The purpose of this post is to sketch an argument for the nonexistence of God based upon the logical incompatibility of divine aseity and the existence of God. In Martin’s and Monnier’s taxonomy of arguments for atheism (see The Impossibility of God, Buffalo: Prometheus, 2003), this argument would be classified as a “deductive disproof of the existence of God.”
The Doctrine of Divine Aseity Formulated
Let us begin by defining the doctrine of divine aseity as follows:
(A1) God does not depend on anything distinct from himself for his existing; and
(A2) Everything distinct from God depends on God’s creative activity for its existing.
The Logical Argument from Platonism
(1) If God as defined by classical theism exists, then everything distinct from God depends on God’s creative activity for its existing. [from A2]
(2) If Platonism is true, then there exist Platonic entities, entities which are distinct from God but do not depend on God’s creative activity for their existence. [from definition of Platonism]
(3) Platonism is true. [premise]
(4) Therefore, God as defined by classical theism does not exist. [from (1)-(3)]
I am well aware that Christian scholars have written numerous defenses of divine aseity against Platonism. I am also well aware that Platonism is controversial in its own right, i.e., independent of the conflict with divine aseity. For both reasons, I do not claim to argue that the argument is sound; rather, I only claim that the argument is valid.
 See, e.g., Bergmann and Bower.