Must God create a world? Aquinas's answer and Kretzmann's critique
Goodness is by its very nature diffusive of itself and thereby of being. Norman Kretzmann considers that it follows that if God is perfect goodness itself, and goodness is essentially diffusive of itself and of being, then the diffusiveness is something necessary. For this reason, the volition to create is a consequence not of God's free choice, as St. Thomas Aquinas asserts, but of His very nature. Kretzmann's argument is not valid when we consider Aquinas's metaphysics of goodness. Thomas argues that the essence of goodness consists in that it is a perfection in a thing and thus in some way desirable, and so Thomas does not understand the self-diffusion involved in the Dionysian Principle as implying primarily or exclusively the operation of an efficient cause, as does Kretzmann, but that of a final cause. Final cause focuses the active power of the efficient cause so that it produces this rather than that; it specifies the object. Final causality applies to God too. God creates for the sake of an end that must admit to be something that already exhibits perfection and thus goodness. However, the goodness in this case is His own, which is one with His essence. God's end and sufficient reason in creating is His own goodness, and it is that goodness alone that He must will necessarily. Therefore creation is unnecessary, and so God creates in freedom, for love of His own goodness. Moreover, in Aquinas God's essence is His esse, which makes Him self-existing being, not a being that is received in or from any other. If the Creator is self-subsisting and infinite Being, then He needs no being outside of Himself, which implies freedom in the creative act. Kretzmann had a difficulty in conceiving the distinction between God and creation that can be understood fully only within the context of the revelatory tradition from which such conception emerges. Furthermore, in the Christian revelatory tradition goodness is diffused maximally and optimally within the Trinity, which satisfies the diffusiveness principle and renders creation unnecessary.
Rapaglia, Eric Dean, "Must God create a world? Aquinas's answer and Kretzmann's critique" (2015). ETD Collection for Fordham University. AAI3727395.