Christianity provided a theory about the nature of the human being and about why humans fail to achieve the "good". Humans lie, envy, lust, cheat, hate and betray. One can know and even recognize the good and still go against it. A person can know what is right but fail to desire it. However, Christianity held a high ideal of good. Goodness is intrinsic in Jesus. No heaven is needed as a reward to motivate Jesus to do good. Nor can hell be used as a threat to force obedience. The aim of the Christian life was to develop a good life simply because it was right to be good. As Paul puts it, believers should "be conformed to the image of his Son" and "be imitators of me, as I am of Christ". However, such life does not come naturally to human beings and thus there must be a transformation of one's source of motivation rather than actions alone.
The issue becomes clearer when looking at the law as it appears in the Old Testament. Israel receives commands, judgments, rituals, sabbaths, sacrifices, boundaries, food laws, purity laws and other rules. Law provides a precise definition of what justice, holiness, worship, mercy, obedience and other virtues look like within the realm of God. Such laws guide worship, memory, communal life and political structures. They can direct a person what is right, warn against evils and reveal one's sins. But laws cannot inspire the heart to love what is commanded.
Israelite history reveals again and again that the presence of the law is not enough. In Jeremiah 31:33, God promises to write his law "within them, and I will write it on their hearts." God goes further in Ezekiel 36:26-27 promising, "I will give you a new heart, and a new spirit I will put within you," and also, "I will put my Spirit within you, and cause you to walk in my statutes." These statements by God refer to a need for transformation beyond the reach of mere laws.
Jesus is the starting point of the new human life according to Christianity. Paul puts Adam and Christ side by side. The word Adam means both man or humankind. Romans 5 talks about sin and death introduced by the one man. First Corinthians 15 says, "As in Adam all die, so also in Christ shall all be made alive," calls Christ "the last Adam," and adds, "As was the man of dust, so also are those who are of the dust, and as is the man of heaven, so also are those who are of heaven." The man of dust and the man of heaven are contrasted as representing two forms of mankind: old humanity in its decay and humanity transformed by Christ as its new head.
Paul describes believers as "a new creation" and also writes that God "has delivered us from the domain of darkness and transferred us to the kingdom of his beloved Son". Romans 6 says that those baptized into Christ Jesus are baptized into his death, buried and resurrected in order to "walk in newness of life." The same thing is expressed in Colossians 2 where the believers are declared "buried with him in baptism" and "raised with him through faith." According to Ephesians 2:19, believers are "fellow citizens with the saints and members of the household of God." The old life comes under death with Christ. A new life rises with him. Being in Christ, being transferred into his kingdom, and entering that people belong to the same movement.
In Genesis 19:17, God judges Sodom and instructs Lot and his family to leave the city forever. "Escape for your life. Do not look back." Then in Genesis 19:26, "Lot's wife, behind him, looked back, and she became a pillar of salt." Jesus quotes this event later in Luke saying, "Remember Lot's wife." He adds, "Whoever seeks to preserve his life will lose it, but whoever loses his life will keep it." Lot's wife has left the physical destruction of Sodom, but her allegiance remains with it.
This is how I understood the story of Lot's wife: Sodom represents the old world, that is, the world full of familiarity, reputation, comfort, routines, social practices and a lifestyle that defines one's identity. Lot's wife refuses to leave the condemned old world behind because it feels like home. God closes one world and takes responsibility for the next. The content of faith is more than affirmation of beliefs. It requires one to abandon the claims of the old world over self.
For me, Christianity promised not only that believers would be ready for the coming kingdom. It said that the kingdom had already started ruling and therefore Christians would be ruled by that kingdom while still living on earth. Jesus says the kingdom is "at hand" and "in the midst of you." Paul describes the kingdom as "righteousness and peace and joy in the Holy Spirit", and also describes believers as "fellow citizens". According to Colossians, believers have already been transferred into the kingdom of the Son.
My understanding of the kingdom was influenced by Augustine who wrote in Confessions: "My weight is my love." In City of God he distinguishes between two cities formed "by two loves": the earthly by the love of oneself and the heavenly by the love of God. He also says these two cities are "entangled together in this world, and intermixed until the last judgment effects their separation." Two cities represent two spheres of loyalties and two ways of living. They exist simultaneously now, intertwined with each other, and salvation meant citizenship in one of them.
What held it together for me was this: Christianity did not stop at telling people to do good. It claimed that a person could become good. It also made the purpose of the Christian life on earth clear: to be remade by grace so that this new life itself would point to the cross, bear good works as its fruit, and draw others into the City of God.