known?
In Personal Knowledge, Polanyi’s strategy is to examine how what can be said or, more broadly, articulated both leaves room for, and depends on, something outside what can be articulated. There are two key arguments of relevance to this chapter. One depends on limits on the kind of representation available to summarise explicit knowledge in science, thus indicating a space for tacit knowledge. The other depends on an analysis of what is involved in recognition (an argument which promises to impact on diagnostic judgement), which also connects to Polanyi’s views of how linguistic representation in general is possible. I will suggest that this latter argument is the fundamental argument but start with the former.
To examine the limits of scientific representation, Polanyi considers the understanding that a skilled surgeon has of the spatial configuration and orientation of organs in the body. He argues that this cannot be captured in a representation.
The major difficulty in the understanding, and hence in the teaching of anatomy, arises in respect to the intricate three-dimensional network of organs closely packed inside the body, of which no diagram can give an adequate representation. Even dissection, which lays bare a region and its organs by removing the parts overlaying it, does not demonstrate more than one aspect of that region. It is left to the imagination to reconstruct from such experience the three-dimensional picture of the exposed area as it existed in the unopened body, and to explore mentally its connections with adjoining unexposed areas around it and below it.
The kind of topographic knowledge which an experienced surgeon possesses of the regions on which he operates is therefore ineffable knowledge. [Polanyi 1962: 89]
The claim here is that three-dimensional spatial knowledge is ineffable, or tacit, because it cannot be captured in a representation. Polanyi goes on to argue that even if all human bodies were identical and even if there were a map comprising cross sections based on ‘a thousand thin slices’ of the body, that in itself would not articulate the knowledge of a trained surgeon. Someone knowing merely the former ‘would know a set of data which fully determine the spatial arrangement of the organs in the body; yet he would not know that spatial arrangement itself’ [89]. An additional act of interpretation or imagination is needed. But because that act cannot itself be encoded in a representation, according to Polanyi, it remains tacit.
This argument is a little surprising. Polanyi concedes that the set of cross sectional representations, presumably alongside some further information about their inter-relations such as their order and distance apart, ‘fully determine[s] the spatial arrangement of the organs’ and yet denies that this amounts to an articulation of the three-dimensional understanding.
Without the further information about the relations between the set of maps, the maps alone would not be an articulation of the skilled surgeon’s knowledge. But then neither would they fully represent the arrangement of bodily organs. With the addition of that further information, however, why would this not count as an articulation of the surgeon’s knowledge? If so it would be explicit, rather than merely tacit, knowledge?
A further possible clue to Polanyi’s thinking runs thus:
The difficulty lies here entirely in the subsequent integration of the particulars and the inadequacy of articulation consists altogether in the fact that the latter process is left without formal guidance. The degree of intelligence required from the student to perform the act of insight which ultimately conveys to him the knowledge of the topography, offers here a measure of the limitations of the articulation representing this topography. [ibid: 90]
But there remains something strange about this line of thought. If the integration of the partial representations, such as the set of cross sections, were left without formal guidance then it would be clear why the partial representations could not articulate the surgeon’s knowledge. But neither would they determine the arrangement of organs as Polanyi has previously asserted.
The difficulty with interpreting this argument is that of balancing the claim that spatial configuration is both determined by what can be represented but remains ineffable and thus tacit rather than explicit. I think that the clue to its interpretation is to realise that whether a symbol logically determines anything always, according to Polanyi, depends on a tacit element. This is supported by a different argument.
I may ride a bicycle and say nothing, or pick out my macintosh among twenty others and say nothing. Though I cannot say clearly how I ride a bicycle nor how I recognise my macintosh (for I don’t know it clearly), yet this will not prevent me from saying that I know how to ride a bicycle and how to recognise my macintosh. For I know that I know how to do such things, though I know the particulars of what I know only in an instrumental manner and am focally quite ignorant of them. [ibid: 88]
Polanyi suggests that the skill involved in the example of recognising a macintosh is akin to the practical skill of cycle riding. In both cases, the ‘knowledge-how’ depends on something which is not explicit: the details of the act of bike riding or raincoat recognition. Whilst one can recognise one’s own macintosh, in the example, one is ignorant, in some sense, of how. Thus how one does this is tacit.
If this argument were successful it would be of general significance because it would also apply to the recognitional skill which underpins classification such as diagnosis in psychiatry but also lingusitic labelling generally. Indeed, Polanyi makes this connection explicitly.
[I]n all applications of a formalism to experience there is an indeterminacy involved, which must be resolved by the observer on the ground of unspecified criteria. Now we may say further that the process of applying language to things is also necessarily unformalized: that it is inarticulate. Denotation, then, is an art, and whatever we say about things assumes our endorsement of our own skill in practising this art. [ibid: 81]
This connection between denotation and tacit recognitional skills appears to be the fundamental argument for the importance of tacit knowledge for explicit scientific accounts. Polanyi summarises the connection thus:
If, as it would seem, the meaning of all our utterances is determined to an important extent by a skilful act of our own – the act of knowing – then the acceptance of any of our own utterances as true involves our approval of our own skill. To affirm anything implies, then, to this extent an appraisal of our own art of knowing, and the establishment of truth becomes decisively dependent on a set of personal criteria of our own which cannot be formally defined.... [E]verywhere it is the inarticulate which has the last word, unspoken and yet decisive... [ibid: 70-71]
Note that the argument for the claim about the art of denotation being tacit seems to rest on an appeal to the apparently clearer case of the recognition of particulars – such as a particular macintosh – which, he argues, depends on features of which one is focally ignorant. There is a difference between the two cases. The example he gives concerns a particular macintosh as one’s own among a pile of them. It is not the judgement that the object is a macintosh, but the recognition (re-cognition) of that particular macintosh. But I will ignore that difference in what follows.
To justify his claim about denotation he needs to defend the general claim that explicit recognition of something as an instance of a type, such as ‘macintosh’, is based on the implicit recognition of subsidiary properties of which one is focally ignorant. In other words, to recognise a feature (F, say) one must a) always recognise it in virtue of something else (subsidiary features G, H and I, eg.) of which b) one is focally ignorant. But it is not clear that either part of this claim is true.
To consider the claim, it will help to make clearer what Polanyi means by focal attention and subsidiary awareness. Elsewhere he uses the sample of pointing to something using a finger.
There is a fundamental difference between the way we attend to the pointing finger and its object. We attend to the finger by following its direction in order to look at the object. The object is then at the focus of our attention, whereas the finger is not seen focally, but as a pointer to the object. This directive, or vectorial way of attending to the pointing finger, I shall call our subsidiary awareness of the finger. [Polanyi 1967a: 301]
In attending from the finger to the object, the object is the focus of attention whilst the finger, though seen, is not attended to. Note, however, that the finger is not invisible. It could itself be the object of focal attention were it attended to. This suggests that the first part of the general claim that Polanyi needs itself faces an objection based on a regress. The recognition of an instance of a type or kind depends on subsidiary awareness of something else which could have been the object of focal awareness and thus would have depended on subsidiary awareness of something else.
This is a potential rather than a vicious regress. (It is not that in order to have subsidiary awareness of something one must already or actually have had focal awareness of it or anything else. Combined with Polanyi’s general claim, that thought would have generated a vicious regress.) Nevertheless, even the potential regress suggests something implausible about Polanyi’s general claim. It does not seem reasonable to think that it is always the case that recognition of the instantiation of a kind depends on subsidiary awareness of something else. Take the case of the recognition that something is an instance of redness. Surely the recognition that x is red turns on a matter of focal awareness of its colour, not subsidiary awareness of anything else?
Polanyi seems to assume that the question of how one recognises something to be of an instance of a particular kind always has an informative answer (and to cover cases where it is not obvious what this is, the second move he makes is to assume that it is tacit). But whilst it sometimes may have an informative answer, there is no reason to think that it always has. In the next section I will return to this point. This line of thought puts the first part of Polanyi’s claim – that to recognise a feature (F, say) one must a) always recognise it in virtue of something else (subsidiary features G, H and I, eg.) – under pressure. What of the second aspect: that one must be focally ignorant of the subsidiary features?
Even in cases where one recognises a particular as an F in virtue of its subsidiary properties G, H, I, and cannot give an independent account of those properties, it is not clear that one need be focally ignorant of them. It may be, instead, that the awareness one has of G, H, I is manifested in the recognition of something as an F or a particular F. One might say, I recognise that this is a macintosh (or even my macintosh) because of how it looks here with the interplay of sleeve, shoulder and colour even if one could not recognise a separated sleeve, shoulder or paint colour sample as of the same type. Whilst it seems plausible that one might not be able to say in context-independent terms just what it is about the sleeve that distinguishes a macintosh from any other kind of raincoat (one may, for example, lack the vocabulary of fashion or tailoring) that need not imply that one is focally ignorant of, or not attending to, just those features that make a difference. Recognition may depend on context-dependent or demonstrative elements, such as recognising shapes or colours for which one has no prior name. But if anything, that suggests one has to be focally aware, not focally ignorant, of them.
In summary, two claims seem to support Polanyi’s case. First, one is sometimes focally unaware of features that underpin one’s recognitional abilities. Second, one cannot always say in general term on what features one’s recognition depends. But these do not support the general claim that (focal) recognition of one feature always depends on merely subsidiary awareness of something else. And if not, then Polanyi has not offered a general reason to hold that recognition is a tacit skill.
The tacit element in recognition
I argued in the previous section that Polanyi’s argument for the role of a tacit element in science turns on an argument that it is fundamental in recognition, including the recognition which underpins the ‘art of denotation’. Polanyi suggests that tacit knowledge is that which falls outside linguistic articulation or representation. But such representation presupposes recognitional know-how rather than the other way round. So the know-how that constitutes recognition is not itself articulated but rather tacit.
I argued, however, that Polanyi’s argument for the role of tacit knowledge in recognition is not successful because he has to assume that to recognise a feature (F, say) one must a) always recognise it in virtue of something else (subsidiary features G, H and I, eg.) of which b) one is focally ignorant. But neither point – a) and b) – is compelling. There are, however, two other arguments which were both framed at about the same time as Polanyi’s and which seem to suggest limits both to what can be put into words (which resistance Polanyi takes to indicate tacit-status) and the importance of a practical dimension underlying linguistic competence, picking up Polanyi’s second clue. These are Gilbert Ryle’s argument that knowledge-how is a concept logically prior to the concept of knowledge-that and Ludwig Wittgenstein’s regress argument concerning understanding a rule. I will now explore the extent to which these support Polanyi’s emphasis on a tacit dimension.
Ryle’s argument takes the form of a regress.
If a deed, to be intelligent, has to be guided by the consideration of a regulative proposition, the gap between that consideration and the practical application of the regulation has to be bridged by some go-between process which cannot by the pre-supposed definition itself be an exercise of intelligence and cannot, by definition, be the resultant deed. This go-between application- process has somehow to marry observance of a contemplated maxim with the enforcement of behaviour. So it has to unite in itself the allegedly incompatible properties of being kith to theory and kin to practice, else it could not be the applying of the one in the other. For, unlike theory, it must be able to influence action, and, unlike impulses, it must be amenable to regulative propositions. Consistency requires, therefore, that this schizophrenic broker must again be subdivided into one bit which contemplates but does not execute, one which executes but does not contemplate and a third which reconciles these irreconcilables. And so on for ever. [Ryle 1945: 2]
There has been a recent flurry of literature on the precise nature of this argument and thus whether it is successful [eg Stanley and Williamson 2001; Noë 2005; for detailed assessment see Gascoigne and Thornton forthcoming]. But it seems to involve something like the following regress:
Suppose all know-how can be articulated (put into words) as a piece of knowledge-that: grasping some proposition that p. Grasping the proposition that p is itself something one can do successfully or unsuccessfully, so it is also a piece of know-how. So, on the theory in question, it will involve grasping another proposition, call this q. But grasping the proposition that q is itself something one can do successfully or unsuccessfully, so it is also a piece of know-how. So, on the theory in question, it will involve grasping another proposition, call this r.... etc
If the first step of the reductio is designed to ‘articulate’ or represent a piece of otherwise merely tacit knowledge at the heart of recognition, it will lead to a regress. Ryle himself suggests that it can be used to undermine what he calls an ‘intellectualist legend’ which attempts to explain practical knowing-how though a deeper, theoretical form of knowing-that based on grasping a proposition. His counter argument is that, since grasping a proposition can be done well or badly, the only way to avoid the vicious regress is to grant that intelligence can accrue to, and be manifested in, practical knowledge directly, without further theoretical explanation or underpinning. Knowing-how is more basic than knowing-that.
What is the relationship between Ryle’s argument and Polanyi’s views of tacit knowledge? On the one hand, it offers some nuanced support. Polanyi’s claim that we know more than we can tell as is one of his two main clues to tacit knowing, the second being the connection between knowing and personal skill. Given that Ryle argues that knowing-how cannot be explained through knowing-that or grasp of a proposition – both paradigmatic of what can be put into words – if, following Polanyi’s second clue, tacit knowledge is equated with practical knowledge (of which more below) then Ryle’s argument suggests limits to the way or purpose of putting it into words. It cannot be explained in knowing-that terms.
But, on the other hand, the idea that practical knowledge can express intelligence directly – without needing to inherit it from grasp of a proposition – suggests the following thought which runs counter to Polanyi’s claim that we know more than we can tell. (And thus it puts Polanyi’s two clues in tension.) Consider the following piece of practical knowledge: the ability to recognise a raincoat as a macintosh and thus denote it ‘macintosh’. Why is the denoting of raincoats as ‘macintoshes’ not what articulating or expressing this piece of recognitional knowledge amounts to, thus discharging any tacit element? In this particular example, because it involves linguistic denotation, why is that not putting all the relevant knowledge in play into words (calling this coat a ‘macintosh’, eg.)? Why assume, as Polanyi does, that there is always a further, though tacit, answer as to how one recognises that something is an instance of a general kind?
These questions flag a possibility that Polanyi neglects: that recognitional knowledge might both be fully expressible (and thus, intuitively, not tacit in the sense of silent) nor grounded in further tacit elements. But at the same time, Ryle does provide support for the fundamental importance of the practical dimension. Might that be used to justify a conception of tacit knowledge independently of Polanyi’s own arguments?
I will address that question by looking at a related regress argument which dates from about the same time: Ludwig Wittgenstein’s discussion of rule following. Wittgenstein considers what is grasped by someone who has grasped a mathematical rule or series which he approaches via the idea of teaching the +2 series:
Now we get the pupil to continue a series (say + 2) beyond 1000–and he writes 1000, 1004, 1008, 1012.
We say to him: “Look what you’ve done!”–He doesn’t understand. We say: “You were meant to add two: look how you began the series!”–He answers: “Yes, isn’t it right? I thought that was how I was meant to do it.”–Or suppose he pointed to the series and said: “But I went on in the same way.”–It would now be no use to say: “But can’t you see....?”–and repeat the old examples and explanations.–In such a case we might say, perhaps: It comes natural to this person to understand our order with our explanations as we should understand the order: “Add 2 up to 1000, 4 up to 2000, 6 up to 3000 and so on.” [Wittgenstein 1953: §185]
In passages such as these, Wittgenstein seems to stress the infinite possibilities of divergence and thus the infinite possibilities of a breakdown of communication. Given his concurrent criticisms, in surrounding passages of the Philosophical Investigations, of appeal to physiological mechanisms, mental talismans and platonic structures, objective features of the structure of reality and independent of us, to explain our grasp of going on in the correct way, it can seem the most fragile contingency that communication is possible [cf Lear 1982]. The problem is the apparent mismatch between, on the one hand, the idea of infinite range of rules and, on the other, the scanty resources for teaching them.
Whence comes the idea that the beginning of a series is a visible section of rails invisibly laid to infinity? Well, we might imagine rails instead of a rule. And infinitely long rails correspond to unlimited applications of a rule. [Wittgenstein 1953: §218]
But since teaching rules is possible only either by paraphrase, which merely postpones the problem of explaining the paraphrase, or by finite examples, which seem to underdetermine the rule which governs a potentially unlimited number of cases, grasp of a rule seems to need some further helping hand.
This line of thought suggests, albeit mistakenly, a role for tacit knowledge. The thought runs: since everything that can be said still allows for the kind of misunderstanding exemplified by Wittgenstein’s hypothetical deviant pupil, the grasp of a rule that a normal pupil acquires must be based on something unsaid and implicit. It must depend on a tacit element. This seems to support Polanyi’s slogan that we know more than we can tell. It can also seem to fit Wittgenstein’s own conclusion:
What this shews is that there is a way of grasping a rule which is not an interpretation, but which is exhibited in what we call “obeying the rule” and “going against it” in actual cases. [ibid: §202]
The problem with this thought is that it accepts what Wittgenstein opposes: an uncritical view of the metaphor of rules as rails ‘invisibly laid to infinity’ fundamentally distinct from our capacity to articulate them. This is a platonic view of the underpinnings of our concepts which somehow latch onto the independent structure and is one of Wittgenstein’s targets.
The platonic picture is reinforced by one response to the cases of deviant pupils. They show, according to this response, both that any finite set of examples underdetermines a correct understanding of the rule but also that such correct understanding must involve grasp of a structure which is independent of human judgement. Since no actual human enumeration of the pattern seems enough to determine it, it must be super-human. Hence the metaphor of rails laid to infinity. But whereas real rails can bend and break, the rails in the metaphor cannot. They are supernatural. With that picture of the way rules determine correct moves in place, there is a substantial role for tacit knowledge to bridge the gap between what can be made explicit in the sublunary realm and the ideal platonic standard.
This picture is wrong for two reasons, however. The first objection is that it undermines the possibility of communication. If understanding depends on a combination of something which can be expressed but which stops short of a rule and an inexpressible tacit element which fills the gap, how can the right tacit element be communicated in any particular case? The hybrid account cannot escape the problem that the deviant pupil seems to raise. The deviant pupil might fill in the gap with the wrong tacit element since nothing that can be expressed is enough to guide the selection of tacit element.
The second objection is that it is unnecessary. Whilst Wittgenstein rejects philosophical explanations (via mental mechanisms or platonic structures) of our grasp of rules (by pointing out they could not determine what they are supposed to), he does not promote a kind of sceptical gap between what can be manifested and what must be understood for communication, a gap that has thus to be filled by a tacit element. To the contrary, he undermines the idea that there is any such gap in the first place. For example, he argues that there is a conceptual connection between what a teacher can express and what a student can grasp in the examples which manifest the teacher’s meaning.
“But do you really explain to the other person what you yourself understand? Don’t you get him to guess the essential thing? You give him examples,--but he has to guess their drift, to guess your intention.” – Every explanation which I can give myself I give to him too. – “He guesses what I intend” would mean: various interpretations of my explanation come to his mind, and he lights on one of them. So in this case he could ask; and I could and should answer him. [ibid: §210]
“But this initial segment of a series obviously admitted of various interpretations (e.g. by means of algebraic expressions) and so you must first have chosen one such interpretation.”–Not at all. A doubt was possible in certain circumstances. But that is not to say that I did doubt, or even could doubt…[ibid: §213]
Recognising that understanding can be expressed in examples, for those with eyes to see at least, undermines the idea that there is a gap between sublunary explanations and rules understood as platonic structures and thus a need, there, for tacit knowledge to bridge that gap. A finite series of examples, or a particular verbal explanation, or even a signpost, can express the very rule in question without the need for an underlying tacit interpretation. Thus there is no support in Wittgenstein’s discussion of understanding for Polanyi’s slogan that we know more than we can tell. What we know, we can express and in the case of denotation, put into words.
Wittgenstein’s discussion also suggests a response to Polanyi’s assumption that the focal recognition of one thing depends on tacit or subsidiary awareness of something else. If the role of the subsidiary elements serves as the tacit grounds for an understanding of what is focally recognised, if they provide a kind of interpretation of it, then Wittgenstein’s discussion undermines that picture. The account of understanding as depending on a combination of an explicit and a tacit elements cannot be generally true. This, thus, undermines the motivation for Polanyi’s arguments in the previous section. Polanyi does not provide a reason to think that recognitional judgement is tacit nor to think that acts of denotation do not fully manifest one’s recognitional know-how.
But whilst Ryle’s and, especially, Wittgenstein’s regress arguments do not support a connection between tacit knowledge and inexpressibility, they do suggest an important link between the practical groundings of knowledge and a more modest construal of the slogan that we know more than we can tell.
Consider a rule which can be partly codified in an informal statement such as that the digits always follow the pattern: ‘0, 2, 4, 6, 8, 0 etc’ or more fully codified in an explicit mathematical formula or principle. Someone who understands such a rule may understand a general principle or perhaps a set of related principles using some of them to explain others. They may thus be able to articulate what they understand the rule to be in general and context-independent terms. Nevertheless, even with such a codifiable rule, understanding it cannot be independent of understanding its instances. One needs to know, in Wittgenstein’s phrase, how to go on.
Wittgenstein gives an example of someone who grasps a series either with, or without, having a formula in mind:
It is clear that we should not say B had the right to say the words “Now I know how to go on”, just because he thought of the formula – unless experience shewed that there was a connexion between thinking of the formula – saying it, writing it down – and actually continuing the series...
We can also imagine the case where nothing at all occurred in B’s mind except that he suddenly said “Now I know how to go on” – perhaps with a feeling of relief; and that he did in fact go on working out the series without using the formula. And in this case too we should say – in certain circumstances – that he did know how to go on. [ibid: §179]
The passage makes a connection between understanding and an ability to take part in a practice explicit. But there is also something implicit in this example. It involves particular cases. Whatever the general criteria there may be for understanding a rule, such as restating or summarising it in general terms, such understanding also requires grasp that this particular number, for example, is the next number in the sequence. One needs to know that how to recognise or proffer a particular number which – whatever its size, colour and font – counts as an instance of the rule because it is an instance of the next number, for example 8.
This is the connection that lies at the heart of the rule following considerations. Understanding of a general rule involves the ability to recognise particular cases. The regress argument targets attempts to explain this connection in non-practical terms. It undermines putative explanations of the practical ability to recognise new cases as instances of a general rule in other terms such as by invoking sub-personal mechanisms or supernatural and platonic structures. But as the example of the deviant pupil shows, when one abstracts away from our actual shared abilities and responses, it is impossible to recover what is understood when one understands a rule. Nothing impersonal can capture the way a subject can see in the examples given a general rule and then recognise new instances as going on in the same way. Thus both Ryle and Wittgenstein share an emphasis on what I called Polanyi’s second clue: the practical groundings of knowledge.
But the regress arguments also suggest a qualified version of the first clue, especially as it applies both to recognition and more explicitly practical knowledge. The point is not that such knowledge cannot be expressed but that it cannot be expressed in context-independent terms. Practical knowledge requires context-dependent sensitivity. This suggests a way to draw on Polanyi’s suggestions, if not his explicit arguments, for tacit knowledge. Tacit knowledge is best thought of as context-dependent practical knowledge or ‘personal knowledge’ in Polanyi’s phrase. Further, if the regress argument is correct, it lies at the heart of explicit knowledge that can be articulated or codified in context-independent terms.
So understood, it also seems relevant to psychiatric diagnosis. In particular, it is relevant to the dominance of the criteriological approach to diagnosis and its attempt to underpin reliability. The moral of the regress argument is that there are limits to the extent to which this can be achieved since codification rests on a bed of practical skills.
Tacit knowledge, clinical judgement recognition and psychiatric symptoms
I began by outlining the importance of reliability and thus the stress on operationalism for psychiatric taxonomy and diagnosis. For the last half century, syndromes have been defined in terms of conjunctions and disjunctions of symptoms which have themselves been described in terms as free of aetiology as practical. (For some conditions, such as PTSD, that would be impossible.) Thus the diagnosis of a specific syndrome is justified in a particular subject if he or she has enough of the relevant symptoms.
This approach is aimed at closing the principled gap between syndrome and subject and thus increasing inter-rater reliability among clinicians. Because of the way both ICD and DSM base syndromes on a combination of conjunction and disjunction of symptoms, it is possible that a syndrome so defined may apply to two individuals with little, or even no, overlap of symptoms. But these differences are codified rather than left to an overall uncodified clinical judgement. Further, the heritage of operationalism suggests a hope that individual symptoms can be tied to subjects through a kind of measuring operation.
There remains, however, a potential gap between the textbook or diagnostic manual articulation of a symptom and a presenting individual. The concepts of specific symptoms are, despite their specificity, general concepts that can be instantiated in an unlimited number of actual or potential cases. So how can one judge that a general concept applies to a specific individual case or individual person? How can one recognise that the individual exemplifies a type?
One can attempt to bridge this apparent gap in purely general and impersonal terms so as to codify psychiatric expertise. Textbooks of psychiatry can describe, rather than merely list, symptoms. But whatever descriptive account they give of symptoms, there will always be a distinction of kind between their general descriptions and concepts (which potentially apply to any number of individuals) and any particular presenting individual who may or may not exemplify or instance them. Determining that they do instance or exemplify such general concepts calls for clinical judgement.
The regress arguments from the previous section suggests that there are limits to the extent to which operational definitions or criteriological approaches to diagnosis can, in a quest for reliability, exclude the exercise of skilled individual judgement. It is thus worth noting that there has been something of an anti-operationalist backlash within psychiatry.
Criticising the ability of the DSM criteria to capture the nature of schizophrenia, Mario Maj, for example, argues that:
One could argue that we have come to a critical point in which it is difficult to discern whether the operational approach is disclosing the intrinsic weakness of the concept of schizophrenia (showing that the schizophrenic syndrome does not have a character and can be defined only by exclusion) or whether the case of schizophrenia is bringing to light the intrinsic limitations of the operational approach (showing that this approach is unable to convey the clinical flavour of such a complex syndrome). In other terms, there may be, beyond the individual phenomena, a ‘psychological whole’ (Jaspers, 1963) in schizophrenia, that the operational approach fails to grasp, or such a psychological whole may simply be an illusion, that the operational approach unveils. [Maj 1998: 459-60]
In fact, Maj favours the former hypothesis. He argues that the DSM criteria fail to account for aspects of a proper grasp of schizophrenia, for example, the intuitive ranking of symptoms (which have equal footing in the DSM account). He suggests that there is, nevertheless, no particular danger in the use of DSM criteria by skilled, expert clinicians for whom it serves merely as a reminder of a more complex underlying understanding. But there is problem in its use to encode the diagnosis for those without such an additional prior understanding:
If the few words composing the DSM-IV definition will probably evoke, in the mind of expert clinicians, the complex picture that they have learnt to recognise along the years, the same cannot be expected for students and residents. [ibid: 460]
Maj’s criticism that the DSM criteria do not capture a proper, expert understanding of the diagnosis of schizophrenia raises the question of how or why that could be the case. If the criticism is right, is it that the wrong criteria have been used: either the wrong symptoms and / or the wrong rules of combination? Or is there something more fundamentally wrong with the criteriological approach as applied to psychiatry? Josef Parnas suggests the latter. In a paper describing pre-operational approaches to taxonomy and diagnosis as a ‘disappearing heritage’ he comments on an underlying difference in attitude towards signs and symptoms of schizophrenia.
When the pre-DSM-III psychopathologists emphasized this or that feature as being very characteristic of schizophrenia, they did not use the concept of a symptom/sign as it is being used today in the operational approach. This latter approach envisages the symptoms and signs as being (ideally) third person data, namely as reified (thing-like), mutually independent (atomic) entities, devoid of meaning and therefore appropriate for context-independent definitions and unproblematic assessments. It is as if the symptom/sign and its causal substrate were assumed to exhibit the same descriptive nature: both are spatio-temporally delimited objects, ie, things. In this paradigm, the symptoms and signs have no intrinsic sense or meaning. They are almost entirely referring, ie, pointing to the underlying abnormalities of anatomo-physiological substrate. This scheme of ‘symptoms = causal referents’ is automatically activated in the mind of a physician confronting a medical somatic illness. Yet the psychiatrist, who confronts his ‘psychiatric object’, finds himself in a situation without analogue in the somatic medicine. The psychiatrist does not confront a leg, an abdomen, not a thing, but a person, ie, broadly speaking, another embodied consciousness. What the patient manifests is not isolated symptoms/ signs with referring functions but rather certain wholes of mutually implicative, interpenetrating experiences, feelings, beliefs, expressions, and actions, all permeated by biographical detail. [Parnas 2011: 1126]
The claim here is that the criteriological approach has the wrong model of psychiatric symptoms and signs in two respects. Just as smoke can mean fire or tree rings the age of a tree, the criteriological approach takes signs to be free standing items which causally indicate underlying states. (Smoke is distinct from, but can be caused by, fire and so in a particular context smoke can factively mean fire.) Furthermore, these relations are independent of one another: they are atomic. By contrast, Parnas suggests, psychiatric signs and symptoms are both essentially meaning-laden and also mutually interdependent wholes. It is the latter claim which plays the more important role in his criticism.
One argument for their interdependence is that it is only in particular contexts that symptoms are reliable. Thus, for example, mumbling speech is comparatively widespread (Parnas estimates 5% of the population) but in – and only in – the context of other features such as ‘mannerist allure, inappropriate affect, and vagueness of thought, it acquires a psychopathological significance’ [ibid: 1126]. So the effectiveness of the sign is context-dependent. In some contexts it is indicative and in others not. But Parnas goes further by suggesting a more than merely additive view. Grasp of psychiatric symptoms is an overall gestalt experience, likened to seeing the figure of the duck-rabbit first as a rabbit and then suddenly as a duck: seeing the signs and symptoms under an overall aspect.
A Gestalt is a salient unity or organization of phenomenal aspects. This unity emerges from the relations between component features (part-whole relations) but cannot be reduced to their simple aggregate (whole is more than the sum of its parts)... A Gestalt instantiates a certain generality of type (eg, this patient is typical of a category X), but this typicality is always modified, because it is necessarily embodied in a particular, concrete individual, thus deforming the ideal clarity of type (universal and particular). [ibid: 1126]
So the model of diagnosis is one in which the skilled clinician gasps the right diagnosis as a whole in which different aspects can be seen as abstractions from that whole rather than as its basic building blocks. Such a view would accommodate Maj’s suggestion that criteriological elements serve as reminders for already skilled clinicians. They do – on this view – in the sense that after the fact, such articulations of the overall picture are possible, as a musical note may be divided into its pitch, tone and duration whilst it cannot be built up from those as independent building blocks. But that does not imply that the expert judgement of the whole could be built up from the individual criteria understood in isolation.
I think that this is also the clue to understanding the nature of Parnas and his colleagues recent EASE project: the Examination of Anomalous Self-Experience. Prima facie, this might seem to be merely a more detailed version of a criteriological approach with a more thorough description of symptoms in a forlorn attempt to eliminate the need for clinical judgement in bridging the gap between general description and particular presenting individual. It is, after all, described by them thus:
The Examination of Anomalous Self-Experience (EASE) is a symptom checklist for semi-structured, phenomenological exploration of experiential or subjective anomalies that may be considered as disorders of basic or ‘minimal’ self-awareness. [Parnas et al 2005: 236]
But despite this, the EASE approach stresses the need for flexible conversational relations between clinician and patient or client, rather than a structured interview, and the development of practical recognitional skills:
The interviewer must possess good prior interviewing skills, detailed knowledge of psychopathology in general and of the schizophrenia spectrum conditions in particular, and he should pass an EASE 3-day training course, comprising (1) a 1-day theoretical seminar, (2) a number of supervised interviews and (3) provisional assessment of reliability. [ibid: 239]
In other words, the reliability of the method is underpinned by shared practical judgements as well as theoretical knowledge and fits Parnas’ stress on a gestalt or holistic view of the nature of diagnosis rather than a criteriological view.
To what extent, then, does this alternative approach depend on tacit knowledge? There are two reasons to think of the kind of diagnostic judgement outlined by Parnas as relying on tacit knowledge in the way I have described it: as context-dependent practical knowledge. First, and negatively, is the claim that the expertise involved cannot be codified in context-independent terms, as the DSM and ICD criteria require. But second, recognising a diagnostic whole as a kind of gestalt, seen with its own internal organisation, is an example of the same kind of judgement involved in recognising a new case as an instance of a grasped, prior rule or concept: an essentially context-sensitive judgement.
Maj’s criticisms of the operational criteria for schizophrenia and Parnas’ opposing view of the nature of diagnosis more generally suggest an alternative view of how diagnostic reliability might be achieved. The operational approach attempts to codify psychiatric expertise and thus play down a role for a tacit dimension in clinical expertise. But philosophical analysis suggests that this project could never be completed. There is no alternative to a practical judgement, of ‘how to go on’, in Wittgenstein’s phrase. The alternative accepts that diagnostic judgement cannot be so codified and takes it instead to be an exercise of skilled recognitional clinical judgement, a form of tacit knowledge under the most plausible understanding of that phrase.
Bayer, R. and Spitzer, R.L. (1985) ‘Neurosis, psychodynamics and DSM-III’ Archives of General Psychiatry 42: 187-96
Bridgman, P.W. (1927) The Logic of Modern Physics, New York: Macmillan
Hempel, C.G. (1994) ‘Fundamentals of taxonomy’ in Sadler, J.S. Wiggins, O.P. and Schwartz, M.A. (eds) Philosophical Perspectives on Psychiatric Diagnostic Classification, Baltimore: Johns Hopkins: 315-331
Lear, J. (1982) ‘Leaving the world alone’ Journal of Philosophy 79: 382-403
Maj, M. (1998) ‘Critique of the DSM-IV operational diagnostic criteria for schizophrenia’ The British Journal of Psychiatry 172: 458-460
Noë, A. (2005) ‘Against intellectualism’ Analysis 65: 278-90
Parnas, J. (2011) ‘A Disappearing Heritage: The Clinical Core of Schizophrenia’ Schizophrenia Bulletin 37: 1121–1130
Parnas, J., Møller, P., Kircher, T., Thalbitzer, J., Jansson, L., Handest, P. and Zahavi, D. (2005) ‘EASE: Examination of Anomalous Self-Experience’ Psychopathology 38: 236–258
Polanyi, M. (1962) Personal Knowledge, Chicago: University of Chicago Press
Polanyi, M. (1967a) ‘Sense-giving and sense-reading’ Philosophy 42: 301-325
Polanyi, M. (1967b) The Tacit Dimension, Chicago: University of Chicago Press
Ryle, G. (1949) The Concept of Mind, London: Hutchinson.
Ryle, G (1945) ‘Knowing How and Knowing That’ Proceedings of the Aristotelian Society, 46: 1-16
Shorter, E. (1997) A History of Psychiatry, New York: John Wiley and Sons
Stanley, J. and Williamson, T. (2001) ‘Knowing how’ The Journal of Philosophy 97: 411-444.
Wittgenstein, L. (1953) Philosophical Investigations, Oxford: Blackwell.