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All of Avo's Comments + Replies

Avo10y00

That's a very good summary of Caves' argument, thanks for providing it.

EDIT: I upvoted you, but now I see someone else has downvoted you. As with me, no reason was given.

I am new here at LW. I thought it would be a place for rational discussion. Apparently, however, this is not a universally held belief here.

1gjm10y

There's a pretty good level of rational discussion here, better than in most online fora I know of. Some people are pretty trigger-happy with the downvotes (and some get so worked up over political disagreements that they will go back and downvote many random unrelated comments of yours from the past -- but that's near-universally agreed to be bad and tends to get them banned eventually) but nowhere's perfect. And I think the majority of downvotes are genuinely deserved, though I can't see how anything in this thread deserves them.

Doomsday Argument Map

Avo10y10

Why is that case "non random"? A randomly selected person could well turn out to be a 1 month old child. If you know in advance that this is not typical, then you already know something about median life expectancy, and that is what you are using to make your estimate, not the age of the selected person.

Do you have a criticism of Caves' detailed mathematical analysis? It seems definitive to me.

And: to the person who keeps downvoting me. Are you treating my "arguments as soldiers", or do you have a rational argument of your own to offer?

1turchin10y

Look, some one may say: "A fair coin could fail heads 20 times in row and you will win million dollar". And it is true. But this does not disprove more general statement that: "playing coin for money has zero expected money win". The same situation is this Caves and DA. We could imagine situation there DA is wrong, but its is true in most situations (where it is applyable) See also my large comment about Caves to gjm.

5turchin10y

In Cave case this argument was nonrandom, because he knew that median life expectancy was 80 years, and deliberately choose extremely young person. So he was cheating. If he would need really random person he should apply to him self or reader. It will be real experiment. I decided not to search math errors in his calculations, because I don't agree this his notion of "randomness".

Doomsday Argument Map

Avo10y10

For a general analysis along the same lines of life expectancies of various phenomena, see Carl Caves, "Predicting future duration from present age: Revisiting a critical assessment of Gott's rule", http://arxiv.org/abs/0806.3538 . Caves shows (like Dieks) that the original priors are the correct ones. In my example of the biologist and the the bacterium, the biologist is correct.

1turchin10y

I know the paper, read it and found a mistake. The mistake is that while illustrating his disproval of DA, he creates special non random case, something like 1 month child for estimation of median life expectancy. It means that he don't understand the main idea of DA logic, that is we should use one random sample to estimate total set size.

Doomsday Argument Map

Avo10y30

I've been doing some more reading on DA, and I now believe that the definitive argument against it was given by Dennis Dieks in his 2007 paper "Reasoning about the future: Doom and Beauty". See sections 3 and 4. The paper is available at http://www.jstor.org/stable/27653528 or, in preprint form, at http://www.cl.cam.ac.uk/~rf10/doomrev.pdf Dieks shows that a consistent application of DA, in which you use the argument that you are equally likely to be any human who will ever live, requires you to first adjust the prior for doom that you would hav... (read more)

1turchin10y

Thanks for the link. Does it work on toy models of DA in other domains? For example, if I ask your age and you will say "30 years old" (guessing), I can conclude from it that medium human life expectancy is around several decades years with 50 per cent confidence, and that it is less than 1000 years with 95 per cent confidence. Which priors I am using here?

Doomsday Argument Map

Avo10y00

At least some DA proponents claim that there should always be a change in the probability estimate, so I am pleased to see that you agree that there are situations where DA conveys no new information.

1turchin10y

The situation would change, if I were Adam, first man in the world, and a priory will be able to start exponential human growth with P= 50 per cent probability (or think so). After finding that I am Adam, I would have to update this probability to lower. The way I update depends of sampling method - SSA or SIA but both result in early doom. SSA says that I am in short world. SSI said that my apriory estimation of universal distribution of short and long civilization may be wrong. It would be especially clear if apriory P would not 50 percent, but say 90 per cent.

Doomsday Argument Map

Avo10y10

OK, let me rephrase the question.

The biologist has never heard of DA. He sets up the initial conditions in such a way that his expectation (based on all his prior knowledge of biology) is that the probability of exponential growth is 50%.

Now the biologist is informed of DA. Should his probability estimate change?

1turchin10y

Probably, not, as he has a lot of information about the subject. DA is helpful in case if you don't have any other information about the subject. Also DA is statistical argument thereby it could not be disproved by counterexample. It is always possible to construct a situation where it will not work. Like some molecules in the air are not moving, despite the fact that median velocity is very high. It may be used in such problems as bus waiting problem (variant of Laplace sunrise problem). If last bus was 5 minutes ago, want is the probability that it will come in next 1 millisecond, next 5 minutes? next 1 year?

Doomsday Argument Map

Avo10y00

So do you agree with me that, in the experiment I described (a biologist sets up a petri dish with a specific set of initial conditions, and wants to find out if a small bacteria colony will grow exponentially under those conditions), DA logic cannot be applied (by either the biologist or the bacterium) to judge the probable outcome?

1turchin10y

DA should be applied to the situation where we know our position in the set, but do not know any other evidence. Of course if we have another source of information about the set size it could overweight DA-logic. If in this experiment the substrate is designed to support bacterial growth, it have is very strong posteriory evidence for future exponential growth. But if you put random bacteria on random substrate it most likely will not grow. In this case DA works. DA here says that 1 bacteria most likely will have only several off springs, and it is true for most random bacteria on random substrates. So, will DA works here or not depends of details of the experiment with you did not provide.

Doomsday Argument Map

Avo10y-10

I claim that self-sampling plays no essential role in DA logic.

If you think that self-sampling is essential, then you still must allow one of the bacteria in the petri dish to use DA logic about its own future. If you do not allow the biologist to use DA logic, then the bacterium and the biologist will make different predictions about the likely future. One of them must be more accurate than the other (as revealed by future events). If it is the bacterium that is more accurate, what prevents the biologist from adopting the bacterium's reasoning? I argue th... (read more)

1turchin10y

(I did not downvote you) Look, we could replace "self sampling" with "random". Random bacteria (from all existing bacteria on Earth) will not start exponential growth. Infinitely small subset of all bacteria will start it. There is no difference between prediction of statistic and biologist in this case. DA is statistical argument. It just say that most of random bacteria will not start exponential growth. The same may be true for young civilizations: most of them will not start exponential growth in the universe. But some may be.

Doomsday Argument Map

Avo10y-10

I think it is an excellent idea to try DA logic in other domains.

Example: A a biologist prepares a petri dish with some nutrients, and implants a small colony of bacteria. The question is: will this colony grow exponentially under these conditions? According to DA logic (with a reference class of all bacteria that will ever live in that petri dish), the biologist does not need to bother doing the experiment, since it is very unlikely that the colony will grow exponentially, because then the current bacteria would be atypical.

To the best of my knowledge,... (read more)

1turchin10y

Your example is not DA-style, because observer is not self-sampled here. Observer is not bacteria in this experiment. (By the way, most from all existing bacteria is not starters of exponential colonies) I may suggest another experiment: you tell me your age and I will tell your life expectancy based on DA-logic.

[Link] Using mindkillers to promote rationality

Avo10y100

You must have written the article off-campus while logged into the OSU proxy server. All links are the ones provided by the OSU proxy. This allows you to read subscription-only journals while off campus, but if you copy them, they won't work for anyone else. Salon won't be able to help you.

It does indicate that Salon doesn't proofread or copyedit, which is good to know.

4Gleb_Tsipursky10y

Ah, thanks for clarifying, makes sense. Oh well, such is life.