Joseph F. Kelly considers heresies and the historical forces that shaped them. In his customarily engaging style, he demonstrates that historical forces and human beings of particular historical eras play a major role in how both orthodoxy and heresy come into being and how they are understood. Far from reducing orthodoxy and heresy to historical forces, he shows rather that a grasp of the historical context of both is essential in understanding them and especially in determining what might be orthodox or heretical.