Why God's Unchangeability Is So Important
Christians confess God to be unchangeable. He does not change or mutate. He is immutable. For many today, however, this doctrine seems archaic and odd.
Archaic because the doctrine is called "the immutability of God" and odd because God seems to change. After all, he creates the world, is sometimes angry, and at other times generous. Most of all, God entered into the world of change when he became man, when he became incarnate. The apostle John asserts, "the Word became flesh" (John 1:14).
But despite our perception of God changing, God does not change. Instead, we change and God consistently (read: changelessly) expresses himself towards us. (I wrote on this here). Even if all this is persuasive, you might still think, "So What? Why Does it Matter?" Here's my answer: a changing god is not perfectly compassionate, comforting, or (conceivably) faithful. In other words, a changing god is not God.
Imagine If God Changed
Imagine that God changes. Let's say that you pray for God to be compassionate to you. And God starts being compassionate to you, but he grows in his compassion over ten years. And finally, God shows an absolute love for you that brings you delight. You might enjoy this. But you probably would wish that God gave you this delight ten years prior. And it would at least give you a reason to pause and consider: was God less compassionate to my grandmother, if, say, he is growing in love by learning more day-by-day?
Or consider another scenario. Picture in your mind that you are suffering from a disease. God is your rock, your faithful support. And yet, sometimes his still small voice soothes your pain and gives you hope. But you do something wrong or some event dramatically affects God. He might stop soothing you or being your rock in this dire time.
Or imagine yet another scenario. God promises 2,000 years ago to save anyone who believes in him. God promises to send those who pursue him to heaven and those who hate him to hell. But God grows over 2,000 years and decides to change the plan. Perhaps you relied on God and looked forward to paradise. But when you die you enter into nothingness, oblivion, or even a lake of fire. This god changed the game on you without you knowing.
Reflections
Now, these scenarios might be a bit extreme. If God is love, it seems highly unlikely that he would go back on his promises, even if he grew or changed in what it means for him to be love. It's possible but unlikely.
Still, it's possible.
What's more probable is the first scenario. God could be more compassionate to you than he was to your grandmother. And how exactly would this be a good thing, and how exactly would God be perfect? To be perfect is to love perfectly. But, if he grows in his love, then how can he perfectly love? How can he be essentially love for God is love (1 John 4:8)?
A God who does not change is God. He is reliable. He comforts you as the God of all comfort. He soothes you while you suffer. His promises will faithfully come to pass.
And isn't this infinitely better than the alternative? I think so. And this is why the doctrine of God's immutability matters.