The appeal of string theory among physicists is particularly astonishing in light of the fact that no one knows, as yet, exactly what 'it' is.
It doesn't even have a proper name: The latest, most powerful, incarnation is cryptically called "M" theory--where M can stand for Magic, Mother, Mystery, Matrix or Membrane.
So why do physicists take it seriously? What makes it science rather than superstition or idle philosophizing akin to figuring out how many angels can dance on the head of a pin?
One answer is: String theory strikes many physicists as too beautiful not to be true.
"I think it's the most fantastic set of interconnected rules which has ever been known," said Harvard physicist Andrew Strominger. "Nobody in this field is clever enough to have invented something like that."
Since only nature is ingenious enough to devise such a theory, these physicists argue, it must be rooted in reality.
The more compelling answer is: It works. Over the last few years, string theory has produced a seemingly unending string of what physicists call "string theory miracles."
"It's as if some guys had set out to design a better can opener and wound up with an interstellar space ship," said Harvard physicist Sidney Coleman, one recent convert.
Since 1995, string theory has pulled off a series of spectacular successes that made even its staunchest critics take a second look.
For example, one complex paradox revolved around those empty pits of warped space-time known as black holes. Strominger and his colleagues showed that black holes could be constructed out of strings. Indeed, they showed that under the right conditions, black holes could transform into elementary particles, like water freezing into ice.
The result helped propel string theory to the forefront. "If you have a theory that can come to grips with a problem that's been around for 20 years, it builds confidence," said physicist David Gross, director of the Institute for Theoretical Physics at UC Santa Barbara.
In a second major coup, string theory vastly simplified mathematical tools for dealing with more traditional problems in four-dimensional space, including standard particle physics. Suddenly, the ethereal world of strings had real applications to problems involving known elementary particles.
"These were results other [non-string] physicists could relate to," said physicist Nathan Seiberg of the Institute for Advanced Studies. "It solved problems they'd been bothered by."
In other words, physicists put faith in string theory for the same reason the rest of us put faith in other things we don't understand, like jet planes and computers: They get us places we want to go.
The difference is that at least somebody understands the underlying science of planes and computers, and no one as yet understands what underlies string theory.
Columbia University physicist Brian Greene compares string theory to a computer dropped into the 19th century. It does seemingly miraculous things, but no one can figure out how, for the simple reason that the essential science behind it hasn't yet been invented.
Greene said: "Today's physicists are in possession of what may well be the Holy Grail of modern science, but they can't unleash its full predictive power until they succeed in writing the full instruction manual."