There is a great deal of speculation about the work of the Holy Spirit. Jesus gives us a clear idea of what the Holy Spirit does in this world. He, the Holy Spirit, bears witness to Jesus. The Holy Spirit is the one who enters our hearts and minds and convicts us that the Bible and the Gospel are true. We make the best effort we can to answer the questions of the lost and declare clearly the Good News of Christ, but it is the Holy Spirit who brings people to true belief.
Do you know in your heart that Christianity is real? If you do, it is because God has opened your eyes by the work of the Holy Spirit (John 3)?