One of the major ambitions of medieval alchemists was to discover the elixir of life, a sovereign remedy capable not only of healing the body but of transforming it. Given the widespread belief that care for the body came at the cost of care for the soul, it might seem surprising that any Franciscan would pursue the elixir, but those who did were among its most outspoken and optimistic advocates. They believed they could distill a substance that would purify, transmute, and ennoble the human body as well as the soul. In an age when Christians across Europe were seeking material evidence...