What is dirt? What does it really mean to be dirty? Or clean? Dirt and cleaning are often associated with ideas of guilt, otherness and social control, but also with living responsibly and in harmony with the environment. In this learned, witty and groundbreaking study, Olli Lagerspetz offers a persuasive discussion of dirt and its ramifications in philosophy and culture. He argues that questions of dirt and soiling can neither be reduced to hygiene nor to ritual pollution. Instead, they are part and parcel of almost every human activity. As participants in material culture, we produce things and dispose of them but we also engage with them practically, aesthetically and morally. The book ranges through subjects and times, from Heraclitus of Ephesus, through the Renaissance, via Ludwig Wittgenstein, Martin Heidegger and Mary Douglas, to the hygienic products of modernity, ending with abject art. Lagerspetz constantly questions current thinking on the subject, and proposes a new view of dirt based on our physical engagement with the world. A Philosophy of Dirt is essential reading for scholars and students of philosophy, as well as all who feel soiled and want to know why.