Triangles abounded in the intellectual culture of early modern Europe—the Christian Trinity was often mapped as a triangle, for instance, and perspective, a characteristic artistic technique, is based on a triangular theory of vision. Renaissance artists, for their part, often used shapes and lines to arrange figures into a triangle on the surface of a painting—a practice modern scholars call triangular composition. But is there secret meaning in the triangular arrangements artists used, or just a pleasing symmetry? What do triangles really tell us about the European Renaissance and its most beguiling works of art? In this book, Rebecca Zorach takes us on a lively hunt for the triangle’s embedded significance. From the leisure pursuits of Egyptian priests to Jacopo Tintoretto’s love triangles, Zorach explores how the visual and mathematical properties of triangles allowed them to express new ideas and to inspire surprisingly intense passions. Examining prints and paintings as well as literary, scientific, and philosophical texts, The Passionate Triangle opens up an array of new ideas, presenting unexpected stories of the irrational, passionate, melancholic, and often erotic potential of mathematical thinking before the Scientific Revolution.