1:12 boast. Paul boasts not in his own ability, but in having a clear conscience and morally upright conduct. Paul’s simplicity and godly sincerity are not the result of following the conventional wisdom of the world, but depend on “the grace of God.” When Paul boasts he takes no credit for himself. It is the triumph of God’s grace in him.
earthly wisdom. In this verse Paul introduces his denial of the charge that he had worldly motives for changing his plans to visit Corinth. Distinguishing divine wisdom (expressed in the cross of Christ) from “earthly” wisdom was a problem for some Corinthian believers. Worldly wisdom led to divisions in the church (1 Cor. 1:10–4:7), and by the standards of such wisdom Paul was not acceptable as an apostle (10:2–6).