Book excerpt: There is a lot of talk about heresy these days. The frequency and volume of accusations suggest that some Christians have lost a sense of the gravity of the word. On the other hand, many believers have little to no familiarity with orthodox doctrine or the historic distortions of it. What’s needed is a strong dose of humility and restraint, and also a clear and informed definition of orthodoxy and heresy. Know the Heretics provides an accessible “travel guide” to the most significant heresies throughout Christian history. As a part of the KNOW series, it is designed for personal study or classroom use, but also for small groups and Sunday schools wanting to more deeply understand the foundations of the faith. Each chapter covers a key statement of faith and includes a 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.