“In other words, it is as close as we can get right now-and very much close enough for a first approximation,” said Unit Dee. “We are now ready for preliminary long-range climate calculation.”

Kresh half-expected to see the planet’s surface evolve and change, as he had seen so many times before on simglobes and other climate simulators. And he did see at least a little bit of that-or thought he did. But the globe itself was covered in a blizzard of layered data displays that sprawled over its surface. Isobar mappings for temperature, air pressure, humidity, color-coded scatter diagrams of populations for a hundred different species, rainfall pattern displays, seasonal jet-stream shifts, and a dozen other symbol systems Kresh couldn’t even begin to recognize, all of them shifting, rising, dropping, interacting and reacting with each other, a storm of numbers and symbols that covered the planet. The changes came faster and faster, until the symbols and numbers and data tags merged into each other, blurred into a faintly flickering cloud of gray that shrouded the entire planet.

And then, in the blink of an eye, it stopped. The cloud of numbers was gone.

A new planet hung in the air before Kresh. One in which the old world could be clearly seen, and recognized, but new and different all the same. Alvar Kresh had seen many hypothetical Infernos in his day, seen its possible futures presented a hundred times in a hundred different ways. But he had never seen this Inferno before. The tiny, isolated, spots of green here and there were gone, or rather grown and merged together into a blanket of cool, lush green than covered half of Terra Grande. There were still deserts, here and there, but they were the exception, not the rule-and even a properly terraformed planet needed some desert environments.

The sterile, frozen, lifeless ice of the northern polar icecap had vanished completely, replaced by the Polar Sea, a deep-blue expanse of life-giving liquid water. Even at this scale, even to Kresh’s untrained eye, he could see that sea levels had raised worldwide. He wondered for a moment where the water had come from. Had the control units assumed that the importation of comet ice would continue? Or was the water-level rise caused by thawing out the icecaps and breaking up the permafrost? No matter. The fact was that the water was there, that life was there.

“That’s the best, most positive projection I’ve ever seen,” Soggdon said. Kresh, a trifle startled, turned and looked over his shoulder. She was standing right behind his chair, gazing at the globe display in astonishment. “Hold on. I want to do a blind feed of the audio to your headset.”

“What’s a blind feed?” Kresh asked.

Soggdon picked up a headset identical to the one Kresh wore. Soggdon looked to Kresh as she put them on. “Dee and Dum will think you cannot hear what they say to me. When she talks to you, she is talking to a simulant. When she talks to me, a real human being, she cuts all links to any simulants, so as not to complicate the experiment by letting the simulants hear things they shouldn’t. In reality you’ll be able to hear it. But it is important-vitally important-that you have no reaction to what she says to me, or vice versa. In Dee’s universe, you are just a simulated personality inside a computer. I am a real person outside the computer. You have no way of knowing I exist. Do you understand?”

“Yes,” said Kresh, hoping he did. He had the sense that he had stepped into a hall of mirrors. It was getting hard to tell the fantasies from the realities.

“Good,” said Soggdon, and turned on the manual switch on her headset. “Dee, Dum-this is Soggdon monitoring from outside the simulation.”

“Good mornnning, Doctor. Weee havvve beeen connnversssing with the Kresh simulllannt. “ The two voices spoke in unison again, but Soggdon did not seem to be bothered by it. Having heard each voice by itself, Kresh was able to notice something that had escaped him before. When the two units spoke in unison, it was not merely the two chanting together. The voice of the two together spoke in a cadence that did not belong to either of the two speaking by itself. The unison voice made different word choices, responded in a way that was different from Dee or Dum. The unison voice was not merely two beings talking as one. It was the two merging into one new being, in some ways greater, in some ways lesser than the sum of its parts. Dee and Dum linked so intimately that they became a third, and distinct, personality. Or was it merely Dee who did so? If Dum was truly nonsentient, then he could have no personality. Plainly there were mysteries to delve into-but just as plainly they would have to wait for another day. “The Kresh simulant asked us to consider the result of producing a Polar Sea.”

“Yes, I know,” said Soggdon. “And I see you have produced an impressive planetary projection as a result. Would either or both of you care to comment on it?”

“Both willl speeak, and then eachhh,” said the unison voice. “We havvve prrojected forward four ttthousand yearss, as we have found that a wellll-planned operrational sequenzzze will result in a zzzero-maintenance planetary ecologggy within apprrroximately three hundred years. In our projection, the planetary climmmate remainss intrinsically stable, selfffcorrecting, and self-enhancing throughout the period of the metasimulation. There is no apparent danger of recollapse evident in any of the data for the end of the metasimulation period.”

Kresh frowned. Metasimulation? Then he understood. The unison voice was using the term to refer to a simulation inside a simulation-which was what it had been, so far as Dum and Dee were concerned.

Dum spoke next. “Reference to unit Dum’s prior objections in regard to ecological and economic damage. Projections show that the damage to the general ecology and gross planetary product caused by digging inlets for the Polar Sea would be fully compensated for within fifteen years of project completion.”

But if the first two aspects of the combined control system made it all seem wonderful, the third voice pulled everything back down to reality. “It all sounds quite splendid,” said Dee. “There is, of course, the slight problem of it being quite impossible. We ran the metasimulation based on the assumption that it would be possible to dig the channels. It is not possible to dig them. An interesting exercise, I grant you-but it is not one that has a great deal of connection to the world of our simulation.”

“I was afraid she was going to say that,” Soggdon muttered as she switched off her mike. “You’d think she’d be the least sensible of the three possible personality aspects, but instead Dee’s always the one to stick the pin in the balloon. She always reminds us of the practicalities.”

“Maybe this time they’re a bit more possible than you think,” Kresh said. He keyed his own mike back on, and tried to phrase things so that he would not reveal that he had overheard the conversation with Soggdon.

“Unit Dee, that’s a very promising projection there. I take it you think creating the Polar Sea would be a good idea?”

“It is a good idea that cannot be realized, Governor,” said Unit Dee. “You do not have the resources, the energy sources, or the time to construct the needed inlets.”

“That is incorrect,” Kresh said. “It is possible there is a practical, doable, way to dig those inlets. I came here to have you evaluate the proposed procedure. I first wanted to see if the effort would be worthwhile. I see now that it would be.”

“What is the procedure in question?” asked Unit Dee.

Kresh hesitated a moment, but then gave up. There was no way to describe the idea that didn’t sound dangerous, desperate, even insane. Well, maybe it was all three. So be it. “We’re going to break a comet up, and drop the fragments in a line running from the Southern Ocean to the Polar Depression,” he said. Even as he spoke, he realized that he hadn’t put any modifiers or conditionals in. He hadn’t said they might, or they could, or they were thinking of it. He had said they were going to do it. Had he made up his mind without knowing it?