Diseases such as AIDS today, or leprosy in earlier times, push those suffering from them to the margins of society - or keep them within society, provided there is some guarantee that everyone else will be safe. These diseases are of such nightmarish proportions that this social logic seems well-founded. So of course it sounds like sheer absurdity when we hear the witness of the monasticism of the Egyptian desert (ca. 5th c.). Abba Agathon, we are told, was aflame with such love that he wanted to find a leper and exchange his own body for that of the leper!