Tagiri was shaken. "I don't care that I don't understand the science of it," she said. "I only know that I hate it."

"It's always frightening to deal with something that is counterintuitive," said Maniam.

"Not at all," said Tagiri, trembling. "I didn't say I was frightened. I'm not. I'm angry and ... frustrated. Horrified."

"Horrified about the mathematics of time?"

"Horrified at what we are doing, at what the Interveners actually did. I suppose that I always felt that in some sense they went on. That they sent their machine and then went on with their lives, comforted in their miserable situation by knowing that they had done something to help their ancestors."

"But that was never possible," said Manjam.

"I know it," said Tagiri. "And so when I really thought about it, I imagined them sending the machine and in that moment they sort of -- disappeared. A clean painless death for everyone. But at least they had lived, up to that moment."

"Well," said Maniam, "how is clean, painless nonexistence any worse than a clean, painless death?"

"You see," said Tagiri, "it's not. Not any worse. And not any better, either, for the people themselves."

"What people?" said Marjam, shrugging.

"Us. Manjam. We are talking about doing this to ourselves."

"If you do this, then there will have been no such people as ourselves. The only aspect of our causal network that will have any future or past are those that are connected to the creation of the physical bodies and mental states of the persons you send into the past."

"This is all so silly," said Diko. "Who cares about what's real and what isn't real? Isn't this what we wanted all along? To make it so that the terrible events of our history never happened in the first place? And as for our own history, the parts that will be lost, who cares if a mathematician calls us dirty names like 'unreal'? They say such slanders about the square root of minus two, as well."

Everyone laughed, but not Tagiri. They did not see the past as she saw it. Or rather, they didn't feel the past. They didn't understand that to her, looking through the Tempoview and the TruSite II, the past was alive and real. Just because the people were dead did not mean that they were not still part of the present, because she could go back and recover them. See them, hear them. Know them, at least as well as any human being ever knows any other. Even before the TruSite and the Tempoview, though, the dead still lived in memory, some kind of memory. But not if they changed the past. It was one thing to ask humankind of today to choose to give up their future in the hope of creating a new reality. That would be hard enough. But to also reach back and kill the dead, to uncreate them as well -- and they had no vote. They could not be asked.

We must not do this, she thought. This is wrong. This win be a worse crime than the ones we are trying to prevent.

She got up and left the meeting. Diko and Hassan tried to leave with her, but she brushed them off. "I need to be alone," she said, and so they stayed behind, returning to a meeting that she knew would be in shambles. For a moment she felt remorse at having greeted the physicists' triumphant moment with such a negative response, but as she walked the streets of Juba that remorse faded, replaced by one far deeper.

The children playing naked in the dirt and weeds. The men and women going about their business. She spoke to them all in her heart, saying, How would you like to die? And not only you, but your children and their children? And not only them, but your parents, too? Let's go back into the graves, open them up, and kill them all. Every good and evil thing they did, all their joy, all their suffering, all their choices -- let's kill them all, erase them, undo them. Reaching back and back and back, until we finally come to the golden moment that we have chosen, declaring it worthy to continue to exist, but with a new future tied to the end of it. And why must all of you and yours be killed? Because in our judgment they didn't make a good enough world. Their mistakes along the way were so unforgivable that they erase the value of any good that also happened. All must be obliterated.

How dare I? How dare we? Even if we got the unanimous consent of all the people of our own time, how will we poll the dead?

She picked her way down the bluffs to the riverside. In the waning afternoon, the heat of the day was finally beginning to break. In the distance, hippos were bathing or feeding or sleeping. Birds were calling, getting ready for their frenzied feeding on the insects of the dusk. What goes through your minds, Birds, Hippopotamuses, Insects of the late afternoon? Do you like being alive? Do you fear death? You kill to live; you die so others can live; it's the path ordained for you by evolution, by life itself. But if you had the power, wouldn't you save yourselves?

She was still there by the river when the darkness came, when the stars came out. For a moment, gazing at the ancient light of the stars, she thought: Why should I worry about uncreating so much of human history? Why should I care that it will be worse than forgotten, that it will be unknown? Why should that seem to be a crime, when all of human history is an eyeblink compared to the billions of years the stars have shone? We will all be forgotten in the last exhalation of our history; what does it matter, then, if some are forgotten sooner than others, or if some are caused to have never existed at all?

Oh, this is such a wise perspective, to compare human lives to the lives of stars. The only problem is that it cuts both ways. If in the long run it doesn't matter that we wipe out billions of lives in order to save our ancestors, then in the long ran saving our ancestors doesn't matter, either, so why bother changing the past at all?

The only perspective that matters is the human one, Tagiri knew. We are the only ones who care; we are the actors and the audience as well, all of us. And the critics. We are also the critics.

The light of an electric torch bobbed into view as she heard someone approaching through the grass.

"That torch will only attract animals that we don't want," she said.

"Come home," said Diko It isn't safe out here, and Father's worried."

"Why should he be worried? My life doesn't exist. I never lived."

"You're alive now, and so am I, and so are the crocodiles."

"If individual lives don't matter," said Tagiri, "then why bother going back to make them better? And if they do matter, then how dare we snuff some out in favor of others?"

"Individual lives matter," said Diko. "But life also matters. Life as a whole. That's what you've forgotten today. That's what Manjam and the other scientists also forgot. They talk of all these moments, separate, never touching, and say that they are the only reality. Just as the only reality of human life is individuals, isolated individuals who never really know each other, never really touch at any point. No matter how close you are, you're always separate."

Tagiri shook her head. "This has nothing to do with what is bothering me."

"It has everything to do with it," said Diko. "Because you know that this is a lie. You know that the mathematicians are wrong about the moments, too. They do touch. Even if we can't really touch causality, the connections between moments, that doesn't mean they aren't real. And just because whenever you look closely at the human race, at a community, at a family, all you can ever find are separate individuals, that doesn't mean that the family is not also real. After all, when you look closely enough at a molecule, all you can see are atoms. There is no physical connection between them. And yet the molecule is still real because of the way the atoms affect each other."

"You're as bad as they are," said Tagiri, "answering anguish with analogies."