Who are these natural men?
They are what they are by nature, by birth, by practice and by choice (Eph. 2:12; 4:18). Our Lord said, "that which is born of the flesh is flesh" (John 3:6). The natural man will not receive, believe, embrace or welcome the things of the Spirit of God. These things of the Spirit of God have to do with the gospel of the Lord Jesus Christ (John 16:13-15). His person (1 Tim. 3:16), His work as High Priest and Mediator (Heb. 2:17; 9:12) and His glory (Rev. 5:9-14). All the scriptures have a clear and unwavering message that Jesus Christ Himself is everything in salvation (Col. 3:11). These are the things the natural man and the carnal mind counts as foolishness and will not receive (1 Cor. 1:18). He has no capacity to understand them because they are spiritually discerned. He has no appetite to feed upon Christ (John 6:35), no thirst for the water of life (John 4:10-14), no eyes to behold the beauty of Christ (Isa. 53:1-3). To sum this all up, the carnal mind lacks the spiritual nature and life in Christ which can love and appreciate the glorious truths of the word of God. The carnal mind is enmity (deep seated hatred) against God (Rom. 8:7).
Who are these spiritual men?
The text says, "He that is spiritual judgeth (discerns, understands, receives) all things." They are what they are by the grace of God (1 Cor. 15:10). By God’s infinite grace they have been made new creatures in Christ (2 Cor. 5:17). They know what they know by the spiritual revelation of the Holy Spirit, "But as it is written, Eye hath not seen, nor ear heard, neither have entered into the heart of man, the things which God hath prepared for them that love him. But God hath revealed them unto us by his Spirit: for the Spirit searcheth all things, yea, the deep things of God" (1 Cor. 2:9-10). The spiritual man is not the one who is simply religious, but one who has been made righteous in Christ (1 Cor. 1:30). This does not mean that the spiritual man does not have any fleshly nature. He still does have the old nature of the flesh, which is still sinful (Rom. 7:25). However, he has something now that he never did possess before, life in Christ Jesus (1 John 5:20). Nor does this mean that the spiritual man has perfect understanding in regard to all spiritual mysteries. Paul said that we see in part and preach in part (1 Cor. 13:9). But the believer does understand all things necessary to grasp by faith the truth of salvation revealed in Christ (Col. 2:9-10).