To Stir a Restless Heart tells for the first time the story of how Thomas Aquinas conversed with his contemporaries about the dynamics of human nature’s longing for God, and documents how he deliberately utilized Greek, Arabic, Hebrew, and Latin sources to develop a version of Aristotelian natural desire that was uniquely Augustinian: natural desire seeks the complete fulfillment of human nature “insofar as is possible,” and so comes to rest in the highest end that God offers to it. Depending on whether God offers the free gift of grace to humanity, one and the same natural desire can come to rest in knowing God through creatures or seeing God directly.