There have been, of course, many other insatiable polymaths, and even the Renaissance produced other Renaissance Men. But none painted the Mona Lisa, much less did so at the same time as producing unsurpassed anatomy drawings based on multiple dissections, coming up with schemes to divert rivers, explaining the reflection of light from the earth to the moon, opening the still-beating heart of a butchered pig to show how ventricles work, designing musical instruments, choreographing pageants, using fossils to dispute the biblical account of the deluge, and then drawing the deluge. Leonardo was a genius, but more: he was the epitome of the universal mind, one who sought to understand all of creation, including how we fit into it.

His first principle stated broadly that the most useful art was the one which could most easily be communicated. Painting was communicable to all since its appeal was made to the eye. While the painter proceeded at once to the imitation of nature, the poet's instruments were words which varied in every land. He took the Platonic view of poetry as a lying imitation, removed from truth. He called the poet a collector of other men's wares, who decked himself in their plumage. Where poetry presented only a shadow to the imagination, painting offered a real image to the eye; and the eye, as the window of the soul

The painter who draws merely by practice and by eye, without any reason, is like a mirror which copies every thing placed in front of it without being conscious of their existence.

He had searched to find a scientific basis for art, and discovered it in the imitation of nature, based on rational experience.

Seek knowledge for its own sake. Not all knowledge needs to be useful. Sometimes it should be pursued for pure pleasure. Leonardo did not need to know how heart valves work to paint the Mona Lisa, nor did he need to figure out how fossils got to the top of mountains to produce Virgin of the Rocks. By allowing himself to be driven by pure curiosity, he got to explore more horizons and see more connections than anyone else of his era.

While at Windsor Castle looking at the swirling power of the “Deluge drawings” that he made near the end of his life, I asked the curator, Martin Clayton, whether he thought Leonardo had done them as works of art or of science. Even as I spoke, I realized it was a dumb question. “I do not think that Leonardo would have made that distinction,” he replied.

Leonardo had almost no schooling and could barely read Latin or do long division. His genius was of the type we can understand, even take lessons from. It was based on skills we can aspire to improve in ourselves, such as curiosity and intense observation. He had an imagination so excitable that it flirted with the edges of fantasy, which is also something we can try to preserve in ourselves and indulge in our children.

Kenneth Clark referred to Leonardo’s “inhumanly sharp eye.” It’s a nice phrase, but misleading. Leonardo was human. The acuteness of his observational skill was not some superpower he possessed. Instead, it was a product of his own effort. That’s important, because it means that we can, if we wish, not just marvel at him but try to learn from him by pushing ourselves to look at things more curiously and intensely. In his notebook, he described his method — almost like a trick — for closely observing a scene or object: look carefully and separately at each detail. He compared it to looking at the page of a book, which is meaningless when taken in as a whole and instead needs to be looked at word by word. Deep observation must be done in steps: “If you wish to have a sound knowledge of the forms of objects, begin with the details of them, and do not go on to the second step until you have the first well fixed in memory.

"What genuine painters do is to reveal the underlying psychological and spiritual conditions of their relationship to their world; thus in the works of a great painter we have a reflection of the emotional and spiritual condition of human beings in that period of history. If you wish to understand the psychological and spiritual temper of any historical period, you can do no better than to look long and searchingly at its art. For in the art the underlying spiritual meaning of the period is expressed directly in symbols. This is not because artists are didactic or set out to teach or to make propaganda; to the extend that they do, their power of expression is broken; their direct relations to the inarticulate, or, if you will, 'unconscious' levels of the culture is destroyed. They have the power to reveal the underlying meaning of any period precisely because the essence of art is the powerful and alive encounter between the artist and his or her world." (pg 52)

"Nature is full of infinite reasons which have not yet passed into experience." He conceived it to be the painter's duty not only to comment on natural phenomena as restrained by law, but to merge his very mind into that of nature by interpreting its relation with art.

It was the opinion of Leonardo that the temporary nature of music caused its inferiority to painting. Although durability was in itself no absolute test, — else the work of coppersmiths would be the highest art, — yet in any final scale, permanence could not altogether be disregarded. Music perished in the very act of its creation, while painting preserved the beautiful from the hand of time.

Painting it's a blind man profession. Painter is painting not what he sees but what he feels.

With so much knowledge written down and disseminated and so many ardent workers and eager patrons conspiring to produce the new, it was inevitable that technique and style should gradually turn from successful trial and error to foolproof recipe. The close study of antique remains, especially in architecture, turned these sources of inspiration into models to copy. The result was frigidity — or at best cool elegance. It is a cultural generality that going back to the past is most fruitful at the beginning, when the Idea and not the technique is the point of interest. As knowledge grows more exact, originality grows less; perfection increases as inspiration decreases. In painting, this downward curve of artistic intensity is called by the sug- gestive name of Mannerism. It is applicable at more than one moment in the history of the arts. The Mannerist is not to be despised, even though his high competence is secondhand, learned from others instead of worked out for himself. His art need not lack individual character, and to some connoisseurs it gives the pleasure of virtuosity, the exercise of power on demand, but for the critic it poses an enigma: why should the pleasure be greater when the power is in the making rather than on tap? There may be no answer, but a useful corollary is that perfection is not a necessary characteristic of the greatest art.

This inability to ground his fantasies in reality has generally been regarded as one of Leonardo’s major failings. Yet in order to be a true visionary, one has to be willing to overreach and to fail some of the time. Innovation requires a reality distortion field. The things he envisioned for the future often came to pass, even if it took a few centuries. Scuba gear, flying machines, and helicopters now exist. Suction pumps now drain swamps. Along the route of the canal that Leonardo drew there is now a major highway.