4:17 This I say therefore, and testify in the Lord,
 

that you no longer walk as the rest of the Gentiles also walk, in the futility of their mind,
4:18 being darkened in their understanding, (Rom 1:18-28)
alienated from the life of God,

because of the ignorance that is in them, because of the hardening of their hearts;

4:19 who having become callous gave themselves up to lust,
to work all uncleanness with greediness.

4:20 But you did not learn Christ that way;
4:21 if indeed you heard him,

and were taught in him, even as truth is in Jesus:

4:22 that you put away, as concerning your former way of life, the old man,

that grows corrupt after the lusts of deceit;

4:23 and that you be renewed in the spirit of your mind,
4:24 and put on the new man,  (Col 3:9,10; Gal 2:20; 2Cor 5:17)

who in the likeness of God has been created in righteousness and holiness of truth.

4:25 Therefore, putting away falsehood, speak truth each one with his neighbor.
For we are members one of another.
4:26 "Be angry, and don't sin." Don't let the sun go down on your wrath, (Ps 4:4)
4:27 neither give place to the devil.
4:28 Let him who stole steal no more; but rather let him labor,
working with his hands the thing that is good,
that he may have something to give to him who has need.
4:29 Let no corrupt speech proceed out of your mouth,
but such as is good for building up as the need may be,
that it may give grace to those who hear.
4:30 Don't grieve the Holy Spirit of God, in whom you were sealed for the day of redemption.
4:31 Let all bitterness, wrath, anger, outcry, and slander,
be put away from you, with all malice.
4:32 And be kind to one another, tenderhearted, forgiving each other,
just as God also in Christ forgave you.

Eph 4:17 So I tell you this, and insist on it in the Lord, that you must no longer live as the Gentiles do, in the futility of their thinking.

The way you think affects how you live. Your world view affects your decisions. The word for "futile" indicates that which is vain, devoid of truth and appropriateness, or perverse and depraved. Paul speaks such a state saying, "For although they knew God, they neither glorified him as God nor gave thanks to him, but their thinking became futile and their foolish hearts were darkened. Although they claimed to be wise, they became fools." Rom 1:21,22 A depraved mind is an effect of rejecting the knowlege of God. For "since they did not think it worthwhile to retain the knowledge of God, he gave them over to a depraved mind, to do what ought not to be done." Rom 1:28

So consider in what ways your lifestyle reflects a vain or depraved way of thinking.

Eph 4:18 They are darkened in their understanding and separated from the life of God because of the ignorance that is in them due to the hardening of their hearts.

What is the root of a darkened understanding about God and the root of an ungodly lifestyle? The root is a hardened heart.  Because such people love sin, they don't seek God and thus remain ignorant. "This is the verdict: Light has come into the world, but men loved darkness instead of light because their deeds were evil." John 3:19 "The light shines in the darkness, but the darkness has not understood it." John 1:5

But follow Jesus and you will be enlightened as to the knowlege of God and a lifestyle pleasing to him. When Jesus spoke again to the people, he said, "I am the light of the world. Whoever follows me will never walk in darkness, but will have the light of life." John 8:12

Eph 4:19 Having lost all sensitivity, they have given themselves over to sensuality so as to indulge in every kind of impurity, with a continual lust for more.

And God allows such people to be given over to such things if they reject him.

"My people would not listen to me; Israel would not submit to me. So I gave them over to their stubborn hearts to follow their own devices." Ps 81:11,12

"Therefore God gave them over in the sinful desires of their hearts to sexual impurity for the degrading of their bodies with one another. They exchanged the truth of God for a lie, and worshiped and served created things rather than the Creator— who is forever praised. Amen.  Because of this, God gave them over to shameful lusts. Even their women exchanged natural relations for unnatural ones. In the same way the men also abandoned natural relations with women and were inflamed with lust for one another. Men committed indecent acts with other men, and received in themselves the due penalty for their perversion." Rom 1:24-27

Yes homosexuality is an effect of loving one's passions more than God and consequently rejecting the knowledge of God resulting in a depraved mind, a depraved heart and a corrupt conscience, incapable of discerning right from wrong.

Eph 4:20-22  You, however, did not come to know Christ that way. Surely you heard of him and were taught in him in accordance with the truth that is in Jesus. You were taught, with regard to your former way of life, to put off your old self, which is being corrupted by its deceitful desires

A person cannot come to know Christ by following the passions of their flesh. Coming to know Christ is a humiliating painful process abhorent to the flesh. Our conscience being awakened, we come through the acknowledgment and contempt for our sins with the intent of leaving our sinful lifestyle. And much of the Christian life is devoted to denying our flesh its former indulgences, lusts and passions. Such desires formerly deceived us with false promises of fulfillment but only brought corruption. For "the heart is deceitful above all things, And desperately wicked." Jer 17:9

"At one time we too were foolish, disobedient, deceived and enslaved by all kinds of passions and pleasures. We lived in malice and envy, being hated and hating one another." Titus 3:3

"Put to death, therefore, whatever belongs to your earthly nature: sexual immorality, impurity, lust, evil desires and greed, which is idolatry. Because of these, the wrath of God is coming. You used to walk in these ways, in the life you once lived." Col 3:5-7

Eph 4:23,24 to be made new in the attitude of your minds; and to put on the new self, created to be like God in true righteousness and holiness.

The first thing to be renew is the attitude of mind. "Do not conform any longer to the pattern of this world, but be transformed by the renewing of your mind. Then you will be able to test and approve what God’s will is— his good, pleasing and perfect will." Rom 12:2 "bringing every thought into captivity to the obedience of Christ" 2Cor 10:5

So "put on the new self, which is being renewed in knowledge in the image of its Creator." Col 3:10

Eph 4:26,27 "In your anger do not sin": Do not let the sun go down while you are still angry, and do not give the devil a foothold.

A dispassionate person is one who doesn't allow his passions to cloud his judgments. Yes there are legitimate reasons to get angry. God get's angry and we are to conform to his image. But God also is longsuffering. And besides, our emotions are often clouded by sin. One indication that our anger has sin in it is when we lose control over it. The devil can gain a foothold through roots of bitterness.

"Know that the LORD has set apart the godly for himself; the LORD will hear when I call to him. In your anger do not sin; when you are on your beds, search your hearts and be silent. <Selah> Offer right sacrifices and trust in the LORD." Ps 4:3-5

Eph 4:28 He who has been stealing must steal no longer, but must work, doing something useful with his own hands, that he may have something to share with those in need.

Paul even disregards his legitimate entitlement to get paid for ministry saying, "I have not coveted anyone’s silver or gold or clothing. You yourselves know that these hands of mine have supplied my own needs and the needs of my companions. In everything I did, I showed you that by this kind of hard work we must help the weak, remembering the words the Lord Jesus himself said: ‘It is more blessed to give than to receive.’"Acts 20:33-35

Christians are not only to cease from stealing , But also to work, being productive, so what we can practice generosity. Consider what useful things you are doing in order to have resources to share with the needy. And if you are being an unnecessary financial burden to others, diverting their resources away from the truly needy - GET A JOB! !

Eph 4:29  Do not let any unwholesome talk come out of your mouths, but only what is helpful for building others up according to their needs, that it may benefit those who listen.

Jesus said, "I tell you that men will have to give account on the day of judgment for every careless word they have spoken." Mt 12:36  But conversely words can edify. Words are powerful things, often underestimated. God left us with His Spirit and with His Word. And "the word of God is living and active." Heb 4:12a God says of His Word, "my word that goes out from my mouth: It will not return to me empty, but will accomplish what I desire and achieve the purpose for which I sent it." Is 55:11 Likewise with us. Peter writes, "If anyone speaks, he should do it as one speaking the very words of God." 1Pet 4:11a Words influence. Words have impact. So consider carefully what you say. "Let your conversation be always full of grace, seasoned with salt, so that you may know how to answer everyone." Col 4:6 And pray, "Set a guard over my mouth, O LORD; keep watch over the door of my lips." Ps 141:3  Let us learn to speak by listening to the Lord and receiving the grace given Isaiah who said, "The Sovereign LORD has given me an instructed tongue, to know the word that sustains the weary. He wakens me morning by morning, wakens my ear to listen like one being taught." Is 50:4

Eph 4:30 And do not grieve the Holy Spirit of God, with whom you were sealed for the day of redemption.

Paul mentioned previously of their eternal security saying, "You also were included in Christ when you heard the word of truth, the gospel of your salvation. Having believed, you were marked in him with a seal, the promised Holy Spirit,
14  who is a deposit guaranteeing our inheritance"Eph 1:13,14 And also in 2Cor 1:22, "God set his seal of ownership on us, and put his Spirit in our hearts as a deposit, guaranteeing what is to come." Yet despite being eternally secure it is possible to grieve the Holy Spirit who lives in us much as parents are grieved when their children sin. God has feelings too.

Note that while warning them in this case he is not threatening them with condemnation, much as some are quick to do today. However he does use a harsher warning in chapter 5 as we will see, and elsewhere he also presents this balance between not overreacting nor underreacting to sin, much as the Lord says in Heb 12:5,6, "My son, do not make light of the Lord’s discipline, and do not lose heart when he rebukes you, because the Lord disciplines those he loves, and he punishes everyone he accepts as a son." The Christian attitude towards the feeling of guilt brought on by sin is neither to make light of it nor to lose heart and become depressed. The Christian's attitude is the middle road taking into account both God's holiness and God's grace.

Eph 4:31 Get rid of all bitterness, rage and anger, brawling and slander, along with every form of malice

Likewise he says, "Now you must rid yourselves of all such things as these: anger, rage, malice, slander, and filthy language from your lips. Do not lie to each other, since you have taken off your old self with its practices." Col 3:8-9

These speak of one's disposition - the attitude of one's heart. "The good man brings good things out of the good stored up in his heart, and the evil man brings evil things out of the evil stored up in his heart. For out of the overflow of his heart his mouth speaks." Luke 6:45  So "Above all else, guard your heart, for it is the wellspring of life." Pr 4:23

So control your temper or your temper will control you. "Better a patient man than a warrior, a man who controls his temper than one who takes a city." Pr 16:32  And "a fool always loses his temper, But a wise man holds it back."Pr 29:11

While the worldly swing between free uninhibited expression and being disingenuous, the Christians are to speak the truth while exercising self-control over one's passions.

Eph 4:32  Be kind and compassionate to one another, forgiving each other, just as in Christ God forgave you.

As you may have been noticing, much of Colossians is in parallel with Ephesians as it says, "Therefore, as God’s chosen people, holy and dearly loved, clothe yourselves with compassion, kindness, humility, gentleness and patience. Bear with each other and forgive whatever grievances you may have against one another. Forgive as the Lord forgave you." Col 3:12,13

But it is not unconditional forgiveness which Paul is referring to here. For while God loves everyone unconditionally, his forgiveness is conditional. And thus Jesus also teaches concerning relationships between Christians says, "If your brother sins, rebuke him, and if he repents, forgive him." Luke 17:3 That's the way God forgives. So be kind as God is kind. Be compassionate as God is compassionate. And forgive in the same manner as God forgives.