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I think this post's assumption that intelligent life is inevitable is unsupported. Just because lots of systems are Turing complete doesn't at all imply that in

I think this post's assumption that intelligent life is inevitable is unsupported. Just because lots of systems are Turing complete doesn't at all imply that intelligent life or even life in general is likely to arise from a random initial state. There's no support in the post for this jump in logic. I think the solution to the Fermi paradox is that intelligent life is just spectacularly unlikely, and that we're the only intelligent life in the observable universe. I think most people reason that we're probably not that special, that our conditions aren't too rare, and that the likelihood of intelligent life given those conditions must be somewhat good, but I don't think any of this reasoning is valid given the anthropic principle. I think the fact that we find ourselves in a world where we're alone is evidence for the sheer unlikelihood of life. If there were many values of the fine structure constant that could create a universe with any life at all, then I would guess that across that range of values, there would be more variation where some values would create a universe with rare lonely life and some values would create a universe where life was more plentiful. In that case, we would be more likely to find ourselves in a universe where life was more plentiful. But if there were a tighter range of possible constant values that create a universe with any life at all, then I would expect less variation with only universes with rare lonely life. Given that we find ourselves in a universe with rare lonely life, that seems like evidence that there isn't much room for variation in the constants while staying life-supporting.

coldtea 6y ago
>but I don't think any of this reasoning is valid given the anthropic principle And that concludes the circle in your circular argument in support of the antrhopic principle :-)
- AgentME 6y ago
  In that paragraph, I was trying to argue that the observation of us being alone and the anthropic principle are compatible and related in a way that if either one were missing, we should be skeptical of the other. I think that's valid and distinct from a circular argument. (And then in the last paragraph, I wasn't trying to argue for the anthropic principle, but to argue that given the anthropic principle and the observation we're alone, then I think it's correct to believe that the specific values of physical constants that we observe are likely to be necessary for intelligent life.)
srl 6y ago
I think there are two jumps in logic I made, one more defensible than the other. The first: > Loads of systems exhibit Turing universality, so a small change in alpha shouldn't break that property of our universe. (I consider this relatively indefensible, and the weakest part of my argument.) The other is > Turing universality => intelligent life is inevitable, or at least likely. I think that this second piece, although not discussed explicitly in the post, can be defended. It's not a highbrow argument, just that often-made observation that, if a "computer" requires finite size and finite energy to create, then somewhere in the universe, a computer will come into being by random chance.
TillE 6y ago
It's somewhat reasonable to assume that we're the only intelligent life in our corner of the galaxy (the practical reach of an artificial radio signal), but the observable universe is a really, really big place.
- AgentME 6y ago
  It's been estimated that self-replicating Von Neumann probes could populate our galaxy in 10 million years. I haven't seen an estimate about them populating multiple galaxies, but I assume many could be hit within some multiple of that, and the growth would be exponential. Even if most intelligent life generally doesn't decide to make self-replicating probes, it only takes one civilization in the history of the (observable) universe to do it to make a huge effect. It's possible that life is just likely enough that none of them have yet chosen to or have been alive long enough to create self-replicating probes, but I don't think it's correct to assume that the likelihood value for life would be on the extreme upper end of the range that's compatible with our observations.
vl 6y ago
The problem is that frequentist logic doesn’t work if you have only one sample. Effectively we can’t distinguish between “we are just seeing very unlikely scenario”, “it’s just early and we are the first”, and “life is extremely unlikely”.

coldtea 6y ago

>but I don't think any of this reasoning is valid given the anthropic principle And that concludes the circle in your circular argument in support of the antrhopic principle :-)

AgentME 6y ago
In that paragraph, I was trying to argue that the observation of us being alone and the anthropic principle are compatible and related in a way that if either one were missing, we should be skeptical of the other. I think that's valid and distinct from a circular argument. (And then in the last paragraph, I wasn't trying to argue for the anthropic principle, but to argue that given the anthropic principle and the observation we're alone, then I think it's correct to believe that the specific values of physical constants that we observe are likely to be necessary for intelligent life.)

srl 6y ago

I think there are two jumps in logic I made, one more defensible than the other. The first: > Loads of systems exhibit Turing universality, so a small change in alpha shouldn't break that property of our universe. (I consider this relatively indefensible, and the weakest part of my argument.) The other is > Turing universality => intelligent life is inevitable, or at least likely. I think that this second piece, although not discussed explicitly in the post, can be defended. It's not a highbrow argument, just that often-made observation that, if a "computer" requires finite size and finite energy to create, then somewhere in the universe, a computer will come into being by random chance.

TillE 6y ago

It's somewhat reasonable to assume that we're the only intelligent life in our corner of the galaxy (the practical reach of an artificial radio signal), but the observable universe is a really, really big place.

AgentME 6y ago
It's been estimated that self-replicating Von Neumann probes could populate our galaxy in 10 million years. I haven't seen an estimate about them populating multiple galaxies, but I assume many could be hit within some multiple of that, and the growth would be exponential. Even if most intelligent life generally doesn't decide to make self-replicating probes, it only takes one civilization in the history of the (observable) universe to do it to make a huge effect. It's possible that life is just likely enough that none of them have yet chosen to or have been alive long enough to create self-replicating probes, but I don't think it's correct to assume that the likelihood value for life would be on the extreme upper end of the range that's compatible with our observations.

vl 6y ago

The problem is that frequentist logic doesn’t work if you have only one sample. Effectively we can’t distinguish between “we are just seeing very unlikely scenario”, “it’s just early and we are the first”, and “life is extremely unlikely”.