Originally published in 1987, this book is about the classification of bodily conditions into diseases. It provides a full account of the concept of disease, examining the issue of whether disease status is something we discover or invent and the issue of whether disease attributions involve implicit value judgements. It investigates whether bodily conditions fall into natural kinds and whether these debates can be settled by discovering whether there are any natural boundaries dividing conditions into diseases and non-diseases. It considers whether the notion of disease is an evaluative notion or whether judgements about disease status are purely descriptive. The issue of whether other cultures with different values are justified in making different disease judgements is also discussed.