WRITING THE LIFE of a genius can make someone feel like a fool. After being absorbed by Isaac Newton for twenty years, his biographer Richard S. Westfall confessed that he understood him less well than before he started. The problem was that he and Newton had almost nothing in common. Westfall could not measure himself against such a genius, “ a man not finally reducible to the criteria by which we comprehend our fellow beings. ” Newton was “ wholly other ” ; he did not think the way most people do, nor did he leave a model to follow. Moreover, he knew he was different. People seldom mattered to Newton, and often he treated them as if he wished they had never existed. But when he cared about something, he saw it with incredible, unshakable clarity: the world became transparent to him. Such clarity can seem more than human—at once inspiring and monstrous. Meanwhile the biographer plods along in the cloudy world where most of us live.

As a type of genius, Bobby Fischer had much in common with Newton. Both grew into their gifts in a brown study of intense isolation, while they played games with themselves; and they liked to imagine that they could make their own rules. Both were ruthlessly competitive, so convinced of their superiority that they were reluctant to acknowledge that anyone could rival them except by cheating. And therefore a shadow of fear hung over each of them, the threat of losing a game or making a mistake and being exposed as mortal. Both shrank from the public eye and from publication, though they expected to be idolized and often were. They subscribed alike to outlandish conspiracy theories, and succumbed to the illusion that their genius at chess or mathematics extended to fields like politics and religion, whose secrets only they could decode. No one really knew either of them. Occasionally patrons and friends stepped in to shelter them from harm, but even benefactors had to be on guard lest they be suspected of taking advantage or cashing in on the acquaintance. Late in life, despite their self-sufficiency, Newton and Fischer each became attached to an attractive young person, and each was crushed when the relationship fell apart. And ultimately, though others cared for them at times (and Fischer found a wife), they lived and died alone.

Yet still that peerless, eerie clarity shone through. On one occasion when Fischer was in his prime, I was part of a circle that formed around him while he analyzed an endgame. His fingers flew over the pieces; he crowed over his moves. I was by far the weakest player in that group, which included some world-class grandmasters, yet Fischer gleefully bossed us all as if we were children. Perhaps bravado and arrogance drove the display. But the overwhelming impression it left was of an effortless simplicity. While the spell lasted, the pieces fell naturally into their places, destined to follow the one true path to an end that seemed, in retrospect, inevitable. Hence a complicated position, whose many forking and difficult choices would require any ordinary master to sink into deep thought, resolved into elemental, self-evident logic. Let there be light.

If Bobby Fischer was the greatest chess player of all time (which might be disputed by Garry Kasparov), the reason was not only that he saw further than others or that he worked harder or that he was more relentless. Most of all, it was his ability to see more clearly. Although he made a host of brilliant moves, the ones I could never predict often shocked me by simplifying the game. He would swiftly trade off powerful pieces that most players love to fondle—a dominant bishop, or a knight that commanded key squares—in order to convert his advantage to something neat and direct. The “ truth ” of a position energized him.

During the World Championship match in Reykjavik in 1972, which put chess on the map in this country and everywhere else, Boris Spassky gradually gained some ground by steering into lines that resisted precise calculation. Sometimes he would sacrifice a pawn for no clear reason, except to make the game into a labyrinth or a muddle. In the long run this strategy did not work; Fischer was just too strong to be confused. But the plan cleverly struck at the source of his strength. Newton proved his genius by showing that light is a compound of heterogeneous rays, and that white light is not the absence of color but a mixture of all sorts of colors. At its best, Fischer’s genius reduced the nearly infinite complexities of chess, its dark materials and mysteries, to combinations as clear and bright as white light.