text: Before going to bed Wednesday evening, Caitlin had set up a Google alert for news stories that contained the word "Webmind," and she'd selected the "as it happens" option, meaning she'd be emailed as soon as such a story was indexed. When she crawled out of bed on Thursday at 8:00 a.m., she had 1,143 emails from Google; she couldn't possibly read them all, or even glance at each one, and—
  
  And that drove reality home for her: she couldn't deal with all the news on even one topic, and yet Webmind could handle that, plus countless other things effortlessly. He could as easily give the same level of attention to hundreds, or thousands, or millions, of other individual humans that he gave to her, juggling relationships with whatever number of people wanted them, and not even be slowed down. He could make all of them feel as special as she did. She was not at all sure she liked that thought.
  
  After a moment, Caitlin right-clicked—such a handy feature, that!—on four of the news stories at random and had Firefox open each one in its own tab. She began reading them. She still wasn't good at skimming text, but the word "Webmind" was highlighted each time it occurred, and that let her jump to relevant sentences.
  
  The first one was from the Detroit Free Press:
  
  . . . purport to be from an entity calling itself "Webmind." But experts advise caution about accepting this claim.
  
  Rudy Markov, professor of computer science at the University of Michigan, says, "The language employed in the email message was awfully colloquial. You'd expect much more precision from a machine."
  
  And Gunnar Halvorsen, whose blog "AI, Oh, My!" has long been a popular destination for those interested in artificial intelligence, says that the similarities between the structure of the World Wide Web and that of the human brain have been greatly exaggerated.
  
  "You might as reasonably expect the highway system, which is full of things we call arteries, to actually start pumping blood," he wrote in a posting today.
  
  But Paul Fayter, a historian of science at York University in Toronto, Canada, said, "Teilhard de Chardin predicted this decades ago, when he wrote about the noösphere. I'm not at all surprised to see it come to pass..."
  
  Caitlin clicked on the next tab. This one contained a piece from New Scientist Online.
  
  . . . but trying to trace the origin of Webmind messages has proven difficult. Standard network utilities such as traceroute come up a cropper.
  
  "There's no doubt that botnets are involved," said Jogingder Singh of BT. "That's a typical way to disguise the true origin of a message."
  
  And the disappearance of spam doesn't impress him. "It's long been known that the vast bulk of spam is generated by only a couple hundred spammers," he says. "Doubtless many of them know each other. They could easily decide to refrain from sending spam for a day to make one message stand out. Although I admit to being puzzled by why they're trying this particular scam, which, so far at least, hasn't asked anyone to send money..."
  
  Caitlin smiled at that one. Traceroute, she knew, worked by modifying the time-to-live values stored in the headers of data packets, which were the morsels of information that flew around the Internet. But she and Kuroda had theorized that the actual material making up Webmind's consciousness consisted of mutant packets whose time-to-live counters didn't respond to normal commands.
  
  Still, the notion that the clearing out of spam was the doing of spammers would have struck her as crazy even if she didn't know the truth. People believed millions of nutso things with less evidence than Webmind had put forward for his own existence. Why they were being skeptical now, she didn't know.
  
  She remembered once being in a bookstore with her father, back in Austin. He'd surprised her by speaking up, and not even to her, as they walked down the aisles. "Lady," he'd said, "there's no other kind."
  
  Which had prompted blind Caitlin to ask what was going on. "There was a woman looking at a book entitled Astrology for Dummies," he'd said. People believed in that, but they were doubting this!
  
  Caitlin and her mother spent the morning answering questions from Webmind; it was being inundated with emails, and it wanted advice on how to respond to many of them.
  
  But by noon, she and her mom had to take a break—they had both skipped breakfast and were starving. And, while her mother was making sandwiches for them, Caitlin brought up something that had been bothering her for a few days. "So, um, Mom, I told Bashira that you're a Unitarian."
  
  Everything was fascinating the first time you saw it; Caitlin watched as her mother spread something yellow on the bread. "Guilty as charged," she replied.
  
  She'd been aware back in Austin that her mother disappeared to "fellowships" several times a year—sometimes on a weeknight, sometimes on a Sunday morning—but that was really all she knew about it. "But, um, what does that mean, exactly? Bashira asked, and I didn't know the answer."
  
  "In a nutshell? Unitarians are Christians who don't believe Christ was divine."
  
  That surprised her. "So, you're a Christian?"
  
  Her mom was now dealing cold cuts onto the bread. "More or less. But it's called Unitarianism as opposed to Trinitarianism—none of that Big Daddy, Junior, and the Spook stuff for us."
  
  "Still, aren't Christians supposed to wear crosses?"
  
  "Well, maybe if there are vampires in the area."
  
  Caitlin frowned. "A Christian who doesn't believe Christ was divine? What does that even mean? I mean, if you don't think Jesus is God's son, then—then..."
  
  Her mother poured two glasses of milk. "You don't have to think Darwin is divine to be a Darwinian—you just have to think his teachings make sense."
  
  "Oh. I guess."
  
  She motioned for Caitlin to move out to the dining room, and she brought out two plates, each holding a sandwich, then brought out the glasses of milk. "Jesus is the guy who said, 'Blessed are the peacemakers, ' " her mom said. "That seems pretty good to me." She took a bite of her sandwich. "In fact, there's a good game-theoretical basis for believing that. A guy named Robert Axelrod once organized a game-theory tournament. He asked people to submit computer programs designed to play against other computer programs in an iterated prisoner's dilemma—that's one where you keep playing the game over and over again. He wanted to find out what the optimal solution to the prisoner's dilemma was."
  
  Caitlin took a bite of her own sandwich, and—ah, the yellow stuff had been mustard.
  
  "There were fourteen entries," her mother said. "And, to Axelrod's surprise, the simplest entry—it required just five lines of computer code—won. It was called Tit for Tat, and it had been submitted by Anatol Rapoport, who, as it happens, was at the University of Toronto. Tit for Tat took a very simple approach: start with cooperation, then do whatever the other player did on the previous move. To put it another way, Tit for Tat starts off as a peaceful dove, and only becomes a hawk if you become one first. But as soon as you stop defecting, it goes back to cooperating—it's a peacemaker, see?"
  
  "Cool," said Caitlin, taking another bite.
  
  "Axelrod spent a lot of time trying to figure out why Tit for Tat beat everything else. He decided it was because of its combination of being nice, retaliatory, forgiving, and clear. By nice, he meant it was never the first to defect. And its retaliation—defecting back if you defected against it—discouraged the other side from continuing to defect after trying it once. Its forgiveness helped restore mutual cooperation—it didn't hold a grudge; as soon as you went back to cooperating, it went back to cooperating, too. And by clarity, Axelrod meant Tit for Tat's strategy was easily understandable by the other player."
  
  Caitlin thought about all that—a fair bit of complexity, and even the appearance of advanced, reasoned, ethical behavior—emerging from something so simple. It reminded her of—
  
  Of course!
  
  It reminded her of cellular automata, of the processes she could see in the background of the World Wide Web that had apparently given rise to Webmind: a simple rule or set of rules that caused packets in the background to flip back and forth between two states, generating complex patterns. Could an endlessly iterating prisoner's dilemma, or some other game-theoretical problem, be the rule underlying Webmind's consciousness? That'd be cool.
  
  But something else was puzzling her, too. "Why's it called Tit for Tat? What do tits have to do with it?"
  
  Her mother tried to suppress a grin. "It's an old phrase, and it's been distorted over the years. It used to be tip for tap—and both 'tip' and 'tap' mean to strike lightly and sharply."
  
  "Oh." Not nearly as interesting. "You called Tit for Tat a peacemaker—but isn't tipping and tapping really all about getting even?"
  
  "Well, that's one way of looking at it; it is retaliatory."
  
  "And, um, you said that this has something to do with Jesus. Getting even is so Old Testament. The New Testament has Jesus saying—um, something about not doing that."
  
  Caitlin's mother astonished her by quoting scripture—accurately, she presumed; it was something she'd never heard her do before. " 'Ye have heard that it hath been said, An eye for an eye, and a tooth for a tooth: But I say unto you, That ye resist not evil: but whosoever shall smite thee on thy right cheek, turn to him the other also.'"
  
  "Um," said Caitlin. "Yeah. Like that." She paused. "So, what's the game-theoretical strategy for that?"
  
  "That's what we call Always Cooperate—or AllC, for short, "All" and the letter C: you cooperate no matter what the other person does. Except..."
  
  "Yes?"
  
  "Well, there's more to it than that. The next verses say, 'And if any man will sue thee at the law, and take away thy coat, let him have thy cloak also. And whosoever shall compel thee to go a mile, go with him twain.' 'Twain' means 'two'—that's where the phrase 'go the extra mile' comes from. So, it's all about not just giving them what they want, but giving them more than they asked for. I don't know, call it DoubleAllC, or something like that."
  
  "But... hmmm." Caitlin frowned. "I mean, you can't play DoubleAllC very long—you'll run out of stuff." But then she got it. "Ah, but that's the Christian thing, right? The reward isn't in this life, it's in the next one."
  
  "For a lot of Christians, yes."
  
  "But, um, if you don't believe Christ is divine, Mom, do you believe in heaven?"
  
  "No. When you die, you're gone."
  
  "So does DoubleAllC, or even just plain old Always Cooperate, really make sense for a Unitarian—for someone who doesn't believe there's a reward to be had in an afterlife? I mean, DoubleAllC and AllC can't win unless they're playing against people using the same strategy. And you obviously aren't—not in the scenario described: you've been struck on one cheek first, so you know you're playing against someone who defects at least part of the time. In what game-theory way does turning the other cheek make sense? I mean, presumably the other guy is just going to hit you again."
  
  Her mother lifted her eyebrows. "Ah, but see, you're missing something. The easiest games to model are two-person games, but real life is an n-person game: it involves a large and variable number of players. You might lose a lot to one person, but gain more than you expected from someone else. Person A might be cruel to you, but person B, seeing that, might be even more kind to you because of it. And when you're playing with a lot of people, the game goes on indefinitely—and that makes a huge difference. The examples in the Old Testament couldn't be endlessly iterated: an eye for an eye can only go two rounds—after that, you're out of eyes. Even a tooth for a tooth ends after a maximum of thirty-two rounds."
  
  Caitlin took a sip of milk, and her mother went on. "That's the problem with two-person iterated games: they eventually come to an end. Sometimes they end because, like with the dollar auction, players just give up because it's become ridiculous. And sometimes they end because the players run out of time.
  
  "In fact, there was a famous case of a game theorist being brought in to IBM to do some management-training exercises. He divided the managers into teams and had them play games in which cooperating was the best strategy—which was the point he wanted them to learn.
  
  "Everything worked fine until just before 4:00 p.m., when the seminar was scheduled to end. Suddenly, one of the teams turned on the other and kept defecting. That team won, but the first team felt so betrayed, IBM had to send its members off for therapy, and it was months before they'd work at all with members of the other team again."
  
  "Wow," said Caitlin.
  
  "But if you take the whole of humanity as the field of players, then your interaction doesn't end even if any one specific player drops out. That's why reputation is so important, see? You've bought things on eBay, right? Well, that's a perfect example: how you've treated other people shows up in your Feedback rating. The world knows if you defect. We're all interconnected in a..."
  
  ". . . a worldwide web?" said Caitlin.
  
  She smiled. "Exactly." She gobbled the last of her sandwich. "Speaking of which, we should get back upstairs..."
  
  "All right," said Tony Moretti, pacing down one side of the control room at WATCH. "Reports. Shel, you first."
  
  Shelton Halleck was leaning forward in his chair, his arms crossed in front of him on the workstation, the one with the snake tattoo on top. He was plainly exhausted. "We've been through everything Caitlin Decter has written with a fine-toothed comb," he said. "And everything Malcolm and Barbara Decter and Kuroda have written, too, but there's nothing about how Exponential actually works—nothing that contradicts what Decter told the CSIS agents, but nothing that confirms it, either."
  
  "All right," said Tony. "Aiesha, what have you got?"
  
  She looked more awake than Shel, but her voice was raw. "Maybe something, maybe nothing," she said. "Caitlin set up a webcam chat with an Internet cartographer at the Technion a while ago: Anna Bloom is her name." A dossier came up on the middle of the three big screens, showing a picture of an elderly gray-haired woman. "We weren't monitoring Caitlin's traffic back then, so we don't have a recording of the video chat—but I can't think of any reason for a girl in Canada to talk to a Web scientist in Israel except to discuss the structure of Exponential."
  
  "We could get the Mossad to speak to this Bloom," said Tony. "The Technion is in Jerusalem?"
  
  "No, Haifa," Aiesha said. She turned and looked at the series of digital clocks on the back wall. "It's almost 11:00 p.m. there."
  
  "There's no time to waste," Colonel Hume said. "Let me call her directly—one computer expert to another. It's time to cut through all the bull."
  
  Caitlin's instant messenger bleeped and the words Mind-Over-Matter is now available popped up. She felt her heart racing.
  
  Hi, she typed.
  
  Hey! Matt replied. How was your day?
  
  Fine, ty.
  
  I've got the stuff from your locker, he replied. OK if I come by?
  
  Caitlin was surprised to find her heart pounding. She paused, trying to think of something suitably witty or sexy to say, but then she mentally kicked herself for hesitating, because poor Matt must have been on tenterhooks. Sure! she wrote, and then, to take the sting out of her delay, she added a trio of smiley faces.
  
  W00t! he wrote. 'Bout half an hour, OK?
  
  This time she replied immediately: Yes.
  
  Heading out. *poof *
  
  Caitlin crossed the hall to speak to her mother, who was typing away with Webmind in her study.
  
  "A friend's coming over," Caitlin said.
  
  Her mother looked up from her keyboard. "Who is it?"
  
  Caitlin found herself slightly embarrassed. "They were in my math class."
  
  But the pronoun obfuscation did not get past her mom. "It's a boy," she said at once.
  
  "Um, yes."
  
  "Is it Trevor?"
  
  "No! Don't worry, Mom. He won't be back."
  
  "Well, okay," she said, and—
  
  And there it was, that look she'd seen before: her mother trying to suppress a grin. "But, sweetheart," she added, "you might want to clean yourself up a bit."
  
  Cripes! She'd been so intent on Webmind that she hadn't brushed her hair today, and she looked down now and saw that she was wearing just about the rattiest T-shirt she owned. And—gak!—she hadn't showered for two days. She hurried down the hall to the bathroom.