Early Modern writing on clerical celibacy, both Catholic and Protestant, owed much in terms of content and structure to earlier manifestations of the same controversy. The reassertion of clerical celibacy at the Council of Trent established the issue as a permanent marker of the divisions within Christendom, and defined a discipline for the Catholic church which has continued to the present day. However, the history of clerical celibacy, both the ideal and the reality, has as times a Delphic ambiguity to it. By searching in the past for the modern discipline of the church, it is easy to conclude that the origins of clerical celibacy lie in the post-apostolic period, possibly as late as the eleventh century. Defined as 'unmarried', the celibate priesthood has been argued to be an invention of the medieval church; defined as 'continent' the celibate priesthood has been presented as the practice of primitive Christianity.