Permutation City

Paul stared at him coldly. "Don't lie to me, it's a waste of time. As soon as I had a Copy who survived, I was going to explain everything --"

Squeak. The djinn said drily, "Or so we thought."

Paul's certainty wavered. "You're telling me that your great ambition is finally being fulfilled -- and you haven't even mentioned it to the one woman . . . ?"

Squeak. Durham's face turned to stone. "I really don't wish to discuss it. Can we get on with the experiment, please?"

Paul opened his mouth to protest -- and then found he had nothing to say. All his anger and jealousy suddenly dissipated into . . . embarrassment. It was as if he'd just come to his senses from a daydream, an elaborate fantasy of a relationship with someone else's lover. Paul and Elizabeth. Elizabeth and Paul. What happened between them was none of his business. Whatever his memories suggested, that life wasn't his to live anymore.

He said, "Sure, let's get on with the experiment. Time is just rushing by. You must have turned forty-five . . . what, a day ago? Many happy returns."

Squeak. "Thanks -- but you're wrong. I took some shortcuts while you were asleep: I shut down part of the model -- and cheated on most of the rest. It's only the fourth of June; you got six hours' sleep in ten hours' real time. Not a bad job, I thought."

Paul was outraged. "You had no right to do that!"

Squeak. Durham sighed. "Be practical. Ask yourself what you'd have done in my place."

"It's not a joke!"

Squeak. "So you slept without a whole body. I cleaned a few toxins out of your blood at a non-physiological rate." The djinn seemed genuinely puzzled. "Compared to the experiments, that's nothing. Why should it bother you? You've woken up in exactly the same condition as you'd be in if you'd slept in the normal way."

Paul caught himself. He didn't want to explain how vulnerable it made him feel to have someone reach through the cracks in the universe and relieve him of unnecessary organs while he slept. And the less the bastard knew about his Copy's insecurities, the better -- he'd only exploit them.

He said, "It bothers me because the experiments are worthless if you're going to intervene at random. Precise, controlled changes -- that's the whole point. You have to promise me you won't do it again."

Squeak. "You're the one who was complaining about waste. Someone has to think about conserving our dwindling resources."

"Do you want me to keep on cooperating? Or do you want to start everything again from scratch?"

Squeak. The djinn said mildly, "All right, you don't have to threaten me. You have my word: no more ad hoc intervention."

"Thank you."

Conserving our dwindling resources? Paul had been trying hard not to think about money. What would the djinn do when he could no longer afford to keep him running -- if Paul chose not to bale out once the experiments were over? Store a snapshot of the model, of course, until he could raise the cash flow to start it up again. In the long term, set up a trust fund; it would only have to earn enough to run him part-time, at first: keep him in touch with the world, stave off excessive culture shock . . . until the technology became cheap enough to let him live continuously.

Of course, all these reassuring plans had been made by a man with two futures. Would he really want to keep an old Copy running, when he could save his money for a deathbed scan, and "his own" immortality?

Squeak. "Can we get to work, now?"

"That's what I'm here for."

This time, the model would be described at the standard time resolution of one millisecond, throughout -- but the order in which the states were computed would be varied.

Squeak. "Experiment two, trial number one. Reverse order."

Paul counted. "One. Two. Three." Reverse order. After an initial leap into the future, he was now traveling backward through real time. It would have been a nice touch if he'd been able to view an external event on the terminal -- some entropic cliche like a vase being smashed -- knowing that it was himself, and not the scene, that was being "rewound" . . . but he knew that it couldn't be done (quite apart from the fact that it would have ruined the experiment, betraying the difference between subject and control). In real time, the first thing to be computed would be his model-time-final brain state, complete with memories of everything that "had happened" in the "preceding" ten seconds. Those memories couldn't include having seen a real broken vase assemble itself from fragments, if the vase hadn't even been smashed yet. The trick could have been done with a simulation, or a video recording of the real thing -- but that wouldn't have been the same.