Do we worship the one true God in truth? Or are ideas of God such that in reality we do not believe in the Christian God, but in some other, just as the Muslim or Jew or Jehovah's Witness does not believe in the Christian God, but in some other?
You may say, how can I tell? Well, the test is this. The God of the Bible has spoken in his Son. The light of the knowledge of his glory is given to us in the face of Jesus Christ. Do I look habitually to the person and work of the Lord Jesus Christ as showing me the final truth about the nature and the grace of God? Do I see all the purposes of God as centering upon him?
If I have been enabled to see this, and in mind and heart to go to Calvary and lay hold of the Calvary solution, then I can know that I truly worship the true God, and that he is my God, and that I am even now enjoying eternal life, according to our Lord's own definition, "Now this is eternal life: that they may know you, the only true God, and Jesus Christ, whom you have sent"(John 17:3)
-J.I. Packer "Knowing God"