This article examines the philosophical role of illness. It briefly surveys the philosophical role accorded to illness in the history of philosophy and explains why illness merits such a role. It suggests that illness modifies, and thus sheds light on, normal experience, revealing its ordinary and therefore overlooked structure. Illness also provides an opportunity for reflection by performing a kind of suspension (epoché) of previously held beliefs, including tacit beliefs. The article argues that these characteristics warrant a philosophical role for illness. While the performance of most philosophical procedures is volitional and theoretical, however, illness is uninvited and threatening, throwing the ill person into anxiety and uncertainty. As such it can be viewed as a radical philosophical motivation that can profoundly alter our outlook. The article suggests that illness can change the ways in which we philosophise: it may shape philosophical methods and concerns and change one's sense of salience and conception of philosophy.