Arianism has been called the 'archetypal Christian heresy' - a denial of the divine status of Christ. In this examination, now augmented with new material, Rowan Williams argues that Arius himself was a dedicated theological conservative whose concern was to defend the free and personal character of the Christian God. His 'heresy' grew out of the attempt to unite traditional biblical language with radical philosophical ideas and techniques, and was, from the start, involved with issues of authority in the church.

Williams raises the wider questions of how heresy is defined and how certain kinds of traditionalism transform themselves into heresy.