The case I am responding to is in this fascinating article by Stijn Vanheule. Vanheule draws on Gottlob Frege's theory of linguistic reference, which is an important move because the philosophy of language is an extremely promising lens for thinking about the conceptual viability of diagnosis.
Frege revolutionised the philosophy of language by better articulating what it is for words to refer to something. He has been called a Descriptivist about meaning, and although it is beyond the scope of this post to go into what that means, the Stanford Encyclopedia of Philosophy has a good explanation here.
Frege's position led him to differentiate three elements of linguistic reference: the thing being referred to, or referent of the sign (Bedeutung), the shared sense of the sign (Sinn) and the individual representation/idea of the sign (Vorstellung). In other words, Bedeutung is to the thing we are talking about when we use a word, Sinn is the definition of the word we use to talk about it, and Vorstellung is the "representation that occurs in the mind of the individual". A philosopher would probably take me to task for this fast and loose definitions, and Vanheule's paper provides more detail if you're interested.
Vanheule claims that the DSM, in its project to disambiguate the shared sense of mental illness labels (the Sinn), has overlooked the "person-specific ideas and representations" (the Vorstellung). He concludes that classification style diagnosis is thus "unworkable" for psychotherapy and that psychological formulation should be considered instead.
My article acknowledges the value of this approach, but I suggest that an unnecessary dialectic has opened up between Case-Formulation and Diagnosis. Vanheule's use of Frege can also be adopted in the reverse fashion; to make the case for diagnosis. If it is unhelpful to neglect one of Frege's three elements of linguistic reference, then the effacement of "Sinn" is just as unworkable as the effacement of "Vorstellung". Rather than discard diagnosis altogether we need to continue to improve it and use it alongside approaches that emphasise the personal aspects of meaning.