Semantic Vagueness in Psychiatric Nosology

Abstract:Many discussions in the philosophy of psychiatry hinge on, among other things, the concepts of disorders, the role of underlying mechanisms, and the merits of various diagnostic models. Yet, some such disputes rest on assumptions about vagueness in the sense of susceptibility to the Sorites paradox as opposed to mere uncertainty in clinical practice. Studying borderline cases of psychiatric conditions—those where it is indeterminate whether applying a diagnosis is appropriate—may shed light on broader debates about the nature and boundaries of these conditions. In this article, I will argue that if psychiatric vagueness exists, then some instances of it stem at least partially from how we describe the world instead of the state of the world or what we know about it. In other words, vagueness in psychiatric terms and concepts is at least in part semantic and neither solely epistemic nor solely ontic. On this view, slight differences in how various linguistic communities apply diagnostic terms modify their referents, making their precise extension indeterminate. This implies that we can sometimes answer questions about diagnosis by settling disagreements about language, which may provide traction in debates about the philosophy of nosology and help inform psychiatric practice.