“What’s the difference?”

“It’s not just that you can’t have a block of ice in a star, but that you can’t get it there, you can’t keep it there—there is no coherent history that can include it. See, it’s not just about what is possible—since anything is possible in Hemn space—but what is compossible, meaning all the other things that would have to be true in that universe, to have a block of ice in a star.”

“Well, I actually think you could do it,” Emman said. The praxic gears were turning in his head. This was what he did for a living; he’d been pulled out of his job at a rocket agency to serve as technical advisor to Ignetha Foral. “You could design a rocket—a missile with a warhead made of thick heat-resistant material with a block of ice embedded in it. Make this thing plunge into the star at high velocity. The heat-resistant material would burn away. But just after it did, for a moment, you’d have a block of ice embedded in a star.”

“Okay, that’s all possible,” I said, “but it’s a way of answering the question ‘what other things would have to be true about a cosmos that included a block of ice in a star?’ If you were to go to that cosmos and freeze it in that moment of time—”

“Okay,” he said, “let’s say the teleporter has a user interface feature that makes it easy to freeze time by looping back to the same point over and over.”

“Fine. And if you did that and looked at the region around the ice, you’d see the heavy nuclei of the melted heat shield swirling around in the star-stuff. You’d see the trail of rocket exhaust in space, leading all the way back to the scorch marks on the launch pad. That launch pad has to be on a planet capable of supporting life smart enough to build rockets. Around that launch pad you’d see people who had spent years of their lives designing and building that rocket. Memories of that work, and of the launch, would be encoded in their neurons. Speelies of the launch would be stored in their reticules. And all of those memories and recordings would mostly agree with one another. All of those memories and recordings boil down to positions of atoms in space—so—”

“So those memories and recordings, you’re saying, are themselves parts of the configuration encoded by that point in Hemn space,” Emman said, loudly and firmly, as he knew he was getting it. “And that is what you mean about compossibility.”

“Yes.”

“Ice in a star could be encoded by many Hemn space points,” he said, “but only a few of them—”

“A vanishingly tiny few,” I said.

“Include all the records—coherent, mutually consistent records—of how it got to be there.”

“Yes. When you go all praxic on me and dream up the ice missile delivery system, what you’re really doing is figuring out what Narrative would create the set of conditions—the traces left behind in the cosmos by the execution of that project—that is compossible with ice in a star.”

We walked on for a bit and he said, “Or to give a less dignified example, you can’t look at Suur Karvall’s outfit—”

“Without having to reconstruct in your mind the sequence of operations needed to tie all those knots.”

“Or to untie them—”

“She’s a Hundreder,” I warned him, “and the Convox won’t last forever.”

“Don’t get too attached. Yeah, I know. But I could still get a date with her in 3700—”

“Or become a fraa,” I suggested.

“I might have to, after this. Hey, do you know where you’re going?”

“Yeah. I’m following you.”

“Well, I’ve been following you.”

“Okay, that would mean that we’re lost.” And we stumbled about until we encountered a pair of grandsuurs out for a stroll, and asked them for directions to the Edharian chapterhouse.

“So,” Emman said, after we’d set out on the right track, “the bottom line is that in any one particular cosmos—excuse me, on any one particular worldtrack—things make sense. The laws of nature are followed.”

“Yes,” I said. “That’s what a worldtrack is—a sequence of Hemn space points strung together just so, to make it look like the laws of nature are preserved.”

“I’m going to put that in teleporter terms, since that’s how I’ll be explaining it to people,” he said. “The whole point of the teleporter is that it could take you to any other point at any moment. You could jump randomly from one cosmos to another. But only one point in Hemn space encodes the state that the cosmos you’re in now will have at the next tick of the clock, if the laws of nature are followed—right?”

“You’re on the right track,” I said, “but—”

“Where I’m going with this,” he said, “is as follows: the people to whom I have to explain this have heard of the laws of nature. Maybe even studied them a bit. They’re comfortable with that. Now suddenly I come in and start talking about Hemn space. A new concept to them. I give them a big explanation—I talk about the teleporter, the ice in the star, and the scorch marks on the launch pad. Finally one of these people raises his hand and says, ‘Mr. Beldo, you have squandered hours of our valuable time giving us a calca on Hemn space—what, pray tell, is the bottom line?’ And my answer is, ‘If you please, sir, the bottom line is that the laws of nature are followed in our cosmos.’ And he’s going to say—”

“He’s going to say, ‘We already knew that, you idiot, you’re fired!’”

“Exactly! Which is when I have to run off and become a fraa, preferably in Karvall’s math.”

“So you are asking me—”

“What do we gain that is consequential by adopting the Hemn space model? You already mentioned it makes it easier to do theorics—but Panjandrums don’t do theorics.”

“Well, for one thing, it is actually not the case that, at any given point, there is only one next point that is consistent with the laws of nature.”

“Oh, are you going to talk about quantum mechanics?”

“Yeah. An elementary particle can decay—which is compatible with the laws of nature—or it can not decay—which is also compatible with the laws of nature. But decaying and not decaying take us to two different points in Hemn space—”

“The worldtrack forks.”

“Yeah. Worldtracks fork all the time, whenever quantum state reduction seems to occur—which is a lot.”

“But still, whatever worldtrack we happen to be on still always obeys the laws of nature,” he said.

“I’m afraid so.”

“So, back to my original problem—”

“What does Hemn space get us? Well, for one thing, it makes it a heck of a lot easier to think about quantum mechanics.”

“But Panjandrums don’t think about quantum mechanics!”

I had nothing to say; I just felt like a clueless avout.

“So, do you think I should mention the Hemn space thing at all?”

“Let’s ask Jesry,” I proposed. “He’s cool-looking.” For we had reached the Edharian cloister, and I spied him on a path, drawing diagrams in the gravel with a stick while a fraa and a suur stood by watching and laughing delightedly. In the moonlight these people looked as though they’d been sketched in ash on a fireplace floor. Still, they cut altogether different figures. Jesry looked like a young prophet from some ancient scripture next to the fraa and the suur, who came from more cosmopolitan orders that went in for fancy wraps. This morning at Inbrase I’d felt like a real hick when I’d looked at how the other avout dressed. But that was just me. Put the same outfit on Jesry and he became awe-inspiringly rugged, simple, austere, and, well, manly. I understood, as I looked at him, why Fraa Lodoghir had been so keen to plane me. There was something about the Edharian contingent that impressed people. Orolo had made us into stars. Lodoghir had seen the Plenary as an opportunity to take one of us down a peg.

“Jesry,” I called.

“Hi, Raz. I am not one of those people who think you sucked at the Plenary.”