Throughout his life Leonardo da Vinci carried notebooks 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 Medici courts, even jokes. The present selection gives coherence to this rich kaleidoscope of ideas. From it emerges the portrait of a true Renaissance man, whose habit of rigorous enquiry, 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.