# Tag Archives: Simulation

## Fading Past Blocks Simulation Argument

The simulation argument was famously elaborated by Nick Bostrom. The idea is that our descendants may be able to create simulated creatures like you, and put them in simulated environments that look like the one you now find yourself in. If so, you can’t be sure that you are not now one of these future simulated people. The chance that you should assign to this possibility depends on the number of such future creatures, relative to the number of real creatures like you today.

More precisely, let P be the fraction of descendant civs that become able to create these ancestors simulations, I the fraction of these that actually do so, N the average number of ancestors simulated by each such civ per ancestor who once existed, and S the chance that you are now such an ancestor sim. Bostrom says that S = P*I*N/(P*I*N+1), and that N is very large, which implies that either P or I is very small, or that S is near 1. That is, if the future will simulate many ancestors, then you are one.

However, I will now show that this argument collapses if we allow the inclination to simulate ancestors to depend on the time duration that has elapsed between those ancestors and the descendants who might simulate them. My main claim is that our interest in the past generally seems to fall away with time faster than the rate at which the population grows with time. For example, while over the last century world population has doubled roughly every 40 to 60 years, this graph shows much faster declines in how often books mention of each of these specific past years: 1880, 1900, 1920, 1940, 1960.

Let us now include this fading past effect in a simple formal model. Let t denote a cultural “time” (not necessarily clock time), relative to which population (really a density of observer-moments) grows exponentially forever, while interest in the past declines exponentially. More formally, assume that it is already possible to create ancestor sims, that population grows as eg*t, that a constant fraction a of this population is turned into simulated ancestors, and that the relative fraction of these simulated ancestors associated with simulating a time t units into the past goes as eb*g*t. Thus for b>1 per-person interest in past people falls as e-(b-1)*g*t.

Given these assumptions, the ratio of future ancestors simulations of the current population to that actual current population is F = a*b/(b-1), and S = F/(F+1). So, for example, if at any one time 10% of people are ancestor simulations, and if interest in the past falls by 12% every time population rises by 10%, then a = 0.1, b = 1.2, and F = 0.6, giving each person who seems to be real a S = 3/8 chance of instead being an ancestor simulation. If a = 0.001 instead, then F = 0.006, and each person should estimate a S =~0.6% chance of being an ancestor simulation.

The above assumed that ancestor sims are possible and are being done now. If instead sims can’t start being created until c time units in the future, then we instead have F = a*(b/(b-1))*e(b-1)*g*c, giving an even smaller chance S of your being an ancestor simulation.

By the way, these calculations can also be done in terms of rank. If all people in history are ordered in time, with r=0 being the first person ever, and all others having r>0, then we could assume that a fraction a of people are always ancestor simulations, and that interest in past people falls as rb, and we’d again get the same result F = a*b/(b-1).

Thus given the realistic tendency to have less interest in past people the further away they are in time, and the likely small fraction of future economies that could plausibly be devoted to simulating ancestors, I feel comfortable telling you: you are most likely not an ancestor simulation.

Added 9pm: See this more careful analysis by Anders Sandberg of falling interest in year names. Seems to me that fall in interest is in fact faster than the population growth rate, even a century after the date.

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## Why Neglect Social Results?

For many decades I’ve heard people argue about the possibility of ems, i.e., brain emulations (also called “uploads”). Many like to talk about whether ems are possible, when they might happen, and if ems would be conscious, or whether they would “be me.”  People also love to read fiction set in worlds where there are ems. Almost twenty years ago I wrote a short article on the social implications of a world of emulations — what that would actually be like. But that didn’t kick-start much interest in the subject – most discussion is still on possibility, timing, consciousness, identity, and story settings.

Over the years I’ve also heard many people argue about the possibility that we live in a computer simulation. Twelve years ago I wrote a short article “How to live in a simulation,” on how you should live your life differently to take this possibility into account. That article also didn’t kick-start much interest in social implications. Today, most discussion of the simulation possibility continues to focus on using it as a setting for fiction, on the chances that it is true, on clues for inferring if it is true, and on what it implies for identity, consciousness, physics, etc. There remains almost no discussion of life strategies conditional on a simulation.

I just now noticed how similar are these situations, a similarity that cries out for explanation. I see three somewhat related candidate explanations:

1. The sorts of people who most like these topics are techies, who mostly don’t believe that social and human sciences exist, and thus aren’t interested in hearing about  applications of such sciences.
2. People are mainly interested in these sorts of topics as ways to stretch and stress-test their basic concepts. So only people with a library of grand social concepts are interested in using these topics to stretch and stress-test such concepts. There aren’t many such people.
3. I personally did a poor job of introducing these topics. Had someone more prestigious or articulate done the job, there might well be much larger conversations now about these topics.

Whatever the explanation, this bodes poorly for interest in my more elaborated book-length discussion of the social implications of ems. However, I will soldier on nonetheless.

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