17 This I say, therefore, and testify in the Lord, that you should no longer walk as the rest of the Gentiles walk, in the futility of their mind, 18 having their understanding darkened, being alienated from the life of God, because of the ignorance that is in them, because of the blindness of their heart; 19 who, being past feeling, have given themselves over to lewdness, to work all uncleanness with greediness. 20 But you have not so learned Christ, 21 if indeed you have heard Him and have been taught by Him, as the truth is in Jesus: (Ephesians 4:17–21, NKJV)
Evil thinking produces evil living. Paul describes the futile, dark, alienating ignorance that blinded the hearts of the pagans idolaters (the “Gentiles”). Ephesus was full of such people (cf. Acts 19:21-41). Removing the true God and knowledge of His truth from one’s thoughts always dulls one’s consciousness of sin, which invariably leads to choosing all manner of lewd, impure and greedy conduct. The gospel of Jesus teaches us to purify our hearts in order to live holy lives. The truth found in Jesus Christ does not keep us in sin. His truth does not lead us into more sin. Truth teaches us to put off the old man of sin (conversion to Christ) and to put on “the new man” of “true righteousness and holiness” (Eph. 4:17-19, 24).