The efficient cause provides some difficulty for Aquinas’s appropriation of Lombard’s definition. An efficient cause is the agent that brings about the act. According to Aquinas, Lombard’s definition identifies the efficient cause with God in the part that reads, “which God works in us without us.” Aquinas does not apply this part of the definition to an Aristotelian definition of virtue. The Christian thinkers who preceded Aquinas developed a distinction between the traditional moral virtues that are discussed by philosophers and the theological virtues, which exceed human abilities and are directly about God (Bejcvy 1990). Influenced by this tradition, Aquinas distinguishes between virtues that are described by the philosophers and those that are known and acquired through divine help. Aquinas holds that this part of the definition applies only to those Christian virtues that are caused directly by God and are described as “infused virtues.” Since they exceed natural powers, they cannot be acquired; their acts cannot be performed without divine help.
Osborne seems to be assuming that if we remove the clause, we are removing the need for divine help, but I don't think this is what Aquinas means. Aquinas is quite clear that we need divine help for all virtue, including acquired virtue. If we remove the phrase, “which God works in us without us”, from the Augustinian definition as brought together in Lombard, what we get is the genus that includes both infused and acquired virtue. The difference is really in Osborne's "caused directly by God"; or, in other words, in the "without us" part of the Augustinian definition. As he puts it (ST 2-1.55.4ad6), in acquired virtue God still works in us, but in the way in which He works in every will and nature, i.e., as first mover or remote efficient cause, not as proximate or immediate cause. But it's tricky to be precise about such a matter in a brief space, since we don't have a convenient ethical vocabulary for discussing the infused/acquired virtue distinction, so this might just be inadvertence.
