On rumors Leonardo da Vinci drew the image as a reflection of himself
"There is no way of saying for sure. There just aren't images of Leonardo that will tell us this, and he certainly didn't admit to it himself. I do think that you can say that the figure that's in that picture corresponds in nice ways to existing descriptions of Leonardo that exist. He was described as being very finely built, strong, very beautiful with locks of hair that curled and went down to his shoulders. There are a couple of possible renderings of him, one that survives in a sculpture from Florence and another that's in a fresco from Milan, and they both look a bit like that figure as well.
"To me, though, even if you can't say for sure that the figure looks like Leonardo, at a kind of metaphorical level, I absolutely believe that it's a self-portrait in that I see him looking at himself in that picture and trying to make sense of himself."
On da Vinci as a young man
"You have the myth of him as this kind of fully formed genius with a big beard kind of gazing presciently off into the distance and transcending his age. But at the time I'm talking about in the book, which is the 1470s and 1480s, he is coming of age; he's learning the tricks of the trade, he is apprenticing himself to other artists and making mistakes and living it up as well. And then he's trying to make a living, and he's not necessarily doing that well.
"He had a horrible problem with deadlines. He, I think today, probably would have been diagnosed with ADD. He started things and kept starting them again and again and again, getting deflected by his own kind of ravenous mind into doing researches into other things. If you commissioned a painting from him, good luck."
On da Vinci's lack of formal education
"He was a real autodidact. He was raised, in his early years at least, in the town of Vinci and probably didn't receive a whole lot of formal schooling. And that hobbled him in some ways when he got to Florence and then after he moved to Milan where he drew Vitruvian Man in one way, simply because he wasn't very good at Latin.
"... In his notebooks, he even got these touching little attempts of his to teach himself Latin, you know, conjugating verbs and things. And he certainly got better as time went on, but he relied a lot on the help of others. He constantly was writing down in his notebooks people he wanted to consult about this or that question on this or that topic. He must have been both a fascinating guy to spend time with but also probably exhausting."
On whether da Vinci drew the Vitruvian Man as a God figure
"I think there's absolutely that going on, and especially of, you think of it as part of a continuum. ... There are a lot of images of maps of the world and maps of the cosmos where you've got a circle and a square and then this human figure that's at once representing — usually in the Christian context, Christ — but then also the kind of father figure, God.
"... The circle, since ancient times, connoted, you know, things divine and cosmic. It's the perfect shape, that all of its points on its circumference are equidistant from the center, and it was the shape that governed all of the supposed concentric fears that made up the cosmos. And then you've got the human element of things, the square, where you bring things down to Earth and make sense of them, set them right."