In the supposed recovery of "Classical Theism," Aristotelian philosophy has been smuggled in and, in its Thomistic form, has been uncritically accepted as biblical. Critical thinking is in short supply as many once solid Reformed Evangelicals has succumbed to the dizzying intellect of Thomas Aquinas, believing they have retrieved THE biblical orthodoxy they have been missing their entire lives. This conversion to Thomism is disturbing because it is an implicit rejection of Sola Scriptura, where the philosophy of Aristotle and Thomas determines one's thinking processes instead of the Bible.
One area where critical thinking has disappeared is the embrace of the phrase "act follows being" (agere sequitur esse), a phrase associated with Aristotelianism. The idea is that every action must have a cause, and therefore elucidating the causes of a thing helps us to understand its actions or operations. As a general guide, the principle can hold true for some objects. However, the problem comes with objects with a free will or free agency. Since the notion of free will implies that the will is not determined by nature, although we can agree that the will is influeced and limited by nature, this poses a problem for this principle. If act necessarily follows being, then the will is not free and hard determinism is true.
Why is that so and what does that mean? If act necessarily follows being, then the being of a thing circumscribes and even dictates its actions. For an immutable subject, that implies that the acts of the subject are necessarily so. The subject cannot do otherwise. When applied to God, this means that every action taken by God is a necessary action that He must do in order to be God. This does not make God dependent on creation, for He is still the cause of creation. However, that makes creation necessary, the election of certain people necessary, and the reprobation of other people necessary. There cannot be any contingency in God's relation to the world.
What does this mean for how we think about God? Do we believe God has free will, the freedom to not create this world, and the freedom to not save anyone if He so chooses to? If you hold to the principle that act follows being, then you must necessarily hold to hard determinism even as it pertains to God. You must deny God has free will, for God must always act as the first cause to effect the cosmos. You must deny that God cannot not create the world, cannot not elect certain people and reprobate certain people.
Needless to say, this does not sound like the God of the Bible, who creates as He pleases, and whose election unto salvation is based purely on His good pleasure (Eph. 1:5, 11). God most certainly cannot violate His nature, but His will is not determined by His nature, unless you want to claim there is something in God that makes one sinner electable and the other reprobatable.