Leonardo Da Vinci, arguably the central figure of the Renaissance, has long been considered by many a man of mystery. This is in spite of the fact that we have an unparalleled set of documents which illuminate his thought processes, interests, and deepest beliefs. We have access to hundreds of pages of his notes, jottings, sketches, doodles, and musings, including lists of books he read and even scraps of financial records. All of the known Da Vinci papers as of the mid-19th century are included here in this magnificent collection. What emerges is the picture of a rationalist. For instance, Da Vinci was one of the first to question the Biblical account of the Flood. He saw the fossils of sea creatures on the tops of mountains and concluded that these could not have been deposited in a forty day flood. He looked at river valleys and did the math; they could only have been eroded over huge horizons of time.