One of the motivations for the new philosophy of psychiatry is the need to understand changing ideas in mental health care. In the last century, changes in both physical and biological theory prompted work in philosophy of physics and philosophy of biology to understand those fields better, attempts which were continuous with empirical work. At the start of this century, changes in psychiatry promise increased interest in the philosophy of psychiatry as an attempt, alongside empirical research, to understand the conceptual underpinnings of mental heath care. While philosophical methods are distinct from empirical methods, the work is truly interdisciplinary, growing organically from the complexities of demand on psychiatric care and, although philosophical, carried out by philosophers and psychiatrists alike. One focus is the nature of clinical judgement in psychiatric diagnosis. In this short note I will briefly sketch some issues that arise from a current idea: that psychiatric diagnosis should include idiographic elements.
Idiographic understanding and comprehensive diagnosis
There has been a recent growth in emphasis on the importance of idiographic understanding in psychiatric diagnosis. The World Psychiatric Association (WPA) advocates the development of a 'comprehensive' model of diagnosis or assessment. A WPA workgroup charged with formulating an 'International Guidelines for Diagnostic Assessment' (IGDA) has published a guideline called 'Idiographic (Personalised) Diagnostic Formulation' which recommends an idiographic component within psychiatric diagnoses. If accepted, skilled psychiatric diagnostic judgement will have to include an idiographic as well as nomothetic component. What would this involve?
In psychology, the popular use of the distinction between idiographic and nomothetic was widely ascribed to the personality psychologist G W Allport. It is generally taken to refer to a distinction between qualitative research based on individual case studies and quantitative cohort-based research. But this way of drawing a distinction need not amount to a distinction of kind. The distinction between research on individuals and cohorts, for example, may not be significant if individuals are described in general terms.
If 'qualitative' is defined merely in opposition to mathematically encoded or statistical methods then, again, that need not correspond to any underlying methodological distinction. In geology, for example, both mathematical and non-mathematical descriptions are used depending on context, but this does not reflect any significant methodological differences.
The term 'idiographic' was first introduced, in a contrast with 'nomothetic', by the Kantian philosopher of science Wilhelm Windelband in 1894 in this way:
'In their quest for knowledge of reality, the empirical sciences either seek the general in the form of the law of nature or the particular in the form of the historically defined structure. On the one hand, they are concerned with the form which invariably remains constant. On the other hand, they are concerned with the unique, immanently defined content of the real event. The former disciplines are nomological sciences. The latter disciplines are sciences of process or sciences of the event. The nomological sciences are concerned with what is invariably the case. The sciences of process are concerned with what was once the case. If I may be permitted to introduce some new technical terms, scientific thought is nomothetic in the former case and idiographic in the latter case' (Windelband1 pp. 175-176).
Nomothetic approaches chart lawlike, or nomological, generalities. Idiographic understanding concerns individual cases described in non-general ways. Both are forms of empirical inquiry, both can deserve the label 'science' but the form of intelligibility is different. Windelband emphasises the idea that the distinction is not one of subject matter but method. …