Know the Heretics is a short book examining beliefs of historical heresies in Christian history. It is designed for personal study or classroom use, or for small groups and Sunday school classes who want to understand more about the foundations of their faith. Each chapter covers a key statement of faith and includes discussion of its historical context; a simple explanation of the unorthodox teaching, the orthodox response, and a key defender; reflections of contemporary relevance; and discussion questions.

Holcomb argues that the heretics of the early church were not trying to create non-orthodox heresies but trying to clarify or simplify the theology of the Trinity. So most of the heresies in this book are about the Trinity, and part of the reason for that is that Holcolm focuses on those because a council was organized against them.

What I appreciate about this book is Holcomb pointing out that differences of opinion in Christianity should not flippantly be called heresy when they are not:

Key quote: "Though this group of heresy-hunters often say they’re motivated by concern for the faith once for all delivered to the saints, their practice of labeling every diverging belief as heresy has the opposite effect. Rather than making much of right belief, they minimize its importance by making, for example, the mode of baptism to be as important as the divinity of Christ. When everything is central, nothing is."

Holcomb says we should look at the Nicene Creed as the defining orthodoxy of the Christian faith:

"The Nicene Creed is a historic, globally accepted ecumenical creed that encapsulates the good news of the gospel into a short and rich summary. It covers the basic essentials of (1) who God is, (2) what God is like, and (3) how God saves. If a believer authentically holds to the Nicene Creed, we should not call them a heretic, no matter how strongly we believe they are gravely in error on the details or on other doctrines. A good shorthand for heresy, then, is to ask, “œCan they say the Nicene Creed and mean it without their fingers crossed?” If the answer is yes, they may still be wrong, and they may be heterodox, but we cannot call them heretics, because they fit within the bounds of historic Christianity."