This change has also been viewed more ambiguously. For example, Vinge wrote of machine intelligence in a paper in 1993: "Within 30 years, we will have the technological means to create superhuman intelligence. Shortly after, the human era will be ended."

Although Vinge does not specify whether this is a good or bad thing, the comment echoes another famous quote that the Polish mathematician Stanislaw Ulam attributed to John von Neumann in a 1958 conversation: "The ever-accelerating progess of technology ... gives the appearance of approaching some essential singularity in the history of the race beyond which human affairs as we know them could not continue." The Ulam/von Neumann reference may be the first use of the word singularity in this context.

Kurzweil's understanding of the Singularity, in contrast, is an unclouded one in which machine intelligence and human brains fuse for a future in which human/ machine hybrids invent ever-smarter machines and hybrids, and do this at ever- accelerating rates. They achieve a kind of immortality.

Kurzweil envisions the possibility of downloading brains and reconstituting them, thereby successfully propagating one person's consciousness, bringing a whole new perspective to Alan Turing's take on the question of whether machines can be said to think. (The Turing Test suggests that the important question for artificial intelligence is whether a human judge can discriminate between the responses of another human and those of a machine.)

Even biological immortality is possible, according to Kurzweil, because of what he calls the three overlapping revolutions of GNR -- genetics, nanotechnology and robotics. The superhuman intelligences of the coming decades will know which genes to turn on and off in order to prolong life indefinitely. Nanotechnology will enable the infusion of human bodies with robotic servants to repair biological tissues and aid in the downloading of brains.