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komponisto comments on Philosophy: A Diseased Discipline - Less Wrong
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The first question should really be: what does the apparent conceivability of zombies by humans imply about their possibility?
Philosophers on your side of the debate seem to take it for granted (or at least end up believing) that it implies a lot, but those of us on the other side think that the answer to the cogsci question undermines that implication considerably, since it shows how we might think zombies are conceivable even when they are not.
It's been quite a while since I was actively reading philosophy, so maybe you can tell me: are there any reasons to believe zombies are logically possible other than people's intuitions?
Thanks for laying this out. I'm one of the people who thinks philosophical zombies don't make sense, and now I understand why-- they seem like insisting that a result is possible while eliminating the process which leads to the result.
This doesn't explain why it's so obvious to me that pz are unfeasible and so obvious to many other people that pz at least make enough sense to be a basis for argument. Does the belief or non-belief in pz correlate with anything else?
Since no physical law is logically necessary, it is always logically possible that an effect could fail to follow from a cause.
I'm aware that the LW community believes this, but I think it is incorrect. We have an epistemological dispute here about whether non-psychological facts (e.g. the fact that zombies are coherently conceivable, and not just that it seems so to me) can count as evidence. Which, again, reinforces my point that the disagreement between me and Eliezer/Lukeprog concerns epistemological principles, and not matters of empirical fact.
For more detail, see my response to TheOtherDave downthread.
At least around here, "evidence (for X)" is anything which is more likely to be the case under the assumption that X is true than under the assumption that X is false. So if zombies are more likely to be conceivable if non-physicalism is true than if physicalism is true, then I for one am happy to count the conceivability of zombies as evidence for non-physicalism.
But again, the question is: how do you know that zombies are conceivable? You say that this is a non-psychological fact; that's fine perhaps, but the only evidence for this fact that I'm aware of is psychological in nature, and this is the very psychological evidence that is undermined by cognitive science. In other words, the chain of inference still seems to be
people think zombies are conceivable => zombies are conceivable => physicalism is false
so that you still ultimately have the "work" being done by people's intuitions.
How do you know that "people think zombies are conceivable"? Perhaps you will respond that we can know our own beliefs through introspection, and the inferential chain must stop somewhere. My view is that the relevant chain is merely like so:
zombies are conceivable => physicalism is false
I claim that we may non-inferentially know some non-psychological facts, when our beliefs in said facts meet the conditions for knowledge (exactly what these are is of course controversial, and not something we can settle in this comment thread).
I know that people think zombies are conceivable because they say they think zombies are conceivable (including, in some cases, saying "zombies are conceivable").
To say that we may "non-inferentially know" something appears to violate the principle that beliefs require justification in order to be rational. By removing "people think zombies are conceivable", you've made the argument weaker rather than stronger, because now the proposition "zombies are conceivable" has no support.
In any case, you now seem as eminently vulnerable to Eliezer's original criticism as ever: you indeed appear to think that one can have some sort of "direct access" to the knowledge that zombies are conceivable that bypasses the cognitive processes in your brain. Or have I misunderstood?
Depending on what you mean by 'direct access', I suspect that you've probably misunderstood. But judging by the relatively low karma levels of my recent comments, going into further detail would not be of sufficient value to the LW community to be worth the time.
You're still getting voted up on net, despite not explaining how, as you've claimed, the psychological fact of p-zombie plausibility is evidence for it (at least beyond references to long descriptions of your general beliefs).
Actually he seems to have denied this here, so at this point I'm stuck wondering what the evidence for zombie-conceivability is.
I believe he's trying to draw a distinction between two potential sources of evidence:
Richard is saying that his justification for his belief that p-zombies are conceivable lies in his successful conception of p-zombies. So what licenses him to believe that he's successfully conceived of zombies after all? His answer is that he has direct access to the contents of his conception, in the same way that he has access to the contents of his perception. You don't need to ask, "How do I know I'm really seeing blue right now, and not red?" Your justification for your belief that you're seeing blue just is your phenomenal act of noticing a real, bluish sensation. This justification is "direct" insofar as it comes directly from the sensation, and not via some intermediate process of reasoning which involve inferences (which can be valid or invalid) or premises (which can be true or false). Similarly, he thinks his justification for his belief that p-zombies are conceivable just is his p-zombie-ish conception.
A couple of things to note. One is that this evidence is wholly private. You don't have direct access to his conceptions, just as you don't have direct access to his perceptions. The only evidence Richard can give you is testimony. Moreover, he agrees that testimony of this sort is extremely weak evidence. But it's not the evidence he claims that his belief rests on. The evidence that Richard appeals to can be evidence-for-Richard only.
Another thing is that the direct evidence he appeals to is not "neutral." If p-zombies really are inconceivable, then he's in fact not conceiving of p-zombies at all, and so his conception, whatever it was, was never evidence for the conceivability of p-zombies in the first place (in just the same way that seeing red isn't evidence that you're seeing blue). So there's no easy way to set aside the question of whether Richard's conception is evidence-for-him from the question of whether p-zombies are in general conceivable. The worthiness of Richard's source of evidence is inextricable from the actual truth or falsehood of the claim in contention, viz., that p-zombies are conceivable. But he thinks this isn't a problem.
If you want to move ahead in the discussion, then the following are your options:
I hope this helps clear things up. It pains me when people interpret their own confusion as evidence of some deep flaw in academic philosophy.
I was very deliberately ignoring this distinction: "people" includes Richard, even for Richard. The point is that Richard cannot simply trust his intuition; he has to weigh his apparent successful conception of zombies against the other evidence, such as the scientific success of reductionism, the findings from cognitive science that show how untrustworthy our intuitions are, and in particular specific arguments showing how we might fool ourselves into thinking zombies are conceivable.
This would appear to violate Aumann's agreement theorem.
This is a confusion of map and territory. It is possible to be rationally uncertain about logical truths; and probability estimates (which include the extent to which a datum is evidence for a proposition) are determined by the information available to the agent, not the truth or falsehood of the proposition (otherwise, the only possible probability estimates would be 1 and 0). It may be rational to assign a probability of 75% to the truth of the Riemann Hypothesis given the information we currently have, even if the Riemann Hypothesis turns out to be false (we may have misleading information).
My position could be described by any of those three options -- in other words, they seem to differ only in the interpretation of terms like "conceivable", and don't properly hug the query.
I must do so to the extent I believe zombies are in fact inconceivable. But I don't see why it should be a conversation-stopper: if Richard is right and I am wrong, Richard should be able to offer evidence that he is unusually capable of determining whether his apparent conception is in fact successful (if he can't, then he should be doubting his own successful conception himself).
I can assent to this if "conceive" is interpreted in such a way that it is possible to conceive of something that is logically impossible (i.e. if it is granted that I can conceive of Fermat's Last Theorem being false).
"Private knowledge" in this sense is ruled out by Aumann, as far as I can tell. As for "direct access", well, that was Eliezer's original point, which I agree with: all knowledge is subject to some uncertainty due to the flaws in human psychology, and in particular all knowledge claims are subject to being undermined by arguments showing how the brain could generate them independently of the truth of the proposition in question. (In other words, the "genetic fallacy" is no fallacy, at least not necessarily.)
I think it's overwhelmingly likely that I'm seeing blue, but I could turn out to be mistaken.
I would categorize my position as somewhere between 1 and 2, depending on what you mean by "conceiving". I think he has a name attached to some properties associated with p-zombies and a world in which they exist, but this doesn't mean a coherent model of such a world is possible, nor that he has one. That is, I believe that following out the necessary implications will eventually lead to contradiction. My evidence for this is quite weak, of course.
I can certainly talk about an even integer larger than two that is not expressible as the sum of two primes. But that doesn't mean it's logically possible. It might be, or it might not. Does a name without a full-fledged model count as conceiving, or not? Either way, it doesn't appear to be significant evidence for.
I think the critics of Richard Chappell here are taking route 2 in your categorization.
If it helps (which I don't expect it does), I've been pursuing the trail of this (and related things) here.
Thus far his response seems to be that certain beliefs don't require evidence (or, at least, don't require "independent justification," which may not be the same thing), and that his beliefs about zombies "cohere well" with his other beliefs (though I'm not sure which beliefs they cohere well with, or whether they coheres better with them than their negation does), and that there's no reason to believe it's false (though it's not clear what role reasons for belief play in his decision-making in the first place).
So, the Bayesian translation of his position would seem to be that he has a high prior on zombies being conceivable. But of course, that in turn translates to "zombies are conceivable for reasons I'm not being explicit about". Which is, naturally, the point: I'd like to know what he thinks he knows that I don't.
Regarding coherence, and reasons to believe it's false: the historical success of reductionism is a very good reason to believe it's false, it seems to me. Despite Richard's protestations, it really does appear to me that this is a case of undue reluctance on the part of philosophers to update their intuitions, or at least to let them be outweighed by something else.
Good point. I think my biggest frustration is that I can't tell what point Richard Chappell is actually making so I can know whether I agree with it. It's one thing to make a bad argument; it's quite another to have a devastating argument that you keep secret.
You would probably have had more opportunity to draw it out of him if it weren't for the karma system discouraging him from posting further on the topic. Remember that next time you're tallying the positives and negatives of the karma system.
I don't follow: he's getting positive net karma from this discussion, just not as much as other posters. Very few of his comments, if any, actually went negative. In what sense in the karma system discouraging him?
Yes, slightly positive. Whether something encourages or discourages a person is a fact, not about the thing considered in itself, but about its effect on the person. The fact that the karma is slightly net positive is a fact about the thing considered in itself. The fact that he himself wrote:
tells us something about its effect on the person.
since "logically possible" just means "conceviable" there doesn't need to be.