I believe he's trying to draw a distinction between two potential sources of evidence:
- The factual claim that people believe zombies are conceivable, and
- The actual private act of conceiving of zombies.
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.
The evidence that Richard appeals to can be evidence-for-Richard only
This would appear to violate Aumann's agreement theorem.
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...The worthiness of Richard's source of evidence is inextricable from the actual truth or falsehood of the claim in contention
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).
If you want to move ahead in the discussion, then the following are your options:
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.
1.You simply deny that Richard is in fact conceiving of p-zombies.
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).
2.You accept that Richard can successfully conceive of p-zombies, but that this isn't good evidence for their possibility
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).
3. You deny that we have direct access to anything, or that access to conceptions in particular is direct, or that one can ever have private knowledge.
"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.)
Specifically, you'd better not be led to deny the rationality of believing that you're seeing blue when, e.g., you highlight this text.
I think it's overwhelmingly likely that I'm seeing blue, but I could turn out to be mistaken.
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.
I don't think Richard said anything to dispute this. He nev...
Part of the sequence: Rationality and Philosophy
Eliezer's anti-philosophy post Against Modal Logics was pretty controversial, while my recent pro-philosophy (by LW standards) post and my list of useful mainstream philosophy contributions were massively up-voted. This suggests a significant appreciation for mainstream philosophy on Less Wrong - not surprising, since Less Wrong covers so many philosophical topics.
If you followed the recent very long debate between Eliezer and I over the value of mainstream philosophy, you may have gotten the impression that Eliezer and I strongly diverge on the subject. But I suspect I agree more with Eliezer on the value of mainstream philosophy than I do with many Less Wrong readers - perhaps most.
That might sound odd coming from someone who writes a philosophy blog and spends most of his spare time doing philosophy, so let me explain myself. (Warning: broad generalizations ahead! There are exceptions.)
Failed methods
Large swaths of philosophy (e.g. continental and postmodern philosophy) often don't even try to be clear, rigorous, or scientifically respectable. This is philosophy of the "Uncle Joe's musings on the meaning of life" sort, except that it's dressed up in big words and long footnotes. You will occasionally stumble upon an argument, but it falls prey to magical categories and language confusions and non-natural hypotheses. You may also stumble upon science or math, but they are used to 'prove' things irrelevant to the actual scientific data or the equations used.
Analytic philosophy is clearer, more rigorous, and better with math and science, but only does a slightly better job of avoiding magical categories, language confusions, and non-natural hypotheses. Moreover, its central tool is intuition, and this displays a near-total ignorance of how brains work. As Michael Vassar observes, philosophers are "spectacularly bad" at understanding that their intuitions are generated by cognitive algorithms.
A diseased discipline
What about Quinean naturalists? Many of them at least understand the basics: that things are made of atoms, that many questions don't need to be answered but instead dissolved, that the brain is not an a priori truth factory, that intuitions come from cognitive algorithms, that humans are loaded with bias, that language is full of tricks, and that justification rests in the lens that can see its flaws. Some of them are even Bayesians.
Like I said, a few naturalistic philosophers are doing some useful work. But the signal-to-noise ratio is much lower even in naturalistic philosophy than it is in, say, behavioral economics or cognitive neuroscience or artificial intelligence or statistics. Why? Here are some hypotheses, based on my thousands of hours in the literature:
Of course, there is mainstream philosophy that is both good and cutting-edge: the work of Nick Bostrom and Daniel Dennett stands out. And of course there is a role for those who keep arguing for atheism and reductionism and so on. I was a fundamentalist Christian until I read some contemporary atheistic philosophy, so that kind of work definitely does some good.
But if you're looking to solve cutting-edge problems, mainstream philosophy is one of the last places you should look. Try to find the answer in the cognitive science or AI literature first, or try to solve the problem by applying rationalist thinking: like this.
Swimming the murky waters of mainstream philosophy is perhaps a job best left for those who already spent several years studying it - that is, people like me. I already know what things are called and where to look, and I have an efficient filter for skipping past the 95% of philosophy that isn't useful to me. And hopefully my rationalist training will protect me from picking up bad habits of thought.
Philosophy: the way forward
Unfortunately, many important problems are fundamentally philosophical problems. Philosophy itself is unavoidable. How can we proceed?
First, we must remain vigilant with our rationality training. It is not easy to overcome millions of years of brain evolution, and as long as you are human there is no final victory. You will always wake up the next morning as homo sapiens.
Second, if you want to contribute to cutting-edge problems, even ones that seem philosophical, it's far more productive to study math and science than it is to study philosophy. You'll learn more in math and science, and your learning will be of a higher quality. Ask a fellow rationalist who is knowledgeable about philosophy what the standard positions and arguments in philosophy are on your topic. If any of them seem really useful, grab those particular works and read them. But again: you're probably better off trying to solve the problem by thinking like a cognitive scientist or an AI programmer than by ingesting mainstream philosophy.
However, I must say that I wish so much of Eliezer's cutting-edge work wasn't spread out across hundreds of Less Wrong blog posts and long SIAI articles written in with an idiosyncratic style and vocabulary. I would rather these ideas were written in standard academic form, even if they transcended the standard game of mainstream philosophy.
But it's one thing to complain; another to offer solutions. So let me tell you what I think cutting-edge philosophy should be. As you might expect, my vision is to combine what's good in LW-style philosophy with what's good in mainstream philosophy, and toss out the rest:
Note that this is not just my vision of how to get published in journals. It's my vision of how to do philosophy.
Meeting journals standards is not the most important reason to follow the suggestions above. Write short articles because they're easier to follow. Open with the context and goals of your article because that makes it easier to understand, and lets people decide right away whether your article fits their interests. Use standard terms so that people already familiar with the topic aren't annoyed at having to learn a whole new vocabulary just to read your paper. Cite the relevant positions and arguments so that people have a sense of the context of what you're doing, and can look up what other people have said on the topic. Write clearly and simply and with much organization so that your paper is not wearying to read. Write lots of hand-holding sentences because we always communicate less effectively then we thought we did. Cite the relevant literature as much as possible to assist your most careful readers in getting the information they want to know. Use your rationality training to remain sharp at all times. And so on.
That is what cutting-edge philosophy could look like, I think.
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