From
Leonardo da Vinci by Walter Isaacson:
What made Leonardo a genius, what set him apart from people who are merely extraordinarily smart, was creativity, the ability to apply imagination to intellect. His facility for combining observation with fantasy allowed him, like other creative geniuses, to make unexpected leaps that related things seen to things unseen. “Talent hits a target that no one else can hit,” wrote the German philosopher Arthur Schopenhauer. “Genius hits a target no one else can see.” Because they “think different,” creative masterminds are sometimes considered misfits, but in the words that Steve Jobs helped craft for an Apple advertisement, “While some may see them as the crazy ones, we see genius. Because the people who are crazy enough to think they can change the world are the ones who do.
What also distinguished Leonardo’s genius was its universal nature. The world has produced other thinkers who were more profound or logical, and many who were more practical, but none who was as creative in so many different fields. Some people are geniuses in a particular arena, such as Mozart in music and Euler in math. But Leonardo’s brilliance spanned multiple disciplines, which gave him a profound feel for nature’s patterns and crosscurrents. His curiosity impelled him to become among the handful of people in history who tried to know all there was to know about everything that could be known.
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.