The Christian writer A.W. Tozer once said, “What comes into our minds when we think about God is the most important thing about us.” What we know about God affects how we know God. And how we know God affects everything in our lives. Theology Proper, that is the study of the doctrine of God, is a crucial and yet remarkably over-looked discipline. As the chairman for our presbytery’s examination committee, I have learned that a major seminary in PCA circles does not include a single book or volume on Theology Proper in their curriculum. Not one book on the doctrine of God! Perhaps God is just assumed. Perhaps it is supposed that everyone is already on the same page with God. Perhaps it is thought that there are more important things to spend time on. Whatever the case, it is indicative that we have not taken Tozer’s words to heart. This is to our detriment.
The Westminster Shorter Catechism #4 asks the important question, “What is God?” When we answer that question, we are doing Theology Proper. We are using words to describe and discuss the attributes of God. These attributes are often categorized as communicable or incommunicable attributes. Communicable attributes are those attributes which can be communicated or expressed in some way by people, though to a lesser degree. God is good. People can be good. God is wise. People can be wise. Incommunicable attributes, on the other hand, are those attributes which cannot be communicated or expressed by people. God is immutable. People change. God is eternal. People are bound in time. God is infinite. People are bound in space. The incommunicable attributes are vitally important because we cannot think of God as just like us, only better. He is wholly other than us. “I am the LORD, and there is no other” (Isa. 45:5).
The attribute of immutability means that God does not change. Everything in creation changes. But God remains. He is the same, his years have no end (Ps 102:26-28). God is unchangeable in his being, thought, will, plans, and decisions. “For I the LORD do not change” (Mal 3:6). In him “there is no variation or shadow due to change” (James 1:17). Simply put, if God were not immutable, he would not be God.
If we view God as perfect, as “someone than whom none greater can be conceived,” then we must see God as immutable. Any kind of variation destroys perfection. If something must vary or change, then it cannot be perfect. For God to be perfect and eternal, it requires him to be immutable. The Puritan theologian Stephen Charnock wrote, “If God doth change it must either be to a greater perfection than he had before, or to a lesser… If to the better, he was not perfect, and so was not God. If to the worse, he will not be perfect, and so he will no longer be God after that change.” Immutability is essential to God being perfect.
Classical theologians describe God as pure being or pure actuality. There is no becoming in God. There is no potential in God. Coaches describe the athlete who isn’t quite at his peak as “having potential.” Real Estate agents describe houses that need some work as “having potential.” Potential requires growth, development, change. Potentiality also means the ability to be affected by something external. God, however, is pure actuality. God is not acted upon. He is, as Aquinas describes, the “unmoved mover.” Everything in the world is moved. If you were to follow that chain to the beginning, you would find God. God as pure act or actuality helps maintain the Creator/creature distinction.
Some object to this attribute by saying an immutable God is a static, inert, or dead God. A God who cannot change cannot interact or be in relationship with his creation. This kind of mutualism has always been held in varying degrees by theologians, and even surprisingly by some well-known evangelical theologians. But this view of God is a caricature. If God is perfect, then far from being inert or dead, God is so active as to be pure actuality. No change to his nature could make him more active.
Others object to the immutability of God by pointing to some passages in Scripture which seem to say that God does change (e.g. Gen 6:6, Ex 32:14). But citing these passages to defend a mutable God requires a myopic hermeneutic. In the moment the passage appears as if God changes. But in context is shows God is doing exactly as he said. Typically, these expressions are anthropopathisms. They are an imposition of human emotions upon God in order to communicate God’s displeasure of sin. Read in this way, the mutability of God disappears.
The immutability of God is a central attribute. In many ways it holds the other attributes together. God’s immutability in time is his eternality. His immutability in space is his omnipresence. His immutability means that he is simple. Charnock says it is the “glory” that belongs to “all the attributes of God” because it is the “center wherein they all unite.” In short, God does not change. A God who changes is not God. This is of great importance for our faith, for if God changes then our salvation would be in doubt. The covenant promises of God are sure and steadfast only because we know God will not change his mind. An immutable God is our Rock (Ps 62:2, 2 Sam 22:2-3). He alone is a God worthy of our worship.
 Barrett, None Greater, 10.
 Quoted in Dolezal, All That Is in God, 19.
 See Dolezal, 21–28.
 Barrett, None Greater, 98.