Abstract
Aquinas argues that an agent's act may be voluntary, involuntary, or even non-voluntary. An agent performs a non-voluntary act on these conditions: (a) the agent does not know the act falls under a certain description D, (b) the act under D is not contrary to the agent's will, and (c) if the agent had known that the act fell under D, the agent would still have performed it. Aquinas's full account of non-voluntary acts is terse and ambiguous and seems to contradict his fuller, more articulate, and philosophically rich views on voluntary and involuntary acts. The appearance of inconsistency, however, is illusory. Once understood, his account of non-voluntary acts clarifies various aspects of his theory of responsibility that are hard to glean from other discussions and reveals just how strongly Aquinas is inclined to Augustinian internalism.