There is a very simple rule of thumb in the Church: if it has been done before it can be done again, writes Michael Walsh. In all, 22 cardinals have resigned in a history which stretches back at least to the eighth century, during which there have been just over 4,000 men holding the office. And it is an office. Rather to the irritation of cardinals in the high Middle Ages who felt they deserved better, there is no sacramental seal attached. In Catholic theology as currently taught you can stop acting like a priest or a bishop (or, for that matter, a deacon), but because of the sacramental seal you cannot stop being one. It is perfectly possible to stop being a cardinal. The origins of the role lie in early medieval Rome. Cardinals were the bishops of the dioceses surrounding the city (th