I challenge any Calvinist to ask to be filled with the Holy Spirit as the Apostles were filled on the Day Of Pentecost.
The Holy Spirit will reveal the Truth to you.
The reason that there is so much division in Christianity is that there are too many Word-only Christians and too many Spirit-only Christians and not enough Spirit And Word Christians.
Jesus said that those who REALLY worship correctly will worship in Spirit And Truth.
The Holy Spirit brings unity in the Body made up of many different members by enabling a single view of Christ and His gift of Grace.
You can't be One With Christ and not One with other people who are In Christ.
You cannot be In Christ without His Word Of Truth and His Spirit Of Truth.