For this reason I subscribe to the common saying that God is the object of faith, yet it requires qualification. For Christ is not without reason called “the image of the invisible God.” This title warns us that, unless God confronts us in Christ, we cannot come to know that we are saved. Among the Jews the scribes obscured with false glosses what the prophets had taught concerning the Redeemer. Yet in spite of this, Christ took to be commonly known, as if received by general agreement, that there is no other remedy for a hopeless condition, no other way of freeing the church, than the appearance of the Mediator. Indeed, Paul’s teaching was not commonly known — as it ought to have been — that “Christ is the end of the law” Yet this is true and certain, as is perfectly clear from the Law itself and the Prophets. I am not yet discussing faith because there will be a more suitable place for it elsewhere. Only let the readers agree on this point: let the first step toward godliness be to recognize that God is our Father to watch over us, govern and nourish us, until he gather us unto the eternal inheritance of his Kingdom. Hence, what we have recently said becomes clear, that apart from Christ the saving knowledge of God does not stand. From the beginning of the world he had consequently been set before all the elect that they should look unto him and put their trust in him.
In this sense Irenaeus writes that the Father, himself infinite, becomes finite in the Son, for he has accommodated himself to our little measure lest our minds be overwhelmed by the immensity of his glory. Fanatics, not reflecting upon this, twist a useful statement into an impious fantasy, as if there were in Christ only a portion of divinity, outflowing from the whole perfection of God. Actually, it means nothing else than that God is comprehended in Christ alone. John’s saying has always been true: “He that does not have the Son does not have the Father.” For even if many men once boasted that they worshiped the Supreme Majesty, the Maker of heaven and earth, yet because they had no Mediator it was not possible for them truly to taste God’s mercy, and thus be persuaded that he was their Father.
Accordingly, because they did not hold Christ as their Head, they possessed only a fleeting knowledge of God. From this it also came about that they at last lapsed into crass and foul superstitions and betrayed their own ignorance. So today the [Muslim] Turks, although they proclaim at the top of their lungs that the Creator of heaven and earth is God, still, while repudiating Christ, substitute an idol in place of the true God.
John Calvin, Institutes, 2.6.4 (Battles edition).