This seminar will explore what it means for something to be unable to go wrong, using as a focus the Medieval exploration of the question whether God could create a rational creature that was impeccable by nature. The seminar will examine the treatment of this question in the works of St. Thomas, as well as those of other scholastics, as applied to different topics: material bodies, human beings, separated substances, and God. A reading knowledge of Latin is required for this seminar.