In order to persuade people, you must adapt to these differences. Carson lists eight motivations to use when appealing to non-Christians to believe the gospel. I have combined and simplified his categories down to six:
- Sometimes the appeal is to come to God out of fear of judgment and death. Hebrews 2:14-8 speaks about Christ delivering us from the bondage of the fear of death. In Hebrew 10:31, we are told it is a terrible thing to fall under the judgment of the living God.
- Sometimes the appeal is to come to God out of a desire for release from the burdens of guilt and shame. Galatians 3:10-12 tells us we are under the curse of the law. Guilt is not only objective; it can also be a subjective inner burden on our consciences (Ps 51). If we feel we have failed others or even our own standards, we can feel a general sense of shame and low self-worth. The Bible offers relief from these weights.
- Sometimes the appeal is to come to God out of appreciation for the "attractiveness of truth." Carson writes: "The truth can appear wonderful... [they can] see its beauty and its compelling nature." In 1 Corinthians 1:18, Paul states that the gospel is foolishness to those who are perishing, but to those who are being saved it is the power of God. Yet, immediately after this statement, Paul argues that the wisdom of the cross is the consummate wisdom. Paul is reasoning here, appealing to the mind. He is showing people the inconsistencies in their thinking (e.g. "your culture's wisdom is not wisdom by its own definition"). He holds up the truth for people to see its beauty and value, like a person holding up a diamond and calling for others to admire it.
- Sometimes the appeal is to come to God to satisfy unfulfilled existential longings. To the woman at the well Jesus promised "living water" (John 4). This was obviously more than just eternal life — he was referring to an inner joy and satisfaction to be experienced now, something the woman had been seeking in men.
- Sometimes the appeal is to come to God for help with a problem. There are many forms of what Carson calls "a despairing sense of need." He points to the woman with the hemorrhage (Matt. 9:20-1), two men with blindness (Matt. 9:27), and many others who go to Jesus first for help with practical, immediate needs. Their heart language is, "I'm stuck; I'm out of solutions for my problems. I need help for this!" The Bible shows that Jesus does not hesitate to give that help, but he also helps them see their sin and their need for rescue from eternal judgment as well (see Mark 2:1-12; Luke 17:11-19).
- Lastly, the appeal is to come to God simply out of a desire to be loved. The person of Christ as depicted in the Gospels is a compellingly attractive person. ... There is an instinctive desire in all human beings to be loved. A clear depiction of Christ's love can attract people to want to have a relationship with him.
These are six ways that the biblical authors use to persuade people, and notice what a motley assortment they are. Some are what we might call "sticks," while others are "carrots." ... Sometimes the need is short term... while others want to escape judgment and hell in the long term— an equally practical concern! [Tim Keller, Center Church: Doing Balanced, Gospel-Centered Ministry in Your City (Grand Rapids, MI: Zondervan, 2012), 114-5]
All Christians should want others to turn to Jesus in faith. But does that mean that we should encourage people to turn to Christ for any reason whatsoever? Surely not, for all who reject the health and wealth "gospel" certainly think that turning to Christ in order to be rich and healthy is the wrong reason to turn to Christ (not to mention that it doesn't actually work in most cases). So although we want people to turn to Christ, we want them to turn to Jesus for the right reasons.
Keller, seemingly borrowing from D.A. Carson, here lists 6 motivations for people to turn to Jesus. Now, it is one thing to say that people have less than pure reasons for turning to Christ, which happens many times. It is however another thing if we are to say that these motivations are legitimate reasons and should be promoted. So the question is not whether people have these reasons when they decided to follow Jesus; I am sure many new converts do have one or some of these reasons, but whether we should be promoting them as legitimate reasons like how Keller is doing here.
First however is the exegesis, which is really bad for the most part. The passages in Hebrews is exhortation within the church, not reasons to become a believer. The Galatians passage cited for the second reason is a statement of objective factual guilt, and says nothing about one's subjective feelings of guilt. Psalms 51 was written by David, a regenerate believer, in confessions of his sins; it is not the conversion prayer of an unbeliever. The 1 Corinthians 1 passage does indeed speak about the beauty of the Gospel truth. Paul however was not showing "inconsistency in their thinking" but shooting the unbelievers' thinking down as being foolish and weak, and more importantly the whole epistle was addressed to the Corinthian church to encourage them to stand fast in the "foolishness" of the Cross, not addressed to unbelievers to embrace the beauty of the Gospel truth. The John 4 passage cited for the 4th reason is probably the only good exegesis among the rest, as Jesus did appeal to the Samaritan woman at the well. The fifth reason fails to convince since these are narrations of people seeking Jesus for healing which He did, but that is different from Jesus appealing to them to come to Him because He can help them with their problems. The last reason is merely an observation without biblical support. While empirically likely to be true, that's different from saying that we ought to tell people to come to Jesus so they can feel loved.
The motivations themselves don't seem great either. The first reason, out of fear of judgment and death, seems more akin to having an idea of faith in Christ as being a "hell insurance policy." While certainly better than nothing, fear of damnation by itself is insufficient for true faith in Christ, otherwise the Devil would have long since have this "faith," but rather a person has to actually be broken over his own sins and trust Christ's righteousness alone for salvation. The second reason is purely psychological, and while repentance does sometimes express itself psychologically, it is a grave error to appeal to their subjective psychological state without addressing the objective reality of guilt, for otherwise Christianity becomes a psychological salve, and if another religion offers a better "salve," they will take it.
The third reason is plausible, yet while we can speak about the brilliance of the truths of Christianity, ultimately faith in Christ is not merely intellectual. One finally has to trust in Christ for salvation, and not just think Christianity is the most coherent religion. A person convinced cognitively of the truths of Christianity who however does not apply it to his own life in repentance over his own sins is just as lost as a pagan, in fact twice the son of damnation since they know the truth but held it in unrighteousness! Concerning the 4th, 5th and 6th reasons, the main thing is that Christ did not necessarily promise that all our needs (for love, for help with a problem, for existential longings) would be fulfilled in this life. What if the person comes to Christ and her need is unmet? Will she reject the Christian faith because she did not get what was promised by the evangelist? Yes, Christ do meet the needs of His people, but that does not mean every single thing we desire He will give us. A person who felt lonely will not necessarily be suddenly surrounded by friends after he turned in faith to Christ for example. As for asking Jesus for help with a problem, what if the person asked God for help and God did not seem to answer? Should the person reject the claims of Christianity because God did not "answer" his request as some evangelist claimed He would?
People do have mixed motivations for coming to Christ in faith, and the Good Shepherd will not turn them out just because they don't have the "correct motivations" for coming to Him. But we should not therefore encourage these motivations as if they are good motivations for coming to Him, and most definitely not give promises of God's help where biblical proof is lacking.