What is it that makes for illness? In trying to answer this question we are perennially tempted to look toward the causes of illness - diseases for example - and away from the work that the concept does for us. In what follows I pay closer attention to that work by relating the concept of illness to that of character. The discussion also considers the question of what we are to make of the concept of mental illness and how it relates to physical illness. I shall both draw on and dispute a claim of Wittgenstein's and a claim made in a paper by T S Champlin. The remark from Wittgenstein is (Culture & Value p.54) 'Madness need not be regarded as an illness. Why shouldn't it be seen as a sudden - more or less sudden - change of character?' First however I turn to Champlin's paper.
Champlin is amongst those who consider the concept of 'mental illness' to be derived from 'physical illness' or, more perspicuously, from what, before the concept of 'mental illness' was invented, was simply called 'illness'. Unlike those (like Neil Pickering) who consider 'mental illness' a conceptual metaphor, Champlin considers it formed by 'secondary sense' and offers an analogy to help us grasp this. The analogy suggests the model of a 'rhyme for the eye' which stands to a 'rhyme for the ear' in the same kind of relation as 'mental illness' stands to 'physical illness'. So just as we may call the end of two lines of poetry which look the same even if sounding differently (...he'd read quite enough / ...of The Golden Bough) a 'rhyme for the eye', so too we may talk of an 'illness of the mind' even when we don't have to do with such features as are essential to illnesses 'of the body'.
But what is it that grounds (by way not of justification but of inspiration) the extension? Champlin suggests that 'the counterpart to position at the end of the line which facilitated the extension of the word 'rhyme' to cover rhymes for the eye but not the ear was that, typically, the mentally ill have in common with the physically ill the fact that they behave in ways similar to the physically ill. They often look ill and fail to carry on with their normal lives and need to be cared for by others.' Well, I don't buy this. For those who are mentally ill often don't look ill, they may never really have had normal lives or may be carrying on with what for them is a normal life in a mentally ill way, and they may not need to be cared for by others to a greater extent than the rest of us. These consequential difficulties do not take us into what it is for the mind to itself become 'ill'. So I suggest we keep the analogical idea - mental and physical illness needn't share something in common in virtue of which they are both illnesses; instead of something in common we need to look for a counterpart - but think again about what the counterpart is.
Wittgenstein asks - in what was presumably intended as a rhetorical question, although I shall treat it otherwise - why we don't talk not of mental illnesses but of sudden changes in character. The remark does the helpful work it does by virtue of shaking us out of the idea that we could, with our concept of 'mental illness', meaningfully be said to here have hit upon 'the right concept'. (We play the language game, and that's enough.) It also helpfully brings the concept of 'illness' into relation with that of 'character'. But what I want to suggest is that the whole point of the concept of 'illness' is that, precisely, we don't sanction an inference to the idea of a change of moral character, and that the whole point of 'mental illness' is that we may continue to draw on such exculpatory benefits in cases where the attribution of a character change is even more tempting.
Here's my main claim: Illness essentially involves changes in personal disposition which would, unless we reference that defeating condition which is the illness ascription itself, be seen as constituting a decline in moral character. Thus when we are ill we are disinclined to work, to take care of our responsibilities to others, to exercise our talents, to enjoy our appetites for life, to cultivate and spread hope. We are instead inclined to withdrawal, sloth, pessimism, self-preoccupation. Were such changes to happen to someone in the absence of disease we should say of that person that they had developed a poorer character. Such habits essentially find a negative moral evaluation, but thankfully we may be excused by being ill! The concept of 'illness' allows us to keep our virtues intact, if you like. In this way the concept of 'illness' does important work in regulating our social and occupational interactions. We cut the ill person some moral slack, discharge them of responsibilities, give them a sick note, do not hold them accountable for incompetencies to the same extent, etc. That the concept should be open to abuse by the pity-seeker or the work-shy is an important part of it. But another important part of it is that the mentally competent adult who is ill is able to acknowledge that he is ill. That he can do this is also an important part of our not ascribing character change to him. He himself offers illness as a legitimate excuse.
Now what about mental illness? What I suggest is that the excusing function of the concept of 'illness' is also central to the identity of 'mental illness'. And the person we call 'mentally ill' also starts to do things which would, were it not for the leeway we afford her, be judged as showing failure of moral character. She becomes preoccupied with herself, she stops respecting the shared norms that constitute conversational sense, she shows failures in courage and resolve, she shows less solicitude with others and does not make genuine heartfelt emotional contact with them. In short she demonstrates what looks to be a deficiency of humanity. Were it not for our saying of her that she is mentally ill then we should say of her that she was not being her better self, and if the difficulties were enduring then we should say that she had a change of character for the worse. However, the person who is the paradigm of the mentally ill has 'lost touch with reality'. Unlike the physically ill adult, she does not say of herself that she is ill. She may have moments of insight and during those say that she is unwell at the moment. Or she may look back at her past thoughts and deeds and say 'I was really ill during that time'. But in the moment of mental illness itself she does not say of herself 'this is illness'.
It is this, I am suggesting, which discriminates the mentally from the physically ill. In both cases the positive functioning of the concept is to defeat a moral judgement to do with bad character. In the physical case it works through citing bodily ailment: the person, we now allow, has the same good character, it is just that his character enactment is currently blocked by his bodily infirmity. In the mental case we also find the same helpful defeating function, and here we also say that the person is 'not herself' rather than that she has succumbed to vice. And we do this even though she in her adult self is not willing to say 'I am ill'. She 'lacks insight' and this lack is constitutive of her illness being a mental illness; she suffers a detachment from reality i.e. a foundational disturbance in her reason (notice I do not write: 'in her reasoning').
Addendum: The above discussion aims to discern some underlooked necessary, although not of course sufficient, conditions for talk of illness. I thought just append here what seems essential to me in illness generally and mental illness in particular. Whilst we may have what today we call a disease without feeling dis-easy, we become ill when we are, for example, overwhelmed by a disease. When you get the flu, for example, your body is overwhelmed. For a while you might have been 'fighting off' the virus. But then it gets to a point when your usual homeostatic mechanisms that maintain ordinary energy and balance collapse. You get a temperature, can't muster energy, feel hot and cold and achey all at the same time. Your health has broken down.
In mental illness you also suffer a 'break down'. The breakdown here is of the normal processes which keep you from being overwhelmed by painful emotional experience. Normally we find ways to deal with shame, grief, guilt, envy, fear, anxiety, and anger. We symbolise them in words and encase them in narratives, we take appropriate assertive action, we take time out to grieve i.e. to accommodate to loss. When this doesn't work we sublimate or repress. But when even these defences break down we become overwhelmed. This, I believe, is the basis of the use of illness talk when it comes to the mind. What we analogise between is the overwhelm of the normal self-regulating mechanisms in the case of bodily illness and in the case of emotional experience. The person who breaks down is no longer able to cope with reality. In the case of mental illness it is because what we call 'symbolisation' breaks down (i.e. the ability to put as yet inchoate affect into thinkable form is overwhelmed). In the case of physical illness it is because the regulation of appetite and energy provision and temperature breaks down. The analogy is so natural that it is surprising that the concept of mental illness didn't become more widespread earlier than it did.