At the heart of the Church of England's continuing debate about marriage and human sexuality is the question of the development of doctrine. Would it be a legitimate development of Church of England doctrine to say that it is right to bless those in same-sex sexual relationships, that marriage can be between two people of the same sex and that it would be right to ordain those who are in same-sex marriages?

Noviter Non Nova addresses this question. It argues that historical evidence shows that Christian doctrine has continuously and rightly developed since the time of the Apostles as every generation of Christians has expressed what they believe in new ways in new situations. However, this book also argues that a study of the accounts of the development of doctrine given by Vincent of Lerins, John Henry Newman, and Maurice Wiles leads to the conclusion that while it is legitimate for Christians to express their faith in new ways, using new words (noviter), the content of what they express must not be new (non nova) because the Church does not have the authority to teach anything that goes beyond what is laid down in the apostolic witness contained in the New Testament.

This book further argues that the principle that the content of Christian doctrine cannot rightly change means that it would not be a legitimate development to bless same-sex sexual relationships, recognise same-sex relationships as marriages or ordain those in such relationships. The Church of England's calling is instead to give a fresh explanation of the importance of the traditional Christian teaching that marriage is a relationship between two people of the opposite sex and that sexual activity can only rightly take place within marriage.