We live in a spiritual universe. The spiritual is the idea behind the action. The wind that fills the sail. Jesus compared the spiritual to the wind in John 3:8. And like the wind, the spiritual is the unseen force that impacts the physical realm.
The problem with mankind is not physical in nature. We are not the products of a bad environment, a bad education system, or bad political structures. And our problem is not bad behavior. All these are symptoms of the real problem, which is spiritual in nature.
The story of mankind is the Tale of Two Cities. The earthly city, Babylon, and the heavenly city, Jerusalem. And it is the story of two types of citizens - those who are under the rule of the "prince of the power of the air", and those who are under the rule of the Son of God.
Babylon has it's beginnings in the opening chapters of the bible. God's command was to fill the whole earth and subdue it. But the people of Babylon had other ideas. They wanted to unite themselves in a central place in order to glorify the name of man. They said in Genesis 11:4, "Let us build for OURSELVES a city, and a tower whose top will reach into heaven, and let us MAKE OURSELVES A NAME."
Babylon also appears in the ending chapters of the bible in Revelation 17 and 18, and represents the worship of the one world ruler and the economic system which rules the world. The spirit of Babylon is the spirit of a man-centered world. It's all about ME and MAN. James rebukes worldly wisdom in James 3 characterizing it by "jealousy and selfish ambition". The man who is a citizen of Babylon lives a life centered around his own personal ambitions and self-aggrandizement.
Jerusalem is the city of God. And we are told in Hebrews 11:10 that this is the city "whose architect and builder is God." The New Jerusalem, where the people of God will someday dwell, is described for us in Revelation 21 & 22. In the center of this city is the throne of God and the Lamb. And from this throne and from the Lamb flows a river of the water of life. Along this river on each side is a tree of life. These trees produce twelve kinds of fruit every month, and the leaves are for the healing of the nations.
Leaves are photosynthesis receptors that convert light into energy. And the light of this new city is God Himself. These trees are a type of heavenly citizens (Psalm 1:3) - receiving their nourishment from the water of life, or the Spirit of God, and being energized by the light of God, which is the truth of God. And the light energizing these leaves produces the "peaceable fruit of righteousness", as James says, where we live not according to selfish ambition, but rather an "others-centered" life. And the fact that there are two trees could well represent both the Jew and Gentile citizens.
The issue of salvation is an issue of citizenship. Are we being ruled by the "prince of this world", according to the principles jealousy and selfish ambition? Or are we being ruled by the Son of God, who nourishes us with His Spirit and energizes us with His word? Are we living in the kingdom that is "Me-centered", or the kingdom that is "God-centered" and "others-centered". That is the question.
Our natural born citizenship is the the kingdom of Babylon, the kingdom of man-centeredness. The kingdom which Christ calls us to is the New Jerusalem, where we follow King Jesus. Entrance into this kingdom is absolutely free. It's paid for. It is simply a matter of accepting that payment for our citizenship, and swearing our allegiance to the King. Everything else flows from that.
"If you confess with your mouth Jesus as Lord and believe in your heart that God raised Him from the dead, you will be saved." Romans 10:9