Christianity can be proven true using common sense. And that is when analyzing the motives of the early Christians.
Jews wanted a messiah to restore the Kingdom of Israel. Jesus did not do that. So if he was not the messiah, what would be the motive of the Christian Jews to make up a religion where the messiah did not do that? That common sense argument proves that Jesus is the messiah.
Another thing that proves that Christianity is true is the doctrine of hell. While previous religions believed in a hell for the wicked to be punished in the afterlife, Christianity is the first religion that has people who don't believe in it's deity go to hell. Islam borrowed that concept from Christianity. If Christianity is not true, why would the early Christians make up a religion where non believers go to hell. It would not make the religion seem appealing, and their goal was to get converts. This is another proof that Christianity is true and that the early Christians learned about hell from Jesus.
Another thing that proves that Christianity is true is that it forbids sex outside of marriage. People are naturally horny, so what would be the motive to make up a religion that represses sex. That is another proof that Christianity is true.