Since the days of the early church, Christians have struggled to understand the relationship between two seemingly contradictory concepts in the Bible: law and gospel. If, as the apostle Paul says, the law cannot save, what can it do? Is it merely an ancient relic from Old Testament Israel to be discarded? Or is it still valuable for Christians today? Helping modern Christians think through this complex issue, seasoned pastor and theologian Sinclair Ferguson carefully leads readers to rediscover an eighteenth-century debate that sheds light on this present-day doctrinal conundrum: the Marrow Controversy. After sketching the history of the debate, Ferguson moves on to discuss the theology itself, acting as a wise guide for walking the path between legalism (overemphasis on the law) on the one side and antinomianism (wholesale rejection of the law) on the other.