the wisdom of their joining together, as this might lead to the evolution of such problematic life-forms asHomo sapiens.

Early in this book, Kurzweil introduces the reader to his visionary theory of technological evolution as a process of creating patterns of increasing complexity and order. He strongly disagrees with previous forecasters of future technological development who relied on an “intuitive linear view of history,” whereas he favors an exponential view. He divides the trajectory of evolution into six epochs, the first four of which refer to the past and present. His Epochs Five and Six are concerned with speculative future developments. In Epoch One atoms and molecules made their appearance. Epoch Two was a period during which life and the precise digital mechanisms for reproducing it appeared. In Epoch Three, early animals’ capacity to recognize patterns became highly sophisticated because of their complex brains, which eventually allowed humans to understand the world through abstract models. In Epoch Four, Kurzweil analyzes the evolution of human-created technologies, from simple machines to advanced computers capable of sensing, storing, and evaluating elaborate patterns of information.

Central to the book’s thesis is Epoch Five, during which, Kurzweil conjectures, the biological intelligence of human brains will be initially augmented and then transcended by nonbiological intelligence (this is the Singularity). During the sixth and final epoch, this nonbiological intelligence will spread beyond Earth into the rest of the universe. As the title of his book makes clear, Kurzweil believes that the Singularity of Epoch Five is near. By using a Moore’s Law-like extrapolation, he calculates that the hardware and software to model human intelligence will be in place by the end of the 2020’s. In other words, he believes that this is when AI machines will pass the Turing test, in which a human interrogator, in electronic contact with an unseen computer and human, is unable to tell the difference between the two. So sure is Kurzweil of the correctness of this prediction that he has a twenty-thousand-dollar wager with a skeptic.

Because his law of accelerating returns is so important to his analyses and predictions, Kurzweil devotes pages to proving that revolutionary technological achievements have been occurring in shorter and shorter times. Unlike Charles Darwin, who tried to eliminate any notion of hierarchical order in his theory of evolution, Kurzweil strongly insists that technological evolution inevitably leads to better machines, and these “higher” machines are appearing at an accelerated rate. For example, it took about fifty years for the telephone to become widely integrated into society, but such integration for the cell phone took only a decade. In 1990 it cost about ten dollars to sequence a base pair in the deoxyribonucleic acid (DNA) molecule, whereas in 2004 it cost only a few cents.

The reason, according to Kurzweil, that technological evolution differs so dramatically from random biological evolution is that intelligent humans can orchestrate the evolution of machines. It took millions of years of biological evolution to produce a human brain, but Kurzweil thinks that it will take only decades for humans to reverse-engineer the human brain to create “strong AI” (artificial intelligence that exceeds human intelligence).

To achieve the computational capacity of the human brain, several new technologies will be necessary. Kurzweil believes that nanotubes, very tiny, elongated structures made from carbon atoms, are the most likely technology to prolong the exponential growth of computer power when ICs are no longer viable. The ability to scan the brain is increasing exponentially and, by using brain-scan information, scientists will be able to simulate neuronal networks that will be functionally equivalent to certain brain regions.

As helpful as these new tools are for modeling the brain, Kurzweil recognizes the importance of understanding the brain from within, and this is where nanobots become essential. Nanobots are very tiny robots, about the size of a human blood cell. By populating the brain with billions of nanobots, scientists will finally be able to grasp the awe-inspiring details of the tiniest brain components and how they work.

According to Kurzweil, three overlapping revolutions will usher in the Singularity, which he predicts will occur in 2045: genetics, nanotechnology, and robotics (GNR). The genetic revolution will allow science to cure degenerative diseases, conquer cancer, and reverse aging. Nanotechnology will allow the inexpensive, molecule by molecule creation of innovative biological and physical artifacts. Some of these tiny machines have already been made, and Kurzweil sees no difficulties in eventually manufacturing molecular devices that will remove toxins from the environment and travel within the human bloodstream to perform various diagnostic and therapeutic tasks. Robots will also play a significant role in the Singularity revolution. According to Minsky, such intelligent robots will become people’s new children.

Once nonbiological intelligence appears, it will evolve much more rapidly than biological intelligence. The Singularity will constitute a change more far-reaching than any previous revolution in human history. Kurzweil envisions a utopian symbiotic society of the human and artificial in which nanobots in human bodies will maintain organs in optimum states of health, and nanobots in brains will allow humans to expand their intelligence trillionfold and to change personalities at will. If wars do occur in this Kurzweilian world, they will be more benign than previous wars, waged with robotic systems that are smaller, faster, lighter, and smarter than present military technologies.

Ultimately, nonbiological intelligence will grow to such an extent that the Earth will be too small to contain it, says Kurzweil, and he thus predicts that nonbiological astronauts, and not biological humans, will be the colonizers not only of this galaxy but also, eventually, of the entire universe. His analysis of such a cosmic future leads him to the interesting conclusion that humans are most likely unique in the universe. If the law of accelerating returns is valid, then it applies throughout the universe to many other extraterrestrial civilizations. At least some of these advanced civilizations should have gone far beyond the Singularity, and they therefore should have made contact with Earth. Because they never have, Kurzweil concludes that they do not exist, and it is humankind’s duty to spread human intelligence throughout the cosmos. If the speed of light is an unconquerable limit, then this will take billions of years, but Kurzweil hopes that ways around this limitation may be found.

Kurzweil calls himself a Singularitarian, and many have seen him as the father of a movement. Some have interpreted his vision as a new religion, with its promise of immortality through technology. He responds that his ideas and values are not substitutes for those of traditional religions, as his vision is not a matter of faith but of understanding technological trends. Nevertheless, his ideas, if they become realized, will transform religions, as they will all institutions. Throughout these revolutionary changes Kurzweil emphasizes that two ethical principles will be preeminent for all: respect for consciousness (his version of the biblical Golden Rule) and the significance of knowledge.

Though he is an unrepentant optimist, Kurzweil recognizes that technologies have not always resulted in unmixed blessings to humanity, and so he analyzes the “deeply intertwined promise and peril of GNR.” In one example he gives, nanobots, particularly if they can self-replicate, could escape into the environment and cause serious damage. Similarly, nonbiological intelligence could escape human control and become totalitarian, leading to the annihilation of biological intelligence. These and other dangers Kurzweil minimizes, believing in the technological fix because, by the time such technologies reach a potentially perilous stage, humans will have created the technologies that will eliminate their detrimental potential. He is more concerned about the negative influence of Luddites and antitechnologists than about the actualized dreams of technophiles.

From responses to his earlier writings, Kurzweil is well aware that he has a plethora of critics. Toward the end of this book he presents his responses to “a panoply” of criticisms. His responses to these criticisms have to be read while keeping in mind that he controls how such critiques are formulated. For example, he spends considerable space responding to John Searle’s arguments attacking his belief that the brain’s mind is simply a computer program, which means, of course, that there is no barrier to the creation of conscious thinking machines. For Searle, a computer program merely manipulates symbols, whereas a human brain attaches meaning to them. Kurzweil finds Searle’s arguments “tautological,” and he insists that Searle does not have a correct understanding of future computer programs that will be based on the reverse-engineering of the brain.

Kurzweil is a futurist, but he insists that he is not writing science fiction. The scientist and science-fiction writer Isaac Asimov once said that he wrote his stories as finger exercises for the future. Similarly, Kurzweil wrote this book so that society can begin to analyze today the implications that the Singularity will have for future. Philosophers have pointed out that Kurzweil makes a logical error in his many extrapolations. Sir Karl Popper has called this the inductivist error. An example of a classic inductivist error is the way in which physicists once extrapolated their many observations of electrons to conclude that all electrons are negatively charged; this conclusion was proved false with the discovery of the positron, the positively charged electron.

Writers who are aware of the history of technology have challenged Kurzweil’s optimism. Edward Tenner, in his Why Things Bite Back: Technology and the Revenge of Unintended Consequences (1996), analyzes numerous examples of the adverse effects of introduced technologies. Cautionary tales such as Mary Shelley’s Frankenstein (1817) and Aldous Huxley’s Brave New World (1932) have warned readers about the arrogance of scientists who overestimate the benefits of technologies while minimizing their hazards. Some of the readers of The Singularity Is Near think that the Singularity could bring about human extinction rather than a utopia. Kurzweil disagrees with these pessimistic views, and he has a simple response to his many critics: Wait and see if the Singularity actually occurs.