Re: Evidence for the simulation argument

From: Wei Dai <>
Date: Mon, 15 Jan 2007 10:12:51 +0800

Jason wrote:
>I assumed bounded memory due to the limited amount of matter and energy
> available to build the computer. For instance I've seen it said that the
> total information content of this universe is about 10^90 bits. If a
> civilization gathered all the mass and energy available in their universe
> to
> build a computer, they could only accurately simulate universes with an
> information content less than or equal to that of their host universe.

But as I said, limited amount of matter and energy only implies limited
memory if space is also bounded. See By spreading the energy over
an ever increasing volume of space, we can obtain unbounded memory. This is
essentially the same principle as get an unlimited number of computational
steps from finite energy by continually slowing down the rate of
computation. So again I don't know why you assume one thing but not the

Perhaps a more general form of your argument (which doesn't depend on the
above assumption) is that any kind of computational limits we see today (in
practice, not just in theory) could be taken as evidence that we're in a
simulated universe, since simulated universes are likely to have fewer
computational resources than base universes. The fact that we can
theoretically obtain unbounded memory or number of computational steps would
be irrelevant to this argument since the simulation could end before we have
the technology to do so.

An alternative explanation that I favor for the presence of computational
limits is that they are necessary for the evolution of sentience. Without
computational limits, an organism can respond to its environment in an
apparently intelligent manner by using brute force algorithms, therefore
sentience would have little evolutionary advantage. If this explanation is
correct, then all civilizations have to go through a early phase where they
are computational constrained, and the presence of computational limits is
no longer an additional argument for being in a simulation. ("Additional"
here means additional to the fact that we seem to be living in an early
phase of a civilization, which I think is the evidence of the original
simulation argument.)

As for the simulation argument itself, I've suggested previously that
instead of thinking "which kind of universe am I likely to be in", it makes
more sense to consider myself as being "simultaneously" in all universes
that contain me, and to decide my actions based on their effects on the
overall multiverse. Given this kind of philosophy, we can see that while
there may be many many simulated universes that contain us, the effects of
our actions on a single base universe (which may be computationally
unlimited once we move beyond this early phase) can easily outweigh the
effects on all of the simulated universes. Therefore it doesn't make sense
to place more consideration on the simulated universes when we reason or
make choices.

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Received on Sun Jan 14 2007 - 21:16:25 PST

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