Abstract
ABSTRACTMedical diagnosis is sometimes used by critical realists and others as an exemplar of a form of inference across time in which a current empirical observation points backwards to the conditions of its emergence and forwards to a possible future outcome or progression. Accordingly, its practice warrants critical exploration to confirm its legitimacy as a philosophical reference point. The strengths and weakness of the exemplar are appraised using case brief case studies. The limitations of medical diagnosis are discussed in the wider context of the sociology of medical knowledge, the social determinants of ill-health and the role of commercial interests in shaping diagnostic practice. The conclusion is cautious, not nihilistic. Diachronic inference in medicine, as in other disciplines working in and with open systems, can be respected for its advantages to humanity. However, this brings with it the perennial caution of epistemic humility and a needed tolerance of uncertainty..