But now, in his 39th year, Lanier has turned sour on his own futuristic visions. Lanier recently published "One-half a Manifesto" at Edge.org, an online intellectual forum. The 9,000-word treatise rebukes the "resplendent dogma" of today's au courant visionaries: the irrational belief "that biology and physics will merge with computer science." The essay also takes techno-titans such as the roboticist Hans Moravec to task for working to create thinking, self-replicating machines while ignoring the fact that such research will only "cause suffering for millions of people."

Lanier's turnaround is impressive. He is, after all, a man who spent much of the last 20 years telling us that the real world would merge with the virtual, creating new forms of community that would enhance the quality of our lives. The one-time evangelist has suddenly become a skeptic.

"My world has gone nuts for liking computers too much and not seeing them clearly for what they are," he says in an interview with Salon about the essay.

What they are, Lanier argues, is far from the omnipotent engines of destruction envisioned by other scientists-turned-cautionaries such as Sun Microsystems' Bill Joy. Nor are they saviors, declares Lanier. Neither the evil nanobots of Joy's nightmare, nor the poverty-curing "mind children" that Moravec envisions are possible, says Lanier. Simply put, software just won't allow it. Code can't keep up with processing power now, and it never will.

"Software is brittle," he says. "If every little thing isn't perfect, it breaks. We have to have an honest appreciation for how little progress we've made in this area."

On the surface, Lanier's stance appears to resemble that of Joy, the influential programmer who used the pages of Wired magazine to condemn Moravec and others for desiring to build sentient machines without acknowledging the apocalyptic dangers. But Lanier ultimately takes quite a different tack. Joy condemned science for what it could do; Lanier condemns it for failing to recognize what it can't. Lanier's upstart argument yields a uniquely here-and-now version of computer science ethics and an entirely different, but equally frightening form of what Lanier calls "Bill's version ... of the Terror."

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