It was only a decade after Nietzsche was carried from Turin to an institution in Switzerland in some form of butterfly net that some of the more remarkable properties of the relic began to surface. While he passed his final days in catatonia, the shroud was exhibited and photographed for the first time. An amateur named Segundo Pia took pictures of the separate frontal and dorsal images of the 6-foot-tall man. These images overlay a set of bloodstains congruent with wounds from the process of torture and crucifixion described in the gospels.

To the naked eye, it's not that impressive -- the lights and darks seem strangely jumbled. But when Pia developed his plates, the negatives revealed positive images of photographic quality, never before seen or suspected, of the bearded man. It seemed the shroud image itself had been, at least since it surfaced in southwest France in the 14th century, a negative that had predated the invention of photography by half a millennium.

Twentieth century examination has found that extensive skeletal detail is subtly visible in the image; vertebrae, the roots of the teeth and bones of the skull show up as they would appear in an X-ray. The most convincing descriptions of how the "image areas" of cloth were formed suggest that a pattern of thread fibers was oxidized and dehydrated from exposure to some form of radiation.

To date, none of the modern students of the cloth who consider it the manufactured hoax of an anonymous medieval artisan have enjoyed anything but complete embarrassment in trying to reproduce it themselves. Those who think it did cover Jesus' body and that the image was formed by an "event" in the tomb are left to discuss why in 1988 the linen cloth was found by carbon dating to be from the 14th century.

When people ask me what I think the cloth is, I usually respond that the barriers to explaining the shroud as a forgery are greater than those to explaining a flaw in the protocol of the C14 dating -- a flaw that might prove a first century origin after all. A great deal of physical data has been compiled and published in peer-reviewed journals by shroud researchers -- many of whom are well-credentialed doctors and scientists who came to the shroud through their specialties, such as forensic medicine. Much of this data indicates that the shroud is, indeed, extraordinary. Nothing in my own experience suggests that religious miracles occur, but I feel no responsibility to try to explain what did happen.

I arrived in Turin just as Nietzsche did for the first time: at midday on a bright Thursday aboard a train from Milan. Like the philosopher, I walked north from the Porta Nuova station in the direction of the Palazzo Reale in search of a room. Nietzsche was immediately intoxicated by the city and wrote to a theologian:

Turin! ... This is really the town I can use now! Aristocratic tranquillity has been preserved here in everything ... a unity of taste, which extends even to the color (the whole city is yellow or reddish brown). And for the feet as the eyes it is a classical place! What safety, what pavements, not to speak of the omnibuses and trams which are so well run they evoke wonder! No, what serious and splendid squares! ... Evenings on the Po Bridge: superb! Beyond Good or Evil!!

Brilliant Careers: Sound and Vision Audio and video highlights of our Brilliant Careers profiles