According to Paul’s epistles, the entire human race may be divided into these five (5) categories.

1. The lost unregenerate man who is destined for "the lake of fire": He is the fallen sons of Adam, they are "without God" and therefore "without hope in the world" (Eph 2:12 (below). Paul thus refers to the Ephesian Christians who in the past were "Gentiles in the flesh." This is before they were regenerated (Titus 3:5) and saved by God's grace through faith in Christ.  Then also before Christ's "Spirit of life" was deposited into their spirits (1Cor 6:17), Thus, Paul wrote "That at that time (previously) ye (Gentiles) were without Christ, being aliens from the commonwealth of Israel, and strangers from the covenants of promise, having no hope, and without God in the world" (Ephesians 2:12)
2. The babe in Christ: When a person sees himself as a sinner and trusts Christ as his Saviour, he is “born again” and becomes a “babe in Christ.” Babes can and should grow, so these are fed milk. Everybody loves a baby, but the joy that fills the hearts of loving parents turns to bitterest sorrow if their baby fails to grow.

Thus, Paul wrote “I…could NOT speak unto you as unto spiritual, but as unto carnal (fleshly, non-spiritual), even (that is) as unto BABES in Christ. I have fed you with milk, and not with meat: for hitherto ye were not able to bear [digest] it, neither yet now are ye able” (1Cor 3:1-2).

1. The carnal (fleshly) Christian: This is the yet "fleshly" believer is what the Bible calls "carnal." He who is still bonded with "the World" and the desires of the flesh. He is one who, though perhaps a Christian for many years, has not grown, due to his remaining love of the world and the outer things of the fallen flesh nature. He lives  by "the mind of the flesh." He is still in bondage to the world. He may love and be occupied with so many things other than Christ; sport, TV, entertainment, his work, his achievements, his investments, his new car or house, his social work... all the things that he does for himself. Most of his talk is of these the "things of the world," thus, revealing his heart and the things that have first place in it. He still has to be treated as a babe in Christ. The Corinthian believers were examples of this.

Thus, Paul wrote: "Even so we, when we were children, were in bondage under the elements of the world: (Galatians 4:3)

"For they that are after the flesh do mind the things of the flesh; but they that are after the Spirit the things of the Spirit." Romans 8:5 (KJV)

1. The natural (soulish) man: He is a soulish Christian (Greek, psuchikos, the man of the soul). He lives life by his own mind, emotions, and self-will, not really knowing and therefore not trusting Christ within Him as his new life. He is one who, though perhaps a Christian for many years, has not grown, due to indifference to and neglect of the Word of God and he also has resisted the training of the Spirit in his life. Hence, he lives, and as a pastor may even preach the word, by his soul's self-effort.

The words "natural man" here below is from the one Greek word "psuchikos," meaning, "the man of the soul." Most people wrongly assume the word “natural” here refers to an unsaved man, a non-Christian. However, in context of the book of Corinthians we must note that Paul was writing to the carnal babes at Corinth who actually are Christians who are not spiritual; they are still “natural” (Greek, psuchikos, the man of the soul). This means they live by their soul, the psyche (psuche), their psychological self, their emotions and/or intellect; they live independent of “the Spirit of Christ” within them. Therefore, they cannot receive or know the things of the Spirit (1Cor 2:14).

Bible knowledge is helpful to point us to trust Christ and the truth of “the gospel of the grace of God” to be saved, but this alone does not make one "spiritual." No matter how studied and knowledgeable of the Bible he may be, “the natural man,” living independent of the "Spirit of Christ" in him, does not yet trust and yield to Christ’s “Spirit of life” in his spirit for his discernment. Thus, he is still blinded; due to his being unchanged of heart, he is "the natural man" - “the man of the soul.”

Thus, Paul wrote: “The Natural Man (Gk. psuchikos, the man of the soul) receiveth not the things of the Spirit of God: for they are foolishness unto him: neither can he know them, because they are spiritually discerned” (ICor.2:14).

1. The spiritual Christian: is one who, through prayerful study of the Word of God, and yielding to "the Spirit of Christ" within, has grown to spiritual maturity. He is no longer merely a child of God; he is a “man of God”. He is the opposite of the "natural man."  He knows what life on earth is in accord with God's eternal plan, because he has the mind of Christ working in and through him in his living.

Thus, Paul wrote: "Which things also we speak, not in the words which man's wisdom teacheth, but which the Holy Ghost teacheth; comparing spiritual things with spiritual. 14 But the natural man receiveth not the things of the Spirit of God: for they are foolishness unto him: neither can he know them, because they are spiritually discerned. 15 BUT he that is spiritual judgeth all things, yet he himself is judged of no man. 16 For who hath known the mind of the Lord, that he may instruct him? But we have the mind of Christ." (1 Corinthians 2:13-16)