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paulfchristiano comments on Bayesian Epistemology vs Popper - Less Wrong Discussion
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Having read the website you linked to in its entirety, I think we should defer this discussion (as a community) until the next time you explain why someone's particular belief is wrong, at which point you will be forced to make an actual claim which can be rejected.
In particular, if you ever try to make a claim of the form "You should not believe X, because Bayesianism is wrong, and undesirable Y will happen if you act on this belief" then I would be interested in the resulting discussion. We could do the same thing now, I guess, if you want to make such a claim of some historical decision.
Edit: changed wording to be less of an ass.
In its entirety? Assuming you spent 40 minutes reading, 0 minutes delay before you saw my post, 0 minutes reading my post here, and 2:23 writing your reply, then you read at a speed of around 833 words per minute. That is very impressive. Where did you learn to do that? How can I learn to do that too?
Given that I do make claims on my website, I wonder why you don't pick one and point out something you think is wrong with it.
Fair, fair. I should have thought more and been less heated. (My initial response was even worse!)
I did read the parts of your website that relate to the question at hand. I do skim at several hundred words per minute (in much more detail than was needed for this application), though I did not spend the entire time reading. Much of the content of the website (perfectly reasonably) is devoted to things not really germane to this discussion.
If you really want (because I am constitutively incapable of letting an argument on the internet go) you could point to a particular claim you make, of the form I asked for. My issue is not really that I have an objection to any of your arguments--its that you seem to offer no concrete points where your epistemology leads to a different conclusion than Bayesianism, or in which Bayesianism will get you into trouble. I don't think this is necessarily a flaw with your website--presumably it was not designed first and foremost as a response to Bayesianism--but given this observation I would rather defer discussion until such a claim does come up and I can argue in a more concrete way.
To be clear, what I am looking for is a statement of the form: "Based on Bayesian reasoning, you conclude that there is a 50% chance that a singularity will occur by 2060. This is a dangerous and wrong belief. By acting on it you will do damage. I would not believe such a thing because of my improved epistemology. Here is why my belief is more correct, and why your belief will do damage." Or whatever example it is you would like to use. Any example at all. Even an argument that Bayesian reasoning with the Solomonoff prior has been "wrong" where Popper would be clearly "right" at any historical point would be good enough to argue about.
Do you assert that? It is wrong and has real world consequence. In The Beginning of Infinity Deutsch takes on a claim of a similar type (50% probability of humanity surviving the next century) using Popperian epistemology. You can find Deutsch explaining some of that material here: http://groupspaces.com/oxfordtranshumanists/pages/past-talks
While Fallible Ideas does not comment on Bayesian Epistemology directly, it takes a different approach. You do not find Bayesians advocating the same ways of thinking. They have a different (worse, IMO) emphasis.
I wonder if you think that all mathematically equivalent ways of thinking are equal. I believe they aren't because some are more convenient, some get to answers more directly, some make it harder to make mistakes, and so on. So even if my approach was compatible with the Bayesian approach, that wouldn't mean we agree or have nothing to discuss.
Using my epistemology I have learned not to do that kind of thing. Would that serve as an example of a practical benefit of it, and a substantive difference? You learned Bayesian stuff but it apparently didn't solve your problem, whereas my epistemology did solve mine.
It doesn't take Popperian epistemology to learn social fluency. I've learned to limit conflict and improve the productivity of my discussions, and I am (to the best of my ability) Bayesian in my epistemology.
If you want to credit a particular skill to your epistemology, you should first see whether it's more likely to arise among those who share your epistemology than those who don't.
That's a claim that only makes sense in certain epistemological systems...
I don't have a problem with the main substance of that argument, which I agree with. Your implication that we would reject this idea is mistaken.
Hmm? I'm not sure who you mean by we? If you mean that someone supporting a Popperian approach to epistemology would probably find this idea reasonable than I agree with you (at least empirically, people claiming to support some form of Popperian approach seem ok with this sort of thing. That's not to say I understand how they think it is implied/ok in a Popperian framework).
No. It provides an example of a way in which you are better than me. I am overwhelmingly confident that I can find ways in which I am better than you.
Could you explain how a Popperian disputes such an assertion? Through only my own fault, I can't listen to an mp3 right now.
My understanding is that anyone would make that argument in the same way: by providing evidence in the Bayesian sense, which would convince a Bayesian. What I am really asking for is a description of why your beliefs aren't the same as mine but better. Why is it that a Popperian disagrees with a Bayesian in this case? What argument do they accept that a Bayesian wouldn't? What is the corresponding calculation a Popperian does when he has to decide how to gamble with the lives of six billion people on an uncertain assertion?
I agree that different ways of thinking can be better or worse even when they come to the same conclusions. You seem to be arguing that Bayesianism is wrong, which is a very different thing. At best, you seem to be claiming that trying to come up with probabilities is a bad idea. I don't yet understand exactly what you mean. Would you never take a bet? Would never take an action that could possibly be bad and could possibly be good, which requires weighing two uncertain outcomes?
This brings me back to my initial query: give a specific case where Popperian reasoning diverges from Bayesian reasoning, explain why they diverge, and explain why Bayesianism is wrong. Explain why Bayesian's willingness to bet does harm. Explain why Bayesians are slower than Popperians at coming to the same conclusion. Whatever you want.
I do not plan to continue this discussion except in the pursuit of an example about which we could actually argue productively.
e.g. by pointing out that whether we do or don't survive depends on human choices, which in turn depends on human knowledge. And the growth of knowledge is not predictable (exactly or probabilistically). If we knew its contents and effects now, we would already have that knowledge. So this is not prediction but prophecy. And prophecy has build in bias towards pessimism: because we can't make predictions about future knowledge, prophets in general make predictions that disregard future knowledge. These are explanatory, philosophical arguments which do not rely on evidence (that is appropriate because it is not a scientific or empirical mistake being criticized). No corresponding calculation is made at all.
You ask about how Popperians make decisions if not with such calculations. Well, say we want to decide if we should build a lot more nuclear power plants. This could be taken as gambling with a lot of lives, and maybe even all of them. Of course, not doing it could also be taken as a way of gambling with lives. There's no way to never face any potential dangers. So, how do Popperians decide? They conjecture an answer, e.g. "yes". Actually, they make many conjectures, e.g. also "no". Then they criticize the conjectures, and make more conjectures. So for example I would criticize "yes" for not providing enough explanatory detail about why it's a good idea. Thus "yes" would be rejected, but a variant of it like "yes, because nuclear power plants are safe, clean, and efficient, and all the criticisms of them are from silly luddites" would be better. If I didn't understand all the references to longer arguments being made there, I would criticize it and ask for the details. Meanwhile the "no" answer and its variants will get refuted by criticism. Sometimes entire infinite categories of conjectures will be refuted by a criticism, e.g. the anti-nuclear people might start arguing with conspiracy theories. By providing a general purpose argument against all conspiracy theories, I could deal with all their arguments of that type. Does this illustrate the general idea for you?
I think it's wrong as an epistemology. For example because induction is wrong, and the notion of positive support is wrong. Of course Bayes' theorem is correct, and various math you guys have done is correct. I keep getting conflicting statements from people about whether Bayesianism conflicts with Popperism or not, and I don't want to speak for you guys, nor do I want to discourage anyone from finding the shared ideas or discourage them from learning from both.
Bets are made on events, like which team wins a sports game. Probabilities are fine for events. Probabilities of the truth of theories is problematic (b/c e.g. there is no way to make them non-arbitrary). And it's not something a fallibilist can bet on because he accepts we never know the final truth for sure, so how are we to set up a decision procedure that decides who won the bet?
We are not afraid of uncertainty. Popperian epistemology is fallibilist. It rejects certainty. Life is always uncertain. That does not imply probability is the right way to approach all types of uncertainty.
Bayesian reasoning diverges when it says that ideas can be positively supported. We diverge because Popper questioned the concept of positive support, as I posted in the original text on this page, and which no one has answered yet. The criticism of positive support begins by considering what it is (you tell me) and how it differs from consistency (you tell me).
Almost, but you seem to have left out the rather important detail of how actually make the decision. Based on the process of criticizing conjectures you've described so far, it seems that there are two basic routes you can take to finish the decision process once the critical smoke has cleared.
First, you can declare that, since there is no such thing as confirmation, it turns out that no conjecture is better or worse than any other. In this way you don't actually make a decision and the problem remains unsolved.
Second, you can choose to go with the conjecture that best weathered the criticisms you were able to muster. That's fine, but then it's not clear that you've done anything different from what a Bayesian would have done--you've simply avoided explicitly talking about things like probabilities and priors.
Which of these is a more accurate characterization of the Popperian decision process? Or is it something radically different from these two altogether?
When you have exactly one non-refuted theory, you go with that.
The other cases are more complicated and difficult to understand.
Suppose I gave you the answer to the other cases, and we talked about it enough for you to understand it. What would you change your mind about? What would you concede?
If i convinced you of this one single issue (that there is a method for making the decision), would you follow up with a thousand other objections to Popperian epistemology, or would we have gotten somewhere?
If you have lots of other objections you are interested in, I would suggest you just accept for now that we have a method and focus on the other issues first.
But some are criticized and some aren't.
But how is that to be judged?
No, we always go with uncriticized ideas (which may be close variants of ideas that were criticized). Even the terminology is very tricky here -- the English language is not well adapted to expressing these ideas. (In particular, the concept "uncriticized" is a very substantive one with a lot of meaning, and the word for it may be misleading, but other words are even worse. And the straightforward meaning is OK for present purposes, but may be problematic in future discussion.).
Yes, different. Both of these are justificationist ways of thinking. They consider how much justification each theory has. The first one rejects a standard source of justification, does not replace it, and ends up stuck. The second one replaces it, and ends up, as you say, reasonably similar to Bayesianism. It still uses the same basic method of tallying up how much of some good thing (which we call justification) each theory has, and then judging by what has the most.
Popperian epistemology does not justify. It uses criticism for a different purpose: a criticism is an explanation of a mistake. By finding mistakes, and explaining what the mistakes are, and conjecturing better ideas which we think won't have those mistakes, we learn and improve our knowledge.
Yes, we will have gotten somewhere. This issue is my primary criticism of Popperian epistemology. That is, given what I understand about the set of ideas, it is not clear to me how we would go about making practical scientific decisions. With that said, I can't reasonably guarantee that I will not have later objections as well before we've even had the discussion!
So let me see if I'm understanding this correctly. What we are looking for is the one conjecture which appears to be completely impervious to any criticism that we can muster against it, given our current knowledge. Once we have found such a conjecture, we -- I don't want to say "assume that it's true," because that's probably not correct -- we behave as if it were true until it finally is criticized and, hopefully, replaced by a new conjecture. Is that basically right?
I'm not really seeing how this is fundamentally anti-justificationist. It seems to me that the Popperian epistemology still depends on a form of justification, but that it relies on a sort of boolean all-or-nothing justification rather than allowing graded degrees of justification. For example, when we say something like, "in order to make a decision, we need to have a guiding theory which is currently impervious to criticism" (my current understanding of Popper's idea, roughly illustrated), isn't this just another way of saying: "the fact that this theory is currently impervious to criticism is what justifies our reliance on it in making this decision?"
In short, isn't imperviousness to criticism a type of justification in itself?
OK then :-) Should we go somewhere else to discuss, rather than heavily nested comments? Would a new discussion topic page be the right place?
That is the general idea (but incomplete).
The reason we behave as if it's true is that it's the best option available. All the other theories are criticized (= we have an explanation of what we think is a mistake/flaw in them). We wouldn't want to act on an idea that we (thought we) saw a mistake in, over one we don't think we see any mistake with -- we should use what (fallible) knowledge we have.
A justification is a reason a conjecture is good. Popperian epistemology basically has no such thing. There are no positive arguments, only negative. What we have instead of positive arguments is explanations. These are to help people understand an idea (what it says, what problem it is intended to solve, how it solves it, why they might like it, etc...), but they do not justify the theory, they play an advisory role (also note: they pretty much are the theory, they are the content that we care about in general).
One reason that not being criticized isn't a justification is that saying it is gets you a regress problem. So let's not say that! The other reason is: what would that be adding as compared with not saying it? It's not helpful (and if you give specific details/claims of how it is helpful, which are in line with the justificationist tradition, then I can give you specific criticisms of those).
Terminology isn't terribly important. David Deutsch used the word justification in his explanation of this in the dialog chapter of The Fabric of Reality (highly recommended). I don't like to use it. But the important thing is not to mean anything that causes a regress problem, or to expect justification to come from authority, or various other mistakes. If you want to take the Popperian conception of a good theory and label it "justified" it doesn't matter so much.
You're equivocating between "knowing exactly the contents of the new knowledge", which may be impossible for the reason you describe, and "know some things about the effect of the new knowledge", which we can do. As Eliezer said, I may not know which move Kasparov will make, but I know he will win.