“Rigorous idiography” is a term I’ve been using for probably a decade or more now. My first paper in this area was Evans, Hughes, & Houston (2002) Significance testing the validity of ideographic methods: a little derangement goes a long way. British Journal of Mathematical and Statistical Psychology, 55(2), 385–390, https://doi.org/10.1348/000711002760554525. Now (2026) that seems to be now open access via ResearchGate here.
I hadn’t hit on the generic term “rigorous idiography” back then but the idea is that there are forms of data that are purely idiographic: a picture, description or summary that is unique to, and of, an individual. However, absence of any simple dimension on which the data can be ranked or rated against that of any other individual doesn’t preclude us doing things rigorously with such data where we can.
I have no wish to see qualitative data reduced by quantification where it’s not appropriate or helpful and that would probably apply to most therapy narrative data. However, there are data that are purely idiographic but which can still be susceptible to rigorous mathematical analyses that help strengthen the argument that the data contains important and meaningful information. This is the domain I am calling “rigorous idiography”.
One now completely accepted example, though not quite what I’m talking about, is analysis of fingerprint data: the patterns are essentially unique to each of us and we have good descriptive terms to classify them, but the differences between them don’t reduce to a few dimensions on which they can be compared. Despite this the rigorous ways to describe them allows them to be used to identify individuals. A more recent and similar example is the genome: we each have a unique one and there is no single dimension that compares any one with any other, nor even a small set of such dimensions. However, we can describe them completely rigorously and identify differences between people on them.
I happened to come on the method of derangements through repertory grid data but the method is applicable to any descriptive data about a set of individuals and I am keen to see it used for a wide variety of qualitative descriptors as I think it will help dent the widespread quantitative researchers’ denigration of such data.
My more recent paper, with Jo-anne Carlyle and Clara Paz is clearer in describing the method of derangements and in mapping the similarities and differences from the statistics of the null hypothesis significance testing approach to nomothetic data. That paper is also open access: Evans, C., Carlyle, J., & Paz, C. (2023). Rigorous idiography: Exploring subjective and idiographic data with rigorous methods—The method of derangements. Frontiers in Psychology, 13, 1007685. https://doi.org/10.3389/fpsyg.2022.1007685.
There are other tools like this, the method of mismatched cases is another that has had a small amount of use in our area, I think the first was Levine, F. J., & Luborsky, L. (1981). “The core conflictual relationship theme. A demonstration of reliable clinical inference by the method of mismatched cases.” In Object and self: A developmental approach. Essays in honor of Edith Jacobson. (pp. 501–526). International Universities Press. I’m clear this is an area that could be developed with huge impact.
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