He clamped his gaping mouth shut, unsure how to handle the social nuances. A second cloud of coiling blue streamers formed a clear picture of Lamurk, eyebrows knotted in fury. The foggy figures hovered in confrontation, Hari smiling, Lamurk scowling.

 And Lamurk looked the fool, with bulging eyes and pouting lips.

 “Time for a graceful exit,” Hari’s lieutenant whispered. Hari was only too glad to agree.

 When they got home, he was sure that there had been a bit extra in the stim he was handed, something that freed his tongue. Cer­ tainly it was not the slow-spoken, reflective Seldon who had traded jabs with Lamurk. He would have to watch that.

 Dors simply shook her head. “It was you. Just a portion of you that doesn’t get out to play very much.”

 6.

 “Parties are supposed to cheer people up,” Yugo said, sliding a cup of kaff across Hari’s smooth mahogany desktop.

 “Not this one,” Hari said.

 “All that luxury, powerful people, beautiful women, witty hangers-on—I think I could have stayed awake.”

 “That’s what depresses me, thinking back over it. All that power! And nobody there seems to care about our decline.”

 “Isn’t there some old saying about—”

 “Fiddling while Roma burns. Dors knew it, of course. She says it’s from pre-Empire, about a Zone with pretensions of grandeur. ‘All worms lead to Roma’ is another one.”

 “Never heard of this Roma.”

 “Me either, but pomposity springs forth eternal. It looks comic in retrospect.”

 Yugo moved restlessly around Hari’s office. “So they don’t care?”

 “To them it’s just backdrop for their power games.”

 Already the Empire had worlds, Zones, and even whole arcs of spiral arms descended into squalor. Still worse, in a way, was a steady slide into garish amusements, even vulgarity. The media swarmed with the stuff. The new “renaissance” styles from worlds like Sark were popular.

 To Hari the best of the Empire was its strands of restraint, of subtlety and discretion in manners, finesse and charm, intelligence, talent, and even glamour. Helicon had been crude and rural, but it knew the difference between silk and swine.

 “What do the policy types say?” Yugo sat halfway on Hari’s desk, avoiding the control functions implanted beneath a woody veneer. He had come in with the kaff as a pretext, fishing for gossip about the exalted. Hari smiled to himself; people relished some aspects of hierarchy, however much they griped about it.

 “They’re hoping some of the ‘moral rebirth’ movements—like revised Ruellianism, say—will take hold. Put spine into the Zones, one of them said.”

 “Ummm. Think it’ll work?”

 “Not for long.”

 Ideology was an uncertain cement. Even religious fervor could not glue an empire together for long. Either force could drive formation of an empire, but they could not hold against greater, steady tides—principally, economics.

 “How about the war in the Orion Zone?”

 “Nobody mentioned it.”

 “Think we’ve got war figured right in the equations?” Yugo had a knack for suddenly putting his finger on what was bothering Hari.

 “No. War was an overesteemed element in history.”

 Certainly war often gained center stage; no one continued to read a beautiful poem when a fist fight broke out nearby. But fist fights did not last, either. Further, they joggled the elbows of those trying to make a living. To engineers and traders alike, war did not pay. So why did wars break out now, with all the economic weight of the Empire against them?

 “Wars are simple. But we’re missing something basic—I canfeel it.”

 “We’ve based the matrices on all that historical data Dors dug out,” Yugo said a bit defensively. “That’s solid.”

 “I don’t doubt it. Still…”

 “Look, we’ve got over twelve thousand years of hard facts. I built the model on that.”

 “I have a feeling what we’re missing isn’t subtle.”

 Most collapses were not from abstruse causes. In the early days of Empire consolidation, local minor sovereignties flourished, then died. There were recurrent themes in their histories.

 Again and again, star-spanning realms collapsed under the weight of excessive taxation. Sometimes the taxes supported mercenary armies which defended against neighbors, or which simply kept domestic order against centrifugal forces. Whatever the ostensible cause of taxes, soon enough the great cities became depopulated, as people fled the tax collectors, seeking “rural peace.”

 But why did they do that spontaneously?

 “People.” Hari sat up suddenly. “That’s what we’re missing.”

 “Huh? You proved yourself—remember? the Reductionist The-orem?—that individuals don’t matter.”

 “They don’t. But people do. Our coupled equations describe them in the mass, but we don’t know the critical drivers.”

 “That’s all hidden, down in the data.”

 “Maybe not. What if we were big spiders, instead of primates? Would psychohistory look the same?”

 Yugo frowned. “Well…if the data were the same…”

 “Data on trade, wars, population statistics? It wouldn’t matter whether we were counting spiders instead of people?”

 Yugo shook his head, his face clouding, unwilling to concede a point that might topple years of work. “It’s gotta be there.”

 “Your coming in here to get details of what the rich and famous do at their revels—where’s that in the equations?”

 Yugo’s mouth twisted, irked now. “That stuff, it doesn’t matter.”

 “Who says?”

 “Well, history—”

 “Is written by the winners, true enough. But how do the great generals get men and women to march through freezing mud? When won’t they march?”

 “Nobody knows.”

 “We need to know. Or rather, the equations do.”

 “How?”

 “I don’t know.”

 “Go to the historians?”

 Hari laughed. He shared Dors’ contempt for most of her profes­ sion. The current fashion in the study of the past was a matter of taste, not data.

 He had once thought that history was simply a matter of grubbing in musty cyberfiles. Then, if Dors would show him how to track down data—whether encoded in ancient ferrite cylinders or polymer blocks or strandware—then he would have a firm basis for mathem­ atics. Didn’t Dors and other historians simply add one more brick of knowledge to an ever-growing monument?

 The current style, though, was to marshal the past into a preferred flavor. Factions fought over the antiquity, over “their” history vs. “ours.” Fringes flourished. The “spiral-centric” held that historical forces spread along spiral arms, whereas the “Hub-focused” main­ tained that the Galactic Center was the true mediating agency for causes, trends, movements, evolution. Technocrats contended with Naturals, who felt that innate human qualities drove change.

 Among myriad facts and footnotes, specialists saw present politics mirrored in the past. As the present fractured and transfigured, there seemed no point of reference outside history itself—an unreliable platform indeed, especially when one realized how many mysterious gaps there were in the records. All this seemed to Hari to be more fashion than foundation. There was no uncontested past.

 What contained the centrifugal forces of relativism—let me have my viewpoint and you can have yours—was an arena of broad agreement. Most people generally held that the Empire was good, overall. That the long periods of stasis had been the best times, for change always cost someone. That above the competing throng, through the factions shouting what were essentially family stories at each other, there was worth in comprehending where humanity had passed, what it had done.

 But there agreement stopped. Few seemed concerned with where humanity, or even the Empire, was going. He had come to suspect that the subject was ignored, in favor of your-history-against-mine, because most historians unconsciously dreaded the future. They sensed the decline in their souls and knew that over the horizon lay not yet another shift-then-stasis but a collapse.

 “So what do we do?” Hari realized that Yugo had said this twice now. He had drifted off into reverie.

 “I…don’t know.”

 “Add another term for basic instincts?”

 Hari shook his head. “People don’t run on instinct. But they do behave like people—like primates, I suppose.”

 “So…we should look into that?”

 Hari threw up his hands. “I confess. I feel that this line of logic is leading somewhere—but I can’t see the end of it.”

 Yugo nodded, grinned. “It’ll come out when it’s ripe.”

 “Thanks. I’m not the best of collaborators, I know. Too moody.”

 “Hey, never mind. Gotta think out loud sometimes, is all.”

 “Sometimes I’m not sure I’m thinking at all.”

 “Lemme show you the latest, huh?” Yugo liked to parade his in­ ventions, and Hari sat back as Yugo accessed the office holo and patterns appeared in midair. Equations hung in space, 3D-stacked and each term color-coded.

 So many! They reminded Hari of birds, flocking in great banks.

 Psychohistory was basically a vast set of interlocked equations, following the variables of history. It was impossible to change one and not vary any other. Alter population and trade changed, along with modes of entertainment, sexual mores, and a hundred other factors.

 Some were undoubtedly unimportant, but which? History was a bottomless quarry of factoids, meaningless without some way of winnowing the hail of particulars. That was the essential first task of any theory of history—to find the deep variables.

 “Post-diction rates—presto!” Yugo said, his hand computer sus­ pending in air 3D graphs, elegantly arrayed. “Economic indices, variable-families, the works.”

 “What eras?” Hari asked.

 “Third millennia to seventh, G.E.”

 The multidimensional surfaces representing economic variables were like twisted bottles filled with—as Yugo time-stepped them—sloshing fluids. The liquids of yellow and amber and virulent red flowed around and through each other in a supple, slow dance. Hari was perpetually amazed at how beauty arose in the most un­ likely ways from mathematics. Yugo had plotted abstruse econo­ metric quantities, yet in the gravid sway of centuries they made delicate arabesques.

 “Surprisingly good agreement,” Hari allowed. The yellow surfaces of historical data merged cleanly with the other color skins, fluids finding curved levels. “And covering four millennia! No infinities?”

 “That new renormalization scheme blotted them out.”

 “Excellent! The middle Galactic Era data is the most solid, too, correct?”

 “Yeah. The politicians got into the act after the seventh millenni­ um. Dors is helpin’ me filter out the garbage.”

 Hari admired the graceful blending of colors, ancient wine in transfinite bottles.

 The psychohistorical rates linked together strongly. History was not at all like a sturdy steel edifice rigidly spanning time; it rather more resembled a rope bridge, groaning and flexing with every footfall. This “strong coupling dynamic” led to resonances in the equations, wild fluctuations, even infinities. Yet nothing really went infinite in reality, so the equations had to be fixed. Hari and Yugo had spent many years eliminating ugly infinites. Maybe their goal was in sight.

 “How do the results look if you simply run the equations forward, past the seventh millennium?” Hari asked.

 “Oscillations build up,” Yugo admitted.

 Feedback loops were scarcely new. Hari knew the general theor­ em, ancient beyond measure: If all variables in a system are tightly coupled, and you can change one of them precisely and broadly, then you can indirectly control all of them. The system could be guided to an exact outcome through its myriad internal feedback loops. Spontaneously, the system ordered itself—and obeyed.

 History, of course, obeyed no one. But for eras such as the fourth to seventh millennium, somehow the equations got matters right. Psychohistory could “post-dict” history.