Anselm on Freedom, part 1
Although they do not address the doctrines of God and creation directly, the works in which Anselm deals most directly and extensively with the question of possibility are his two dialogues on free will, On Freedom of Choice (De libertate arbitrii) and its sequel On the Fall of the Devil (De casu diaboli). Together, these works comprise Anselm’s explanation of how God has made the freedom of choice possible for his rational creatures, and how and in what sense, through this freedom, moral evil has also been made “possible.”
A dialogue between a master and his pupil, Anselm’s On Freedom of Choice opens with the Student asking his Teacher whether “freedom of choice consists in being able to sin and not to sin” (libertas arbitrii est posse pecare et non peccare), as many allege to be the case. The Teacher, as we shall see shortly, denies that freedom of choice includes any such “ability to sin,” yet as I hope to show, he is not as successful in escaping this notion as one might wish him to be. Before considering the Teacher’s response, therefore, it may behoove us to consider the implication’s of the Student’s position on freedom in closer detail. In contemporary philosophical parlance, the characterization of freedom as the ability to sin or not to sin involves the Principle of Alternate Possibilities, the thesis that for any exercise of free choice, two or more equally available and electable options must be present. The possibilism of such a formulation, of course, lies in its characterization of freedom as a capacity to range indifferently (at least so far as the essence of freedom is concerned) over supposedly equally available and electable, but otherwise mutually exclusive options. Freedom, accordingly, would seem to lie not in any suposed intrinsic or natural connection between the will and its actions, but in the comparatively extrinsic consideration that the will should have at its disposal the opportunity not only to perform a given action, but also its opposite. (This suggests, moreover, that the meaning of a given action, so far as it is a free action, is in some sense parasitic upon the meaning of its contrary: to be a free action is for that action to be chosen over against, yet in the presence of, its opposite.) Once again, we see that it is the possible that is allowed to precede and determine what is afterward made actual. More problematic still is the Student’s suggestion that the alternative possibilities supposed to be necessary to comprise freedom lie not in the possibility of doing one good action to the exclusion of another good action, but in an alleged “ability to sin” counterbalancing and in tension with an opposing ability to do the good. What is more, the Student’s formulation would seem to use Augustine’s notion of posse non peccare to invert Augustine’s own privation theory of evil, inasmuch as the ability to do the good has been reconceived not in positive but in privative terms as an “ability not to sin,” thereby suggesting that, if anything, it is the “ability to sin” that is the default orientation of freedom. On such a view of freedom, then, not only is evil effectively elevated into, if not a moral, then at least a real modal and metaphysical possibility—one whose presence is positively required for the existence and exercise of freedom as freedom—but insofar as its spectre now haunts both poles between which freedom operates, evil comes to constitute the total and intrinsic meaning and possibility of freedom. To sin or not to sin—that is the question of freedom.
Seen in this light, it is not surprising to find the Teacher rejecting so dubious an account of freedom in no uncertain terms. He cites as counter-examples the cases of God and the unfallen and confirmed angels, both of whom are free and yet neither of whom possess the Student’s hypothesized “ability to sin.” Over against the possibilism of the Student’s conjecture of an abstract, denatured freedom to sin or not to sin, in other words, the Teacher will take as his provisional characterization of freedom the actual, concrete examples of God and the blessed angels whose freedom, as we shall see shortly, lies not in any alleged ability to prescind itself from the good, but rather in their unwavering commitment to the same.
 On Anselm’s rejection of the Principle of Alternate Possibilities as a requirement for freedom of choice, see, for example, Visser and Williams, Anselm, and Rogers, Anselm on Freedom.