Controlled by the flesh/ Controlled by the Spirit.

Those who live according to the sinful nature have their minds set on what that nature desires;

but those who live in accordance with the Spirit have their minds set on what the Spirit desires.

The mind of sinful man is death, but the mind controlled by the Spirit is life and peace (Rom. 8:5).

The natural man does not accept the things that come from the Spirit of God, for they are foolishness to him, and he cannot understand them, because they are spiritally discerned (I Cor. 2: 14).

The entire New Testament---after the death and resurrection of Christ----seems to revolve around the concept of the "natural man," the first-born, the one descended from Adam, vs. the "spiritual man," the second-born, the one descended from Jesus.  When Jesus told Nicodemus that it was necessary for a man to be "born again," He was speaking about the birth of the second man:

If there is a natural body, there is also a spiritual body.  .... the spiritual did not come first, but the natural, and after that, the spiritual.  The first man was of the dust of the earth, the second man, from heaven.  As was the earthly man, so are those who are of the earth; and as is the man from heaven, so also are those who are of heaven.  And just as we have borne the likeness of the earthly man, so let us bear the likeness of the man from heaven.  I declare to you...that flesh and blood cannot inherit the kingdom of God (I Cor. 44-50).

So how are we "born again" of water and the Holy Spirit?   Genesis tells us that God fashioned the first man from the dust of the earth and breathed into his nostrils the breath of life, and "man became a living being."  In speaking to Nicodemus, Jesus likens being 'born of the Spirit' to the wind/ the breath of God.  Nicodemus could not comprehend, even though he was a "teacher in Israel." 

Later, John the Baptist's disciples complained to John that "everyone [was] going to [Jesus]" on the other side of the Jordan.  John's answer was this:  the one who comes from above is above all; the one who is from the earth belongs to the earth, and speaks as one from the earth.  The one who comes from heaven is above all.  He testifies to what he has seen and heard, but no one accepts his testimony....the one God has sent speaks the words of God; to him God gives the Spirit without limit (John 3: 31-34).

Jesus took on the natural man, the first-born, the one whose mind was set (from the beginning) on the flesh, on what was hostile to God.  This is the man (Adam) who died on the cross, who died as we do, slowly and painfully, in order that the second man, the spiritual man might rise from the earth. 

In the desert at the outset of His ministry, Jesus died to Himself and to what the flesh craved---food, the easy way out, the ability to control---in order to receive from the Father what the Spirit desired---obedience, trust, helplessness/ reliance on God.  He continued to walk for three years in the Spirit until the final moment of obedience, trust, helplessness.  Descending into the earth, He was able to overcome the last enemy---death itself---and rise with the power of the Spirit.  Now, breathing on the Apostles, He continues to breathe His very own life into us. 

We walk no longer according to what the sinful flesh/mind desires, but by receiving from Him the breath of God, are empowered to live according to what the Spirit desires.  Receiving from God the "Spirit without limit," He is now able to bring to new birth all who come to Him, those who trust Him to deliver us from the desires of the flesh, those of the natural man---the one who blames Eve, the one who kills Able, the one who seeks to make a name for himself (Tower of Babel).

Christ confers on those who come to Him the new birth, the Spirit of God.