Luther’s lectures on Romans were given during the years 1515-1516 at the University of Wittenberg. During this time, Luther himself was still learning and reforming, so his later lectures and writings are more developed than what you find in his work on Romans. However, in much of his discussion on Romans he’s on the right track, so to speak. Here’s a very insightful commentary on the themes of ingratitude and idolatry from Romans 1:21-23.
…People even today come to commit spiritual idolatry of a more subtle kind, and it is quite frequent: they worship God not as he is but as they imagine and desire him to be.
Ingratitude, namely, and the love of vanity (i.e., the sense of self-importance and of self-righteousness or, as one says, of “good intentions”) delude people terribly, so that they become incorrigible, unable to believe anything else but that they behave splendidly and are pleasing to God. Thus, they make themselves a gracious God, though this does not correspond to reality. And so they worship the product of their own imagination more truly than the true God himself, who they believe resembles this product of their fancy.
Here now “they change him into the likeness of their own imagination” (Rom. 1:23), which exists only in their corruptible minds that know only carnal desires. See, then, how great an evil ingratitude is: it produces a love of vanity, and this results in blindness, and blindness in idolatry, and idolatry brings about a whole whirlpool of vices.
Gratitude, however, keeps the love for God and thus holds the heart directed toward him. Because it is thereby also illumined, it worships, once it is illumined, only the true God, and to this worship there soon attaches itself the whole chorus of virtues.
Luther’s insight here on the text and the human tendency is quite profound. Unthankfulness and idolatry are related, and Luther very well explains Paul’s teaching on that fact. This is perhaps one reason why the Apostle emphasizes thankfulness in the Christian life (Eph 5:4, 5:20; Phil. 4:6; Col. 2:7, 3:17, 4:2, etc.). So we “give thanks” in all circumstances, because it is God’s will for us in Christ (1 Thes. 5:18)! The Heidelberg Catechism’s structure also picks up on this biblical truth: though guilty we are saved by grace, and our response is gratitude.
The above quotes are found on page 26 of Luther’s Lectures on Romans.
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