A theology of the possible, part 2
One major source in my re-examination of the question of divine power and possibility, especially in relation to Tolkien’s work on the nature of sub-creation, has been the fascinating but difficult work of the late philosopher of religion James Ross (†2010). In his provocative 1986 article, “God, Creator of Kinds and Possibilities: Requiescant universalia ante res,” Ross calls into question the standard, Augustinian-Thomistic doctrine that the archetypes or exemplars of creation are themselves uncreated “divine ideas” existing eternally in the mind of God and determined, not by his will, but by his nature or essence. As Ross characterizes such Christianized Neoplatonism, “God’s prismatic self-knowledge ‘refracts’ a universal domain, the divine ideas of all the kinds of things there might be and of all the things of those kinds there might be” (315). In other words, in knowing himself God knows all the ways in which his essence may be imitated and so participated by his possible creatures.
According to Ross, this traditional, “exemplarist” view of divine knowledge and power is beset by a number of logical, metaphysical, and theological difficulties, and in its stead he proposes to posit a “voluntarist” alternative that takes its inspiration not, ironically, from William of Ockham and his nominalist school (who are themselves “exemplarists,” as Ross defines the term), but from a revisionist reading of the metaphysical theology of St. Thomas Aquinas. Similar to Ockham, for example, Ross is concerned with the way in which the exemplarist view seems to limit divine omnipotence (“God’s power is more awesome,” as Ross exclaims at one point), but unlike Ockham Ross does not resort to a bare logical possibility conceived outside of or extrinsic to the mind and essence of God. Instead, Ross suggests that the possibilities open or available to God in the act of creation are something that God himself creates, albeit not arbitrarily. Hence he says that the domain of God’s power “is realized with its exercise. What is possible ad extra is a result of what God does.”
 Rationality, Religious Belief, and Moral Commitment, eds. Robert Audi and William J. Wainwright (Cornell University Press, 1986), 315.