Anselm’s On the Fall of the Devil, part 10
The Teacher begins his account of this “other cause” for the angels failure to preserve their will for justice by arguing that the devil, more than merely passively failing to will to preserve justice, actually went so far as to actively will his own abandonment of justice. His original justice was lost not through his carelessly dropping it, as it were, but by his intentionally throwing it away. Unsettled by this proposal, the Student attempts to clarify that the will to abandon a thing nevertheless must be preceded by a prior cessation of the will to keep that thing. The reasoning is plausible enough: before one can go about desiring to get rid of a thing, surely he must first become indifferent to the fact of whether or not he retains it. “Who does not see,” the Student asks, “that it is not the case that he [the devil] did not will to keep because he deserted but that he deserted because he did not will to keep? For to one who is keeping something, not-willing-to-keep always precedes willing-to-desert. For someone wills to desert what he has because he does not will to keep it.” Given the course of previous discussions, the Student’s perplexity is appreciable. In On Freedom of Choice the Teacher had admonished him for his possibilist elevation of the ability to sin to the same modal standing within free choice as the ability not to sin; and already in On the Fall of the Devil the Teacher has had to correct him for similarly elevating creaturely non-existence to the same modal status within God’s causal power as their existence. Presumably having learned his lesson and not wanting to make the same mistake a third time, it is tempting to view the Student as now discerning an element of his own earlier errors in the Teacher’s suggestion that the devil fell by actively willing to abandon justice. The angels were created not in a possibilist indifference towards, but with an active, original will for justice. If so, it seems that it would only have been possible (if it is indeed possible) for the devil to arrive at the opposite extreme of willing to abandon justice by first traversing through an intermediate phase wherein he simply failed or ceased in willing that which he was originally given a will for. If no such intermediate stage, however, is deemed necessary to render the will to abandon justice—particularly for someone who already wills justice—as something psychologically possible and accessible, then we would seem to have made an at least partial return to the Student’s earlier, rejected hypothesis that freedom of choice lies in a tension between an ability to sin and an equipotent ability not to sin.
 On the Fall of the Devil 3.
 Ibid: “Quis non videat quia non ideo non voluit tenere, quia deseruit, sed ideo deseruit, quia non voluit tenere? Semper enim tenenti prius est non velle tenere, quam velle deserere. Ideo enim vult aliquis deserere quod tenet, quia non vult tenere.”
 In a different context, Sweeney refers to the Student as “a quick study” who is able to use the Teacher’s own distinctions against him. Sweeney, Anselm of Canterbury, 216.