In 1993, when a now-famous New Yorker cartoon appeared with the caption "On the Internet, no one knows you 're a dog," it was already a clich that cyber-space is a magical place where the bodily limits and petty prejudices of the real world no longer hold. But the number of people who log on every day in search of like minds, novel experiences or safe sex continues to grow exponentially, proving that this is a clich with staying power.

Margaret Wertheim offers an explanation for the Internet's appeal, and it goes way beyond the ideas of previous analysts such as MIT sociologist Sherry Turkle, whose 1997 book Life on the Screen interpreted the Net as a playground for our multiple selves. Cyberspace, Wertheim suggests, fills the spiritual vacuum Western science created when it demoted Heaven from a real celestial place-immaterial, yet inhabiting the same universe as ours-to a mere metaphor for the mystery of death.