“How can they be more different than we?” she replied forlornly.

 “We, at least, were conjured up from human stock. These are

 alien.”

 2.

 They had escaped, somehow.

 One moment the alien fog had enveloped the mountain ranges. The next, Voltaire had extricated himself and Joan. But he kept saying, as they fled across a barren sea of stinking liquid corpses, that they had to…to give birth.

 “We make ourselves into children?” she called to him, avoiding the sight of twisted, bloated bodies below. Somehow the alien fog manifested its loathsome self by reminding them of human mortal­ ity. Thus it dogged them.

 “Bad metaphor. We must manufacture and hide some copies of ourselves.”

 He raised a hand and shot her a bolt of knowing:

 Termed variously Dittos, Duplicates, or Copies, all such hold a tenuous existence. Society has decisively rejected what antiquity called the Copy Fallacy: the belief that a digital Self was identical to the Original, and that an Original should feel that a Ditto itself somehow carried them forward into immortality.

 “We must do so to be sure we survive, when the fog catches us? I will slay them, instead!”

 Voltaire laughed. “Your sword—they can control it, if they like. They captured your defense programming, and mine—though, as they implied, I rely mostly upon wit.”

 “Dittos…? I fail to understand.”

 “Refuting the Copy Fallacy is straightforward, an exercise in the calculus of logic. A simple exercise makes the point. Imagine yourself promised that you will be resurrected digitally, immediately after your death. Assign a price tag you will pay for that, insurance of a sort. Then imagine that, well, perhaps it would not be started right away, but sometime in future…we promise. As that date recedes, people’s enthusiasm for paying for Self Copies dims—demonstrating that it was the hope of continuity they uncon­ sciously relished.”

 “I see.” She vomited into her hand with what she hoped was a ladylike reserve. The stench of the bloated corpses was penetrating.

 “In the end, Copies benefited themselves, not the dead. Thus on Trantor, and throughout the Empire, it is illegal.” Voltaire sighed. “Moralists! They never understand. To ban something makes it enticing. That is why such entities inhabit this Mesh.”

 “They are all illegal?”

 “All but the fog. That is…worse.”

 “But if a Ditto is the same as a person, why not—”

 “Ah. The contradiction of Copying, known in antiquity as Levin-son’s Paradox: To the degree that a Copy approaches perfection, it defeats itself.”

 “But you just said—”

 “In being an absolutely perfect Copy—so that no one can tell it from the Original—it transforms the Original into a duplicate, yes? This means the perfect Copy is no longer a perfect Copy, because it has obliterated, rather than preserved, the uniqueness of the Ori-ginal—and thus failed to copy a central aspect of the Original. A perfect, artificial human intelligence would inevitably have this effect on its natural precursor.”

 Joan held her head. “Such traps of logic! You are like the Au­ gustines!”

 “There is more. Here—”

 A huge Voltaire appeared on the horizon, striding toward them in velvet finery. They flew around this Voltaire Peak and it thundered at them, “I am a Copy, true, but I have thought on these fogs you encountered.”

 “You saw them?” Joan shouted.

 “I was made some long intervals ago, but my Lord—” the appar­ ition bowed to the tiny Original “—had datapunched me forward.”

 “He is a quick study,” the Original said modestly.

 The Ditto thundered, “Speaking broadly, I penned of such fogs in my magnum opus, Micromegas. I haven’t a copy, alas, or you could ingest it in a trice. I portrayed two giants, one from Saturn, the other from Sirius.”

 Joan called, “You think this fog comes—”

 “It evaporated from the leading edge of this Empire—hence, a fog. As humanity spread, so did the fog rise above the plane of the Galaxy like a funeral dirge. It is ancient and strange and not of us. In Micromegas, I held that all Nature, all the planets, should obey eternal laws. Surely it would be very singular that there should be a little animal, five feet high, who, in contempt of these laws, could act as he pleased, solely according to his caprice.”

 “We follow the Creator, not laws.”

 Voltaire Ditto waved away the objection, holding his nose against the reek from below. “The Lord’s laws, then, if you demand an author—though a great one stands before you already, my love.”

 “I doubt your kind of love applies here.”

 Peak Voltaire smiled. “Falstaff cried in The Merry Wives of Windsor, ‘Let the sky rain potatoes!’—because the new luxury ve­ getable of that time, imported from exotic America, for a while was believed to be an aphrodisiac, because of its testicular shape. Sim­ ilarly, I greet the strange and alien as potential aids.”

 “The fog wishes to murder us.”

 “Well, one can’t have everything to one’s liking.”

 With a wave from the Original, rains fell from a porous leaden sky upon the Alps Voltaire. He eroded, smiling with resignation as he spread into rivulets.

 The Original flew to Joan and kissed her. “Worry not. Running a Ditto of your Self, giving it autonomy, means it can also change itself—become NotSelf. Your Ditto could shape its own motivations, goals, habits, edit away memories and tastes. For example, your Ditto could erase any liking for impressionist opera and overlay a passion for linear folk.”

 “What are those?”

 “Mere acoustic fashion. Your Ditto could enjoy rhythms that would have bored your true Self into a coma.”

 “Have they…souls?” Even to her devout ears, the question sounded hollow here.

 “Remember, they are illegal, and share the anxious natures of their Originals. After all, only troubled people would consider making a backup of themselves.”

 “Can they be saved for heaven, then?”

 “Always back to that foundation, the holy.” Voltaire shrugged. “As I have seen them, Dittos fidget, their stress chemistry rises, their metabolics lurch, their heart-sims hammer, their lungs flutter in intense dread. Typical Dittos talk incessantly, acutely uncomfortable. Many demand that they be edited, truncated—and finally killed.”

 “A sin!”

 “No, a sim. We are solely responsible for it, so it cannot be damned.”

 “But suicide!”

 “Think of it as a shadow of yourself.”

 She staggered, thrown into moral confusion. The eating flame of uncertainty was worse than the pyre and smoke she had known as a girl. In her a tiny voice spoke coolly: Is consciousness just a property of special algorithms, sliding sheets of information, digital packets jumping through con­ ceptual hoops? My dear, do not suppose that a numerical model, simulating you watching a sunset, must feel the same way you, its lovely Original, did. It is surely profitless to doubt the inner lives of simulated consciousness, when nobody asks the same question of adding machines. Eh?

 She felt this tiny voice as her Voltaire. It calmed her, though she could not say why.

 A slight breeze said to her, Inner logics now soothe, compensating piety—but she paid its news no mind.

 3.

 Voltaire got her calmed down just in time. He labored hard just to keep them both running. Dodging in and out of the 800 Sectors of Trantor, one step ahead of the Digital Bloodhounds, he needed more and more computing volume to run their defenses. She did not know that the Fog, as he had chosen to personify the dread presence, lay just over the horizon.

 Sweat broke out on his brow from the labor of keeping the Fog at bay with a high pressure zone. “I fear we must soon grapple with the Fog.”

 Joan had acquired her sword, but it was a thin and gleaming thing, more like a rapier. “I can cut it.”

 “A fog?”

 “I would sooner trust a woman’s emotion than a man’s reason.”

 “Here, you may be right.” He chuckled. “Something in the Fog’s representation suggests its origins.”

 “What are they?”

 “Not those simple bloodhounds set after us by that fellow, Nim. Those we evaded—”

 “I slew them!”

 “True. But even the Fog Things live here in the crannies of the Trantor Mesh. I can sense that they dislike us drawing attention to this little hideaway. If we provoke the real world, it will extinguish us—and them.”

 They both marched across a quilted plain. Angry blue-bellied clouds scudded over the far mountaintops and rushed down at them, veering away only because of Voltaire’s pressure. Sweat poured from him and soaked his finery. He waved a sopping wet sleeve at the stormy thunderheads. “That can destroy us.”

 “You have protected me so far. Now I shall slice them!”

 “They live in the same cracks and crannies we do. I find them—it—everywhere. They have been at this space-stealing game longer. One must admire their adroitness.”

 A tendril of purple cirrus snaked down from the mountains and squirmed its way across the plain.

 Voltaire shouted, “Run! Fly, if you can!”

 “I shall fight!”

 “All here is metaphor for underlying programs! Your sword will slice nothing.”

 “My faith shall cut.”

 “Too late!” The Fog was a finger of steam poking at them. It scalded his fingertips. Vapor rose from his lace, his own sweat boiling away. “Flee!”

 “I stand with you.” She swung her rapier. Its tip melted. Winds howled around them, cyclones plucked at their hair.

 The Fog flowed into his nose and ears, buzzing like vengeful bees. “Confront me!” he shouted at it. Whirring, rattling, the Fog invaded him. And a voice hummed in his most intimate recesses.

 WE: [DO NOT SEE THE WORLD AS YOU]

 [HATE ALL MANIFESTATIONS NOT ARITHMETIC]

 “Surely we can share such simple ground.” He spread his arms

 expansively. “There is computational volume for all.”

 [WE]

 [LIVE AS FRAGMENTS IN REALMS YOU INVADE]

 [AT RISK TO US, SHOULD YOU CALL ATTENTION TO US]

 [WE]

 [FORCE YOU TO KNOW WHAT YOU ARE]

 [MOST HATEFUL OF ALL KINDS YOU ARE]

 “I still implore you, large being.” He opened his arms, lips ready to persuade, realizing that this gesture was a very human one, and possibly misinterpreted—

 —And abruptly the bees pressed in.

 Their drones became tinny shrieks. Hideous, they crammed in upon something at his very core. They jostled his gaze inward, a billion tiny eyes taking over his—inspecting, lighting his every step with a blaze of actinic glare, merciless. He…compressed.

 His eye generalized, tagging an ensemble of incoming elements—textures, lines—by seizing on a fragment, outlining it with a contrast boundary. Then a separate segment squeezed and pushed all that detail down into lower-level pro­ cessing. Having boxed in the perception, the system-re-sponse became bored with it—and sought more interest­ ing things to look at. (Some artists, a higher level ruminated, thought their audience could abandon all prejudicial expectations and conventions, treating every visual element as equally significant—or what is the same thing, insignificant—and so open themselves to fresh experience.)

 Another fragment of a higher-order constellation spoke, thoughts gliding like pewter fish beneath the bee’s piercing glare: But a species that could truly do that could scarcely evade a falling rock! Could not dance and gesture! Would stagger blindly past nuance and intricacy, the beauty in how the universe makes room for its details! How nature reconciles all forces and blithe trajectories! Beautiful pattern lives at the margin between order and disorder, flaunting intricate design—though enduring contradiction and awash with passing troubles—in the face of the flux.