The bible teaches us that although we live in a natural body we don't have to live as a lost person or as a 'natural' man. We can live as God wants each of us to live and that is as a mature, 'spiritual' man. Others that are saved may choose to live much less of a spiritual life than others and they become 'carnal' Christians. Let's look at what God's Word teaches about these three.

I Corinthians 2:14 The lost person, or 'natural' man is one who has not received Christ as Savior so he cannot receive or understand spiritual truth. He tries to understand God with his five senses but without the Holy Spirit cannot receive or discern God's truth. He thinks of God's Word as foolishness.
II Corinthians 4:3-4 The lost person, or the 'natural' man has been blinded by Satan and will not receive the Gospel in order to be saved because they refuse to believe God's Word.
Ephesians 4:17-18 The 'natural' man lives with a lack of knowledge about God and has a hostile , indifferent attitude toward the things of God. Their mind is full of excessive pride and is basically worthless as far as being useful in understanding the Word of God.
John 3:19 Whenever the light of the Gospel is presented to the 'natural' man, he rejects Christ because of their love for the world and the things of the world.

I Corinthians 3:1-3 Paul reprimands these Christians because of their immaturity and their worldly life style. They have received Christ but have not grown at all in the faith and live like the unsaved.
Galatians 4:1-3 As long as the 'carnal' Christian needs to be taught the simple things of the Word and act like the world they will never receive the full inheritance that God wants him to have.
Ephesians 4:14 The 'carnal' Christian is prey to false teachers and religions that lie in wait for those that are not wise in the Word and cannot discern right from wrong.
Hebrews 5:12 Here is the reason that most churches today cannot get enough of God's people to fill the necessary leadership positions that are needed for the church to ever reach the potential that God would like all churches to reach for His glory.

I Corinthians 2:9-13 Paul tells us that the 'Spiritual' man receives and retains spiritual truth from the Spirit of God. Also, the 'Spiritual' man searches the scriptures to make sure he is being taught correctly.
Galatians 5:16-18 The 'Spiritual' man is constantly striving to walk in the Spirit and is very conscious of the spiritual battle that is warring within his soul.
Galatians 5:22-26 The mature, 'Spiritual' man will be bearing spiritual fruit in his or her life never looking for self glory but always finding ways to glorify our Lord.
Galatians 6:10 The 'Spiritual' man in you will want to serve others in any way possible, especially the brethren of the church of God.
Galatians 6:1-2 Notice that Paul is addressing the 'Spiritual' people of the church regarding helping those that are backsliders or in need of compassion and help. Only those that are mature can understand the spiritual needs of other Christians and are willing to respond accordingly.