The "I Am" is a present tense statement from God to Moses that the voice he is hearing is from the same God as Abraham, Isaac, and Jacob. God could not say "I was" because that would imply that he no longer is. God could not say "I will" because that would imply he was not yet at that time. Jesus said in the present tense to those who said they had Abraham as their father, "I am before Abraham", also because he could not say, "I was", or "I will be", for the same logical reason.
Exodus 3:4 RSV
When the LORD saw that he turned aside to see, God called to him out of the bush, "Moses, Moses!" And he said, "Here am I."
Exodus 3:6 RSV
And he said, "I am the God of your father, the God of Abraham, the God of Isaac, and the God of Jacob." And Moses hid his face, for he was afraid to look at God.
Exodus 3:11 RSV
But Moses said to God, "Who am I that I should go to Pharaoh, and bring the sons of Israel out of Egypt?"
Exodus 3:14 RSV
God said to Moses, "I AM WHO I AM." And he said, "Say this to the people of Israel, 'I AM has sent me to you.'"
Exodus 3:15 RSV
God also said to Moses, "Say this to the people of Israel, 'The LORD, the God of your fathers, the God of Abraham, the God of Isaac, and the God of Jacob, has sent me to you': this is my name for ever, and thus I am to be remembered throughout all generations.
This is a good example of where Greek philosophy has been incorporated into Biblical Theology. The "I Am" is clearly understood to mean that God is saying "I Am the Lord your God, the God of Abraham, Isaac, and Jacob." There is nothing in this statement that says God is the timeless, immovable, and changeless "pure actuality/Unmoved Mover" conceived by Aristotle.
Potentiality is not just "coming to be". Aristotle defined four kinds of change that he saw in nature that explain "potentiality".
"Change of what a thing is is simple coming-to-be and perishing; change of quantity is growth and diminution; change of affection is alteration; change of place is motion."4 He also said everything in nature "changes from being potentially to being in actuality; a thing changes, for instance, from being potentially white to being actually white."5
When we talk about God's potentiality we mean his potential for "doing things", his creativity, not his being, God is not "coming-to-be". God's potentiality is infinite/unlimited in thought and in power. We are finite/limited in thought and power. God is free to think, and do, what ever and however much he wants, when he wants. He is not limited to doing one thing at a time, but he is not doing all that he can possibly do all at once, that would produce "absolute chaos".
--Dave