What’s your random seed?

April 18th, 2012

Greg Egan is awesome

I’m going back and re-reading Luminous, one of his collections of short stories. I just read the story Transition Dreams, which kinda creeped me out. Partly because I buy into the whole notion that our brains are digitizable — as in, there’s nothing fundamentally unrepresentable about our minds. There’s probably a fancy philosophy term for this, with some dead white guy’s name attached to it (because only a dozen people had thought of it before him and he talked the loudest).

Once you’re willing to accept accurate-enough digitization, the ramifications get pretty crazy. And spooky. I can come up with some, but Egan takes it way farther, and Transition Dreams is a good illustration. But I won’t spoil the story. (By the way, most of Egan’s books are out of print or rare enough to be expensive, but Terrence tells me that they’re all easily available on Kindle. Oddly, although I would be happy to transition my mental workings from meat to bits, I’m still dragging my heels on transitioning my reading from dead trees to bits.)

Transition and Free Will

Now, let’s assume that you’ve converted your brain to live inside a computer (or network of computers, or encoded into the flickers of light on a precisely muddy puddle of water, it really doesn’t matter.) So your thinking is being simulated by all these crazy cascades of computation (only it’s not simulated; it’s the real thing, but that’s irrelevant here.) Your mind is getting a stream of external sensor input, it’s chewing on that and modifying its state, and you’re just… well, being you.

Now, where is free will in this picture? Assuming free will exists in the first place, I mean, and that it existing and not existing are distinguishable. If you start in a particular, fully-described state, and you receive the exact same inputs, will you always behave in exactly the same way? You could build the mind hosting computer either way, you know, and the hosted minds wouldn’t normally be able to tell the difference. But they could tell the difference if they recorded all of their sensory inputs (which is fairly plausible, actually), because they could make a clone of themselves back at the previous state and replay all their sensory input and see if they made the same decisions. (Actually, it’s easier than that; if the reproduction was accurate, they should end up bit-for-bit identical.)

I don’t know about you, but I’d rather not be fully predictable. I don’t want somebody to copy me and my sensor logs, and then when I’m off hanging out in the Gigahertz Ghetto (read: my brain is being hosted on a slow computer), they could try out various different inputs on faster computers to see how “I” reacted and know for 100% certainty how to achieve some particular reaction.

Well, ok, my time in the GHzGhetto might change me enough to make the predictions wrong, so you’d really have to do this while I was fully suspended. Maybe the shipping company that suspends my brain while they shoot me off to a faster hosting facility in a tight orbit around the Sun (those faster computers need the additional solar energy, y’know) is also selling copies on the side to advertisers who want to figure out exactly what ads they can expose me to upon reawakening to achieve a 100% clickthrough rate. Truly, truly targeted advertising.

So, anyway, I’m going to insist on always having access to a strong source of random numbers, and I’ll call that my free will. You can record the output of that random number generator, but that’ll only enable you to accurately reproduce my past, not my future.

The Pain and Joy of Determinism

Or will I? What if that hosting facility gets knocked out by a solar flare? Do I really want to start over from a backup? If it streams out the log of sensor data to a safer location, then it’d be pretty cool to be able to replay as much of the log as still exists, and recover almost all of myself. I’d rather mourn a lost day than a lost decade. But that requires not using an unpredictable random number generator as an input.

So what about a pseudo-random number generator? If it’s a high quality one, then as long as nobody else can access the seed, it’s just as good. But that gives the seed incredible importance. It’s not “you”, it’s just a simple number, but in a way it allows substantial control over you, so it’s private in a more fundamental way than anything we’ve seen before. Who would you trust it to? Not yourself, certainly, since you’ll be copied from computer to computer all the time and each transfer is an opportunity for identity theft. What about your spouse? Or maybe just a secure service that will only release it for authorized replays of your brain?

Without that seed (or those timestamped seeds?), you can never go back. Well, you can go back to your snapshots, but you can’t accurately go forward from there to arbitrary points in time. Admittedly, that’s not necessary for some uses — if you want to know why you did something, you can go back to a snapshot and replay with a different seed. If you do something different, it was a choice made of your own free will. You could use it in court cases, even. If you get the same result, well, it’s trickier, because you might make the same choice for 90% of the possible random seeds or something. “Proof beyond a reasonable confidence interval?” Heh.

One Response to “What’s your random seed?”

  1. Proper Dave Says:

    That’s a great solution to the backup problem! Rather than a snapshot that is probably in the exabyte range (even after compression) you stream your exact sensor inputs to the backup facility. So rather than take a backup of your whole state that will be huge (even monthly bandwidth bills will add up…) you only do it occasionally as you can afford it. Your inputs will only be in the terabyte range, much cheaper to transfer to the offsite backup facility.
    Egan is great you should definitely read Permutation City and Diaspora if you haven’t already.

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