Radical Interpretation and Intellectual Disability: The Principle of Charity and the Typical Mind Fallacy.
Different persons growing up in the same language are like different bushes trimmed and trained to take the shape of identical elephants. The anatomical details of the twigs and branches will fulfil the elephantine form differently from bush to bush, but the overall outward results are alike. (Word and Object, p. 8)
In institutions all around the world live people with severe intellectual disabilities. Such disabilities often go hand in hand with communication difficulties. People can have an inability to understand language through damage to the Wernicke’s area, while others can be born with an inability to speak language through damage to the Broca’s area. Obviously having an inability to speak or understand language does not make communication impossible, animals that have no linguistic abilities nevertheless are very skilled at communicating with each other (See Hauser 1996, and Tomasello 2008). People with profound intellectual disabilities sometimes have serious difficulties communicating their needs and interests. Carers whose role it is to provide help for people with intellectual disabilities to fulfil their life goals, and achieve a full life integrated in society at large, often have difficulties interpreting the attempted communication of the people they are trying to help. Even for two people without profound intellectual disabilities or communication impairments interpreting each other can be difficult. Our linguistic communication is shot through with metaphor and analogies (Lakoff and Johnston 1987, Hofstadter and Sander 2013). When two people converse with each other they share a background theory which they use to interpret what the other is saying to them, and to guide their own prospective speech-acts. Donald Davidson sums up this process as follows:
Here is a highly simplified and idealised proposal about what goes on. An interpreter has, at any moment of a speech transaction, what I persist in calling a theory. (I call it a theory, as remarked above, only because a description of the interpreter’s competence requires a recursive account.) I assume that the interpreter’s theory has been adjusted to the evidence so far available to him: knowledge of character, dress, role, sex, of the speaker, and whatever else has been gained by observing the speaker’s behaviour, linguistic or otherwise. As the speaker speaks his piece the interpreter alters his theory, entering hypotheses about new names, altering the interpretation of familiar predicates, and revising past interpretations of particular utterances in light of new evidence… To put this differently: the theory we actually use to interpret an utterance is geared to the occasion…The speaker wants to be understood, so he intends to speak in such a way that he will be interpreted in a certain way. In order to judge how he will be interpreted, he forms, or uses a picture of the interpreter’s readiness to interpret along certain lines. (A Nice Derangement of Epitaphs pp. 99)
Davidson is picking out a key component of what goes on in interpretation between two people. Both people come to the occasion of interpretation with their own prior theory, a background expectation about the world and the agents it contains. When conversing they try to guess what prior theory the person they are speaking to is using and they use their speech acts in ways they think are congenial with the other person’s prior theory. Ultimately, Davidson argues, understanding takes place when both thinkers converge on a passing theory. Davidson claims that accident aside a passing theory is where agreement is greatest (ibid p. 102). As people talk their prior-theories become more and more alike, and as a result so do their passing theories. Where agreement and understanding coincides so does the people’s passing theory. An important point to note is that Davidson’s theory of interpretation involves maximizing agreement with the person we are conversing with. For Davidson, without a massive shared background of truths that people share, interpretation and hence communication will be impossible. He stresses the importance of maximising agreement in the quote below:
The methodological advice to interpret in a way that optimizes agreement should not be conceived as resting on a charitable assumption about human intelligence that might turn out to be false. If we cannot find a way to interpret the utterances and other behaviour of a creature as revealing a set of beliefs largely consistent and true by our standards, we have no reason to count that creature as having beliefs, or saying anything. (Radical Interpretation p. 137)
So, for Davidson, a shared background set of beliefs in common is a necessary condition of communication taking place. He also argues that it is important to keep in mind, not only the embodied presence of both people communicating with each other, but also to the shared objects of experience of both people. This triangulation of self, other, and shared object of experience is a necessary condition of communication taking place. Communication does not take place in a vacuum, and a theory of communication that ignores the world that both thinkers are communicating about will go badly wrong.
When Davidson speaks about triangulating on a shared object of experience, he is arguing that such triangulation is a necessary condition of communication. There is good empirical evidence which indicates that humans do in fact communicate with each other by triangulating on a shared object of experience (Cavell 2008). Such triangulation is typically facilitated by the way young children automatically track the eye movements of each other and understand what the meaning of pointing is. However this ability is not universal, children with autism are typically bad at tracking eye movement and interpreting the pointing gestures of others (Baron-Cohen 1995). Autistic children who do not also suffer from any kind of intellectual disabilities may experience language delays but with training usually develop language. However with children who suffer from intellectual disabilities and autism the possibility of developing language is greatly decreased. A substantial proportion of people who have an intellectual disability, do so because of some birth trauma, or because of toxins that the child in utero was inadvertently exposed to. So the disability which affects the child can have multiple effects throughout the brain. So, for example, as a result of an accident of birth a child could be born with an inability to understand speech, and an inability to track eye-movements and interpret the pointing gestures. Obviously communicating with a person like this will be extremely difficult, and facilitating communication will require a lot of careful thought on behalf of care givers.
It important, at this point, to discuss some developmental phases children typically go through. A few hours after birth children are drawn to look longer at drawings of human faces than at other patterns (Fantz 1963).From 3 months children are monitoring the eye gaze of others. (Cohen 1995). From 4 months humans have some grasp of object behaviour (Baillargeon, et al., 1985). At 6 months children begin reaching for objects. At 9 months children begin to recognise intentionality. At 9 months proto-declarative referencing begins (Cohen 1995). At 10 months children begin to crawl. Between 9-12 months children begin to engage in triadic behaviours. At 12 months children begin pointing and this brings them deeper into the world of triadic relations. From 12- 16 months children begin to learn 0.3 words per day (Bloom, 2002). From 14-16 months children begin to walk. From 18-23 months children begin to learn 0.8 words per day. Between 18-24 months children recognize themselves in the mirror (Rochat and Straino, 1999). From18-24 months children display a deep understanding of others intentional aims. From 23- 30 months children learn 1.6 words per day. At 30 months children begin to master the distinction between Mass and Count nouns (Gordon, 1985). At 48 months children begin to pass the false belief test. From 4 to 6 years of age children begin explicit mentalising; justifying false beliefs by pointing out misleading reasons. They also begin to understanding higher order mental states (Fritz and Cohen 1995) Up to the age of 6 years children prefer to organise things according to thematic relations .From 9 onwards children begin peak period of language acquisition learning up to 12 words a day.
All of the above developmental facts are important to the child as they begin to learn their language and try to communicate with each other. Some of these developmental regularities are learned while some are the result of innate mechanisms. We have seen above that autistic children who do not go through the pointing phase have extreme communication difficulties. Considered in Davidsonian terms the children’s shared developmental history forms a part of their prior theory which they take for granted when they communicate with each other. Children with profound intellectual disabilities sometimes never pass through these various developmental phases. As a result of this their prior theory is so different than their peers that converging on a passing theory is virtually impossible. When this happens people with profound intellectual disabilities sometimes retreat into their own subjective worlds, and despite their carers best intentions never learn to communicate their needs.
As we saw above when discussing Radical Interpretation Davidson recommends applying what he calls the principle of charity. To do this we need to try and make maximum sense of the utterances of the people we are interpreting. We need to minimize the incoherencies which we attribute to the people who we are trying to interpret. So, for example, if when interpreting the utterances of an alien tribe we encounter we find ourselves ascribing to them a belief in true contradictions we should consider the possibility that we are simply misinterpreting them. It is after all a simpler assumption that we have misinterpreted them than that they hold radically anti-logical views. This principle of charity is a valuable heuristic device to help us when engaging in radical interpretation. Assuming that the person is a lot like us, and holds a lot of the same true beliefs about the world is very important if we want to engage with the person about shared objects in the environment. Shared intentionality (similar belief/desire psychology), and shared background knowledge about the world of ordinary enduring middle sized perceptual objects, helps triangulation on a shared object of experience take place, and hence facilitates communication. However as we saw above with people with profound intellectual disabilities the idea of a principle of charity and prior theories converging as people talk with each other is of limited help.
When we apply Davidson’s approach we run the risk of interpreting people so closely by the lights of our own conceptual scheme that we bracket their otherness. So, for example, Davidson using the principle of charity argues that we should not interpret (or translate) people as believing in true contradictions. However, even within our own linguistic community we have people who believe in true contradictions. Graham Priest’s Dialetheism, is a good example of a theoretical position which accepts the existence of true contradictions. Matte Blanco in his ‘The Unconscious as infinite Sets’ argue that people’s unconscious is governed by a logic that sometimes accepts true contradictions. Blanco and Priest pose a serious difficulty for the Davidson’s principle of charity. An interpreter trying to understand an alien tribe using the principle of charity would end up falsifying the data if they were interpreting an alien version of Priest or Blanco.
A real difficulty with interpreting another is that it is necessary to assume that the person one is interpreting is in most ways similar to you, without making this assumption it is virtually impossible to interpret what the other is saying, however as we saw above this strategy risks us falsifying the data. William James was sensitive to the problem of incorrectly interpreting others because we assume that their minds have the same structure as ours; he called this The Typical Mind Fallacy. He noted how philosophers like Berkeley and Locke misinterpreted each other because they wrongly assumed that all minds were wrongly structured in the same way as their own. This faulty reasoning lead to disputes between Locke and Berkeley, on the nature of abstract ideas, which could have been resolved, if they had not wrongly assumed that all people have the same capacity for mental Imagery (See Berman, (2008) and Berman and King 2014)
So when trying to correctly interpret the communication of another while it is necessary to try and assume that they are mostly like us we must be aware that this tool can lead us astray, me must recognise difference when it manifests itself. For example, children with Williams-Syndrome typically have a different intuitive folk biology to ordinary children. So if someone were to apply a strict principle of charity to the interpretation of those with William-Syndrome this will impede communication rather than help it. So it is important to note that at the beginning of interpreting another person the possibility of missing essential detail is always possible. Amongst people who do not suffer from profound intellectual disability, people sometimes misinterpret each other, because they wrongly believe that the other has a mind just like ours. So, for example, for years colour blindness was not noticed, variation in people’s ability to form mental images was ignored, the existence of synaesthesia (e.g. people who taste colours) was denied. These differences were ignored despite the fact that people could communicate their ideas to each other through language. Given these facts it seems likely that we are not aware of the mode of experience of a lot of people with profound intellectual disabilities who we care for, most of whom do not even have the ability to communicate their experiences to us through language.
In 1968 Russian Neuroscientist wrote his famous The Mind of a Mnemonist about S. V. Shereshevskii who had and almost unlimited memory as a result of his synaesthesia. Luria’s book was important because he not only discussed the neurological and psychological abilities of Shereshevskii but he also told the story about his subjective experience of the world. Contemporary neuroscientist Oliver Sacks, who was heavily influenced by Luria has followed on in this tradition and over the last 40 years has written a series of case studies describing the subjective experience of people suffering from a variety of neurological disorders. Like Sacks and Luria, Vilayanur S Ramachandran has written some beautiful case studies describing the subjective experience of people with various different neurological disorders. What these case studies have revealed is a variety of subjective experiences which are simply amazing and tragic at the same time. So, for example, there are people called prosopagnosiaics who become face-blind, they lose the ability to recognise even their own wives faces. On the other side of the coin there are people with Capgras delusion who can recognise people’s faces, but because of damage to the connection between the amygdala and the inferotemporal cortex, are no longer capable of attaching the same emotional significance to the faces and develop the delusion that their family and friends are imposters. There are people who acquire types of Amusia which makes them find the sound of music intolerable. Sometimes these disorders and ones like them are acquired (through brain damage or a degenerative neurological disorder), while other times they are congenital. In the case of people with profound intellectual disability who have difficulty communicating; disorders like these can go undiagnosed. Behaviour which seems odd may be explained as the result of some kind of acquired disorder. However arranging an MRI or a CT scan can be difficult as the patient may not be able to sit still when being scanned and there may be difficulties in sedating the patient as a result of other meds they are on. Also sometimes the waiting list for an MRI or CT can take months or typically even a year till they can be provided. In the meantime measures need to be taken to help the person with Intellectual disability can lead a fulfilling life and rich life.
So far we have seen that Davidson’s principle of charity as a heuristic tool is useful to interpreting the behaviour of others however it runs the risk of ignoring radical otherness. In his “Unified Theory of Thought and Action” Davidson employs the two formal tools in interpreting the verbal behaviour of the other he uses Bayes Theorem and Tarski’s Theory of Truth. His formal treatment of interpretation is very useful and important and can be applied to data gathered by carers on the ground.
The carer though will go astray if they stick to strictly to Davidson’s principle of charity. It is important to realise that people whose brains are structured radically different from those of others may not enjoy or want the same things as most other people in society. So, for example, a person with intellectual disabilities who is suffering from certain types of Amusia will obviously not like being brought to concerts etc. We can typically judge whether this person who has no language likes music by attending to their behaviour in certain circumstances. Now obviously observing the environmental conditions which cause unhappy or happy behaviour is a minimal requirement for a carer. However, what is important is not just exploring what environmental conditions lead to what behaviours, but using these facts to construct an accurate cognitive map of the person whose behaviour we are interpreting. This cognitive map can be used to help predict the behaviour of the person being cared for and help them experience the world as they choose to.
Everything I have said here may seem to be blindingly obvious. However, I think the important point I want to make is the need to construct accurate models of the people whose behaviour we are interpreting, and to use these models to help us to construct humanistic case studies of the people we are caring for in the mode of Luria, and Sacks. These stories which we construct with the people we are caring for help them to be understood and in a sense join our world as they are. We need to try and rationally reconstruct how the people with profound intellectual disability we are caring for experience the world. We do this by studying their developmental history and seeing what developmental phases they have passed through, and what phases they not passed through; we need to study their actual behaviour in their daily environment, to use any neurological and psychological data we have to discover how they see the world. With these facts in mind we can use the Bayesian analysis and Tarski’s Theory of Truth to construct a model of the beliefs and desires of the people we care for. We can then translate these models into humanistic stories which we use to guide us as we interact with our clients on a daily basis.
Part 2 Interpreting the Mind of the Other
Beneath the uniformity that unites us in communication there is a chaotic personal diversity of connections, and, for each of us, the connections continue to evolve. No two of us learn our language alike, nor, in a sense, does any finish learning it while he lives.
(Word and Object, p. 12)
When you meet another and you want to interpret their behaviour it is best to begin externally to try and triangulate on shared objects of experience in the external world. Doing this is difficult, typically we will use the language of the eyes or pointing gestures to help us latch onto or refer to objects in the external world. As we saw in our last section the majority of children from about the age of 12 months will point to things they want their care giver to get for them. Children follow the direction of their parents gaze and use their own gaze to indicate shared objects in their own environment. This is the beginning of a two year process where the child develops shared intentionality. Again not every child goes through goes through this phase; for example some autistic children are severely developmentally delayed and do not develop shared intentionality as quick as their peers, if at all.
One of our key entering wedges to understanding each other is our ability to triangulate on shared objects of experience. Another key is our ability to say yes, and no. People who through motor damage to their vocal cords or who have severe Broca’s Aphasia, and hence cannot speak, usually have the ability to assent or dissent to propositions spoken to them. Such people can use their heads to nod assent or to shake their heads to indicate dissent. People who have locked in syndrome for whatever reason: Motor Neurone Disease, a severe stroke, or some debilitating accident, can be trained to indicate yes and no through blinking of the eyes: once to indicate yes and twice to indicate no. Trying to communicate with people with Wernicke’s Aphasia is much more difficult and is best achieved by focusing on objects in the external world and using gestures as much as possible.
With people who have specific diagnoses such as Wernicke’s Aphasia, Broca’s Aphasia, Autism, or an inability to speak because of motor difficulties: e.g. severe Cerebral Palsy, speech and language therapists will have set programmes set which have worked (as well as can be expected) in the past. However you don’t always have a clear diagnosis to work with and sometimes you have multiple diagnoses, also the person you are working with personal idiosyncratic experiences, only a tiny portion of which may be captured in care plans and medical notes. So here it is up to the carer who is with the client on a daily basis to try and rationally reconstruct the inner world of the client so a high quality of life can be maintained.
However this task should not be underestimated, we have seen that typical wedges into language may not be available. People may find it difficult to triangulate on a shared object of experience, they may not automatically track eye direction, and if their understanding of language is severely impaired or non-existent then we may not even be able to get the subject to assent of dissent to propositions verbally. However this should not be taken to be an object of despair, we can still track the subjects interests and desires by careful study of what they tend to orientate towards and away from. Though we may need to facilitate this process by providing new opportunities for the client on a daily basis to try and ascertain what aspects of reality they like and dislike.
However, even when we do not face the above problems, interpretation is not as easy as it may seem. We will still face the problem of Underdetermination (henceforth UD). UD is a phenomenon which philosophers have been working on for years. The basic idea of UD is that our total observational data is consistent with more than one theory. Underdetermination has been discussed in detail by philosophers like Quine, Wittgenstein, and Goodman. Linguists like Chomsky have argued that the Underdetermination that faces a child as they learn their first language can only be overcome by postulating innate apparatus.
Most contemporary cognitive scientists agree with Chomsky on this point. I will now cite three of these thinkers to give you a flavour of what how they understand UD. In his book The Language Instinct, Stephen Pinker discusses UD:
A rabbit scurries by, and a native shouts, ‘Gavagai’ What does gavagai mean? Logically speaking, it needn’t be ‘Rabbit’. It could refer to that particular rabbit (Flopsy, for example). It could mean any furry thing, any mammal, or any member of that species of rabbit (say, Oryctolagus), or any other member of that variety of that species (say, chinchilla rabbit). It could mean scurrying rabbit, scurrying thing, rabbit plus the ground it scurries upon, or scurrying in general. It could mean footprint-maker, or habitat for rabbit fleas. It could mean the top half of a rabbit, or rabbit meat on the hoof, or possessor of at least one rabbit’s foot. It could mean anything that is either a rabbit or a Buick. It could mean collection of undetached rabbit parts, or ‘Lo Rabbit hood again, or ‘It rabbiteth’, analogous to ‘it raineth’. The problem is the same when the child is the linguist and the parents are the natives…Figuring out which word to attach to which concept is the Gavagai problem, and if infants start out with concepts corresponding to the kind of meanings that languages use, the problem is partly solved. (1994, 156)
Pinker then goes on to cite the research of the psychologist Ellen Markman to show that it is indeed the case that children are born with concepts which constrain the types of meanings that words can be given. It is Pinker’s view that Quine’s problem is a problem of UD which is solved by the fact that the concepts that children are born with will place innate constraints on the type of meanings that children can attach to words.
The child psychologist Paul Bloom draws a similar conclusion to Pinker:
These problems of reference and generalization are solved so easily by children and adults that it takes philosophers like Quine and Goodman to even notice that they exist. If we see someone point to a rabbit and say ‘gavagai’, it is entirely natural to assume that this is an act of naming and that the word refers to the rabbit and should be extended to other rabbits. It would be mad to think that the word refers to undetached rabbit parts or rabbits plus the Eiffel Tower. But the naturalness of the rabbit hypothesis and the madness of the alternatives is not a logical necessity; it is instead the result of how the human mind works. (2000, 5).
The Harvard linguist Cedric Boeckx echoes the claims of the above thinkers:
Yet, if you think about it, the Gavagai situation is the one we all faced as children trying to acquire the meaning of words. How did we guess that elephant refers to that big grey animal with a long trunk? Because someone pointed to the animal and said elephant? But how did you know what exactly was being pointed at? Surely the finger couldn’t point at the whole elephant; it was your cognitive bias that interpreted the act of pointing in that way. (2010, 41)
There is a lot of debate in contemporary cognitive science as to whether Pinker et al. are justified in postulating innate concepts to overcome UD. However, when it comes to dealing with people who have profound intellectual disabilities, and have not learned to speak, we really need to be careful not to impose our own ontology onto then. Their way of interpreting the world might be radically different from ours, we cannot be sure that they share the same innate apparatus as us, so we must proceed with caution.
Part 3: The Web of Belief
The approach to the problems of meaning, belief, and desire that I have outlined is not, I am sure it is clear, meant to throw any light on how in real life we come to understand each other, much less how we understand our first concepts and our first language. I have been engaged in a conceptual exercise aimed at revealing the dependencies among our basic propositional attitudes at a level fundamental enough to avoid the assumption that we can come to grasp them-or intelligibly attribute them to others-one at a time. My way of performing this exercise has been to show how it is in principle possible to arrive at all of them at once. (Problems of Rationality, p. 166)
When using Davidson’s views on the theory of interpretation we need to be careful not to confuse Davidson’s project with the one I am interested in. My project is primarily a pragmatic one; I am concerned coming up with basic principles which are useful in helping to interpret the behaviour of people with profound Intellectual Disability. Davidson, on the other hand, is concerned with constructing a theory of meaning, and interpretation. Because of our different purposes I use Davidson’s project as needed and dismiss what is not useful to my project. This is no criticism of Davidson’s project as he intended his theories to deal with entirely different problems.
One proviso I should make at the outset is that Davidson limits himself to verbal communication alone. This is because of his belief that we are not justified in attributing propositional attitudes to non-linguistic animals. I will not be following Davidson in this. There is ample evidence from ethno-science that animals without complex language can think using propositional-attitudes.
In his 1987 “A Nice Derangement of Epitaphs” Davidson makes the following claim:
We may say that linguistic ability is the ability to converge on a passing theory from time to time-this is what I have suggested and I have no better proposal. But if we do say this, then we should realise that we have abandoned not only the ordinary notion of a language, but we have erased the boundary between knowing a language and knowing our way around in the world generally. A passing theory is really like a theory at least in this, that it is derived by wit, luck, and wisdom from a private vocabulary and grammar, knowledge of the ways people get their point across, and rules of thumb for figuring out what deviations from the dictionary are most likely. There is no more chance of regularising or teaching, this process than there is of regularising or teaching the process of creating new theories to cope with the new data in any field-for that is what this process involves ( A Nice Derangement of Epitaphs p. 107)
I think that he is correct on this point, and I think it contradicts a lot of his other claims about the necessity of language in order for a creature to have propositional attitudes. On the Davidsonian picture in his “A Nice Derangement of Epitaphs” having a language isn’t a black and white issue, where we can say a person has a language can be considered a sliding scale. I think this is accurate. Do we say a person with Broca’s aphasia has language, or does a person with Wernicke’s aphasia have a language? To a certain degree we can answer yes to the preceding questions and to a certain degree no. Everyone agrees that a deaf person who uses sign language has a language, but what about a person who can use gestures to communicate their needs but who has not mastered the complex sign language that most of their peers do. Again we can answer yes and no to these questions.
Consider Lamh a type of sign language used by children or people with intellectual disabilities. This sign language uses a few basic symbols some of which can be combined with each other; these symbols help the children communicate their basic needs to each other. Now in an obvious sense Lamh is not a language. It lacks the recursive ability to combine a finite amount of symbols into an infinite series; it lacks the complex and grammars typical of the world’s languages. The words used in the language lack the sometimes complex ambiguous context sensitive features of typical language, they lack some of the productive morphological features we find in ordinary language words, and the words are not really compositional. So there is a clear sense in which we can argue that Lamh is not a language. Lamh clearly isn’t an internal generative procedure which we use to link sound and meaning. So it isn’t a language in the sense that Chomsky uses the term.
Lamh is on the other hand an attempt to communicate using signals. A person using Lamh is using the signal with the intention that the person they are communicating with shares the same meaning of the term that they do, and hence will understand them. A person with profound intellectual disability who cannot use Lamh can still try to communicate by indicating objects in the world and saying yes and no if people interpret them correctly or incorrectly. Likewise, a person who cannot move their bodies but who can understand what others are saying to them can assent and dissent to what is being said to them has a language. So, my more expansive use of language is more intuitive than Chomskies, in that it captures all intentional attempts at communication with others. My definition is not really at odds with Chomsky, people can define the word ‘language’ as they please, using language in my expansive way makes sense for my project because it nicely captures the various different communicative abilities of people with different forms of aphasia.
So I think that given Davidson’s (1987) definition of language, his statement that only of creatures with a language can we sensibly attribute propositional attitudes, becomes less controversial. Anybody that is engaging with the world and others, using intentional signals, in however limited a way, has a language on this Davidsonian model.
With the preliminaries out of the way we can now begin to outline the model for interpreting people with profound intellectual disabilities. Davidson notes correctly that when we are trying to understand linguistic utterances we need the locutions of intentional action, belief, desire, meaning, hopes, wishes, attempts etc. These intentional locutions are the background conditions which are needed in order for speech to occur. For Davidson, meaning, belief, and desire are three interlocking terms which cannot be reduced to the other. I think that Davidson is correct on this general point. When we try to interpret the behaviour and communicative intent of people speaking to us we must help ourselves to these interlocked concepts.
Davidson grounds his Unified, Theory of Thought, Meaning and Action, on Ramsey’s decision theory. Ramsey’s Bayesian Decision Theory relies on two basic intensional notions: belief and preference. This Ramsey picture tries to make sense of behaviour by assuming that people being interpreted are rational agents who act in their own best interests. We assume that a person attaches a value to a particular course of action, which is calculated by the outcome that will be achieved by performing an action, and the likelihood that the action will achieve the desired outcome. We do not have to make the assumption that the subject is consciously working out this formula, we only need to assume that the brain is doing the relevant calculations. Ramsey’s Bayesian Decision Theory typically operates in the form of getting subjects to gamble on certain outcomes and judging their beliefs and preferences based on how they choose. This method is a bit complex for the task of interpreting the behaviour of people with intellectual disabilities. So I suggest instead of using gambling we can use the simpler Davidsonian method of testing for assent and dissent to various propositions spoken about the external world.
Davidson correctly notes that “A sentence held true plus interpretation is equal to a belief” (ibid p. 156). So if a rabbit passes by and I say (1) ‘rabbit’ and my client assents, we can conclude that he believes that ‘(1)’ is true. Now to say that a person holds (1) True, means that they believe that (1) is true. If they believe that (1) is true then it follows that they understand the meaning of (1). So, here we can see how we can get meaning and belief out of someone assenting to a sentence. However, if I spent the day with a client questioning him, and determined a list of sentences which he held true, and which sentences he held false, I would have a lot of data but very little theory to explain the data. I would be able to derive meaning and belief from evidence of what environmental factors cause a client to hold a sentence true. Obviously this process is still subject to the massive Underdetermination that we discussed earlier. But we have little choice but to impose our ontology onto the child at the beginning as we begin to interpret what sentences they are assenting to. So, for example, we must assume that they assent ‘Rabbit’ as in ‘a particular rabbit’ as opposed to rabbit as in ‘undetached rabbit part’, ‘particular instance of universal rabbit hood’ etc. As we move into assessing how the various sentences they assent to connect to each other we will remove some indeterminacy. However, at the end of any process of interpretation some indeterminacy will remain.
As we saw above our process of interpretation will involve some degree of imposing our rationality unto the people we are interpreting. So should not interpret people as accepting contradictions, or denying the law of identity etc. Again there are instances where people do accept contradictions, for example, in dreams people report accepting contradictions and breaking the law of identity. The psychologist and logician Matte Blanco takes this to indicate at a deep unconscious level we follow different logical laws. However, outside, of these esoteric examples people typically follow the same logical laws. Anyway we have little choice when we begin to interpret our clients but to accept that they are using the same logical laws as us.
It is best to think of our process of interpreting our clients as uncovering what Quine calls their web of belief. The person we are interpreting has an interconnected set of sentence like beliefs which are related to each other in terms of logic entailment. Sentences which are at the interior of the web are our deepest held truths which we are most wedded to, while sentences at the periphery are our more speculative beliefs. Since these sentences are all indirectly connected to each other, changing the truth value of any sentence will have consequences for the rest the web of belief. We assume that the person holds a web of belief which is somewhat like ours at the core, in terms of ordinary enduring middle sized objects (trees, mountains) and logical laws obeyed. The core of the web of belief can equated with what Davidson calls a prior theory. Davidson correctly notes that when interpreting the behaviour of another we might not be able to make these principles definite but we can at least form heuristic rules of thumb.
When trying to explicate another person’s web of belief, an important piece of evidence to be discovered, is the degree to which a subject will believe that one sentence supports another. So, for example, suppose a subject accepts that sentence (1) The cat is on the mat. Is true. Then an important step is to ask the subject to what degree they think (2) The mat is under the cat. Supports (1) Or to what degree does (3) The cat likes sitting on the mat. Support (1). By understanding how much a subject thinks a series of sentences support or do not support another sentence we can assign numbers and understand the degree to which a person believes the original sentence to be true. In the next blog I will demonstrate how to calculate degrees to which people think one sentence supports another and how this can be used to help in interpret people with profound intellectual disabilities.
 My summary of the developmental stages children go through during the first 9 years of their life is taken from Tomasello “Constructing a Language” (2003), and Paul Bloom “How Children Learn the Meaning of Words 2002)
 See Johnston and Carey (1998) Knowledge and Conceptual Change in Folk-Biology: Evidence from Williams Syndrome.
 While Pinker’s and Bloom’s arguments on this narrow point are similar, obviously this does not imply that they hold the exact same view on the nature of the mind.
 For a detailed discussion of how Chomsky defines ‘language’ see his Knowledge of Language (1986).
 Again Davidson probably wouldn’t agree with me on this point. However, it is not my purpose to defend all aspects of Davidson’s philosophy.