I remember a student once asking Paul Tillich whether it was possible to prove Christianity. Then he went on to explain that Christianity posits its own epistemology. Until you make the leap of faith to enter the arena, there is absolutely nothing logical or reasonable about the Christian belief system, he said. What this means for us is that we cannot by our own reason or strength bring someone to faith in Jesus Christ. All we can do is declare what we ourselves believe, and then rely on the Holy Spirit to see that the faith finds the person.
Logical proof is of no avail in evangelism.
Neither is emotional appeal. I have heard evangelistic preachers play on the emotions of their audiences by telling them how sorry God is that they haven't yet come to him on bended knee. They describe the tears in God's eyes, as he watches lost sinners ignore him. Pretty soon, you start feeling so sorry for God that you want to be saved, just to make God feel better. Emotional appeal like this makes God out to be someone who is just sitting around waiting for people to find him.