Why we should not assume that ‘normal’ is ambiguous

There is a widespread and largely unchallenged assumption within philosophy that the word ‘normal’ is ambiguous: i.e., that it can mean different things in different contexts. This assumption appears in work within topics as varied as the philosophy of biology, medicine, justification, causation, and more. In this paper I argue that we currently lack any independent reason for adopting such an assumption. The reason that would most likely be offered in its favour requires us to ignore an alternative and equally plausible explanation for the seeming variety of different meanings that ‘normal’ is taken to have. Meanwhile, the well-known conjunction reduction test for ambiguity provides no evidence for the ambiguity of ‘normal’, and in fact suggests that maintaining this ambiguity claim is more difficult than has been initially supposed. Therefore, with the way things stand at present, it should not be assumed without argument that ‘normal’ is an ambiguous term.