The point of departure for this article is a review of the discussion between Twaddle and Nordenfelt on the concepts of disease, illness, and sickness, and the objective is to investigate the fruitfulness of these concepts. It is argued that disease, illness, and sickness represent different perspectives on human ailment and that they can be applied to analyze both epistemic and normative challenges to modern medicine. In particular the analysis reveals epistemic and normative differences between the concepts. Furthermore, the article (...) demonstrates, against Nordenfelt's claim, that the concepts of disease, illness, and sickness can exist without a general theory of health. Additionally, the complexity of different perspectives on human ailment also explains why it is so difficult to give strict definitions of basic concepts within modern health care. (shrink)