A craze for intricate metaphors, referred to as conceits, permeated all forms of communication in seventeenth-century Italy and Spain, reshaping reality in highly creative ways. The Age of Subtlety: Nature and Rhetorical Conceits in Early Modern Europe situates itself at the crossroads of rhetoric, poetics, and the history of science, analyzing technical writings on conceits by such scholars as Baltasar Gracian, Matteo Peregrini, and Emanuele Tesauro against the background of debates on telescopic and microscopic vision, the generation of living beings, and the boundaries between the natural and the artificial. It contends that in order to understand conceits, we must locate them within the early modern culture of ingenuity that was also responsible for the engineer's machines, the juggler's sleight of hand, the wiles of the statesman, and the discovery of truths about nature.