Almost since the beginning of the Reformation there were two reactions to the recovery of the gospel: legalism, or nomism, and antinomianism. There are associated doctrines and practices but the core of antinomianism is the rejection of the abiding validity of the moral law. In the 1520s already, there were those who concluded that if we are saved (justified, sanctified, and glorified) by grace alone (sola gratia), through faith alone (sola fide) and the Reformation rightly rejected Rome’s confusion of law and gospel, then we do better not to talk about the moral law at all. Luther reacted strongly against this view. Indeed, he coined the term “antinomian” in his critique. In his Larger Catechism (among many other places) he taught the substance of what Philipp Melanchthon would later call the “third use of the law” (tertius usus legis). Nevertheless, those who are ignorant of Luther continue to repeat the slander that he himself was antinomian. The other great false reaction to the Reformation recovery of the gospel was nomism, i.e., the doctrine that in order to be saved we must obey law as the ground or instrument of our justification or salvation. The nomists were unsatisfied with the Reformation doctrine that new life and true faith given by the Holy Spirit necessarily produces good works as fruit and evidence of our justification and salvation. Then as now, the nomists sought to make works (obedience to the law) either the instrument (alongside of faith) or the ground (the legal basis alongside Christ’s obedience) of our salvation. As one, the confessional Protestant churches (the Lutheran and Reformed) rejected the nomists. The rejection by the confessional Reformed churches of both antinomianism and nomism (or neonomianism) has not kept them from reappearing like clockwork and even, at times, flourishing. It was in the midst of a renewal of both antinomianism and nomism in the 17th century that Edward Fisher published The Marrow of Modern Divinity. Against neonomianism in 18th century Scotland, Thomas Boston reprinted The Marrow and added to it his notes as part of the “The Marrow Controversy.” Today we have neonomians who, as in eighteenth-century Scotland, suggest falsely that The Marrow is antinomian. Perhaps, however, the greatest danger is sheer ignorance of The Marrow. So, to provide some prospective on our current debates over nomism and antinomianism and to help retain the Reformation gospel, The Heidelcast explored The Marrow in some detail.