"17 Now this I say and testify in the Lord, that you must no longer walk as the Gentiles do, in the futility of their minds. 18 They are darkened in their understanding, alienated from the life of God because of the ignorance that is in them, due to their hardness of heart. 19 They have become callous and have given themselves up to sensuality, greedy to practice every kind of impurity. 20 But that is not the way you learned Christ!— 21 assuming that you have heard about him and were taught in him, as the truth is in Jesus, 22 to put off your old self,[f] which belongs to your former manner of life and is corrupt through deceitful desires,23 and to be renewed in the spirit of your minds, 24 and to put on the new self, created after the likeness of God in true righteousness and holiness."
Ephesians 4:17-24
There is one point, however, that we need to underline at the outset, and that is to grasp, from Paul's words in 17-19, what a terrible thing it is not to be converted to Christ and to be lost. One senses the tender concern and compassion in Paul's heart as he pens these solemn words. It was said of D.L. Moody, who in temperament was one of the happiest of men, that he could never speak of a lost soul without his eyes filling with tears. That is the use of such a passage as this for Christians - not merely that we should know the true state of the lost, but that we should feel for them with the compassion of Christ. Think of the tears that our Lord shed over the lost city of Jerusalem: 'If thou hadst known', He cried as He wept, 'even thou, at least in this thy day, the things which belong unto thy peace, but now they are hid from thine eyes'. The whole moral and intellectual character of heathenism, and the pathos of it, its emptiness and meaninglessness and despair, are evidenced not only in these verses before us, but also throughout the New Testament - the ignorance caused by hardness of heart, the alienation, the darkness in their minds, the vanity of life. Paul was surely conscious of all this as he wrote Ephesians, visualising what he had seen when he was in Ephesus and the other cities of Asia, and the question that these verses ask us is: Is this how we react, when we see those who are not Christians all around us?