2 Corinthians 10:3-4

Paul admitted that he walked in the flesh (was only human) but denied that he worked according to the flesh (as carnal Christians and unbelievers do). He was contrasting living in the world and living as a worldling. Carnal weapons like intimidation, manipulation, trickery, double-talk, rumor, and hypocritical behavior are ineffective in spiritual warfare. Reliance on the working of God, however, results in supernatural victories. The spiritual Christian’s weapons are those that Paul later enumerated in Ephesians 6:11-17. The "fortresses" or "strongholds" (Gr. ochuroma, used only here in the New Testament) probably refer to the false arguments of Paul’s opponents (cf. 2 Corinthians 10:5).