Is it possible for a true believer in Christ to apostatize? If so, how? Also, how can professing believers know if they are truly born again? What assurance can they have that they will never renounce their faith? These questions have been asked for centuries as Christians have wrestled with what Scripture says about these matters. The search for answers has instilled strong disagreements among Christian traditions. In this book, we navigate the terrain of this debate by examining the pertinent biblical data, surveying the history of major views that have been advocated by various denominations, and offering a synthesis of all this material in the hopes that readers can see how Scripture assures believers of their security in Christ.