Gregory Boyd from Do You Believe God is Pure Actuality:
The basis of the classical view of God as pure actuality (actus purus) is the Aristotelian notion that potentiality is always potential for change and that something changes only because is lacks something else. So, a perfect being who lacks nothing must be devoid of potentiality, which means it must be pure actuality.
I think this perspective is misguided on a number of accounts.
First, if all our thinking about God is to be centered on Jesus Christ, the definitive revelation of God (Heb. 1:1-3), I don’t see how we could ever come to the conclusion that God is devoid of potentiality. In Christ, God became something he wasn’t previously – namely, a human being. This entails that God had the potential to become a human being. And this alone is enough to dismiss the “God as pure actuality” idea.