John Calvin Commentary Romans 1:14

"I am debtor both to Greeks and to Barbarians, both to the wise and to the foolish." — Romans 1:14 (ASV)

I am a debtor both to the Greeks and to the Barbarians, etc. Those whom he means by the Greeks and the Barbarians, he later explains by adding, both to the wise and to the foolish; Erasmus did not translate these words poorly as “learned and unlearned” (eruditos et rudes), but I prefer to retain Paul’s exact words. He then draws an argument from his own office and suggests that it should not be attributed to his arrogance that he considered himself, in a way, capable of teaching the Romans—however much they excelled in learning, wisdom, and the knowledge of things—since it had pleased the Lord to make him a debtor even to the wise.

Two things should be considered here:

1. The gospel is destined and offered by a heavenly mandate to the wise, so that the Lord may subject all the wisdom of this world to himself. He intends to make every variety of talent, every kind of science, and the loftiness of all arts yield to the simplicity of his doctrine. Furthermore, the wise are to be reduced to the same rank as the unlearned. They are to be made so humble as to be able to bear having as their fellow disciples under their master, Christ, those whom they previously would not have condescended to take as their students.
2. The unlearned are by no means to be driven away from this school, nor should they flee from it through groundless fear. For if Paul was indebted to them, being a faithful debtor, he undoubtedly discharged what he owed. And so, they will find here what they are capable of enjoying.

This also provides a rule for all teachers to follow: namely, to modestly and kindly adapt themselves to the capacities of the ignorant and unlearned.

Consequently, they will be able with greater composure to endure many absurdities and almost countless things that may repel them, which might otherwise overwhelm them. However, they are to remember that they are not so indebted to the foolish as to cherish their folly through excessive indulgence.