Engines of Creation by K. Eric Drexler Reviewed by Hans Moravec The Robotics Institute Carnegie-Mellon University Pittsburgh, PA 15213 (412) 268-3829 March 1986 A new approach to miniaturization is being pursued by enthusiasts in the laboratories of both semiconductor and biotechnology companies, and elswhere. Living organisms are clearly machines when viewed at the molecular scale. Information encoded in RNA ``tapes'' directs protein assembly devices called ribosomes to pluck particular sequences of amino acids from their environment and attach them to the ends of growing chains. Proteins, in turn, fold up in certain ways, depending on their sequence, to do their jobs. Some have moving parts acting like hinges, springs, latches triggered by templates. Others are primarily structural, like bricks or ropes or wires. The proteins of muscle tissue work like ratcheting pistons. Minor modifications of this existing machinery are the core of today's biotechnology industry. The visionaries see much greater possibilities. Proteins to do specific jobs can be engineered even without a perfect model of their physics. Design guidelines, with safety margins to cover the uncertainties, can substitute. The first generation of artificial molecular machinery would be made of protein by mechanisms recruited from living cells. Early products would be simple, like tailored medicines, and experimental, like little computer circuits. Gradually a bag of tricks, and computer design aids, would accumulate to build more complicated machines. Eventually it may be possible to build tiny robot arms, and equally tiny computers to control them, able to grab molecules and hold them, thermally wriggling, in place. The protein apparatus could then be used as machine tools to build a second generation of molecular devices by assembling atoms and molecules of all kinds. For instance, carbon atoms might be laid, bricklike, into ultra strong fibers of perfect diamond. The smaller, harder, tougher machines so produced would be the second generation molecular machinery. Drexler calls the entire scheme @i{nanotechnology}, for the nanometer scale of its parts. By contrast today's integrated circuit microtechnology has micrometer features, a thousand times bigger. Some things are easier at the nanometer scale. Atoms are perfectly uniform in size and shape, if somewhat fuzzy, and behave predictably, unlike the nicked, warped and cracked parts in larger machinery. I found the first third of the book, presenting the technological vision, enthralling. Among the wonders are: mechanical computers, with parts sliding and rotating on single molecular bonds, computing at nanosecond speeds; general purpose assemblers and disassemblers with trillions of 100 atom scale robot arms arrayed on a grid, controlled and supplied by polymer ``tape'' molecules, able to construct or analyse nearly anything, atomic layer by atomic layer; a centimeter cube, neuron by neuron, simulation of a human brain operating a million times as fast. Many of the details are sitting ducks for skeptical potshots, but I found the central point convincing, that atomic scale construction is possible, and inevitable, in the forseeable future - within a lifetime. The second part discusses the human benefits. Self replicating machinery, and especially general assemblers, controlled by intelligent design machines, can create a mind boggling abundance for all. Intelligent robots in the trillions, each thousands of times smaller than a cell, can repair and maintain humans from the inside, entering cells and fixing them, molecule by molecule, guided by master blueprints. Immortality becomes trivial; the resources of space can support all. From time to time, like distant thunder, there are hints of potential ``evil'', to be discussed in the third part. Actually, much of the rumbling was my own grumbling. I found the speculations absurdly anthropocentric. Here we have machines millions of times more intelligent, plentiful, fecund, and industrious than ourselves, evolving and planning circles around us. And every single one exists only to support us in luxury in our ponderous, glacial, @i{antique} bodies and dim witted minds. There is no hint in Drexler's discussion of the potential lost by keeping our creations so totally enslaved. Part three offers a number of unconvincing proposals for maintaining this unnatural status quo despite human mischief and nanomachine rebellion. A central image is the ``gray goo'' scenario - rogue replicators escape our controls, and sweep the world in a life-destroying plague. Natural life's defenses are no match for the much smaller, tougher, faster and vastly smarter artificial beings. Drexler's long term solution is a standing army of tame nanomachines to defend us against outbreaks of nano wildlife: a hyper-sophisticated immune system. I have an image of molecular gestapo agents checking identity papers and summarily executing suspicious characters. It won't work, and doesn't deserve to. Drexler proposes to keep the ``good'' machines in that state by making their hardware and software massively redundant, to prevent spontaneous mutations. On the one hand, this puts the defenders at a disadvantage against fleet footed, rapidly evolving, guerilla nanolife, unencumbered by such bureaucratic baggage. On the other, in a battle of wits, strength and numbers is not enough. Genius grey goo might, for instance, infiltrate the guards with its own agents, cleverly disguised, or with Trojan Horse software, and gradually subvert the defense from inside. Besides this, rogues (refugees?) can escape beyond the frontier of controlled space, and there mass for a frontal assault. The book squirms hard to avoid the conclusion that intelligent nanolife, as presented, will, by sheer merit, displace natural life. Liberated, it will carry the human enterprise in unimaginable directions and distances. Is this evil? If you view conventional humanity as the center and end of creation, then yes. If, instead, you see a universe full of untapped, beckoning, potential, then this is a wonderful development. The smarter @i{children} of our minds will explore it, carrying along our hopes and dreams, admittedly dwarfed by their own enormously larger ponderings. Want to go along? Ask Drexler's medical nanobes to rebuild you from inside out in their own image. Want to stay? Perhaps they have an archeological museum in which to accomodate you. Life there may be very much like the utopia the book promises, gently guided by the nanolife curators. This is an interesting book, well worth reading. Drexler's estimated time to these developments is under fifty years. I concur. Our accelerating technology will soon reach a kind of escape velocity. Some of you human chauvinists may even like Drexler's political suggestions.