Editor's note.

STEPHEN HAWKING, the subject of this month's cover story; "Leaping the Abyss" (page 24), prompts a fascinating and perhaps sordid question: How does such a brilliant mind exist in such a warped and wizened body? By my reckoning, the story's most interesting revelation about the 60-year-old physicist and improbable best-selling author--The Universe in a Nutshell and A Brief History of Time have to rank as two of the most unlikely and unread tomes to ever top the book charts--is that he has been humbled intellectually as well as physically.

To look at the man, of course, is to understand how Hawking has been brutally cut down to size by reality. The Lou Gehrig's disease he has suffered for 20 years has reduced him to a cyborg who can get around only via a motorized wheelchair and who can communicate only via a keyboard and transponder that translate his British thoughts into halting, tinny, American accented speech. He has been robbed even of the ability to chew, so a nurse must spoon-feed him every meal. Such difficulties would overwhelm most of us, but they seem to be little more than trifling inconveniences for Hawking.

Yet he has also been slapped down intellectually--in a way arguably as striking as the details of his physical condition. Back in 1980, "I suggested we might find a complete unified theory by the end of the century," Hawking tells his friend, reason Contributing Editor Gregory Ben-ford. "OK, I was wrong," he says with a computer-generated laugh. "I was a bit optimistic.... But I still think there's a 50-50 chance that we will find a complete unified theory in the next 20 years." At the same time, he grants the possibility that "there is no ultimate theory of physics at all."

In such a moment, Hawking sounds positively postmodern, famously defined by French philosopher Jean-Francois Lyotard as incredulous toward "metanarratives," skeptical about grand theories and belief systems that explain every burp and hiccup...