Anyone who has sampled even a few of the most commonly read Greek texts will have encountered pollution. The pollution of bloodshed is a frequent theme of tragedy: Orestes is driven mad; Oedipus brings plague upon all Thebes. In historical texts we find cities intervening in the internal affairs of others to `drive out the pollution', or making war on account of it. Political orators represent their opponents as polluting demons. Purity is a constant concern in ritual texts, and any Greek underwent many small purifications in his everyday life. Certain abnormal religious movements of the archaic age made `purification' the path to felicity in the afterlife. First published in hardback in 1983, Miasma is the first work in English to treat this theme in detail.