Rather than seeing heresies as simply foils for developing orthodoxy, Joseph Kelly places them in their historical contexts, showing how heresies and their suppression were part of larger contexts, and were often fueled by personal and political factors. In an engaging style Kelly begins with the formulation of doctrine in the early church, opining that in his time Paul might have been considered a heretic for his novel ideas. He then focuses on Montanism, Monophysitism, the Cathars, Roman Catholic Modernism, and Protestant Modernism and Fundamentalism. In each case he succinctly provides theological, political, and biographical background. In each of his material chapters he also details the negative implications of the heresy and the reasons why the developing orthodox parties could not reconcile with those they deemed heretics.

This is not simply an expanded heresiologial history. Kelly sandwiches the content chapters between two of his best chapters. The initial chapter of the book contains a definition of heresy as “the conscious deviation from a publicly proclaimed teaching of a religious body or church” (1), and a careful exposition of the necessity of religious authority both as a precondition and as a correlate of the development of a declaration of a teaching as heresy.

His final chapter, “Dealing with Heresy Today,” sums up what he and the reader learn from the historical treatments of heresy. While heresy is often a response to changing environments for the Church, Kelly concludes that this doesn't mean that the Church needs to give in to heresy, but to reflect on new ways of expressing faith in a changing world. Challenges include accepting that sciences will continue to have an impact on the formulation of church teaching in a world with a changing cosmology, and using social sciences to reflect on how doctrine historically has been formulated, that is, by only a small portion of the Catholic population: ordained men. The existence of theological specialists who are not bishops, including women and lay men, presents its own challenge as young people are increasingly educated in theology by nonclergy and regard them rather than bishops as theological authorities. Sagely he points out that for bishops “their office alone does not make them authoritative” (197).

Other than a few digressions, this small volume is clearly written—even on Monophysitism—and provides necessary background for novice readers, including, for example, an overview of Genesis 1-11 as background for heresies concerning the biblical text, dates, and very brief biographical information on important theologians. It is fairly priced, making it a useful text for undergraduate and beginning graduate courses in theology. It is recommended for college libraries and especially those in seminaries, where future bishops can read about productive and nonproductive approaches to new theologies and old heresies.