Permutation City

by Greg Egan

  As the program zeroed in on the final result, Maria said sharply, “You could have done that for my pyramid, couldn’t you? And let me sleep?”

  Durham shook his head, without looking at her. “Done it from where? I had no access to the border. This is only possible because the other founders have granted me carte blanche.”

  “I think you could have burrowed through somehow, if you’d set your mind to it.”

  He was silent for a while, then he conceded, “Perhaps I could have. I did want you to see Planet Lambert. I honestly believed that I had no right to let you sleep through contact.”

  She hunted for a suitably bitter reply – then gave up and said wearily, “You had no right to wake me – but I’m glad I saw the Lambertians.”

  The code-breaking program said, “In.”

  There was no time left for decorum, for explaining the crisis and justifying the evacuation. Durham issued a sequence of commands, to freeze all the software running in the pyramid, analyze it, extract all the essential data, and bundle it into the new Garden-of-Eden. Riemann and his children need never know the difference.

  The software had other ideas. It acknowledged the access code, but refused to halt.

  Maria turned aside and retched dryly. How many people were in there? Thousands? Millions? There was no way of knowing. What would happen if the changes in the grid engulfed them? Would the worlds they inhabited implode and vanish, like the inanimate City?

  When she could bring herself to look again, Durham had calmly changed tack. He said, “I’m trying to break the lock on communication. See if I can get in on any level, and at least talk to someone. Maybe from the inside they’ll have more control; we can’t halt their software and download it en masse, but maybe they can do that themselves.”

  “You have eleven minutes.”

  “I know.” He hesitated. “If I have to, I can stick around and launch these people separately. I don’t imagine they care whether or not they’re in the same universe as the rest of the Elysians.”

  “Stick around? You mean clone yourself, and launch one version with the rest of us—?”

  “No. Zemansky’s organized a hundred people to verify the launch from within. I don’t have to be there.”

  Maria was horrified. “But – why leave yourself out? Why risk it?”

  He turned to her and said placidly, “I’m not splitting myself, not again. I had enough of that on twenty-four Earths. I want one life, one history. One explanation. Even if it has to come to an end.”

  The program he’d been running beeped triumphantly, and flashed up a message. “There’s a data port for granting physical interaction with one environment, and it seems to be intact.”

  Maria said, “Send in a few thousand robots, sweep the place for signs of life.”

  Durham was already trying it. He frowned. “No luck. But I wonder if—”

  He created a doorway a few meters to his right; it seemed to lead into a lavishly decorated corridor.

  Maria said queasily, “You have seven minutes. The port’s not working: if a robot can’t materialize—”

  Durham stood and walked through the doorway, then broke into a run. Maria stared after him. But there was no special danger “in there” – no extra risk. The software running their models was equally safe, wherever they pretended their bodies to be.

  She caught up with Durham just as he reached an ornate curved staircase; they were upstairs in what seemed to be a large two-story house. He clapped her on the shoulder. “Thank you. Try downstairs, I’ll keep going up here.”

  Maria wished she’d disabled all her human metabolic constraints – but she was too agitated now to try to work out how to make the changes, too awash with adrenaline to do anything but run down corridors bellowing, “Is there anyone home?”

  At the end of one passage, she burst through a door and found herself out in the garden.

  She looked about in despair. The grounds were enormous – and apparently deserted. She stood catching her breath, listening for signs of life. She could hear birdsong in the distance, nothing else.

  Then she spotted a white shape in the grass, near a flowerbed full of tulips.

  She yelled, “Down here!” and hurried toward it.

  It was a young man, stark naked, stretched out on the lawn with his head cradled in his hands. She heard breaking glass behind her, and then a heavy thud on the ground; she turned to see Durham pick himself up and limp toward her.

  She knelt by the stranger and tried to wake him, slapping his cheeks. Durham arrived, ashen, clearly shorn of his artificial tranquility. He said, “I think I’ve sprained an ankle. I could have broken my neck. Don’t take any risks – something strange is going on with our physiology; I can’t override the old-world defaults.”

  Maria seized the man by the shoulders and shook him hard, to no effect. “This is hopeless!”

  Durham pulled her away. “I’ll wake him. You go back.”

  Maria tried to summon up a mind’s-eye control panel to spirit her away. Nothing happened. “I can’t connect with my exoself. I can’t get through.”

  “Use the doorway, then. Run!”

  She hesitated – but she had no intention of following Durham into martyrdom. She turned and sprinted back into the house. She took the stairs two at a time, trying to keep her mind blank, then raced down the corridor. The doorway into the evacuation control room was still there – or at least, still visible. As she ran toward it, she could see herself colliding with an invisible barrier – but when she reached the frame, she passed straight through.

  The clock on the interface window showed twenty seconds to launch.

  When she’d insisted on hanging around, Durham had made her set up a program which would pack her into the new Garden-of-Eden in an instant; the icon for it – a three-dimensional Alice stepping into a flat story-book illustration – was clearly on display in a corner of the window.

  She reached for it, then glanced toward the doorway into Riemann’s world.

  The corridor was moving, slowly retreating. Slipping away, like the buildings of the City.

  She cried out, “Durham! You idiot! It’s going to implode!” Her hand shook; her fingers brushed the Alice icon, lightly, without the force needed to signal consent.

  Five seconds to launch.

  She could clone herself. Send one version off with the rest of Elysium, send one version in to warn him.

  But she didn’t know how. There wasn’t time to learn how.

  Two seconds. One.

  She bunched her fist beside the icon, and wailed. The map of the giant cube flickered blue-white: the new lattice had begun to grow, the outermost processors were reproducing. It was still part of Elysium – a new grid being simulated by the processors of the old one – but she knew the watchdog software wouldn’t give her a second chance. It wouldn’t let her halt the launch and start again.

  She looked back through the doorway. The corridor was still sliding smoothly away, a few centimeters a second. How much further could it go, before the doorway hit a wall, stranding Durham completely?

  Swearing, she stepped toward it, and reached through with one hand. The invisible boundary between the environments still let her pass. She crouched at the edge, and reached down to touch the floor; her palm made contact with the carpet as it slipped past.

  Shaking with fear, she stood up and crossed the threshold. She stopped to look behind the doorway; the corridor came to a dead end, twelve or fifteen meters away in the direction the doorway was headed. She had four or five minutes, at most.

  Durham was still in the garden, still trying to rouse the man. He looked up at her angrily. “What are you doing here?”

  She caught her breath. “I missed the launch. And this whole thing’s … separating. Like the City. You have to get out.”

  Durham turned back to the stranger. “He looks like a rejuvenated Thomas Riemann, but he could be a descendant. One of hundreds. One of millions, for all we know.”<
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  “Millions, where? It looks like he’s alone here – and there’s no sign of other environments. You only discovered one communications port, didn’t you?”

  “We don’t know what that means. The only way to be sure he’s alone is to wake him and ask him. And I can’t wake him.”

  “What if we just … carried him out of here? I know: there’s no reason why doing that should move his model to safer territory – but if our models have been affected by this place, forced to obey human physiology … then all the logic behind that has already been undermined.”

  “What if there are others? I can’t abandon them!”

  Maria wanted to grab him and shake him. “There’s no time! What can you do for them, trapped in here? If this world is destroyed, nothing. If it survives somehow … it will still survive without you.”

  Durham looked sickened, but he nodded reluctantly.

  She said, “Get moving. You’re crippled – I’ll carry Sleeping Beauty.”

  She bent down and tried to lift Riemann – Thomas or otherwise – onto her shoulders. It looked easy when firefighters did it. Durham, who’d stopped to watch, came back and helped her. Once she was standing, walking wasn’t too hard. For the first few meters.

  Durham hobbled alongside her. At first, she abused him, trying insincerely to persuade him to go ahead. Then she gave up and surrendered to the absurdity of their plight. Flushed and breathless, she said, “I never thought I’d witness … the disintegration of a universe … while carrying a naked merchant banker —” She hesitated. “Do you think if we close our eyes and say … we don’t believe in stairs, then maybe—”

  She went up them almost crouching under the weight, desperate to put down her burden and rest for a while, certain that if she did they’d never make it.

  When they reached the corridor, the doorway was still visible, still moving steadily away. Maria said, “Run ahead and … keep it open.”

  “How?”

  “I don’t know. Go and stand in the middle…”

  Durham looked dubious, but he limped forward and reached the doorway well ahead of her. He stepped right through, then turned and stood with one foot on either side, reaching out a hand to her, ready to drag her onto the departing train. She had a vision of him, bisected, one half flopping bloodily into each world.

  She said, “I hope this … bastard was a great … philanthropist. He’d better … have been a fucking … saint.”

  She looked to the side of the doorway. The corridor’s dead end was only centimeters away. Durham must have read the expression on her face; he retreated into the control room. The doorway touched the wall, then vanished. Maria bellowed with frustration, and dropped Riemann onto the carpet.

  She ran to the wall and pounded on it, then sank to her knees. She was going to die here, inside a stranger’s imploding fantasy. She pressed her face against the cool paintwork. There was another Maria, back in the old world – and whatever else happened, at least she’d saved Francesca. If this insane dream ended, it ended.

  Someone put a hand on her shoulder. She twisted around in shock, pulling a muscle in her neck. It was Durham.

  “This way. We have to go around. Hurry.”

  He picked up Riemann – he must have repaired his ankle in Elysium, and no doubt strengthened himself as well – and led Maria a short way back down the corridor, through a vast library, and into a storage room at the end. The doorway was there, a few meters from the far wall. Durham tried to walk through, holding Riemann head first.

  Riemann’s head disappeared as it crossed the plane of the doorway. Durham cried out in shock and stepped back; the decapitation was reversed. Maria caught up with them as Durham turned around and tried backing through the doorway, dragging Riemann after him. Again, the portion of Riemann’s body which passed through seemed to vanish – and as his armpits, where Durham was supporting him, disappeared, the rest of him crashed to the floor. Maria ducked behind the doorway – and saw Riemann, whole, lying across the threshold.

  They couldn’t save him. This world had let them come and go – on its own terms – but to Riemann himself, the exit they’d created was nothing, an empty frame of wood.

  She went back and stepped over him, into Elysium. As the doorway retreated, Riemann’s shoulders came into view again. Durham, sobbing with frustration, reached through and dragged the sleeping man along for a meter – and then his invisible head must have struck the invisible wall, and he could be moved no further.

  Durham withdrew into Elysium, just as the doorway became opaque. A second later, they saw the outside wall of the house. The implosion – or separation – accelerated as the doorway flew through the air above the grounds – and then the whole scene was encircled by darkness, like a model in a glass paperweight, floating off into deep space.

  Maria watched the bubble of light recede, the shapes within melting and reforming into something new, too far away to decipher. Was Riemann dead, now? Or just beyond their reach?

  She said, “I don’t understand – but whatever the Lambertians are doing to us, it’s not just random corruption … it’s not just destroying the TVC rules. That world was holding together. As if its own logic had taken precedence over Elysium’s. As if it no longer needed us.”

  Durham said flatly, “I don’t believe that.” He crouched beside the doorway, weighed down by defeat.

  Maria touched his shoulder. He shrugged free. He said, “You’d better hurry up and launch yourself. The other Elysians will have been removed from the seed, but everything else – all the infrastructure – should still be there. Use it.”

  “Alone?”

  “Make children, if you want to. It’s easy; the utility programs are all in the central library.”

  “And – what? You’ll do the same?”

  “No.” He looked up at her and said grimly, “I’ve had enough. Twenty-five lives. I thought I’d finally discovered solid ground – but now it’s all crumbling into illusions and contradictions. I’ll kill myself before the whole thing falls apart: die on my own terms, leaving nothing to be explained in another permutation.”

  Maria didn’t know how to respond. She walked over to the interface window, to take stock of whatever was still functioning. After a while, she said, “The Autoverse spy software has stopped working – and the entire hub has gone dead – but there’s some last-minute summary data in the copy of the central library you made for the seed.” She hunted through Repetto’s analysis and translation systems. Durham came and stood beside her; he pointed out a highlighted icon, a stylized image of a swarm of Lambertians.

  He said, “Activate that.”

  They read the analysis together. A team of Lambertians had found a set of field equations – nothing to do with the Autoverse cellular automaton – with thirty-two stable solutions. One for each of their atoms. And at high enough temperatures, the same equations predicted the spontaneous generation of matter – in exactly the right proportions to explain the primordial cloud.

  The dance had been judged successful. The theory was gaining ground.

  Maria was torn between resentment and pride. “Very clever – but how will they ever explain four humanoid robots abandoned in a meadow?”

  Durham seemed bleakly amused. “They arrived in a spaceship, didn’t they? Aliens must have sent them, as emissaries. There must be other stars out there – concealed behind a suitable dust cloud.”

  “Why should aliens try to tell the Lambertians about the TVC cellular automaton?”

  “Maybe they believed in it. Maybe they discovered the Autoverse rules … but since they still couldn’t explain the origin of the elements, they decided to embed the whole thing in a larger system – another cellular automaton – complete with immortal beings to create the Autoverse, primordial cloud and all. But the Lambertians will put them straight: there’s no need for such a convoluted hypothesis.”

  “And now the Autoverse is sloughing us off like dead skin.” Maria gazed at the Lamberti
an field equations; they were far more complex than the Autoverse rules, but they had a strange elegance all their own. She could never have invented them herself; she was sure of that.

  She said, “It’s not just a matter of the Lambertians out-explaining us. The whole idea of a creator tears itself apart. A universe with conscious beings either finds itself in the dust … or it doesn’t. It either makes sense of itself on its own terms, as a self-contained whole … or not at all. There never can, and never will be, Gods.”

  She displayed a map of Elysium. The dark stain marking processors which had ceased responding had spread out from the six public pyramids, and swallowed most of the territories of Riemann, Callas, Shaw, Sanderson, Repetto and Tsukamoto. She zoomed in on the edge of the darkness; it was still growing.

  She turned to Durham and pleaded, “Come with me!”

  “No. What is there left for me to do? Descend into paranoia again? Wake up wondering if I’m really nothing but a discredited myth of Planet Lambert’s humanoid alien visitors?”

  Maria said angrily, “You can keep me company. Keep me sane. After all you’ve done to me, you owe me that much.”

  Durham was unmoved. “You don’t need me for that. You’ll find better ways.”

  She turned back to the map, her mind going blank with panic for a moment – then she gestured at the growing void. “The TVC rules are dissolving, the Lambertians are destroying Elysium – but what’s controlling that process? There must be deeper rules, governing the clash of theories: deciding which explanations hold fast, and which dissolve. We can hunt for those rules. We can try to make sense of what went on here.”

  Durham said sardonically, “Onward and upward? In search of higher order?”