This writing represents a landing place after years of personally wrestling with this aspect in defining a doctrine of God.
Impassibility defined: Have no passions. The inability to change passion especially regarding suffering. Not being susceptible to emotion.
Immutability defined: Unchanging and fixed, consistent, constant.
These terms are not synonyms, but they are often used together in reference to God. The passages that support both are: Malachi 3:6*, James 1:17, Psalm 18:2, Hebrews 13:8, Numbers 23:9, 1 Samuel 15:29.
The danger that theologians want to avoid is open theism which is a view that defines God as not knowing the future and being as surprised as we are by each turn of events. It is also the view of God looking down through the corridor of time and learning. Open theism is heretical because it denies God being All Knowing and He must learn something.
In the first few centuries as the Christian faith was established, the apologists took on the philosophers of the day in debate. It is those philosophies that shaped the argument and debate. The terms the philosophers used became the foundation for Christians in their effort to defend and define God.
While defining the purpose of humanity this can be seen in St. Agustine (354-430) took a more Platonian bend compared to St. Thomas Aquinas (1225-1275) went in the direction of Socrates. It was Karl Barth (1886-1968) who decidedly began to divorce Christianity from these terms. He determined these were misleading words from the classical doctrine of God in that they do not fully represent whole truth of defining God’s work.
Immutability
The significance of this was great. This frees us to think of our God on better terms. For on the one hand, God is immutable and impassible. The danger of remaining in this camp is seeing God as frozen, removed, dismissive, unloving, remote and unconcerned.
In the words of J.I. Packer, “Our Father is Jesus like and in Him there is no un-Christlikeness at all.” (John 14:18) If you have seen the son, you have seen the Father. The Son is the exact same image as the Father (Colossians 1).
God is immutable but that does not mean he is immobile. It does not mean he is stuck. What it DOES mean is God is faithful. He is faithful to His own character and promise. In these things God does not change. He is always faithful to His own word, and He is always faithful to His own character.
The people if Judah and Israel in the prophets of Isaiah (2:5), Micah (3:7), Hosea (6:1) et. Al. turned away from His decrees. God was faithful to His decree and His promises. God’s covenant people had turned.
There are quite a few passages on God changing: Exodus 32:14, Psalm 106:45, Jonah 3:10, Genesis 6:6.
The justification for these passages can be found that God’s change is relation to His purpose, His character, His promise in relation to his people. God is completely trustworthy. God is responding to His people by observing their behavior and responding appropriately. If man is persistent in rebellious sin, then God will deal with them in His own holiness. He will not show generosity towards them as he had done before.
This is moral fixity. He is dealing with them regarding their morality. He is consistent (immutable) regarding HIS holiness.
Note Psalm 18:25-26 “With the merciful you show yourself merciful; with the blameless man you show yourself blameless; with the purified you show yourself pure and with the crooked you make yourself seem tortuous.
God’s immutability is a MORAL QUALITY. God has a character and a stated view. His is unchanging towards this.
Impassibility
The impassibility can be viewed in a similar way. God has an eternal decree (Acts 2:23; Ephesians 1:11). God is never a victim. Man cannot make Him sorrowful, sad, angry. He is faithful to His purpose.
As Jesus was on the cross man inflicted pain upon him. They arrested and convicted him. This was a divinely inspired situation and plan. It had been eternally decreed that the Son would suffer this way. Jesus was slain before the foundation of the world (Revelation 13:8).
Jesus was obedient to the Father, even to death on a cross (Philippians 2:5ff). This was an extreme example of God suffering in a way that he forever suffers like we do (Hebrews 2:15; 4:15). Christ was not man’s victim on the cross. This was the Father’s plan of love, and it was worked out by Jesus (John 10:17-18).
Man, sometimes defines God like as if He were human, with our exact emotions. This is what the impassibility was meant to address. But it is a term tied more to Greek philosophical understanding and maybe should be reconsidered.
To restate: Our Father is Jesus like and in Him there is no un-Christlikeness at all. Regarding His eternal decree and purposes, there is no change. Towards us there is joy in our repentance and love for His people. For those who spurn, there is fury and judgement.
S.D.G