In his comment, Dr. Charlton refers to two disparate cases concerning the nature of God and Creation—the first being the conventional conceptualization of God or nothing and the unconventional view of God or chaos.
The first case posits God as the ultimate creator of everything and argues that there would be nothing without God. The second case envisions God as a primary creator who shaped and formed Creation from pre-existing “material” (for lack of a better way of putting it) that was chaotic and purposeless.
God or nothing and God or chaos is another angle from which one can view the old creatio ex nihilo versus creatio ex materia debate.
The God or nothing approach insists upon the absolute necessity of God for the simple reason that without him, nothing could exist or be. God not only is—he absolutely must be, for without Him, there would be nothing but a void of nothingness. In other words, I am must be because there is literally nothing on the other side of that thunderous I am.
Every being needs God, but God needs no other beings. No being is utterly necessary but God. This absolute necessity of God relegates everything in existence or being to the state of contingency. Every being in existence is utterly dependent on God in every way imaginable, even when they exercise their God-given freedom to reject God altogether.
However, the God-given free rejection of the Divine Creator does not negate God’s thunderous I am declaration.
The creatures he created from nothing can never return to the nothing from whence they came. They either come to know and worship him or suffer the consequences of their free rejection, the capacity for which God created from nothing.
The God or chaos case envisages God as the primary creator. Without God, there is no Creation, only chaos. God can still say I am, but his necessity takes on an entirely different hue.
The creatures he shaped existed in some form before entering Creation, so he is not necessary for their core pre-existence as beings but crucial to their existence in Creation.
They come to know him and attempt to understand why they are Creation, or they may reject him and, perhaps, choose to return to the chaos from which they emerged.
Since God did not create the freedom driving such a choice, it remains authentically free.
Note added: I'm not sure if returning to pre-existent chaos is possible, but I imagine that God may grant such an option to beings that do not wish to "be" in Creation.