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Because what else would make a periodic signal? It turned out to be a rotating neutron
star.
One criterion to apply to a potentially purposeful phenomenon is whether it’s
minimal in achieving a purpose. But does that mean that it was built for the purpose?
The ball rolls down the hill because of gravitational pull. Or the ball rolls down the hill
because it’s satisfying the principle of least action. There are typically these two
explanations for some action that seems purposeful: the mechanistic explanation and the
teleological. Essentially all of our existing technology fails the test of being minimal in
achieving its purpose. Most of what we build is steeped in technological history, and it’s
incredibly non-minimal for achieving its purpose. Look at a CPU chip; there’s no way
that that’s the minimal way to achieve what a CPU chip achieves.
This question of how to identify purposefulness is a hard one. It’s an important
question, because radio noise from the galaxy is very similar to CDMA transmissions
from cell phones. Those transmissions use pseudo-noise sequences, which happen to
have certain repeatability properties. But they come across as noise, and they’re set up as
noise, so as not to interfere with other channels. The issue gets messier. If we were to
observe a sequence of primes being generated from a pulsar, we’d ask what generated
them. Would it mean that a whole civilization grew up and discovered primes and
invented computers and radio transmitters and did this? Or is there just some physical
process making primes? There’s a little cellular automaton that makes primes. You can
see how it works if you take it apart. It has a little thing bouncing inside it, and out
comes a sequence of primes. It didn’t need the whole history of civilization and biology
and so on to get to that point.
I don’t think there is abstract “purpose,” per se. I don’t think there’s abstract
meaning. Does the universe have a purpose? Then you’re doing theology in some way.
There is no meaningful sense in which there is an abstract notion of purpose. Purpose is
something that comes from history.
One of the things that might be true about our world is that maybe we go through
all this history and biology and civilization, and at the end of the day the answer is “42,”
or something. We went through all those 4 billion years of various kinds of evolution
and then we got to “42.”
Nothing like that will happen, because of computational irreducibility. There are
computational processes that you can go through in which there is no way to shortcut that
process. Much of science has been about shortcutting computation done by nature. For
example, if we’re doing celestial mechanics and want to predict where the planets will be
a million years from now, we could follow the equations, step-by-step. But the big
achievement in science is that we’re able to shortcut that and reduce the computation.
We can be smarter than the universe and predict the endpoint without going through all
the steps. But even with a smart enough machine and smart enough mathematics, we
can’t get to the endpoint without going through the steps. Some details are irreducible.
We have to irreducibly follow those steps. That’s why history means something. If we
could get to the endpoint without going through the steps, history would be, in some
sense, pointless.
So it’s not the case that we’re intelligent and everything else in the world is not.
There’s no enormous abstract difference between us and the clouds or us and the
cellular automata. We cannot say that this brainlike neural network is qualitatively

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