Re: algorithmic complexity of God

Nick Bostrom (
Tue, 13 Jan 1998 00:15:21 +0000

> Date: Sun, 11 Jan 1998 16:29:05 -0800
> From: Hal Finney <>
> I'm not sure how to take into account the fact that different models
> may allow for the creation of life only with some probability. My
> preference would be to consider models in which the creation of life
> is a certainty. Then you are comparing apples to apples when you count
> the size of the theory.

I don't think there would be any problem factoring in the
consideration that some models just probabilistically imply the
creation of life. That's a fairly simple technical move. What is
philosophically more tricky, however, is to decide what to do about
the fact that different models would have different numbers different
types of living things. Would my existence be more probable given the
universe contains many observers than given it contains few
observers? The assumtion that it would be more probable if the
universe contains many observers is the Self-indication axiom. In my
paper on the Carter-Leslie Doomsday argument, I give some arguments
in favour of the negation of the Self-indication axiom. The bad thing
about holding the negation true, though, is that it makes it hard to
see how to escape the conclusion of the Doomsday argument.

> Two possible theories, as I mentioned, are first that you create all
> possible universes with all different variations on the parameters
> we observe. This is probably a pretty simple theory.

The problem with this theory is that our univers is not what we
should expect it to be if this theory were true. If all locally
possible worlds are instantiated eqully numerously, then we should
not expect to find ourselves in one that is so highly ordered as
ours. For every possible world like this one, there are countless
ones where pink elephants sometimes materialize out of nowhere or
random blue blobs form over houses whose street addresses are prime
numbers. If all these possible worlds were actual, then why are we
not in one of these irregular ones?

Nick Bostrom
London School of Economics
Department of Philosophy, Logic and Scientific Method