Blog 20: 1.12.3 - 1.13.3
After concluding his arguments against idolatry, proving that any use of images in worship is a sacrilege, Calvin turns to a consideration of the Trinity, as taught in Scripture.
In addition to providing a basic definition of the doctrine--there is one and only God in three distinct persons--Calvin introduces some important principles for doing biblical and systematic theology.
One is the principle of accommodation. In speaking of the mystery of God's infinite being, and of the impossibility of measuring him by our own physical senses, Calvin explains why the Bible nevertheless ascribes to him a mouth, ears, eyes, hands, and feet. Of course God does not have a physical body. But by using this familiar imagery to describe himself--lisping, as Calvin calls it--God is accommodating himself to our limited understanding.
The other principle he introduces concerns the use of theological vocabulary. The orthodox definition of the Trinity uses the term "person" to distinguish the Father, the Son, and the Holy Spirit within the one Godhead. But some critics object to this term on the grounds that it is not biblical, but a word of human invention.
Here Calvin defends the appropriate use of terms like "person" (or "Trinity," for that matter) as legitimate labels for biblical truths. Even if they do not come directly from Scripture, theological vocabulary words can help to clarify the complex doctrines of Scripture. Such is the case here, where traditional terminology for the being of God can help us grasp a fundamental truth of the faith: though united in their perfect and undivided essence, the Father, the Son, and the Holy Spirit exist eternally as three persons.