Jesus said, "Unless you are converted and become like children, you will not enter the kingdom of heaven" (Matthew 18:3). Jesus is clear that if a person of this world is to be accepted into this other kingdom—the kingdom of heaven—he must be converted. Put very simply, to be converted is absolutely necessary to enter the kingdom of God.
What does the word conversion mean? In the biblical sense, conversion means a turning—a spiritual turning away from sin in repentance and to Christ in faith. It is a dramatic turning away from one path in order to pursue an entirely new one. It involves turning one's back to the system of the world and its anti-God values. It involves a turning away from dead religion and self-righteousness. It involves a complete pivot, an about-face, in order to enter through the narrow gate that leads to life.
Conversion also involves the idea of changing direction. A true spiritual conversion radically alters the direction of one's life. It is not a partial change wherein one is able to straddle the fence between two worlds. It is not a superficial turning, a mere rearranging of the outward facade of a person's life. Conversion is not a gradual change that occurs over a period of time, like sanctification. Instead, a genuine conversion occurs much deeper within the soul of a person. It is a decisive break with old patterns of sin and the world and the embracing of new life in Christ by faith.
This spiritual conversion is so profound that it involves many changes in a person. It involves a change of mind, which is an intellectual change; and a change of view, a new recognition of God, self, sin, and Christ. It involves a change of affections, which is an emotional change, a change of feeling, a sorrow for sin committed against a holy and just God. It involves a change of will, which is a volitional change, an intentional turning away from sin and a turning to God through Christ to seek forgiveness. The entire person—mind, affections, and will—is radically, completely, and fully changed in conversion.
Theologically speaking, regeneration and conversion are two sides of the same coin. Regeneration is God's sovereign activity by the Holy Spirit in the soul of one who is spiritually dead in sin. Regeneration is the implantation of new life in the soul. Regeneration gives the gifts of repentance and faith. On the other side of the coin, conversion is the response of the one who is regenerated. Esteemed British pastor D. Martyn Lloyd-Jones said: "Conversion is the first exercise of the new nature in ceasing from old forms of life and starting a new life. It is the first action of the regenerate soul in moving from something to something." Regeneration precedes and produces conversion. There is a cause-and-effect relationship between these two. Regeneration is the cause, and conversion is the effect. Put another way, regeneration is the root and conversion is the fruit.
To affirm true conversion implies that there is also false conversion. Put simply, there is such a thing as non-saving faith. Not everyone who says, "Lord, Lord" has entered the narrow gate (Matthew 7:21). People may know the truth and may have felt grief regarding their sin, but it is a selfish sorrow over what their sin has caused them to suffer, not how it has offended a holy God. The most stark example of a false conversion we have in Scripture is that of Judas Iscariot. In a counterfeit conversion, there is no death to self, no submission to the lordship of Christ, no taking up a cross, no obedience in following Christ, no fruit of repentance—only empty words, shallow feelings, and barren religious activities. On the contrary, with a true conversion sin is abhorred, the world renounced, pride crushed, self surrendered, faith exercised, Christ seen as precious, and the cross embraced as one's only saving hope.
The whole purpose of conversion is to bring men and women into a right relationship with God. This is why Christ came, and it is the reason for which He died. It was God who was "in Christ, reconciling the world unto Himself " (2 Corinthians 5:19). Conversion is the crying need of the soul. Until one's life is turned from sin to Christ, nothing else matters.