"To make a vow is a matter of the will, to fulfill one is a matter of necessity," declared late medieval canon law, and religious profession involved the most solemn of those vows. Professed nuns could never renege on their vows and if they did attempt to re-enter secular society, they became apostates. Automatically excommunicated, they could be forcibly returned to their monasteries where, should they remain unrepentant, penalties, including...