Book 1 Chapter 13 Sections 21-24
Finally, Calvin goes to war. Joke. He’s always at war. The Institutes have a perpetual edge, as if Calvin’s arguing against something. Biblical doctrine means firmly holding to and loving truth, and vehemently attacking and dismantling error. There is corresponding love for truth and hate for falsehood in the Christian life.
Here he begins to name specific Trinitarian heresies against which the church should set itself and authoritatively should declare the Word. Part of me was actually left saying: “isn’t Calvin going a bit overboard?” Well, in fact he probably is, as is evidenced by the way he treated Servetus when the latter was captive in Geneva. However one might try, it’s not excusable, although there’s good evidence that Calvin wanted some measure of mercy for the man.
With that in mind, Calvin goes about systematically (surprise!) demolishing the arguments of anti-Trinitarians. He summarizes what he’s going to do near the beginning of the section:
Indeed, if we hold fast to what has been sufficiently shown above from Scripture – the the essence of the one God is simple and undivided, and that it belongs to the Father, the Son, and the Spirit; and on the other hand that by a certain characteristic the Father differs from the Son, and the Son from the Spirit – the gate will be closed not only to Arius and Sabellius but to other ancient authors of error.
In short, Scripture is enough to tell us about God. All we must to is show positively what is true about God therein, and all heresy can be confronted, condemned, and brushed aside as such.
He goes about naming particular anti-Trinitarian heresies: Severtus is mentioned for the first time at length. For him, there is no Trinity, but instead a sort of modalism (where God has different modes that He chooses to display Himself through). He thought of belief in the Trinity as a belief in three gods, and that you couldn’t argue for the Trinity otherwise. Specifically, Servetus thought that Genesis revealed God as Creator, and John revealed God as Logos. Jesus was really God, but only came to be at the moment that God the Father conceived Him to be the next expression of His glory.
Calvin begins to refute these things by going straight to John’s Gospel: Jesus Christ always existed as the Word in eternity past. The Word was both with God and was God… and then became flesh. The Word was not just a separate force; He was God Himself. And then the Word became flesh… the Word Who was both God and separate from God.
Calvin moves on to address heresies that promote the Spirit and Christ being finite creations of the Father that He infused with His a measure of His own deity. But Calvin shows that Christ receives worship as if He was the Father. If Christ receives worship, then one of two possibilities exist: He is God, or He is God’s rival.
Calvin points out that this is the same tension in the way the Father treats Christ: in Philippians 2, Christ is so exulted that it is obvious that He is deity.
… unless he had been God manifested in the flesh he could not have been raised to such a height without God himself striving against himself.
It wouldn’t make sense for Christ to be so exulted by both God and man unless Christ was God.