Given certain anti-Pelagian assumptions he endorses, Aquinas faces an “arbitrariness problem” explaining why God predestines and reprobates the particular individuals he does. One response to the problem that Aquinas offers—biting the bullet and conceding God’s arbitrariness—has a high theoretical cost. Eleonore Stump proposes a less costly alternative solution on Thomas’s behalf, drawing on his notion that our wills may rest in a state of “quiescence.” Her proposal additionally purports to answer the general question why God reprobates anyone at all. I (...) argue that Aquinas’s understanding of the relationship between divine causation and human freedom prevents him from accepting Stump’s proposal as she herself puts it forward; he couldn’t accept it as an answer to the general question. Nevertheless, I claim, granted one controversial but widely accepted assumption—that he isn’t a divine determinist—Aquinas could accept a slightly modified version of her quiescence solution to the arbitrariness problem. Indeed, there is evidence that he did accept some of its key components. (shrink)