Maya nodded.

Night after night they talked these matters over. "Well, a little change of appearance might be in order. You know Phyllis is back, we have to remember that."

"I still can't believe they survived. She must have nine lives."

"In any case we were on too many news shows. We have to take care."

By day Gamete was slowly completed. But it never seemed right to Nirgal, no matter how much he tried to focus on the making of it. It wasn't his place.

News came from another traveler that Coyote would be by soon. Nirgal felt his pulse quicken; to get back under the starry sky again, wandering by night in Coyote's boulder car, from sanctuary to sanctuary....

Jackie stared at him attentively as he talked about it to her. And that afternoon, after they were dismissed from the day's work, she led him down to the tall new dunes and kissed him. When he recovered his wits he kissed back, and then they were kissing pa.s.sionately, hugging each other hard and steaming all over each other's faces. They knelt in the trough between two high dunes, under a pale thin fog, and then lay together in a coc.o.o.n made of their down coats, and kissed and touched each other, peeling down each other's pants and creating a little envelope of their own warmth, huffing out steam and crackling the frost on the sand underneath their coats. All this without a word, merging in one great hot electric circuit, in defiance of Hiroko and all the world. So this is what it feels like, Nirgal thought. Under the strands of Jackie's black hair grains of sand gleamed like jewels, as if minute ice flowers were contained within them. Glories inside everything.

When they were done they crawled up to glance over the dune crest, to make sure no one was coming their way, and then returned to their nest and pulled their clothes over them, for the warmth. They huddled together, kissing voluptuously and without haste. And Jackie prodded him in the chest with a finger and said, "Now we belong to each other."

Nirgal could only nod happily and kiss the long expanse of her throat, his face buried in her black hair. "Now you belong to me," she said.

He sincerely hoped it was true. It was how he had wanted it, for as long as he could remember.

But that evening in the bathhouse Jackie sloshed across the pool, and caught up Dao and gave him a hug, body to body. She pulled back and stared at Nirgal with a blank expression, her dark eyes like holes in her face. Nirgal sat frozen in the shallows, feeling his torso stiffen as if preparing for a blow. His b.a.l.l.s were still sore from coming in her; and there she stood draped against Dao, as she hadn't been in months, staring at him with a basilisk stare.

The strangest sensation swept over him- he understood that this was a moment he would remember all his life, a pivotal moment, right there in the steamy comfortable bath, under the osprey eye of the statuesque Maya, whom Jackie hated with a fine hate, who was now watching the three of them closely, suspecting something. So this was how it was. Jackie and Nirgal might belong to each other, and he certainly belonged to her- but her idea of belonging was not his. The shock of this knocked his breath out, it was a kind of collapse of the roof of his understanding of things. He looked at her, stunned, hurt, becoming angry- she hugged Dao all the more- and he understood. She had collected both of them. Yes, it made sense, it was certain; and Reull and Steve and Frantz were all equally devoted to her- perhaps that was just a holdover from her rule over the little band, but perhaps not. Perhaps she had collected all of them. And clearly, now that Nirgal was a kind of foreigner to them, she was more comfortable with Dao. So he was an exile in his own home, and in his own love's heart. If she had a heart!

He didn't know if any of these impressions were true, didn't know how to find out. He wasn't sure he wanted to find out. He got out of the bath and retreated into the men's room, feeling Jackie's gaze boring into his back, and Maya's too.

In the men's room he caught sight of an unfamiliar face in one of the mirrors. He stopped short and recognized it as his own face, twisted with distress.

He approached the mirror slowly, feeling the strange sensation of momentousness sweep through him again. He stared at the face in the mirror, stared and stared; it came to him that he was not the center of the universe, or its only consciousness, but a person like all the rest, seen from the outside by others, the way he saw others when he looked at them. And this strange Nirgal-in-the-mirror was an arresting black-haired brown-eyed boy, intense and compelling, a near twin to Jackie, with thick black eyebrows and a... a look look. He didn't want to know any of this. But he felt the power burning at his fingertips, and recalled how people looked at him, and understood that for Jackie he might represent the same sort of dangerous power that she did for him- which would explain her consorting with Dao, as an attempt to hold him off, to hold a balance, to a.s.sert her power. To show they were a matched pair- and a match. And all of a sudden the tension left his torso, and he shuddered, and then grinned, lopsidedly. They did indeed belong to each other. But he was still himself.

So when Coyote showed up and came by to ask Nirgal to join him on another trip, he agreed instantly, very thankful for the opportunity. The flash of anger on Jackie's face when she heard the news was painful to see; but another part of him exulted at his otherness, at his ability to escape her, or at least to get some distance. Match or not, he needed it.

A few evenings later he and Coyote and Peter and Michel drove away from the huge ma.s.s of the polar cap, into the broken land, black under its blanket of stars.

Nirgal looked back at the luminous white cliff with a tumultuous mix of feelings; but chief among them was relief. Back there they would burrow ever deeper under the ice, it seemed, until they lived in a dome under the South Pole- while the red world spun through the cosmos, wild among the stars. Suddenly he understood that he would never again live under the dome, never return to it except for short visits; this was not a matter of choice, but simply the way it was going to happen. His fate, or destiny. He could feel it like a red rock in his hand. Henceforth he would be homeless, unless the whole planet someday became his home, every crater and canyon known to him, every plant, every rock, every person- everything, in the green world and the white. But that (remembering the storm seen from the edge of Promethei Rupes) was a task to occupy many lives. He would have to start learning.

Part Two

The Amba.s.sador

Asteroids with elliptical orbits that cross inside the orbit of Mars are called Amor asteroids. (If they cross inside the orbit of Earth they are called Trojans.) In 2088 the Amor asteroid known as 2034 B crossed the path of Mars some eighteen million kilometers behind the planet, and a clutch of robotic landing vehicles originating from Luna docked with it shortly thereafter. 2034 B was a rough ball about five kilometers in diameter, with a ma.s.s of about fifteen billion tons. As the rockets touched down, the asteroid became New Clarke.

Quickly the change became obvious. Some landers sank to the dusty surface of the asteroid and began drilling, excavating, stamping, sorting, conveying. A nuclear reactor power plant switched on, and fuel rods moved into position. Elsewhere ovens fired, and robot stokers prepared to shovel. On other landers payload bays opened, and robot mechanisms spidered out onto the surface and anch.o.r.ed themselves to the irregular planes of rock. Tunnelers bored in. Dust flew off into the s.p.a.ce around the asteroid, and fell back down or escaped forever. Landers extended pipes and tubes into each other. The asteroid's rock was carbonaceous chrondrite, with a good percentage of water ice shot through it in veins and bubbles. Soon the linked collection of factories in the landers began to produce a variety of carbon-based materials, and some composites. Heavy water, one part in every 6,000 of the water ice in the asteroid, was separated out. Deuterium was made from the heavy water. Parts were made from the carbon composites, and other parts, brought along in another payload, were brought together with the new ones in factories. New robots appeared, made mostly of Clarke itself. And so the number of machines grew, as computers on the landers directed the creation of an entire industrial complex.

After that the process was quite simple, for many years. The princ.i.p.al factory on New Clarke made a cable of carbon nanotube filaments. The nanotubes were made of carbon atoms linked in chains so that the bonds holding them together were as strong as any that humans could manufacture. The filaments were only a few score meters long, but were bundled in cl.u.s.ters with their ends overlapping, and then the bundles were bundled, until the cable was nine meters in diameter. The factories could create the filaments and bundle them at speeds that allowed them to extrude the cable at a rate of about four hundred meters an hour, ten kilometers a day, for hour after hour, day after day, year after year.

While this thin strand of bundled carbon spun out into s.p.a.ce, robots on another facet of the asteroid were constructing a ma.s.s driver, an engine that would use the deuterium from the indigenous water to fire crushed rock away from the asteroid at speeds of 200 kilometers a second. Around the asteroid smaller engines and conventional rockets were also being constructed and stocked with fuels, waiting for the time when they would fire, and perform the work of att.i.tude jets. Other factories constructed long wheeled vehicles capable of running back and forth on the growing cable, and as the cable continued to appear out of the planet, small rocket jets and other machinery were attached to it.

The ma.s.s driver fired. The asteroid began to move into a new orbit.

Years pa.s.sed. The asteroid's new orbit intersected the orbit of Mars such that the asteroid came within ten thousand kilometers of Mars, and the collection of rockets on the asteroid fired in a way that allowed the gravity of Mars to capture it, in an orbit at first highly elliptical. The jets continued to fire off and on, regularizing the orbit. The cable continued to extrude. More years pa.s.sed.

A little over a decade after the landers had first touched down, the cable was approximately thirty thousand kilometers long. The asteroid's ma.s.s was about eight billion tons, the cable's ma.s.s was about seven billion. The asteroid was in an elliptical orbit with a periapsis of around fifty thousand kilometers. But now all the rockets and ma.s.s drivers on both New Clarke and the cable itself began to fire, some continuously but most in spurts. One of the most powerful computers ever made sat in one of the payload bays, coordinating the data from sensors and determining what rockets should fire when. The cable, at this time pointing away from Mars, began to swing around toward it, as in the pivoting of some delicate part of a timepiece. The asteroid's...o...b..t became smaller and more regular.

More rockets landed on New Clarke for the first time since that first touchdown, and robots in them began the construction of a s.p.a.ceport. The tip of the cable began to descend toward Mars. Here the calculus employed by the computer soared off into an almost metaphysical complexity, and the gravitational dance of asteroid and cable with the planet became ever more precise, moving to a music that was in a permanent ritard, so that as the great cable grew closer to its proper position, its movements became slower and slower. If anyone had been able to see the full extent of this spectacle, it might have seemed like some spectacular physical demonstration of Zeno's paradox, in which the racer gets closer to the finish line by halving distances... But no one ever saw the full spectacle, for no witnesses had the senses necessary. Proportionally the cable was far thinner than a human hair- if it had been reduced to a hair's diameter, it would still have been hundreds of kilometers long- and so it was only visible for short portions of its entire length. Perhaps one might say that the computer guiding it in had the fullest sensation of it. For observers down on the surface of Mars, in the town of Sheffield, on the volcano Pavonis Mons (Peac.o.c.k Mountain), the cable made its first appearance as a very small rocket, descending with a very thin leader line attached to it; something like a bright lure and a thin fishing line, being trolled by some G.o.ds in the next universe up. From this ocean-bottom perspective the cable itself followed its leader line down into the ma.s.sive concrete bunker east of Sheffield with an aching slowness, until most humans simply stopped paying attention to the vertical black stroke in the upper atmosphere.

But the day came when the bottom of the cable, firing jets to hold its position in the gusty winds, dropped down into the hole in the roof of the concrete bunker, and settled into its collar. Now the cable below the areosynchronous point was being pulled down by Mars's gravity; the part above the areosynchronous point was trying to follow New Clarke in centrifugal flight away from the planet; and the carbon filaments of the cable held the tension, and the whole apparatus rotated at the same speed as the planet, standing above Pavonis Mons in an oscillating vibration that allowed it to dodge Deimos; all of it controlled still by the computer on New Clarke, and the long battery of rockets deployed on the carbon strand.

The elevator was back. Cars were lifted up one side of the cable from Pavonis, and other cars were let down from New Clarke, providing a counterweight so that the energy needed for both operations was greatly lessened. s.p.a.ceships made their approach to the New Clarke s.p.a.ceport, and when they left they were given a slingshot departure. Mars's gravity well was therefore substantially mitigated, and all its human intercourse with Earth and the rest of the solar system made less expensive. It was as if an umbilical cord had been retied.

He was in the middle of a perfectly ordinary life when they drafted him and sent him to Mars.

The summons came in the form of a fax that appeared out of his phone, in the apartment Art Randolph had rented just the month before, after he and his wife had decided on a trial separation. The fax was brief: Dear Arthur Randolph: William Fort invites you to attend a private seminar. A plane will leave San Francisco airport at 9 Dear Arthur Randolph: William Fort invites you to attend a private seminar. A plane will leave San Francisco airport at 9 A.M., A.M., February 22nd 2101 February 22nd 2101.

Art stared at the paper in amazement. William Fort was the founder of Praxis, the transnational that had acquired Art's company some years before. Fort was very old, and now his position in the transnat was said to be some kind of semiretired emeritus thing. But he still held private seminars, which were notorious although there was very little hard information about them. It was said that he invited people from all subsidiaries of the transnat; that they gathered in San Francisco, and were flown away by private jet to someplace secret. No one knew what went on there. People who attended were usually transferred afterward, and if not, they kept their mouths shut in a way that gave one pause. So it was a mystery.

Art was surprised to be invited, apprehensive but basically pleased. Before its acquisition he had been the cofounder and technical director of a small company called Dumpmines, which was in the business of digging up and processing old landfills, recovering the valuable materials that had been thrown away in a more wasteful age. It had been a surprise when Praxis had acquired them, a very pleasant surprise, as everyone in Dumpmines went from employment in a small firm to apprentice membership in one of the richest organizations in the world- paid in its shares, voting on its policy, free to use all its resources. It was like being knighted.

Art certainly had been pleased, and so had his wife, although she had been elegiac as well. She herself had been hired by Mitsubishi's synthesis management, and the big transnationals, she said, were like separate worlds. With the two of them working for different ones they were inevitably going to drift apart, even more than they already had. Neither of them needed the other anymore to obtain longevity treatments, which transnats provided much more reliably than the government. And so they were like people on different ships, she said, sailing out of San Francis...o...b..y in different directions. Like ships, in fact, pa.s.sing in the night.

It had seemed to Art that they might have been able to commute between ships, if his wife had not been so interested in one of the other pa.s.sengers on hers, a vice-chairman of Mitsubishi in charge of East Pacific development. But Art had been quickly caught up in Praxis's arbitration program, traveling frequently to take cla.s.ses or arbitrate in disputes between various small Praxis subsidiaries involved in resource recovery, and when he was in San Francisco, Sharon was very seldom at home. Their ships were moving out of hailing distance, she had said, and he had become too demoralized to contest the point, and had moved out soon afterward, on her suggestion. Kicked out, one could have said.

Now he rubbed a swarthy unshaven jaw, rereading the fax for the fourth time. He was a big man, powerfully built but with a tendency to slouch-"uncouth," his wife had called him, although his secretary at Dumpmines used the term "bearlike," which he preferred. Indeed he had the somewhat clumsy and shambling appearance of a bear, also its surprising quickness and power. He had been a fullback at the University of Washington, a fullback slow of foot but decisive in direction, and very difficult to bring down. Bear Man, they had called him. Tackle him at your peril.

He had studied engineering, and afterward worked in the oil fields of Iran and Georgia, devising a number of innovations for extracting oil from extremely marginal shale. He had gotten a master's degree from Tehran University while doing this work, and then had moved to California and joined a friend who was forming a company that made deep-sea diving equipment used in offsh.o.r.e oil drilling, an enterprise that was moving out into ever-deeper water as more accessible supplies were exhausted. Once again Art had invented a number of improvements in both diving gear and underwater drills, but a couple of years spent in compression chambers and on the continental shelf had been enough for him, and he had sold his shares to his partner and moved on again. In quick succession he had started a cold-environments habitat construction company, worked for a solar panel firm, and built rocket gantries. Each job had been fine, but as time pa.s.sed he had found that what really interested him was not the technical problems but the human ones. He became more and more involved with project management, and then got into arbitration; he liked jumping into arguments and solving them to everyone's satisfaction. It was engineering of a different kind, more engrossing and fulfilling than the mechanical stuff, and more difficult. Several of the companies he worked for in those years were part of transnationals, and he got embroiled in interface arbitration not only between his companies and others in the transnats, but also in more distant disputes requiring some kind of third-party arbitration. Social engineering, he called it, and found it fascinating.

So when starting Dumpmines he had taken the technical directorship, and had done some good work on their SuperRathjes, the giant robot vehicles that did the extraction and sorting at the landfills; but more than ever before he involved himself in labor disputes and the like. This trend in his career had accelerated after the acquisition by Praxis. And on the days when work like that went well, he always went home knowing that he should have been a judge, or a diplomat. Yes- at heart he was a diplomat.

Which made it embarra.s.sing that he had not been able to negotiate a successful outcome to his own marriage. And no doubt the breakup was well known to Fort, or whoever had invited him to this seminar. It was even possible that they had bugged his old apartment, and heard the unhappy mess of his and Sharon's final months together, which wouldn't have been flattering to either of them. He cringed at the thought, still rubbing his rough jaw, and drifted toward the bathroom and turned on the portable water heater. The face in the mirror looked mildly stunned. Unshaven, fifty, separated, misemployed for most of his life, just beginning at his true calling- he was not the kind of person he imagined got faxes from William Fort.

His wife or ex-wife-to-be called, and she was likewise incredulous. "It must be a mistake," she said when Art told her about it.

She had called about one of her camera lenses, now missing; she suspected that Art had taken it when he moved out. "I'll look for it," Art said. He went over to the closet to look in his two suitcases, still packed. He knew the lens was not in them, but he rooted loudly through them both anyway. Sharon would know if he tried to fake it. While he searched she continued to talk over the phone, her voice echoing tinnily through the empty apartment. "It just shows how weird that Fort is. You'll go to some Shangri-La and he'll be using Kleenex boxes for shoes and talking j.a.panese, and you'll be sorting his trash and learning to levitate and I'll never see you again. Did you find it?"

"No. It's not here." When they had separated they had divided their joint possessions: Sharon had taken their apartment, the entertainment center, the desktop array, the lectern, the cameras, the plants, the bed, and all the rest of the furniture; Art had taken the Teflon frying pan. Not one of his best arbitrations. But it meant he now had very few places to search for the lens.

Sharon could make a single sigh into a comprehensive accusation. "They'll teach you j.a.panese, and we'll never see you again. What could William Fort want with you?"

"Marriage counseling?" Art said.

Many of the rumors about Fort's seminars turned out to be true, which Art found amazing. At San Francisco International he got on a big powerful private jet with six other men and women, and after takeoff the jet's windows, apparently double-polarized, went black, and the door to the c.o.c.kpit was closed. Two of Art's fellow pa.s.sengers played at orienteering, and after the jet made several gentle banks left and right, they agreed that they were headed in some direction between southwest and north. The seven of them shared information: they were all technical managers or arbitrators from the vast network of Praxis companies. They had flown in to San Francisco from all over the world. Some seemed excited to be invited to meet the transnational's reclusive founder; others were apprehensive.

Their flight lasted six hours, and the orienteers spent the descent plotting the outermost limit of their location, a circle that encompa.s.sed Juneau, Hawaii, Mexico City, and Detroit, although it could have been larger, as Art pointed out, if they were in one of the new air-to-s.p.a.ce jets; perhaps half the Earth or more. When the jet landed and stopped, they were led through a miniature jetway into a big van with blackened windows, and a windowless barrier between them and the driver's seat. Their doors were locked from the outside.

They were driven for half an hour. Then the van stopped and they were let out by their driver, an elderly man wearing shorts and a T-shirt advertising Bali.

They blinked in the sunlight. They were not in Bali. They were in a small asphalt parking lot surrounded by eucalyptus trees, at the bottom of a narrow coastal valley. An ocean or very big lake lay to the west about a mile, just a small wedge of it in sight. A creek drained the valley, and ran into a lagoon behind a beach. The valley's side walls were covered with dry gra.s.s on the south side, cactus on the north; the ridges above were dry brown rock. "Baja?" one of the orienteers guessed. "Ecuador? Australia?"

"San Luis Obispo?" Art said.

Their driver led them on foot down a narrow road to a small compound, composed of seven two-story wooden buildings, nestled among seacoast pines at the bottom of the valley. Two buildings by the creek were residences, and after they dropped their bags in a.s.signed rooms in these buildings, the driver led them to a dining room in another building, where half a dozen kitchen workers, all quite elderly, fed them a simple meal of salad and stew. After that they were taken back to the residences, and left on their own.

They gathered in a central chamber around a wood-burning stove. It was warm outside, and there was no fire in the stove.

"Fort is a hundred and twelve," the orienteer named Sam said. "And the treatments haven't worked on his brain."

"They never do," said Max, the other orienteer.

They discussed Fort for a while. All of them had heard things, for William Fort was one of the great success stories in the history of medicine, their century's Pasteur: the man who beat cancer, as the tabloids inaccurately put it. The man who beat the common cold. He had founded Praxis at age twenty-four, to market several breakthrough innovations in antivirals, and he had been a multi-billionaire by the time he was twenty-seven. After that he had occupied his time by expanding Praxis into one of the world's biggest transnationals. Eighty continuous years of metastasizing, as Sam put it. While mutating personally into a kind of ultra-Howard Hughes, or so it was said, growing more and more powerful, until like a black hole he had disappeared completely inside the event horizon of his own power. "I just hope it doesn't get too weird," Max said.

The others attendants- Sally, Amy, Elizabeth, and George- were more optimistic. But all of them were apprehensive at their peculiar welcome, or lack of one, and when no one came to visit them through the rest of that evening, they retired to their rooms looking concerned.

Art slept well as always, and at dawn he woke to the low hoot of an owl. The creek burbled below his window. It was a gray dawn, the air filled with the fog that nourished the sea pines. A tocking sound came from somewhere in the compound.

He dressed and went out. Everything was soaking wet. Down on narrow flat terraces below the buildings were rows of lettuce, and rows of apple trees so pruned and tied to frameworks that they were no more than fan-shaped bushes.

Colors were seeping into things when Art came to the bottom of the little farm, over the lagoon. There a lawn lay spread like a carpet under a big old oak tree. Art walked over to the tree, feeling drawn to it. He touched its rough, fissured bark. Then he heard voices; coming up a path by the lagoon were a line of people, wearing black wetsuits and carrying surfboards, or long folded birdsuits. As they pa.s.sed he recognized the faces of the previous night's kitchen crew, and also their driver. The driver waved and continued up the path. Art walked down it to the lagoon. The low sound of waves mumbled through the salty air, and birds swam in the reeds.

After a while Art went back up the trail, and in the compound's dining room he found the elderly workers back in the kitchen, flipping pancakes. After Art and the rest of the guests had eaten, yesterday's driver led them upstairs to a large meeting room. They sat on couches arranged in a square. Big picture windows in all four walls let in a lot of the morning's gray light. The driver sat on a chair between two couches. "I'm William Fort," he said. "I'm glad you're all here."

He was, on closer inspection, a strange-looking old man; his face was lined as if by a hundred years of anxiety, but the expression it currently displayed was serene and detached. A chimp, Art thought, with a past in lab experimentation, now studying Zen. Or simply a very old surfer or hang-glider, weathered, bald, round-faced, snub-nosed. Now taking them in one by one. Sam and Max, who had ignored him as driver and cook, were looking uncomfortable, but he didn't seem to notice. "One index," he said, "for measuring how full the world is of humans and their activities, is the percent appropriation of the net product of land-based photosynthesis."

Sam and Max nodded as if this were the usual way to start a meeting.

"Can I take notes?" Art asked.

"Please," Fort said. He gestured at the coffee table in the middle of the square of couches, which was covered with papers and lecterns. "I want to play some games later, so there's lecterns and workpads, whatever you like."

Most of them had brought their own lecterns, and there was a short silent scramble as they got them out and running. While they were at it Fort stood up and began walking in a circle behind their couches, making a revolution every few sentences. Difficult! Difficult! Art wrote. Art wrote. Continued? Continued?

"We now use about eighty percent of the net primary product of land-based photosynthesis," he said. "One hundred percent is probably impossible to reach, and our long-range carrying capacity has been estimated to be thirty percent, so we are ma.s.sively overshot, as they say. We have been liquidating our natural capital as if it were disposable income, and are nearing depletion of certain capital stocks, like oil, wood, soil, metals, fresh water, fish, and animals. This makes continued economic expansion difficult."

"We have to continue," Fort said, with a piercing glance at Art, who un.o.btrusively sheltered his lectern with his arm. "Continuous expansion is a fundamental tenet of economics. Therefore one of the fundamentals of the universe itself. Because everything is economics. Physics is cosmic economics, biology is cellular economics, the humanities are social economics, psychology is mental economics, and so on."

His listeners nodded unhappily.

"So everything is expanding. But it can't happen in contradiction to the law of conservation of matter-energy. No matter how efficient your throughput is, you can't get an output larger than the input."

Art wrote on his note page, Output larger than input- everything economics- natural capital- Ma.s.sively Overshot. Output larger than input- everything economics- natural capital- Ma.s.sively Overshot.

"In response to this situation, a group here in Praxis has been working on what we call full-world economics."

"Shouldn't that be overfull-world?" Art asked.

Fort didn't appear to hear him. "Now as Daly said, man-made capital and natural capital are not subst.i.tutable. This is obvious, but since most economists still say they are are subst.i.tutable, it has to be insisted on. Put simply, you can't subst.i.tute more sawmills for fewer forests. If you're building a house you can juggle the number of power saws and carpenters, which means they're subst.i.tutable, but you can't build it with half the amount of lumber, no matter how many saws or carpenters you have. Try it and you have a house of air. And that's where we live now." subst.i.tutable, it has to be insisted on. Put simply, you can't subst.i.tute more sawmills for fewer forests. If you're building a house you can juggle the number of power saws and carpenters, which means they're subst.i.tutable, but you can't build it with half the amount of lumber, no matter how many saws or carpenters you have. Try it and you have a house of air. And that's where we live now."

Art shook his head and looked down at his lectern page, which he had filled again. Resources and capital nonsubst.i.tutable- power saws/carpenters- house of air. Resources and capital nonsubst.i.tutable- power saws/carpenters- house of air.

"Excuse me?" Sam said. "Did you say natural capital?"

Fort jerked, turned around to look at Sam. "Yes?"

"I thought capital was by definition man-made. The produced means of production, we were taught to define it."

"Yes. But in a capitalist world, the word capital capital has taken on more and more uses. People talk about human capital, for instance, which is what labor acc.u.mulates through education and work experience. Human capital differs from the cla.s.sic kind in that you can't inherit it, and it can only be rented, not bought or sold." has taken on more and more uses. People talk about human capital, for instance, which is what labor acc.u.mulates through education and work experience. Human capital differs from the cla.s.sic kind in that you can't inherit it, and it can only be rented, not bought or sold."

"Unless you count slavery," Art said.

Fort's forehead wrinkled. "This concept of natural capital natural capital actually resembles the traditional definition more than human capital. It can be owned and bequeathed, and divided into renewable and nonrenewable, marketed and nonmarketed." actually resembles the traditional definition more than human capital. It can be owned and bequeathed, and divided into renewable and nonrenewable, marketed and nonmarketed."

"But if everything is capital of one sort or another," Amy said, "you can see why people would think that one kind was subst.i.tutable for another kind. If you improve your man-made capital to use less natural capital, isn't that a subst.i.tution?"

Fort shook his head. "That's efficiency. Capital is a quant.i.ty of input, and efficiency is a ratio of output to input. No matter how efficient capital is, it can't make something out of nothing."

"New energy sources..." Max suggested.

"But we can't make soil out of electricity. Fusion power and self-replicating machinery have given us enormous amounts of power, but we have to have basic stocks to apply that power to. And that's where we run into a limit for which there are no subst.i.tutions possible."

Fort stared at them all, still displaying that primate calm that Art had noted at the beginning. Art glanced at his lectern screen. Natural capital- human capital- traditional capital- energy vs. matter- electric soil- no subst.i.tutes please Natural capital- human capital- traditional capital- energy vs. matter- electric soil- no subst.i.tutes please- He grimaced and clicked to a new page.

Fort said, "Unfortunately, most economists are still working within the empty-world model of economics."