Humans have potential. We have the potential to get smarter, so we study and learn, and actualize our potential. We have the potential to get stronger, so we lift weights and actualize more strength. We have the potential to gain weight, so we eat more and actualize our potential. So humans have potential that can become actual.
God has no potential, in the sense that He cannot gain more than He already has. He does not have the potential for more wisdom, for He already is actualized all wisdom. He cannot have potential for more power, for He already is actualized infinite power. He does not have the potential for more knowledge, for He already is actualized all knowledge. Therefore God is pure actuality, and has no potential.
This means that what characteristics God has, He has to an infinite degree, so that He is purely actual, with no potential for more. God cannot learn, cannot gain knowledge or power, cannot become more wise than He already is. God cannot become more angry at sin than He already is, and cannot become more joyous at repentence than He already is. God is purely actual (pure act), with no potential.
Further, nothing can move from potential to actual except by something that is already actual. A pile of wood is a potential house, but it cannot move itself from potential to actually being a house, except by someting that is already actual, in this case, a carpenter or an architect. Still further, an effect must pre-exist in the cause. The house must pre-exist in some sense in the architect before it can become actual. The house will be in the architect’s mind before the pile of wood can become a house.
To repeat, nothing in potential can move itself from potential to actual except by something that is already actual. The potential alone cannot actualize itself. Since God in all respects is purely actual with no potential, He can be the cause of moving any potential to actual.
The Bible tells us some things about God’s character. He generally does not cause things unless it is consistent with the nature of the thing. God causes ducks to do duck-like things, because that is the nature of ducks. God causes humans to do human-like things, because that is the nature of humans.
To illustrate how God can cause things withought going against human-like things, we can look at Bible passages such as Acts 4:27-28, which says the following, speaking in a prayer to God: “for truly in this city there were gathered together against your holy servant Jesus, whom you anointed, both Herod and Pontius Pilate, along with the Gentiles and the peoples of Israel, to do whatever your hand and your plan had predestined to take place.” In this passage, we have people like Herod and Pilate, who are not followers of God and have no intention of doing God’s will. Spiritually, they are enemies of God and acting of their own free will. Yet God has determined from eternity what should happen in human history regarding Jesus, and they are accomplishing what God has determined. These men are acting freely, but God can work through man’s free will to accomplish His will. God is actualizing human potential by working through them, without violating their human-like characteristics, which includes free will.
It is the nature of humans to have free will because humans are made in God’s image. God is the primary cause of humans moving from potential to actual, for they cannot actualize their own potential, but still the humans can have completely free will. Thus God can orchestrate all of history, and be in complete control to the point of being the cause of everything moving from potential to actual, yet humans can act with complete free will. This is because God is not limited by anything, including the free will of the creature. God can still cause His will to be accomplished, while working through the free will of man. Thus man can act freely and without coercion, and God be in control, being the primary cause of man and his actions.
Any other explanation either turns man into a brute beast by violating the nature of man as a reasonable being made in God’s image, or limits God by providing a potential that God cannot actualize, or has man actualizing his own potential, which is impossible, for as was shown earlier, only what is already in actuality can move potential to actual.