Indeterminacy in medical classification: On continuity, uncertainty, and vagueness

This chapter aims to clarify the terminology of and relations between ontological, epistemological, and semantic aspects of indeterminacy in medical classification systems. Although classifications of diseases and mental disorders are often characterized as having blurred boundaries, there is no consensus on what exactly this means. The following clarification may remedy this shortcoming: from an ontological point of view, disease entities are found to be discrete or continuous, depending on whether realisation gaps occur. From an epistemological perspective, the certainty of a classification depends on how controversial the assessment of its validity is throughout contexts and how much different legitimate interests of classification users vary. Finally, as semantic categories, medical classifications can be defined precisely or vaguely. The chapter analyses how the ontological, epistemological, and semantic levels are interrelated and how the proposed terminological clarifications may help to disentangle discussions about the validity of medical classifications.