Descartes' Bones by Russell Shorto Page B

suggests the gulf between that time and ours. Today, or twenty years ago, or a century ago, a student of philosophy learned about Descartes as a philosopher, a man who refashioned the landscape of the mind. For the generation that succeeded him, Descartes was that, but he was also an investigator of nature, and, for these men and women, the two things were intricately connected.
    In 1667, Rohault was forty-seven years old, built like a bulldog, with a personality to match. He could be short to the point of irascible with those who failed to grasp a principle he had repeatedly tried to explain. At least part of the shortness came as a byproduct of zeal. His devotion to the master was such that he had married into the circle of Cartesians. His wife was the daughter of Claude Clerselier, caretaker of Descartes’ writings (many of which were as yet unpublished). Like Descartes himself, Rohault was intoxicated with the new means of comprehending the physical world and seemed to believe that any observation, any datum, from whatever field of inquiry, was liable to tip the balance from ignorance toward knowledge and mastery. He had made himself an authority on astronomy, geography, and anatomy. He wrote a detailed commentary on Euclid’s geometry and how to put its principles to work; his
Traité de physique
remained a standard textbook on physics for decades. And he didn’t restrict himself to the scholarly realm but roamed the alleys of Paris in which various craftsmen practiced their trades, watching them build clocks and distill brandy, querying them, trolling for notions and clues and methods.
    This combination of intellect, acute observation, and missionary fervor came together in Rohault’s weekly demonstrations. There was an element of performance involved, and no doubt some of those who came did so for the show. Colored flames, bubbles, explosions: Cartesianism had become a spectacle. It was also rumored to offer glimpses beyond the material, into the realm of the supernatural, and some were titillated by the possibility of peeking behind the screen of ordinary existence. But Rohault and most of his visitors were after something else. There was an order in nature; one could proceed from the unseen bedrock of philosophical principles—the Cartesian method—by rungs up into the realm of matter and its manipulation. His weekly event was a salon, but one in which people took notes, scribbling fast as they tried to grasp something genuinely new.
    The notes taken by an anonymous lawyer who frequented the
mercredis
have survived. This
avocat
’s account of one evening gives a sense of the scope and the intensity that people from all walks of life brought to the abstract stuff of philosophy. Rohault began the lecture by discussing the two states of waking and sleep—“The first sees true,” the lawyer wrote, “the second false”—followed by a discourse on the study of dreams. In these introductory words, Rohault was asking his audience to develop perspective on the mind and its proper functioning. Then he moved into an analysis of Descartes’ reorientation of how we know. The key, he said, was the “cogito,” which gives us certainty about our individual existence. Everything else, the lawyer noted, is only “probability.” And there, in his carefully wrapping that strange and deeply modern word in quotation marks, this nameless amateur philosopher gives us a shiver of what it must have been like, sitting amid the Louis XIV coiffures and the chalk-and-vinegar aroma of face powder, to first glimpse the horizon of the modern world.
    From here, Rohault moved into Descartes’ division of reality into mind and matter. Remarkable—maybe even limitless—improvements were possible in every field of endeavor, but faster coaches, stronger swords, and more sensitive lenses required a truer understanding of the physical world and how we know it.
    What exactly