C’est le privilège du vrai génie, et surtout du génie qui ouvre une carrière, de faire impunément de grandes fautes.

It is the privilege of true genius, and above all genius that opens up a new path, to commit great errors with impunity.
—Voltaire

Bene vixit, bene qui latuit. He lived well who concealed well.
—Descartes’s motto

One evening many years ago, when I was in graduate school, I somehow found myself in conversation with a group of graduate students who were studying political science. Almost everything about that conversation is now lost in the mists of time, except one detail. The conversation had turned to the nature of modernity. I brought up Descartes, and was probably just about to utter the word “dualism” or “technology” when a vivid young man who (as I recall) tabulated election results interrupted: “I really don’t see what someone who lived in the seventeenth century could possibly tell us about the modern world.”

The reply, if any, is not recorded. But the incident remained with me as a sort of cautionary tale. Notwithstanding the indifference with which that tabulator of election results regarded the seventeenth century, it is difficult to name an individual whose thinking did more to pave the way for modernity than René Descartes—born though he was in 1596. Everyone knows Descartes’ famous formula Cogito ergo sum. Almost everybody knows—or supposes he knows—that Descartes espoused a relentlessly dualistic philosophy that made an all-but-impermeable