Atheists campaigning to convert the world from religion present one of history’s comic spectacles. The enemies of religion are shaped by what they reject, so that while they denounce religious beliefs their way of thinking replicates the categories and assumptions in terms of which these beliefs have been framed. Their obsessive concern with belief is itself an inheritance from Christianity. In the ancient world Greco-Roman polytheism was not much concerned with what people believed, any more than Judaism was. Practice was primary – ritual, prayer and the observance of law and custom. Proselytising for universal unbelief, contemporary atheists unwittingly mimic the religion they think they have left behind.