Anselm’s Theology of the Possible, part 15
The Proslogion’s most direct remarks on divine power and possibility appear in his well-known discussion of God’s omnipotence in chapter seven. Anselm introduces the subject of omnipotence in the preceding chapter when, from his premise that God is id quo maior cogitari non potest (“that than which nothing greater can be thought”), he infers that “it is better to be percipient, omnipotent, merciful, and impassible than not.” The first thing we might observe in Anselm’s treatment of God’s omnipotence, accordingly, is his view that such power follows from God’s status as “that than which nothing greater can be thought,” a point I shall return to later. The fact of God’s omnipotence thus established, Anselm’s entire discussion of omnipotence in chapter seven is devoted to reconciling this truth with the paradoxical reality that there are many things we say that God cannot do. In his own version of the infamous question as to whether God can create a rock too heavy for him to lift, Anselm inquires: “But how are you omnipotent if you cannot do everything? And how can you do everything if you cannot be corrupted, or lie, or cause what is true to be false (as, for example, to cause what has been done not to have been done), or many other such things?” In a passage redolent of Lady Philosophy’s argument for the utter impotence of evil in Boethius’s Consolation of Philosophy, Anselm replies:
Or is the ability to do these things not power but weakness? For someone who can do these things can do what is not beneficial to himself and what he ought not to do. And the more he can do these things, the more power misfortune and wickedness have over him, and the less he has over them. So whoever can do these things can do them, not in virtue of his power but in virtue of his weakness. So when we say that he “can” do these things, it is not because he has the power to do them, but because his weakness gives something else power over him… In the same way, then, when someone is said to have the “power” to do or suffer something that is not beneficial to himself or that he ought not to do, by “power” we really mean “weakness.” For the more he has this “power,” the more power misfortune and wickedness have over him, and the less he has over them.
For Anselm as for Boethius before him, whatever function they may serve grammatically in our language, privations such as evil deeds, falsehoods, and corruption represent not a true power on the part of those who do or suffer them, but a form of weakness or impotence. They are not positive possibilities open to acting beings, but certain “un-possibilities,” refusals or deprivations of those real possibilities that belong to things as a consequence of their created actuality. Similar to his near contemporary Peter Damian, Anselm further applies the Boethian (non-)modality of evil to God in a way that allows him to reasonably conclude that, far from God’s omnipotence being somehow threatened or called into question by his “inability” to do these things, divine omnipotence consists precisely in his freedom from such liabilities: “Therefore, Lord God, you are all the more truly omnipotent because you can do nothing through weakness, and nothing has power over you.”
 “Verum cum melius sit te esse sensibilem, omnipotentem, misericordem, impassibilem, quam non esse…” Proslogion 6.
 “Sed et omnipotens quomodo es, si non omnia potes? Aut si non potes corrumpi, nec mentiri, nec facere verum esse falsum: ut, quod factum est, non esse factum, et plura similiter: quomodo potes omnia?” Proslogion 7.
 Proslogion 7.
 On the similarities between Anselm and Boethius here, see D.P. Henry, The Logic of Saint Anselm, 150-4, cited in Whitman, “The Other Side of Omnipotence,” 133n9.