The doctrine of divine impassibility has been much maligned in recent decades by both liberal theologians and more conservative ones who do not fully understand it. Where it is not outright rejected, it is redefined. Some have reformulated the traditional doctrine of divine immutability or unchangeableness to only refer to God’s attributes but not with respect to his relationship with his creatures. They argue that God is relationally mutable and passible while still claiming to hold to a belief in divine immutability. The doctrine of divine impassibility is a subset of the doctrine of divine immutability. God’s immutability describes the impossibility of the potential for change in God. Impassibility states that God does not change with respect to his affections which are his perfections and therefore are not subject to change. God does not experience inner emotional change because he does not have emotions, rather, he is his attributes and his attributes do not change. God’s impassibility not only flows from his immutability, but also from his eternality since he is above time and does not experience time. God cannot be acted upon by any outside force. God’s love is not an emotional state he finds himself in, rather, God himself is love. God is defined by love and his other attributes; they are not things he possesses. His love is not an accidental property that can come and go as we humans experience love.
That means God’s love does not change because love is who God is as one of his attributes and his attributes do not change. God’s response to us based on our standing before him in time does change, but it is not God himself who changes. God is not at one moment loving and then angry or angry and then loving. Instead, he is always eternally loving and eternally opposed to all that is contrary to his holy and just nature. When we are saved, our relationship with God changes, but God does not change. Unlike a human being who has changeable emotions, God is unchangeable in every way. God’s attributes are his perfections; they are not subject to change because they are perfect. That means God cannot actualize a higher degree of love or grow in love for his people. As the Westminster Confession of Faith states, God is most loving, most holy, and most just. His love and other attributes cannot increase or decrease. For God to experience inner emotional change would mean that his attributes change or increase or decrease and therefore are not perfect. That means God is not becoming or constantly taking in new information, but rather, he is the great “I am” who eternally is who he is (Exo 3:14). As one writer comments, “The affirmation of impassibility does not result in removing affections from God; rather, the affirmation of impassibility upholds the fact that God is most loving because He cannot decrease nor increase; He is love! The doctrine of divine impassibility actually stresses the absoluteness of affections in God.”
The language of Scripture concerning God is often analogical rather than univocal in nature. That means Scripture often uses the language of analogy to describe God to accommodate to our human perceptions, explaining actions in terms that we might understand with respect to human actions. Anthropomorphisms are one example of the analogical nature of language concerning God. The authors of Scripture will use human-like language to describe God so that we can better grasp who he is as human beings. An anthropopathism is where the authors of Scripture will use human-like emotions to describe God without intending to communicate a one to one correspondence between us and God. We see an example of this in 1 Samuel 15:35 where God was grieved or regretted that he had made Saul king. But in 1 Samuel 15:29 we read that “the Glory of Israel will not lie or have regret, for he is not a man, that he should have regret.” Numbers 23:19 expresses the same truth: “God is not man, that he should lie, or a son of man, that he should change his mind. Has he said, and will he not do it?” The same exact verb is used in both verses. If we interpret both verses univocally, then we have a contradiction on our hands. But in light of the teaching of the rest of Scripture on the immutability of God, verse 29 should be interpreted univocally and verse 35 should be interpreted analogically. Another example of an anthropopathism in the Bible is Malachi 2:17 where the prophet says, “You have wearied the LORD with your words.” But Isaiah 40:28 says, “He does not faint or grow weary; his understanding is unsearchable.” If both verses are interpreted univocally, then we have a contradiction. Some verses must therefore take precedence over others in defining who God is if we are to make sense of the Bible.
The one who is impassible became passible in the person of Jesus Christ while remaining impassible with respect to his deity. Therefore, the one who is impassible dies with respect to his human nature (Acts 20:28). Everything Jesus does is either with respect to one of his two natures. He does not toggle between one nature and another. As theologians put it, a nature does not subsist outside of a supposit. He acts perfectly according to both natures at the same time. The Son of God who suffered on the cross was at the same time eternally upholding the universe. A divine person who is himself God dies with respect to his human nature. The Father and the Spirit did not die on the cross or ever become incarnate, but were perfectly united with the Son in an inseparable operation when Christ died for our sins. For more information on this topic, I recommend listening to this talk on the subject which has helped me to understand the doctrine of divine impassibility. A recent position paper on the subject is also extremely informative.