The first-century Corinthians provide a negative example from which we can learn. Immediately after the apostle Paul declares that Christians "have the mind of Christ" (I Corinthians 2:16), he informs the Corinthians, "And I, brethren, could not speak to you as to spiritual people but as to carnal, as to babes in Christ. . . . [F]or you are still carnal. For where there are envy, strife, and divisions among you, are you not carnal and behaving like mere men?" (I Corinthians 3:1, 3). Despite their having become Christians through baptism and the laying on of hands, these Corinthians had retained their pre-conversion natures. How do we know this? It exposed itself in their carnal behavior! As Paul says, they were acting just like other people who had not received God's grace.
Their conversion had never really left the starting gate because they had failed to continue in the process of spiritual transformation. The author of Hebrews explains what must occur:
For though by this time you ought to be teachers, you need someone to teach you again the first principles of the oracles of God; and you have come to need milk and not solid food. For everyone who partakes only of milk is unskilled in the word of righteousness, for he is a babe. But solid food belongs to those who are of full age, that is, those who by reason of use have their senses exercised to discern both good and evil. (Hebrews 5:12-14)
Conversion, then, is the process of exercising our senses, not the five senses, but the mental and spiritual faculties of reason, understanding, and judgment. If we are not making judgments about events that are happening in our homes, in our communities, in our workplaces—if we are not determining whether they are right or wrong, and if we are not endeavoring to correct those that are wrong, then we are failing in our conversion. We are, in fact, in danger of neglecting our salvation and drifting away.
The writer, however, is not finished with his instruction. In the next chapter, he shows them what they need to do:
We are confident of better things concerning you, yes, things that accompany salvation, though we speak in this manner. For God is not unjust to forget your work and labor of love which you have shown toward His name, in that you have ministered to the saints, and do minister. And we desire that each one of you show the same diligence to the full assurance of hope until the end, that you do not become sluggish, but imitate those who through faith and patience inherit the promises. (Hebrews 6:9-12)
Notice what he encourages them to do: to show diligence, that is, "earnestness," "zeal," "deep commitment with eagerness." He advises them to dedicate their lives to this spiritual transformation and to stick with it to the end, as this is what those who will inherit the promises do. In other words, they need to launch zealously into a campaign of regaining all their lost ground. As he implies, Christianity is not a religion for the lazy.
The apostle Peter says much the same thing in II Peter 1:2-8:
Grace and peace be multiplied to you in the knowledge of God and of Jesus our Lord, as His divine power has given to us all things that pertain to life and godliness, through the knowledge of Him who called us by glory and virtue. By which have been given to us exceedingly great and precious promises, that through these you may be partakers of the divine nature, having escaped the corruption that is in the world through lust. But also for this very reason, giving all diligence, add to your faith virtue, to virtue knowledge, to knowledge self-control, to self-control perseverance, to perseverance godliness, to godliness brotherly kindness, and to brotherly kindness love. For if these things are yours and abound you will be neither barren nor unfruitful in the knowledge of our Lord Jesus Christ.
He mentions that, since the Father and Christ have given us so much—even allowing us to share in God's nature—we should strive to add to our faith. Just believing that God is and that He has forgiven our sins is not enough (James 2:19). Among other things, we must grow in these qualities: virtue, knowledge, self-control, perseverance, godliness, brotherly kindness, and love. If we work to instill these godly attributes into our characters, we will be producing the kind of fruit that God wants to see in us (John 15:1-8).
Peter concludes his instruction in verses 10-11: "Therefore, brethren, be even more diligent to make your calling and election sure, for if you do these things you will never stumble; for so an entrance will be supplied to you abundantly into the everlasting kingdom of our Lord and Savior Jesus Christ." Spiritual growth and producing fruit are what makes our calling sure. Our maturity as Christians is based upon us zealously, diligently working to move our conversion along.
What is real conversion? It is the transformation of our characters, our intellects, our emotions, our actions, our words, our very thoughts, from the evil way inspired by Satan and man's carnal nature into the divine nature—the very nature of God Himself!
So, how much like God are we? How straight and true is our trajectory to putting on the image of Christ (Romans 8:29)? How much of the old man have we put off, and how much of the new man have we put on (Colossians 3:9-10)? Are we growing in the grace and knowledge of Jesus Christ (II Peter 3:18)? Are we cooperating with God in being transformed to His image (Romans 12:2)? Are we making becoming more like Christ a daily goal (Luke 9:23)?
Though the Corinthians had their problems with carnality—as we all do—they worked to overcome them and began growing. Paul's final words to them in his second epistle should give us encouragement as we "work out [our] own salvation" (Philippians 2:12): "Finally, brethren, farewell. Become complete. Be of good comfort, be of one mind, live in peace; and the God of love and peace will be with you. . . .The grace of the Lord Jesus Christ, and the love of God, and the fellowship of the Holy Spirit be with you all" (II Corinthians 13:11, 14).