  Roper reports a conversation with his father-in-law in which More declared that he would gladly be thrown into the Thames in a sack if only three things could realized: that there should be peace between Christian princes, that turmoil in the church might be settled “in a perfect uniformity of religion”, and that the matter of the king's marriage might come to a good conclusion (Roper 1935: 24–5). If the peace of Cambrai might satisfy his first requirement, the two other issues would prove more problematic. In 1521, as Luther's challenge to the Catholic church gained momentum, King Henry published his Assertio septem sacramentorum, a statement of orthodoxy which won him the title Defender of the Faith from a grateful pope. More appears to have had some editorial role in this, and it marks the beginning of a new phase in his intellectual career, as an apologist for the Catholic faith.  Thirteen years later, writing in his own defence to Thomas Cromwell, More would bitingly observe that his early doubts about the divine institution of papal primacy had been put at rest by the king himself (SL: p.212). Luther's response to the royal book was predictably offensive, and More was put forward to retaliate in kind; his Responsio ad Lutherum (1523) is a vigorous presentation of familiar arguments, without much evidence of engaging with Luther's thought. Basic to his argument is the appeal to tradition, understood as the unwritten deposit of teaching which precedes the Gospel texts and provides the matrix within which they must be interpreted. After his appointment as Chancellor of the Duchy of Lancaster in 1525, he was drawn directly into the campaign against the circulation of heretical books, and in 1528 his old colleague Tunstall, now bishop of London, commissioned him to respond to heretical books. This resulted in a daunting body of writings in the vernacular which extends from A Dialogue Concerning Heresies in 1529 to The Answer to a Poisoned Book in 1534, and some of its aspects are discussed below. 