To change, the thing changing must have the unrealized potential to change. When a thing changes, it must be moved from potentiality to actuality. But the question arises: Can being change?
Ancient thinker Parmenides concluded that being cannot change, since for a being to change would make it move to non-being, which is not change. For the real to cease to exist (become unreal) is not change. Therefore Parmenides held that being cannot change. The apparent change that we observe is therefore an illusion. Parminides believed everthing in the world is one being and change is an illusion. Modern day Buddhists are pantheists who believe that all the change we observe is an illusion.
The first step to the solution is to understand the nature of change. Only by having some continuity from one to the other can we say that the thing has changed. If all components of a thing change, then the former thing has ceased to exist and a new thing has arisen. Instead of change, the former thing ceased existing, and in a separate event a new thing has arisen, neither of which are change. Therefore change is defined as when some component stays the same and some component becomes different.
Next, we must realize the cause of change. To change, a thing must have the potential to change. A plant must have the potential to grow taller before it can actually grow taller. If a thing has no potential, it cannot change.
Further, for a thing to move from potential to actual, the thing must be moved by something that is already actual. To be a cause, the cause must be actual……potential causes are nothing. So for a thing to move from potential to actual, the cause must already be actual so that the cause can do the causing.
So what’s the point? In Thomas Aquinas’ famous five proofs for God, his first way involves things changing from potential to actual. If there is change in the world, something actual must be causing it. An infinite regress of causes is impossible, therefore there must be a first cause of everything that is changing, and this cause must not change. This we know as God.
The theological implications of this are that God cannot change, which gives us the doctrine of immutability of God. If God were to change, He would require potential to change, and would therefore be limited by His potential to change, and something would have to actualize the potential to change in God. Therefore “Jesus is the same yesterday, today, and forever” (Hebrews 13:8) and does not change.