Psychohistorian comments on It's not like anything to be a bat - Less Wrong

15 Post author: Yvain 27 March 2010 02:32PM

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Comment author: Psychohistorian 27 March 2010 09:23:15PM *  0 points [-]

Assume three possible worlds, for simplicity:

A: 1 billion humans. No ETs.

B: 1 billion humans, 1 million ETs

C: 1 billion humans, 1 billion billion billion ETs.

If I am using the anthropic principle and the observation that I am human, these together provide very strong evidence that we are in either world one or world two, with a slightly stronger nudge towards world one. Where we end up after this observation depends on our priors. I agree fully that making additional inferences, such as the probability of other sentient beings increasing due to our own existence, or when we look at the size of the universe, the odds of being alone decrease, affects the end probability.

The inference I described may be unduly restricted, but that is my exact point. The original post made an anthropic inference in isolation - it simply used the fact that there are more animals than humans, and the author is a human, to infer that animals do not have experiences. The form of the argument would not have changed significantly were it used to argue that rocks lack experience. Thus, while the argument is legitimate, it is easily overwhelmed by additional evidence, such as the fact that humans and animals have somewhat similar brains. That was my point: the anthropic principle is easily swamped by additional evidence (as in the ET issue) and so is being overextended here.

Comment author: PhilGoetz 27 March 2010 10:19:03PM *  10 points [-]

You're saying, "I rolled a die. The die came up 1. Therefore, this die probably has a small number of sides."

But "human" is just "what we are". Humans are not "species number 1". So your logic is really like saying, "I rolled a die. The die landed with some symbol on top. Therefore, it probably has a small number of sides."

Comment author: AllanCrossman 27 March 2010 10:32:37PM *  3 points [-]

If the various species of ET are such that no particular species makes up the bulk of sentient life, then there's no reason to be surprised at belonging to one species rather than another. You had to be some species, and human is just as likely as klingon or wookie.

Comment author: wedrifid 28 March 2010 01:01:48PM 0 points [-]

If I am using the anthropic principle and the observation that I am human, these together provide very strong evidence that we are in either world one or world two, with a slightly stronger nudge towards world one.

And here is where we are in simple disagreement. I say that knowing that I am human tells me very little about the configuration of matter in a different galaxy. Things that it does not tell me include, but are not limited to, "is the matter arranged in the form of a childlike humanoid, maybe green or grey. Probably with a big head and that can do complex thinking?"

I claim (and, again, it is a complex topic so I wouldn't bet on myself at odds of more than one gives you, say, 20) that this argument isn't weak evidence that is easily overwhelmed. It is not evidence at all.