In 1 Corinthians 2:6–16, the natural man is compared to the spiritual man and the carnal man. Verse 14 says, “A natural man does not accept the things of the Spirit of God, for they are foolishness to him; and he cannot understand them, because they are spiritually appraised” (NASB). This verse does not define the natural man, as such; rather, it uses the term to describe one who does not understand God’s words and thoughts. The one who can understand God’s words is a “spiritual” man (verse 15).
Dr. Henry Morris, in the New Defender’s Study Bible, gives this comment on verse 14: “The ‘natural’ man, still unsaved, cannot appreciate spiritual truths. He must first understand Christ’s atoning sacrifice for him, but even that is ‘foolishness’ to him (1:18) until the Holy Spirit Himself convicts him of its reality (John 16:7–11).” Basically, the “natural” man is one who does not have the Holy Spirit residing within him. As Jesus said, “Flesh gives birth to flesh, but the Spirit gives birth to spirit” (John 3:6).
Let’s look at some other uses in the Bible of the word natural. In Romans 11:21 we read, “For if God did not spare the natural branches, neither will He spare you.” In 1 Corinthians 15:44–46, “It is sown a natural body, it is raised a spiritual body. If there is a natural body, then there is also a spiritual body.… However the spiritual is not first, but the natural; then the spiritual.” Ezekiel 44:31 speaks of a natural death. Daniel 10:8 speaks of a natural color. James 1:23 speaks of a natural face, and James 3:15 states, “This wisdom is not that which comes down from above, but is earthly, natural, demonic.”
In 1 Corinthians 2, Paul uses the word natural to refer to someone still in his original (sinful) state. The Greek word psuchikos (“natural”) can be defined as “animal,” as opposed to “spiritual.” Natural men are those who are occupied with the things of this material world to the exclusion of the things of God. They are led by instinct rather than by the Spirit of God. They intuitively choose sin over righteousness. They are the “pagans” Jesus refers to in Matthew 6:32 who only seek after the things of this world.
The supernatural work of God is to change the natural man into a spiritual one. When a person trusts Christ, God exchanges what is natural (received from Adam) for what is spiritual (received from Christ). “As in Adam all die, so in Christ all will be made alive” (1 Corinthians 15:22). The Christian life is, therefore, a supernatural one. We do not walk according to the flesh but according to the Spirit (Romans 8:1).
 Got Questions Ministries. (2010). Got Questions? Bible Questions Answered. Bellingham, WA: Logos Bible Software.