Why Does the World Exist?: An Existential Detective Story by Jim Holt Page B

Faubourg Saint-Germain, which adjoined that of a former French prime minister. Now, decades later, he was regaling me with stories of Baron Gottfried von Cramm and Nancy Mitford and the Aga Khan, and urging me to decamp from New York to Paris, where, he claimed, the nightclubs were better and the bacterial flora kept one eternally young.
    Sipping the bracingly pungent herbal stuff the waiter had brought me, I looked around the Flore. At that hour, the café was hardly the “fullness of being” described by Sartre. At a table in the back I spotted Karl Lagerfeld, with his characteristic ponytail, dark glasses, and high white collar, in hushed conversation with one of his muses, who was wearing what looked like black lipstick. Other than that, the place was pretty much empty: le Néant .
    But then there was a noisy burst of activity. A woman of a certain age, evidently an old friend of Jimmy’s, breezed through the front door, accompanied by a pair of what appeared to be Cuban gigolos dressed in shell suits. Giggling and grinding their teeth, this trio sat down with us and began to jabber away. The woman’s face was a sallow mask of leathery jollity, and she talked in a low croak that put me in mind of Jeanne Moreau. I listened with a kind of ironic inattention, but my spirits began to flag.
    It seemed a good time to leave.
    The late-night air was chill and damp. As I started to walk back to my hotel, I glanced across the deserted square at the Église de Saint-Germain-des-Prés, built a thousand years ago. There, in one of the side chapels, reposed the body of Descartes. (Well, most of it, anyway—the whereabouts of his skull and right forefinger is a mystery.)
    I wondered if Sartre, scribbling inside the Café de Flore, used to feel the Cartesian presence from across the square. And Descartes wasn’t the only philosophical specter lurking about. Directly across the Boulevard Saint-Germain from the café is the rue Gozlin, which runs for a single block. It is the last vestige of the rue Sainte-Marguérite, a medieval street that was absorbed into the boulevard during Baron Haussmann’s modernization of Paris in the mid-nineteenth century. There, some centuries ago, stood the Hôtel des Romains, where Leibniz lived for two of the very happy four years of his life he spent in Paris.
    What was Leibniz doing in Paris? As usual with him, intrigue lay behind his visit. He had come to the French capital in 1672 on a secret diplomatic mission to persuade Louis XIV to invade infidel Egypt rather than Christian Germany. The mission was not a success. “As to the project of Holy War,” the Sun King was said to have politely responded to Leibniz, “you know that since the days of Louis the Pious such expeditions have gone out of fashion.” (In the event, France invaded Holland.)
    But Leibniz’s time in Paris was hardly wasted. It was while staying in the Hôtel des Romains, in his thirtieth year—something of an annus mirabilis for him—that he invented the calculus (including the dx notation and the elongated “S” symbol for the integral that are in universal use today). And it was at that hotel, in his room overlooking the present site of the Café de Flore, that Leibniz began to lay the foundations for his later metaphysical philosophy, which would culminate with the posing of the deepest of all questions: Why is there something rather than nothing?
    Both Leibniz and Descartes, in their rationalist way, confronted the mystery of existence. Both decided that the one sure ontological foundation for a contingent world like ours was an entity that carried within itself the logical guarantee of its own existence. Such an entity, they held, could only be God.
    Like his philosophical forebears, Sartre too was a rationalist. Unlike them, he thought that the very idea of God was shot through with contradictions. Either a being has consciousness or it does not. If it does, it is pour soi (“for itself”), an activity rather