Abstract
In the Questions on charity in the ST, Aquinas considers at length the vices opposed to charity, omitting altogether any Question on a vice opposed to mercy. What does the omission reveal about mercy and its difficulties? First, I reject ready-to-hand explanations of the omission. Second, I consider the relation between mercy and compassion, showing that for Thomas the primary impediments to compassion are less vices than psychological forces irreducible to any single vice. Third, I turn to a different set of obstacles to mercy – acts that can arise from compassion, but do not help the person in need. Given these difficulties, how can Thomas take the practice of virtuous mercy to be generally possible? I conclude with a discussion of suffering and the gift of wisdom.