Eph 4:20-24 - Off with the Old, On with the New

20 But you did not learn Christ in this way,
21 if indeed you have heard Him and have been taught in Him, just as truth is in Jesus,
22 that, in reference to your former manner of life, you lay aside the old self, which is being corrupted in accordance with the lusts of deceit,
23 and that you be renewed in the spirit of your mind,
24 and put on the new self, which in the likeness of God has been created in righteousness and holiness of the truth. Created in Righteousness and Holiness

You Have A New Life, A Changed Life!

I posit that verses 20-21, above, are a launching point for the rest of the letter. In verses 20-21 Paul tells them they have received Christ in the right way, and have the truth, and so:

• Their lives have changed from the way they lived as a natural man to a new man. (see vss. 4:22-24).
• Live peaceably with each other by not harming physically or emotionally (see vss. 4:25-32).
• Be imitators of God. Don’t be deceived by immorality (vss. 5:1-14)
• Be careful how you live out your life. Rely on the Holy Spirit (vss. 5:15-21)
• Instructions for married couples and families. Wives (vss. 5:2-24). Husbands (vss. 5:25-33). Children and Fathers (vss. 6:1-4)
• Relations between slaves and masters (vss. 6:5-9)
• Prepare for spiritual battle (vss. 6:10-17)
• Pray for the message of Good News to continue to spread throughout the world (vss. 6:18-20).

V. 20 - “But you did not learn Christ in this way,” -  We do not become children of God, heirs with Christ, in ignorance. It won’t happen when you are driving down the road, and "Prang" you have been magically saved. No. we must hear the message of who Christ is, and what He has done. (See: Rom 10:17; Acts 11:14) We must make a decision, it does not happen by accident. (See: Acts 2:21) We must give up our hardness of heart. The apostle Paul is a good example: He knew who Jesus was; he refused to believe. Jesus is the light, and we must respond to the light. Paul saw the light on the road to Damascus. (Acts 9:1-11) Paul came to the Light, and believed in Jesus. God has taken us out the domain of darkness and into the kingdom of His Son, Jesus. (Col 1:13) When we have the facts, and obey His commands, we can know the truth and it will make us free. (John 8:31-32)

V. 21 - “if indeed you have heard Him and have been taught in Him, just as truth is in Jesus,”

“If indeed you have heard Him” - The “if indeed” is not a question, but more rhetorical along the line of “if you have, and indeed you have...” You have learned Christ in the correct way. Because their understanding was not darkened, their hearts were not hardened, they heard the call of Jesus to believe and be saved.

“Just as truth is in Jesus” - One of the true joys of Christianity is that it is ‘out there’, totally public. It is not a faith with secret knowledge, secret handshakes, mysteries that only "those in the know" can understand. It is straight forward and clear.

• God Loves you.
• Christ came from God and died for you, since you could never repay the debt caused by your sin. 
• Believe and be saved.

Because You Have Learned the Truth...

V. 22-24 - “that, in reference to your former manner of life, you lay aside the old self, which is being corrupted in accordance  with the lusts of deceit, and that you be renewed in the spirit of your mind, and put on the new self, which in the likeness of God has been created in righteousness and holiness of the truth.”

“that” - This easily could be read “So that...” Because, if they learned about Christ in the correct way, and if they heard the call to believe in a Christ, and if they have in them the truth of Jesus as Lord (Paul believes these are all true, because he or someone he trusts has taught them) then the following three things should also be true:

1. Laying aside the old self - The old self, is the natural man, the descendant of Adam, a slave to sin. (See: Rom 6:6, 8:6, 13:12; Col 3:9; Heb 12:1). 
2. Renewing of the mind - All things have been made new for those who are in Jesus. (See: Rom 12:2; John 3:3; 1 Pet 1:3, 23)
3. Putting on a new self - We are in Christ. He is in us. We died when He died. We are resurrected to new life because He has new life. We are no longer slaves to sin. We cannot put on the new self ourselves, it comes from and through Jesus and through Jesus alone. (See: 2 Cor 5:17; Gal 6:15; Col 3:10; Heb 10:20; Rev 21:5)