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. 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. They have become callous and have given themselves up to sensuality, greedy to practice every kind of impurity. But that is not the way you learned Christ! — assuming that you have heard about him and were taught in him, as the truth is in Jesus, to put off your old self, which belongs to your former manner of life and is corrupt through deceitful desires, and to be renewed in the spirit of your minds, and to put on the new self, created after the likeness of God in true righteousness and holiness. – Ephesians 4:17-24 ESV

Futile minds. Darkened understandings. Alienated from God. Ignorant. Hardened hearts. Callous. Slaves to sensuality. Greedy for more impurity.

Paul doesn’t exactly paint a pretty picture of the condition of those outside of Christ. But his purpose seems to be less about exposing the sinful nature of the lost, than about reminding the Ephesian believers of their pre-conversion state. Prior to coming to faith in Christ, they had been in the same condition: Lost and alienated from God. Verse 17 is directly linked to verse one of this same chapter. Paul opened up the chapter by telling them, “I…urge you to walk in a manner worthy of the calling to which you have been called.” Now he is telling them how not to walk. As we have seen before, the Greek word translated “walk” is περιπατέω (peripateō) and it meant “to make one's way, progress” and was most often used by Paul to refer to living life. Paul was encouraging the believers in the church of Ephesus to live their lives differently, because they had been called by God. Rather than living selfish, self-gratifying lives like they did before, they were to conduct themselves in such a way that it honored the One who had called them and restore them to a right relationship with Himself.

Paul’s emphasis on his readers’ previous lost condition was intended to emphasize their supernatural calling by God. In their lost state, their minds were a big part of the problem. Without Christ, their minds were futile, which in the Greek meant “devoid of truth and appropriateness.” Their understanding was darkened. In other words, their thoughts, feelings and desires were “covered with darkness.” That is why the apostle John opened his gospel with the words, “In Him [Jesus] was life, and the life was the Light of men. The Light shines in the darkness, and the darkness did not comprehend it” (John 1:4-5 NASB). Without God’s help, men were incapable of seeing the Light. They were covered in and blinded by darkness. Like a person trapped in a dark room who suddenly finds himself exposed to the daylight, their eyes are incapable of seeing clearly and distinctly. Their eyes are so accustomed to darkness that the light is painful to them. John goes on to say, “There was the true Light which, coming into the world, enlightens every man. He was in the world, and the world was made through Him, and the world did not know Him” (John 1:8-9 NASB).

Paul went on to say that his readers were at one time “alienated from the life of God.” The Greek word Paul used means to “shut out from one's fellowship and intimacy” (“G526 - apallotrioō - Strong's Greek Lexicon (KJV).”" Blue Letter Bible). They had not concept of what it meant to know God or have a relationship with Him. It was King David who wrote:

The fool says in his heart, “There is no God.”     

They are corrupt, they do abominable deeds,     

there is none who does good.

The Lord looks down from heaven on the children of man,     

to see if there are any who understand, who seek after God.

They have all turned aside; together they have become corrupt;     

there is none who does good, not even one. - Psalm 14:1-3 ESV

No one was truly seeking God. They might have been searching for their particular version of God, but they were incapable of seeing or comprehending the one true God. That is why, as Paul writes in Romans, “Claiming to be wise, they became fools, and exchanged the glory of the immortal God for images resembling mortal man and birds and animals and creeping things” (Romans 1:22-23 ESV). And Paul makes it clear to the Ephesians that their former alienation from God had been the result of their own ignorance and hardness of heart. The ignorance Paul speaks of is not just a lack of knowledge, but a moral blindness. And that, coupled with their hardened hearts, rendered them incapable of knowing God or His truth. Their perceptions had been dulled and their minds, blunted. As a result, they found themselves addicted to sensuality and insatiably drawn to more and more impurity. 

And Paul’s point seems to be that no one who finds themselves in that condition chooses to seek after God or has the mental wherewithal to choose Christ. No one with a darkened, hardened, futile mind would naturally seek what God has offered to them in Christ. It would make no sense. Which is why Paul told the Corinthian believers, “when we preach that Christ was crucified, the Jews are offended and the Gentiles say it's all nonsense” (1 Corinthians 1:23 NLT). Paul told the Ephesians, “that is not the way you learned Christ!” In other words, they had not come to a knowledge of Jesus through their own human thinking. They learned Jesus through what Paul called “the foolishness of preaching.”

God in his wisdom saw to it that the world would never know him through human wisdom, he has used our foolish preaching to save those who believe. – 1 Corinthians 1:21 NLT

It had been the proclamation of the Word of God and the regenerating power of the Spirit of God that had made the message of salvation by grace through faith in Christ comprehensible to them. Paul reminded them that “the truth is in Jesus.” And that truth called for them to “throw off your old sinful nature and your former way of life, which is corrupted by lust and deception. Instead, let the Spirit renew your thoughts and attitudes. Put on your new nature, created to be like God — truly righteous and holy” (Ephesians 4:22-24 NLT). Their old natures were corrupt and deceived. Their new natures, provided to them by the indwelling Holy Spirit were capable of new thoughts, attitudes and actions. They were to walk in a manner worthy of their calling – holy, set apart, distinctively different, empowered by the Spirit and in keeping with the will of God. Change is non-optional for believers. Spiritual transformation is not up to us to choose or reject – at least, and not truly be a child of God. Our new natures should crave and desire the things of God. We should want what He wants for us: holiness and righteousness. And our new natures, lived within the context of the body of Christ, should produce a new community that is unlike anything the world has ever seen. Called and committed believers, powered by the Spirit of God and living as brothers and sisters in Christ, should form “a holy temple in the Lord” (Ephesians 2:21 ESV). Our lives, lived together in unity, should prove to the world that the gospel is true and that reconciliation with God brings reconciliation with others.