The apostle proceeded to tell the Corinthians that they had not been viewing things from the spiritual point of view. He was referring specifically to their exaltation of one or another of God's servants above the others (1:10-17). Paul urgently appealed to them to change.
3:1 Here Paul introduced a third category of humanity, namely the "fleshly"(Gr. sarkinos) or "worldly"(NIV) man. The Corinthians were spiritual rather than natural because they possessed the Holy Spirit. Notwithstanding Paul said he could not speak to them as spiritual men. He explained the reason in verse 3. Instead he had to address them as fleshly people, even as babes in Christ. The fleshly believer then is an immature Christian. Immaturity is not blameworthy if one is very young. However if a person has been a Christian for some time and is still immature, his or her condition is blameworthy (cf. 2:6). Such was the condition of the Corinthians.
3:2 When Paul had been with them they were new converts, so he gave them the milk of the Word, the ABCs of the faith (cf. 1 Pet. 2:2). Now when they should have been able to take in more advanced teaching they were not able to do so (cf. Heb. 5:11-14). Their party spirit was one evidence of spiritual immaturity, lack of growth. Their fundamental need was not a change of diet but a change of perspective.
Paul's use of the vocative ("brothers [and sisters]") and second person plural pronouns in verses 1 and 2 indicates that he was addressing the whole church, not just a faction within it (cf. 1:10). The actions of many in the congregation had defiled the whole body.62
3:3 The reason Paul did not feel he should give them more advanced instruction was that their flesh (Gr. sarkikos) still dominated them. As believers they were making provision for the flesh to fulfill its desires rather than following the leading of the Holy Spirit. They were not only immature believers but also carnal Christians. The carnal believer is the fourth type of person Paul mentioned in 2:14-3:4.63
Paul let the Corinthians diagnose themselves. Are not jealousy and strife the works of the flesh (Gal. 5:20)? Did these qualities not indicate that they were conducting themselves as unbelievers, as people who do not even possess the Holy Spirit?64
"Being human is not a bad thing in itself, any more than being sarkinoiis (v. 1). What is intolerable is to have received the Spirit, which makes one more than merely human, and to continue to live as though one were nothing more."65
3:4 Partisanship is a manifestation of human wisdom. All the philosophical schools in Greece had their chief teachers. There was keen competition among these teachers, and there were strong preferences among the students as to who was the best. However this attitude is totally inappropriate when it comes to evaluating the servants of Christ. It is completely contrary to the mind of Christ who Himself stooped to raise others.
This section of verses makes it very clear that it is possible for genuine Christians to behave as and to appear to be unbelievers. The Corinthians' conduct indicated carnality, not lack of eternal life. Prolonged immaturity as a result of carnality is a condition all too prevalent in modern Christianity. Often we mistake carnal Christians for natural men, unbelievers.