Leonardo is famed for his extraordinarily inventive, often prophetic, mind. The radical spirit of inquiry and the sense of proportion manifest in his artistic work characterized his approach to all spheres of knowledge—from the mechanical to the metaphysical. Not only could he conceive of the technical possibility of the submarine centuries before its successful manufacture; he could also anticipate and deplore the destructive uses to which man would put it. Throughout his life he carried notebooks around with him, in which he scribbled down ideas and opinions as they occurred—personal, domestic, scientific, philosophical, artistic—frequently accompanied by explanatory sketches and diagrams. Surviving manuscripts contain drafts of letters, fanciful fables, rough treatises on the art of painting or the power of water, descriptions of the courts of the Medici, even jokes. In this book, Irma Richter gives coherence to this rich kaleidoscope of ideas and impressions. From her representative selection emerges the portrait of a true Renaissance man, whose habit of rigorous inquiry, observation, and experiment, grounded on a philosophic system, led him to conceive of the universe as an organized cosmos corresponding to a work of art.