Leonardo da Vinci's greatest contribution to the arts was his emphasis on technical perfection, which entailed extensive research and a great deal of mathematic acumen. He elevated painting to the level of a science, using detailed sketches of the human body and of natural life to study proportion and scale to a degree unprecedented in Western art. This was what he meant when he said that the "eye was the window on the soul," and he was able to use his work to execute paintings with an incredible degree of precision. The Mona Lisa, the Last Supper, and St. John the Baptist speak to the success of this new, almost scientific approach to art.