The Jerusalem syndrome is a psychological disorder in which a visit to the holy city triggers delusional and obsessive religious fantasies. In its extreme variety, people wander the lanes of the Old City believing they are biblical characters; John the Baptist, say, or a brawny Samson, sprung back to life.

Archaeologists in the Holy Land like to joke that their profession is vulnerable to a milder form of the syndrome. When scientists find a cracked, oversize skull in the Valley of Elah, it can be hard to resist the thought that it might have belonged to Goliath, or to imagine, while excavating the cellars of a Byzantine church, that the discovery of a few wooden splinters might be part of the cross on which Christ died. This milder malady is nothing new. In the mid-19th century, British explorers who came to Jerusalem with a shovel in one hand and a Bible in the other used the holy book as a sort of treasure map in the search for proof of Christianity's origins.

Now an extreme case of the willful jumbling of science and faith is threatening Jerusalem's precarious spiritual balance. It could not come at a worse time: Israeli-Arab peace talks have stalled; Israel has a hawkish government disinclined to compromise; and radical Islamist group Hamas remains powerful among Palestinians. Any tilt in Jerusalem's religious equilibrium could create a wave of unrest spreading far beyond the city's ramparts. Eric Meyers, who teaches Jewish studies and archaeology at Duke University, says: "Right now, Jerusalem is a tinderbox. "