A paradigm is a mental model about how things are or how they work. Until recently (in historical terms), almost all humans held a mental model in which the earth was the center of the cosmos and around it the sun and stars moved in their orbits. Copernicus suggested that this was a false paradigm, an inaccurate model of how things actually are.
People initially scoffed at the suggestion. They could not visualize a model in which a spinning earth moved around the sun. Theologians, long accustomed to a geocentric universe, even deemed the idea blasphemous and unbiblical. After all, hadn't Joshua commanded the sun - and not the earth - to stand still?
When we humans see something a certain way for any period of time, our brains begin to filter out any information that does not correspond to our understanding. Even when we realize that some facts don't fit, we take for granted that the problem lies with the facts and not with our understanding. This is true of all people, whether modern or primitive, religious or irreligious, highly intelligent or mentally challenged.
There is a paradigm, which persists even in the irreligious world, in which humans earn a reward by doing enough good deeds to outweigh their bad deeds. In western cultures the reward is usually eternal life in heaven. In eastern cultures the reward is sometimes an upwardly mobile reincarnation. In both cultures, the world in which these good and bad deeds are carried out is viewed as morally neutral.
When I first became a Christian, churches were still singing a children's song that fit snugly into this false paradigm. It went like this: "Climb, climb up sunshine mountain, heavenly breezes blow. Climb, climb up sunshine mountain, faces all aglow. Turn, turn from sin and doubting, look to God on High. Climb, climb up sunshine mountain, you and I."
In this paradigm people are faced with an arduous task (climbing higher) in what can be a difficult place (a mountain). But the sun is shining down on them and they just need to keep climbing - keep improving. The biblical paradigm is somewhat different. People may be on a mountain or they may be in a valley but in either case, the mountain and the valley are in enemy-held territory. The world is not neutral.
In the biblical paradigm, people may be born into pleasant circumstances or painful, wealth or poverty, polite society or brutish savagery, but whatever their immediate circumstances, they are born into a rogue spiritual state under illegitimate rule. This is why C. S. Lewis said that "fallen man is not simply an imperfect creature who needs improvement: he is a rebel who must lay down his arms." Conversion in the biblical paradigm is laying down arms, not turning over a new leaf. It involves believing in a new leader, changing sides, and giving loyalty to a different kingdom.
Conversion is analogous to a person who is born in a nation under an illegitimate government. All her life she's been told and has believed that things are the way they should be--she just needs to be a better person. But she's begun to realize this is not true. Then she hears there is an underground, an insurgency, and she's been invited to join. Will she trust the rightful leader? Will she join him and his side?
Confessing Jesus as Lord is a revolutionary thing to do. It means joining the kingdom of God with its different values and rules and culture. It means trusting God's acceptance, in spite of one's offenses, because he offers pardon to rebels through Christ. Conversion doesn't mean becoming a nicer person but becoming a new person, God's person, under his rule.
In this paradigm, faith is not just an intellectual assent to a set of dogma, but a life-commitment to God based on confidence in Jesus Christ. That's why "Genuine conversion is a wrenching experience," as Dallas Willard once wrote. We who have experienced it are no longer the same, not because religion has improved us but because God has removed us, in St. Paul's words, "from the kingdom of darkness and transferred us into the Kingdom of his dear son."