But even if we or an angel from heaven should preach to you a gospel contrary to the one we preached to you, let him be accursed.Recently, I’ve been in contact with one of my former students, let’s call him ‘Gary.’ Gary is a fine young man, very bright and very dedicated to being trained for the ministry. Nevertheless I am deeply concerned for him, because Gary rejects the doctrine of the Trinity.
Now, there are some today who would wonder why that should matter, After all, they say, as long as he puts his faith in Jesus and tells others to do the same, who cares whether or not he agrees with me over the details of a 'doctrine' as esoteric as the Trinity. Can’t we just agree to disagree and go on from there? But while that’s fine when it comes to a non-essential issue like “should we use drums during worship?"; being sure about who Jesus is, is not a theological “side issue.” It is central to being “Christian!” In fact, many today have a “false faith” in a “fictional Christ” who cannot save! For no matter how much you believe in a man-made ‘christ’, if the one you’re trusting in does not exist -- in other words, if He is not the biblical Christ -- He can’t do you any good!
That’s why we must always go back to the Bible in order to learn Who Christ really is! It is there, in God’s inerrant Word, that we find God’s own explanation about Who He is and what He’s done. It is there in His word that we read of a God who is One God (Dt 6:4) and yet exists eternally as Three Persons: Father, Son and Holy Spirit (Mt 28:19; 2 Cor 13:14; John 14:16; 1 Pet 1:2, etc). It is through God’s Word that we understand that the Father planned our salvation from eternity, the Son purchased it by His life, death and resurrection, and the Spirit applies it when He opens our hearts to repent and believe the Gospel News!
My prayer is that you will think hard and strive to grasp the truth about Who Jesus is, making sure to measure your faith against the unchanging truth of God’s Word and not just the fragile opinions of man. And while you're at it, pray for ‘Gary’ that God would open His eyes and enable Him to embrace the truth as well!
PS - A good place to being in your study of the Trinity is with James White here or here
He also has a good book on the subject called, "The Forgotten Trinity"
In addition, I would recommend Wayne Grudem, either in his Systematic Theology, or in a series of mp3 sermons
Finally, for a classic and interesting look at the Trinity, there is always Jonathan Edwards' little "Unpublished Essay on the Trinity"