1 Corinthians
2:14 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.
3:1 And I, brethren, could not speak unto you as unto spiritual, but as unto carnal, even as unto babes in Christ.
2 I have fed you with milk, and not with meat: for hitherto ye were not able to bear it, neither yet now are ye able.
3 For ye are yet carnal: for whereas there is among you envying, and strife, and divisions, are ye not carnal, and walk as men?
The natural man in 1 Cor 2:14 does not have to refer to the person who is not born again as some insist.
The natural man referred to in 1 Cor 2:14 signifies the born again believer who is carnal and, in fact, this rendering fits the context of 1 Cor 1 – 3.
The word "natural" is the Greek word psyxikós and the word typically describes the natural ("lower") aspect of humanity, i.e. behavior that is "more of earth (carnality) than heaven."
When we read the first 3 chapters of 1 Corinthians, we see that Paul wrote to the church and pointed out the carnal behavior of the believers.
The church at Corinth was contentious (1 Cor 1:11). They were divided into factions because the believers followed men (1 Cor 3:3-4).
Paul commented that he could go no further in his teaching than the very basics of Christianity – Jesus Christ and Him crucified (1 Cor 2:2) and he fed them with milk and not meat because they were not able to bear it (understand) (1 Cor 3:2).
Born again believers who are "carnal" and who behave like "natural man" cannot understand the wisdom of God in a mystery (1 Cor 2:7) which Paul taught to those who were perfect (1 Cor 2:6) ... not "perfect" as in no sin, but "perfect" as in full grown, adult, mature.
Paul was able to teach those believers who were no longer babes in Christ about the wisdom of God in a mystery, even the hidden wisdom, which God ordained before the world unto our glory (1 Cor 2:7). Paul taught those who needed to be fed the milk of the word (1 Cor 3:1-2) about Jesus Christ and Him crucified (1 Cor 2:2).
However, Paul was unable to teach the hidden wisdom to those who were carnal and who behaved in accordance with who they were in Adam.
That is the meaning of natural man as shown in 1 Cor 2:14.