Newman himself called the Oxford University Sermons, first published in 1843, the best, not the most perfect, book I have done. He added, I mean there is more to develop in it. Indeed, the book is a precursor of all his major later works, including especially the Essay on the Development of Christian Doctrine and the Grammar of Assent. Dealing with the relationship of faith and reason, the fifteen sermons represent Newman's resolution of the conflict between heart and head that so troubled believers, non-believers, and agnostics of the nineteenth century. Their controversial nature also makes them one of the primary documents of the Oxford Movement.