For 450 years, churches throughout the world have been using the Heidelberg Catechism (1563) to instruct God's people in foundational Christian doctrine. When Elector Frederick III (1515-1576) commissioned the preparation of a manual for instructing the youth and guiding the pastors and teachers of his domain, he could not have imagined the profound effect it would have on future generations of Christians. The most widely used, most influential...