Before they achieved renown as patrons of the arts and de facto rulers of Florence, the Medici family earned their fortune in banking. But even at the height of the Renaissance, charging interest of any kind meant running afoul of the Catholic Church’s ban on usury. Tim Parks reveals how the legendary Medicis—Cosimo and Lorenzo “the Magnificent” in particular—used the diplomatic, military, and even metaphysical tools at hand, along with a healthy dose of intrigue and wit, to further their fortunes as well as their family’s standing.