In the work of Leonardo, what role does observation of nature?

In the work of Leonardo, what role does observation of nature (and of the visible world generally) play, and what role is played by imagination, free association, and projection? How do these two aspects of Leonardo’s work relate to each other, and to the problem of representing the infinite and/or the invisible? Discuss, comparing one of Leonardo’s pictures (drawing or painting) to one or more passages from Leonardo’s Notebooks, or to one other text from the course. Write an essay 2000-2300 words in length that responds to one of the following questions. Your essay should involve a close reading of one work of art and one text that we have discussed in class during weeks 1-7.