Tag Archives: Brad DeLong

Deutsch, Popper, Gelman and Shalizi, with a side of Mayo, on Bayesian ideas, models and fallibilism in the philosophy of science and in statistics (I)

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A few years back, when I reviewed David Deutsch's The Beginning of Infinity for Physics Today (see also my short note on the review at this blog), I ended up spending a fair amount of time revisiting an area of perennial interest to me: the philosophy of science, and the status of Popper's falsificationist and anti-inductive view of scientific reasoning. I tend to like the view that one should think of scientific reasoning in terms of coherently updating subjective probabilities, which might be thought of as Bayesian in a broad sense. (Broad because it might be more aligned with Richard Jeffrey's point of view, in which any aspect of one's probabilities might be adjusted in light of experience, rather than a more traditional view on which belief change is always and only via conditioning the probabilities of various hypotheses on newly acquired data, with one's subjective probabilities of data given the hypotheses never adjusting.) I thought Deutsch didn't give an adequate treatment of this broadly Bayesian attitude toward scientific reasoning, and wrote:

Less appealing is Deutsch and Popper’s denial of the validity of inductive reasoning; if this involves a denial that evidence can increase the probability of general statements such as scientific laws, it is deeply problematic. To appreciate the nature and proper role of induction, one should also read such Bayesian accounts as Richard Jeffrey’s (Cambridge University Press, 2004) and John Earman’s (MIT Press, 1992).

Deutsch and Popper also oppose instrumentalism and physical reductionism but strongly embrace fallibilism. An instrumentalist believes that particular statements or entities are not literally true or real, but primarily useful for deriving predictions about other matters. A reductionist believes that they have explanations couched in the terms of some other subject area, often physics. Fallibilism is the view that our best theories and explanations are or may well be false. Indeed many of the best have already proved not to be strictly true. How then does science progress? Our theories approximate truth, and science replaces falsified theories with ones closer to the truth. As Deutsch puts it, we “advance from misconception to ever better misconception.” How that works is far from settled. This seems to make premature Deutsch’s apparent dismissal of any role for instrumentalist ideas, and his neglect of pragmatist ones, according to which meaning and truth have largely to do with how statements are used and whether they are useful.

Thanks to Brad DeLong I have been reading a very interesting paper from a few years back by Andrew Gelman and Cosma Shalizi, "Philosophy and the practice of Bayesian statistics" that critiques the Bayesian perspective on the philosophy of science from a broadly Popperian---they say "hypothetico-deductive"---point of view, that embraces (as did Popper in his later years) fallibilism (in the sense of the quote from my review above).  They are particularly concerned to point out that the increasing use of Bayesian methods in statistical analysis should not necessarily be interpreted as supporting a Bayesian viewpoint on the acquisition of scientific knowledge more generally.  That point is well taken; indeed I take it to be similar to my point in this post that the use of classical methods in statistical analysis need not be interpreted as supporting a non-Bayesian viewpoint on the acquisition of knowledge.  From this point of view, statistical analysis, whether formally Bayesian or "classical" is an input to further processes of scientific reasoning; the fact that Bayesian or classical methods may be useful at some stage of statistical analysis of the results of some study or experiment does not imply that all evaluation of the issues being investigated must be done by the same methods.  While I was most concerned to point out that use of classical methods in data analysis does not invalidate a Bayesian (in the broad sense) point of view toward how the results of that analysis should be integrated with the rest of our knowledge, Gelman and Shalizi's point is the mirror image of this.  Neither of these points, of course, is decisive for the "philosophy of science" question of how that broader integration of new experience with knowledge should proceed.

Although it is primarily concerned to argue against construing the use of  Bayesian methods in data analysis as supporting a Bayesian view of scientific methods more generally, Gelman and Shalizi's paper does also contain some argument against Bayesian, and more broadly "inductive", accounts of scientific method, and in favor of a broadly Popperian, or what they call "hypothetico-deductive" view.  (Note that they distinguish this from the "hypothetico-deductive" account of scientific method which they associate with, for instance, Carl Hempel and others, mostly in the 1950s.)

To some extent, I think this argument may be reaching a point that is often reached when smart people, indeed smart communities of people,  discuss, over many years, fundamental issues like this on which they start out with strong differences of opinion:  positions become more nuanced on each side, and effectively closer, but each side wants to keep the labels they started with, perhaps in part as a way of wanting to point to the valid or partially valid insights that have come from "their" side of the argument (even if they have come from the other side as well in somewhat different terms), and perhaps also as a way of wanting to avoid admitting having been wrong in "fundamental" ways.  For example, one sees insights similar to those in the work of Richard Jeffrey and others from a "broadly Bayesian" perspective, about how belief change isn't always via conditionalization using fixed likelihoods, also arising in the work of the "hypothetico-deductive" camp, where they are used against the simpler "all-conditionalization-all-the-time" Bayesianism.  Similarly, probably Popperian ideas played a role in converting some  "relatively crude" inductivists to more sophisticated Bayesian or Jefferian approach.  (Nelson Goodman's "Fact, Fiction, and Forecast", with its celebrated "paradox of the grue emeralds", probably played this role a generation or two later.)  Roughly speaking, the "corroboration" of hypotheses of which Popper speaks, involves not just piling up observations compatible with the hypothesis (a caricature of "inductive support") but rather the passage of stringent tests. In the straight "falsification"  view of Popper, these are stringent because there is a possibility they will generate results inconsistent with the hypothesis, thereby "falsifying" it; on the view which takes it as pointing toward a more Bayesian view of things (I believe I once read something by I.J.Good in which he said that this was the main thing to be gotten from Popper), this might be relaxed to the statement that there are outcomes that are very unlikely if the hypothesis is true, thereby having the potential, at least, of leading to a drastic lowering of the posterior probability of the hypothesis (perhaps we can think of this as a softer version of falsification) if observed.  The posterior probability given that such an outcome is observed of course does not depend only on the prior probability of the hypothesis and the probability of the data conditional on the hypothesis---it also depends on many other probabilities.  So, for instance, one might also want such a test to have the property that "it would be difficult (rather than easy) to get an accordance between data x and H (as strong as the one obtained) if H were false (or specifiably flawed)".  The quote is from this post on Popper's "Conjectures and Refutations" by philosopher of science D. G. Mayo, who characterizes it as part of "a modification of Popper".  ("The one obtained" refers to an outcome in which the hypothesis is considered to pass the test.)  I view the conjunction of these two aspects of a test of a hypothesis or theory as rather Bayesian in spirit.  (I do not mean to attribute this view to Mayo.)
I'll focus later---most likely in a follow-up post---on Gelman and Shalizi's direct arguments against inductivism and more broadly Bayesian approaches to scientific methodology and the philosophy of science.  First I want to focus on a point that bears on these questions but arises in their discussion of Bayesian data analysis.  It is that in actual Bayesian statistical data analysis "the prior distribution is one of the assumptions of the model and does not need to represent the statistician's personal degree of belief in alternative parameter values".  They go on to say "the prior is connected to the data, so is potentially testable".  It is presumably just this sort of testing that Matt Leifer was referring to when he wrote (commenting on my earlier blog entry on Bayesian methods in statistics)

"What I often hear from statisticians these days is that it is good to use Bayesian methods, but classical methods provide a means to check the veracity of a proposed Bayesian method. I do not quite understand what they mean by this, but I think they are talking at a much more practical level than the abstract subjective vs. frequentist debate in the foundations of probability, which obviously would not countenance such a thing.

The point Gelman and Shalizi are making is that the Bayesian prior being used for data analysis may not capture "the truth", or more loosely, since they are taking into account the strong possibility that no model under consideration is literally true, that it may not adequately capture those aspects of the truth one is interested in---for example, may not be good at predicting things one is interested in. Hence one wants to do some kind of test of whether or not the model is acceptable. This can be based on using the Bayesian posterior distribution as a model to be tested further, typically with classical tests such as "pure significance tests".
As Matthew's comment above might suggest, those of us of more Bayesian tendencies, who might agree that the particular family of priors---and potential posteriors---being used in data analysis (qua "parameter fitting" where perhaps we think of the prior distribution as the (higher-level) "parameter" being fit) might well not "contain the truth", might be able to take these tests of the model, even if done using some classical statistic, as fodder for further, if perhaps less formal, Bayesian/Jeffreysian reasoning about what hypotheses are likely to do a good job of predicting what is of interest.

One of the most interesting things about Gelman and Shalizi's paper is that they are thinking about how to deal with "fallibilism" (Popper's term?), in particular, inference about hypotheses that are literally false but useful. This is very much in line with recent discussion at various blogs of the importance of models in economics, where it is clear that the models are so oversimplified as to be literally false, but nonetheless they may prove predictively useful.  (The situation is complicated, however, by the fact that the link to prediction may also be relatively loose in economics; but presumably it is intended to be there somehow.)  It is not very clear how Popperian "falsificationism" is supposed to adapt to the fact that most of the hypotheses that are up for falsification are already known to be false. Probably I should go back and see what Popper had to say on that score, later in his career when he had embraced fallibilism. (I do recall that he tried introducing a notion of "verisimilitude", i.e. some kind of closeness to the truth, and that the consensus seems to have been---as Gelman and Shalizi point out in a footnote---that this wasn't very successful.)  It seems to that a Bayesian might want to say one is reasoning about the probability of statements like "the model is a good predictor of X in circumstances Y", " the model does a good job capturing how W relates to Z" , and so forth. It is perhaps statements like these that are really being tested when one does the " pure significance tests" advocated by Gelman and Shalizi when they write things like "In designing a good test for model checking, we are interested in finding particular errors which, if present, would mess up particular inferences, and devise a test statistic which is sensitive to this sort of mis-specification."

As I said above, I hope to take up Gelman and Shalizi's more direct arguments (in the cited paper) against "inductivism" (some of which I may agree with) and Bayesianism sensu lato as scientific methodology in a later post. I do think their point that the increasing use of Bayesian analysis in actual statistical practice, such as estimation of models by calculating a posterior distribution over model parameters beginning with some prior, via formal Bayesian conditioning, does not necessarily tell in favor of a Bayesian account of scientific reasoning generally, is important. In fact this point is important for those who do hold such a loosely Bayesian view of scientific reasoning:  most of us do not wish to get stuck with interpreting such priors as the full prior input to the scientific reasoning process.  There is always implicit the possibility that such a definite specification is wrong, or, when it is already known to be wrong but thought to be potentially useful for some purposes nonetheless, "too wrong to be useful for those purposes".

Nagel's Mind and Cosmos, Objective Value, Delong and Blackburn

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I have trouble understanding why critics of Thomas Nagel's Mind and Cosmos are coming down so hard on his belief that value statements---particularly ethical ones, can (some of them, at any rate) be objectively true or false.  I'll consider two examples here.  Brad DeLong's objection seems to me based primarily on his continued mistaken view that Nagel views his reason as infallible.  It's therefore not specific to the case of moral or other value judgments.  Simon Blackburn's objections are more interesting because they are more specific to value judgments, and better address Nagel's actual position.

Brad DeLong seems to think that Nagel's juxtaposition of reasoning in the form modification of a belief about the direction one is driving in, because of its inconsistency with newly acquired evidence, with reasoning like Nagel's "I oppose the abolition of the inheritance tax... because I recognize that the design of property rights should be sensitive not only to autonomy but also to fairness..." is self-evidently ridiculous.  Says Brad:

"I do wonder: Does Gene Callahan have any idea what he has committed himself to when he endorses Thomas Nagel's claim that Nagel has transcendent direct access to truths of objective reality? I think not:

Thomas Nagel: [...my (HB's) ellipsis here, in place of a typo by Brad that repeated part of his own introduction, quoted above, to this quote...] I decide, when the sun rises on my right, that I must be driving north instead of south... because I recognize that my belief that I am driving south is inconsistent with that observation, together with what I know about the direction of rotation of the earth. I abandon the belief because I recognize that it could not be true.... I oppose the abolition of the inheritance tax... because I recognize that the design of property rights should be sensitive not only to autonomy but also to fairness...

Game, set, match, and tournament!"

That last sentence, which is Brad's, seems revealing of a mindset that sometimes creeps into his writing in his blog, less aimed at truth than at victory in some argumentative competition. I like a lot of what he does on his blog, but that attitude, and the related one that reads like an attempt to exhibit his hip and with-it-ness by using internet jargon that the unhip like me have to google ("self-pwnage", which Callahan is said to have committed), are not so appealing. The "transcendent direct access" I have already argued is mostly a straw-man of Brad's own creation, Nagel's point being primarily that (as says immediately following what Brad has quoted) "As the saying goes, I operate in the space of reasons." One aspect of operating in the space of reasons is trying to preserve some consistency between ones various beliefs; that seems to be the nub of the driving example (but we should not forget the important point that there is more than just deductive logic going on here... we have to decide which of the contradictory beliefs to give up). And we are also to some extent doing so (preserving consistency) in the case of the inheritance tax, though the full argument in this case is likely to be much more involved and less clear than in the case of the driving example. Nagel is arguing that we try to square our beliefs about the particular case of the inheritance tax with general beliefs that we (may) hold about how social institutions like property rights should be designed. Focusing on this consistency issue, though, can --- in both factual and ethical situations --- obscure the essential role of factors other than mere consistency in the process of reasoning about what beliefs to hold. As I mentioned in earlier posts, Nagel gives this somewhat short shrift, notably by not discussing inductive reasoning much, though he's clear about the fact that it's needed. But it's remarkable that DeLong---who I would guess shares Nagel's views on the inheritance tax, and possibly even his reasons (although he may also find some strength in arguments involving "social welfare functions) should think that this passage grounds an immediate declaration of victory. I guess it's because he wrongly thinks the issue is about "direct transcendent access".

Even more remarkable is philosopher Simon Blackburn's very similar reaction---if, as I am guessing, his example of "why income distribution in the US is unjust" is prompted in part by Nagel's reference to the inheritance tax. There are points I agree with in Blackburn's article, but then there is this:

According to Nagel, Darwinians can explain, say, why we dislike pain and seek to minimize bringing it about for ourselves and for others we love. But, Nagel thinks, for the Darwinian, its “real badness” can be no part of the explanation of why we are averse to it. So it is another mystery how real badness and other real normative properties enter our minds. Nagel here manifests his founding membership of a peculiar and fortunately local philosophical subculture that thrives by resolutely dismissing the resources of the alternative, Humean picture, which sees our judgement that pain is a bad thing as a useful expression of our natural aversion to it. All he says about this is that it “denies that value judgements can be true in their own right”, which he finds implausible. He is silent about why he thinks this, perhaps wisely, if only because nobody thinks that value judgements are true in their own right. The judgement that income distribution in the US is unjust, for instance, is not true in its own right. It is true in virtue of that fact that after decades of lobbying, chief executives of major companies earn several hundred times the income of their rank-and-file workers. It is true because of natural facts.

Parenthetically, but importantly: I agree with Blackburn's characterization of Nagel as believing that the "real badness"
of pain cannot be a main part of a Darwinian explanation of our aversion to pain. And I disagree with this belief of Nagel's.

However, I don't know what's so peculiar and local about resolutely dismissing (sometimes with plenty of discussion, though one virtue of Nagel's book is that it is short, so a point like this may not get extensive discussion) the Humean view here that this badness is just "natural aversion".  But in any case, Blackburn's discussion of his example is truly weird.  It seems reasonable to view a statement like "income distribution in the US is unjust" as true both because of the "natural facts" Blackburn cites, which explain how it has come to be what it is, and because of the component where the actual "values" come in, which give reasons for our belief that this high degree of inequality, is in fact unjust.  True, according to some theories of justice, e.g. a libertarian one, the genesis of a pattern of income and wealth distribution may be germane to whether or not it is just.  Blackburn might be adducing such an explanation, since he mentions "lobbying" as a cause (and not, say "hard work").  But if so, he still hasn't explained: what's wrong with lobbying?  Why does it cast doubt on the justice of the resulting outcome?  What Nagel means by value judgements being true "in their own right" is not likely that every statement with a value component, like Blackburn's about US income and wealth distribution, is true in and of itself and no reasons can be given for it.  What I think he means is that at some point, probably at many different points, there enters into our beliefs about matters of value an element of irreducible judgement that something is right or wrong, good or bad, and that this is objective, not just a matter of personal taste or "natural aversion".  What Blackburn's statement reads most like, due to his emphasis on "natural facts", is an attempt to substitute the causal factors leading to US income distribution being what it is, for the moral and political considerations---quite involved, perhaps subtle, and certainly contentious---that have led many to judge that it should not be what it is.  It's quite clear from Nagel's discussion of the inheritance tax what he thinks some of those considerations are: "autonomy and fairness". I just don't understand how someone could think that Blackburn's discussion of why US income distribution is unjust is better than an account in terms of concepts like autonomy and fairness---the sort of account that Nagel would obviously give. I've gotten some value from parts of Blackburn's work, even parts of this article, but this part---if this reading is correct---seems monumentally misguided.  Or does he think that the rest of the explanation is that human beings just have a "natural aversion" to income distribution that is as unequal, or perhaps as influenced by lobbying, as the US's currently is.  But you might think that a cursory look at a large part of the Republican party in the US would have disabused him of that notion.

Perhaps I'm being excessively snarky here...advocates, like Blackburn, of the natural aversion view would probably argue that it needs to be supplemented and modified by reasoning.... perhaps it is just that the "irreducibly moral", as opposed to the deductive/analogical reasoning component, of this process, is still just a matter of natural aversion.  I would think more Hobbesian considerations would come into play as well, but that is a matter for (you may be sorry to hear) another post.

Nagel and Delong II: Fallibility and Transcendence

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In my first post on Brad Delong's series of criticisms of Thomas Nagel's new book Mind and Cosmos I focused not on Brad's initial critcism but on a later post that seemed to be implying Nagel put too much weight on "common sense".  In this post I'll focus on Brad's initial criticism, and in particular on what seems to me his misunderstanding of Nagel's arguments concerning reason, as crucially dependent on the notion that reason is infallible at least in some cases.

Brad's critique began with a reaction to some remarks by Tyler Cowen, in particular Cowen's assertion that "People will dismiss his [Nagel's] arguments to remain in their comfort zone, while temporarily forgetting he is smarter than they are and furthermore that many of their views do not make sense or cohere internally."

Now I think it is unfortunate that Cowen is speculating about who's "smarter than" who, and unfortunate that Brad joins him in doing so.  Everyone involved seems to be quite smart, but unfortunately Brad seems to me to be misunderstanding what the main thrust of Nagel's argument is, and where its main weakness lies.  DeLong reacts to Cowen:

And here Tyler appears to me to have gone off the rails. Thomas Nagel is not smarter than we are--in fact, he seems to me to be distinctly dumber than anybody who is running even an eight-bit virtual David Hume on his wetware.

He fixates on a single example taken from Nagel's book and, I think, fails to understand the role Nagel thinks this example plays. Brad seems to think it is crucial that Nagel view reason as infallible. "And my certainty that I know must be correct!" as he puts it in his gloss on Nagel:

Nagel's argument, to the extent that I understand it and that it is coherent, goes roughly like this:

Suppose we think we are going south-southwest and see the sun rising before us. We don't think: "the heuristics of reasoning that have evolved because they tend to boost reproductive fitness conclude that it is very likely that I am not in fact going south-southwest". We think, instead: "I know that the sun rises in front of me when I am going east! Either I am hallucinating, or I must be going roughly east! I deduce this by my reason, and my reason is a mechanism that can see that the algorithm it follows is truth-preserving! My mind is in immediate contact with the rational order of the universe! I don't just think I am going east! I know I am either hallucinating or going east! And my certainty that I know must be correct! And I know that my certainty must be correct--and that triumph of reason cannot be given a purely physical explanation! Since I believe I am not hallucinating, I abandon the belief that I am going south-southwest because of my reason's transcendent grasp of objective reality! My consciousness is an instrument of transcendence that grasps objective reality! And no blind evolutionary process can produce such a transcendent instrument!"

Aspects of this example of Nagel's bothered me as well, but it plays a much less central part in Nagel's book than you might think from Brad's gloss. Note that even the material in quotes is a gloss, not a quote from Nagel, although it draws fairly heavily on him. (Further down in this post, I quote the passage in Nagel from the first appearance of the example to the last explicit reference to it.  Brad's post also contains further material on the general topic of reason directly quoted from Nagel.)  In the context of Brad's post, the term "Nagel's argument" seems to imply that this is the main argument of the book, on which it stands or falls.

As I said, I don't think the example is central. Rather, it is intended as an example of something central to the book, which is the claim that reason has the power --- imperfect and fallible, to be sure --- to get us in touch with objective reality, in a way that helps us transcend the appearance of things from our own particular viewpoint or perspective. It is probably also intended as part of a discussion of how logic --- the avoidance of contradiction --- is an essential part of our ability to engage in more subtle and substantive forms of reasoning. I will discuss this second point later, concentrating for the moment on the first.

Nagel is extremely clear that he does not believe that reason's power to help get us in touch with objective reality is infallible. (See the next quote I display from Nagel for an utterly explicit statement of this.)  It may seem that he is claiming it to be infallible in driving example, but even if he is, that does not seem crucial to his main line of argument. Most of Brad's ridicule of Nagel's argument is directed against the claim of infallibility, so it just misses its target if by "Nagel's argument" is meant, as is clear from the context, the overall line of argument of Nagel's book.

The overall argument of the book is not a single line of reasoning. But some main strands concern the nature and origin of life, of consciousness, and---what is under discussion here----of reason. Here is how Nagel puts his main argument concerning the nature of reason:

Thought and reasoning are correct or incorrect in virtue of something independent of the thinker's beliefs, and even independent of the community of thinkers to which he belongs. We take ourselves to have the capacity to form true beliefs about the world around us, about the timeless domains of logic and mathematics, and about the right thing to do. We don't take these capacities to be infallible, but we think they are often reliable, in an objective sense, and that they can give us knowledge. [Mind and Cosmos, pp. 80-81]

Perhaps some confusion has arisen because of Nagel's use of the word "reliable" elsewhere in the book (e.g. in the excerpt DeLong quotes)...it should not be taken to imply infallibility. In Brad's favor, the "directness" with which Nagel says reason "puts us in touch with the rational order of things" in this particular example, is thought by Nagel to strengthen his case. I just don't think it's the main point.

Lest anyone misunderstand, I don't agree with Nagel that our understanding of reason as part of a process enabling us to --- fallibly, Nagel admits, and partially, I might add --- get in touch with an objective reality that transcends each of our particular perspectives on it, provides support to the view that reason could not have evolved through natural selection.

Brad goes on to propose a counterexample to the claim that the bit of reasoning in Nagel's example is infallible. It is that "During northern hemisphere winter, if you are near the North Pole, it is perfectly possible to see the sun rise due south if you are due solar north of the center of the earth as you come out of the Earth's shadow. And I was. And I did."

Several things can be said about this. The most important one is that Nagel need not and does not claim infallibility. Less important is that Nagel explicitly described his example as one in which "I am driving...". Brad was flying. So Brad's "it happened to me" is not literally true. Moreover the distinction between flying and driving is not an irrelevant one (like that between its being Nagel or DeLong who is doing the reasoning...) but one that is probably relevant. I don't know whether there are any roads near enough the north pole that one could, driving, have the experience Brad did. Perhaps there is land, or at certain times of the year, perhaps there is still enough sea ice, near enough the pole that one could do this off-road, by driving a long way off-road, or bringing a vehicle in by air. Or perhaps not. I really don't think it matters much. There are some background assumptions that are not made explicit, though suggested by the framing of the situation, as there are in most pieces of reasoning.

Here's Nagel's introduction of the example, and its sequel:

But suppose I observe a contradiction among my beliefs and "see" that I must give up at least one of them. (I am driving south in the early morning and the sun rises on my right.) In that case, I see that the contradictory beliefs cannot all be true, and I see it simply because it is the case. I grasp it directly. It is not adequate to say that, faced with a contradiction, I feel the urgent need to alter my beliefs to escape it, which is explained by the fact that avoiding contradictions, like avoiding snakes and precipices, was fitness-enhancing for my ancestors. That would be an indirect explanation of how the impossibility of the contradiction explains my belief that it cannot be true. But even if some of our ancestors were prey to mere logical phobias and instincts, we have gone beyond that: We reject a contradiction just because we see that it is impossible, and we accept a logical entailment just because we see that it is necessarily true.

In ordinary perception, we are like mechanisms governed by a (roughly) truth-preserving algorithm. But when we reason, we are like a mechanism that can see that the algorithm it follows is truth-preserving. Something has happened that has gotten our minds into immediate contact with the rational order of the world, or at least with the basic elements of that order, which can in turn be used to reach a great deal more. That enables us to possess concepts that display the compatibility or incompatibility of particular beliefs with general hypotheses. We have to start by regarding our prereflective impressions as a partial and perspectival view of the world, but we are then able to use reason and imagination to construct candidates for a larger conception that can contain and account fo that part. This applies in the domain of value as well as of fact. The process is highly fallible, but it could not even be attempted without this hard core of self-evidence, on which all less certain reasoning depends. In the criticism and correction of reasoning, the final court of appeal is always reason itself.

What this means is that if we hope to include the human mind in the natural order, we have to explain not only consciousness as it enters into perception, emotion, desire, and aversion but also the conscious control of belief and conduct in response to the awareness of reasons---the avoidance of inconsistency, the subsumption of particular cases under general principles, the confirmation or disconfirmation of general principles by particular observations, and so forth. This is what it is to allow oneself to be guided by the objective truth rather than just by one's impressions. It is a kind of freedom---the freedom that reflective consciousness gives us from the rule of innate perceptual and motivational dispositions together with conditioning. Rational creatures can step back from these influences and try to make up their own minds. I set aside the question whether this kind of freedom is compatible or incompatible with causal determinism, but it does seem to be something that cannot be given a purely physical analysis and therefore, like the more passive forms of consciousness, cannot be given a purely physical explanation either.

If I decide, when the sun rises on my right, that I must be driving north instead of south, it is because I recognize that my belief that I am driving south is inconsistent with that observation, together with what I know about the direction of rotation of the earth. I abandon the belief because I recognize that it couldn't be true. If I put money into a retirement account because the future income it generates will be more valuable to me than what I could spend it on now, I act because I see that this makes it a good thing to do. If I oppose the abolition of the inheritance tax, it is because I recognize that the design of property rights should be sensitive not only to autonomy but also to fairness. As the saying goes, I operate in the space of reasons.[Mind and Cosmos, pp. 91-92]

Gene Callahan criticizes Brad as follows:

So Nagel gives us two beliefs:
1) The sun rises in the east (where I am); and
2) I am driving south, which means the east will be on my left.
And a fact: But the sun is rising to my right!

So Nagel's point is that we cannot continue to hold 1) and 2) simultaneously: "I must give up at least one of them." How could he have said that more plainly?

Then Nagel goes on to state that "IF" (notice, that "if" is right in the original text, I did not add it!) he decides to give up belief 2), it will be because he sees he cannot logically hold 1) and 2) at the same time. Notice what the "if" implies: Nagel clearly understands that he has the option of giving up belief 1) instead! Otherwise, no point to the "if."

Now, Brad Delong comes along and says, "What an idiot! [And he really does insult Nagel like that.] Once, I was in that situation, and I had to give up belief 1)!"

Ahem. One does not disprove the proposition that one ought to give up at least one of two contradictory beliefs by showing how once, one gave up one of two contradictory beliefs.

Brad's response:

Nagel does not believe: "the sun rises in the east (where I am)." Nagel believes: "the sun rises on my right".

Thus the two beliefs that Nagel's reason tells him are in conflict are (a) his belief that he is going south, and (b) his belief he sees the sun rising on his right. The choice he gives himself is between concluding that he is going north and concludeingthat he is hallucinating.

Now I understand that Callahan wishes that Nagel were not Nagel but rather some Nagel' who had added a third belief: (c) "I am in a normal place (but there are weird places on earth where the sun rises in a non-standard way)."

But we go to argument with the Nagel we have, and not the Nagel' Callahan wishes we had.

Callahan would presumably say that Nagel was just being sloppy, and that there is actually an unsloppy Nagel' who had made the argument that Callahan wishes he had made, and whose reason does have transcendental access to objective reality, and that we should deal with the argument not of Nagel but of Nagel'.

But Callahan's confusion of the Nagel' he wishes we were talking about with the Nagel who we are talking about demonstrates my big point quite effectively: powerful evidence that Nagel is a jumped-up monkey using wetware evolved to advance his reproductive fitness, rather than a winged angelic reasoning being with transcendental access to objective reality. No?

I think Callahan is roughly right here. Roughly because it's not obviously correct that "Nagel gives us two beliefs". Callahan's (2) is stated in Nagel's parenthetical introduction of the example (see the quote above). But the parenthetical introduction is probably best read as describing the situation, not explicitly attributing beliefs ("I am driving south", not "I believe I am driving south"). It's clear we're to take as implicit that the subject of the example believes this, though, and when Nagel returns to the example later in the passage I quoted it is made explicit: this is the belief that is given up. That return to the example also makes it clear that there are background beliefs not initially mentioned in Nagel's parenthetical introduction of the example: Nagel mentions "what I know about the direction of rotation of the earth". This is presumably where Callahan gets number (2) namely "The sun rises in the east (where I am)." That seems a correct reading of Nagel, so DeLong's "Nagel does not believe: "the sun rises in the east (where I am)." Nagel believes: "the sun rises on my right"." just seems wrong.  The Nagel of the example believes both of these things (if we understand "the sun rises on my right" to mean something like "the sun is rising on my right".  Brad's misinterpretation is probably based on taking the parenthetical sentence introducing the example as a statement of the two beliefs that are in contradiction, rather than a sketch of a situation in which "I observe a contradiction in my beliefs". (Brad also changes Nagel's "driving south" to "going south", which affects, as I discussed above, whether Brad's flying experience is relevant.)

I think Nagel is getting at several things with this example, in light of the surrounding discussion.

(1) One is the idea that deductive reason helps us access truths about the world that go beyond our own particular perspective on it, because the avoidance of inconsistency is integral to the use of language, which in turn enables us to describe how the world is or might be from a point of view that is not just the perspective of one being that it makes possible. I am not sure what Brad means by "transcendent access" to objective reality--- it may just be a rhetorical flourish, liked "winged" and "angelic". The term "transcendent access" does not appear in Mind and Cosmos. When Nagel uses words with the root "transcend", he is referring to transcending a limited point of view to come up with a view of the world "as it is independently of the thinker's beliefs and even independently of the community of thinkers to which he belongs." (He also uses it---probably in the same sense---to refer to "a transcendent being", a notion he finds unappealing.) In his description of "what it is to be guided by the objective truth" toward the end of the long quote above, he is quite clear that this involves observations and (broadly speaking) "inductive" reasoning ("confirmation and disconfirmation"), and earlier he mentions "imagination" in addition to reasoning. (So if Brad's "Humean heuristics" just means inductive reasoning broadly construed, then it looks like Nagel's on board with it.) When reading the discussion of the driving example in Mind and Cosmos and related passages in The Last Word, I have sometimes felt puzzled about why Nagel seems to be laying such emphasis on deductive reasoning. And in general, I'm slightly frustrated by the relative lack of discussion of induction or related non-inductive aspects of scientific reasoning in Nagel's writings. But I think the quoted passages make clear that for Nagel, reason comprises induction too. I think the reason for his stress on deduction and consistency is the importance --- as Nagel sees it --- of language, and language's intimate link with logic --- to the very formulation of theories and hypotheses, scientific and otherwise. Nagel's emphasis on "directness" in simple cases may or may not be misplaced, but I don't think it's the linchpin of his broader argument.

(2) Secondly, and perhaps more controversially, Nagel believes that we must conceive of our reasoning as autonomous and free---that we cannot view it as a mere disposition. A mere disposition is how Hume, on one reading, viewed "induction", if not deduction... here I think Nagel would disagree with Hume, and perhaps with DeLong, if "mere disposition" is what DeLong means by "Humean heuristics". The key point, for Nagel, is that "In the criticism and correction of reasoning, the final court of appeal is always reason itself." The theory of evolution itself is part of that objective picture of reality, transcending our individual perspectives on it, that reason enables us to arrive at. For Nagel, it would be absurd to let a belief in evolution by natural selection undermine our view that our reasoning, in conjunction with imagination and observation, can get us in touch with and is getting us in touch with objective reality, because our very belief in evolution itself relies on this view. It is this, and not infallibility or "transcendent access" (a term Nagel never uses) that is the most important, and that I think is crucial to his broader argument.  Note that this does not automatically imply that a belief in evolution by natural selection cannot modify our assessment of our reasoning, perhaps leading us to view particular judgments or modes of reasoning as suspect, because arising from heuristics that we can see to be reliable only in certain situations similar to those in which they evolved.  Indeed, Nagel seems overly impressed with this possibility---one of his main grounds for rejection of the notion that there could be an evolutionary-biological explanation of the advent of reason in humans is his view that such an explanation would necessarily undermine our assessment that the reasoning we exercise in conjunction with our other faculties actually is, on balance, tending to get us in touch with objective reality.

Brad does address some of these issues, in response to Callahan's pointing out that they are the main ones; I will take up that part of their discussion in a later post.

Let me here take up an element of the quoted passage from Nagel that is bound to have raised some hackles.
Nagel: "I set aside the question whether this kind of freedom [to decide what to believe and how to act for reasons, i.e. by reasoning -- HB] is compatible or incompatible with causal determinism, but it does seem to be something that cannot be given a purely physical analysis and therefore, like the more passive forms of consciousness, cannot be given a purely physical explanation either."

This really is a key argument for Nagel. However, in my view, it needs to be understood in terms of the subtleties of emergence. As I have written elsewhere, I think there is some crucial unclarity in Nagel (or in my understanding of him) about what "purely physical explanation" might mean. If it means "explanation in terms of the concepts of physics" then I suspect that the hypothesis that "this kind of freedom [...] cannot be given a purely physical explanation [...]" is correct.  (However, I think I still have a substantive disagreement with Nagel on the meaning of "explanation".)   But if we allow an evolutionary biological evolution to use concepts like "reason" (which seems rather reasonable if one is going to try to explain the origin of our ability to reason), it seems to me that this is compatible with our eventually having an evolutionary-biological explanation of its historical origin. Here also I think I disagree with Nagel, who sometimes refers to "physics extended to include biology", suggesting that to him an evolutionary-biological explanation is a kind of purely physical explanation. I've discussed this some in my first post on Mind and Cosmos, and will discuss it more in future posts. There are deep and subtle philosophical and scientific questions involved, but in my view it is here if anywhere that Nagel goes importantly astray in dealing with reason, and not primarily in some actual or putative attribution of infallibility to simple judgements of contradiction, nor even in the notion (which Nagel does appear to subscribe to, but which I'm not sure I want to endorse) that the faculty of avoiding contradiction involves our minds being in "immediate contact with the rational order of things" [Mind and Cosmos, p. 91].

 

 

Nagel and DeLong I: Common Sense

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Brad DeLong has been hammering --- perhaps even bashing --- away at Thomas Nagel's new book Mind and Cosmos (Oxford, 2012).  Here's a link to his latest blow. I think Nagel's wrong on several key points in that book, but I think Brad is giving people a misleading picture of Nagel's arguments.  This matters because Nagel has made very important points --- some of which are repeated in this book, though more thoroughly covered in his earlier The Last Word (Oxford, 1997) --- about the nature of reason, defending the possibility of achieving, in part through the use of reason, objectively correct knowledge (if that is the right word) in areas other than science, and giving us some valuable ideas about how this can work in particular cases, for example, in the case of ethics, in The Possibility of Altruism [Princeton, 1979].

In his latest salvo Brad suggests that "If you are going to reject any branch of science on the grounds that it flies in the face of common sense, require[s] us to subordinate the incredulity of common sense, is not based ultimately on common sense, or is a heroic triumph of ideological theory over common sense--quantum mechanics is definitely the place to start…".  This is preceded by some quotes from Nagel:

  • But it seems to me that, as it is usually presented, the current orthodoxy about the cosmic order is the product of governing assumptions that are unsupported, and that it flies in the face of common sense…
  • My skepticism is… just a belief that the available scientific evidence, in spite of the consensus of scientific opinion, does not… rationally require us to subordinate the incredulity of common sense…
  • Everything we believe, even the most far-reaching cosmological theories, has to be based ultimately on common sense, and on what is plainly undeniable…
  • I have argued patiently against the prevailing form of naturalism, a reductive materialism that purports to capture life and mind through its neo-Darwinian extension…. I find this view antecedently unbelievable— a heroic triumph of ideological theory over common sense…

Now there are things I disagree with here, but Nagel is clearly not claiming that no theory that is not itself a piece of common sense is acceptable. Indeed, the second bullet point makes it clear that he allows for the possibility that scientific evidence could "rationally require" him to subordinate the incredulity of common sense. It is his judgment that it does not in this case. Now---at least with regard to the possibility of an explanation by evolutionary biology of the emergence of life, consciousness, and reason on our planet and in our species, which is what I think is at issue--- I don't share his incredulity, and I also suspect that I would weigh the scientific evidence much more heavily against such incredulity, if I did share some of it.  But Nagel is not commited to a blanket policy of "reject[ing] scientific theories because they fail to match up to your common sense." Regarding the third bullet point, it's perhaps stated in too-strong terms, but it's far from a claim that every scientific theory can directly be compared to common sense and judged on that basis. The claim that scientific theories are "ultimately based in common sense and on what is plainly undeniable" does not imply that this basis must be plain and direct. Logic and mathematics develop out of common-sense roots, counting and speaking and such... science develops to explain "plainly undeniable" results of experiments, accounts of which are given in terms of macroscopic objects... Some of this smacks a bit too much of notions that may have proved problematic for positivism ("plainly undeniable" observation reports?)... but the point is that common sense carries some weight and indeed is a crucial element of our scientific activities, not that whatever aspect of "common sense" finds quantum theory hard to deal with must outweigh the enormous weight of scientific experience and engineering practice, also rooted "ultimately" according to Nagel in common sense, in favor of that theory.

Just for the record I don't find that the bare instrumentalist version of quantum theory as an account of the probabilities of experimental results "flies in the face of common sense" --- but it does seem that it might create serious difficulty for the conception of physical reality existing independent of our interactions with it. At any rate it does not seem to provide us with a picture of that sort of physical reality (unless you accept the Bohm or Everett interpretations), despite what one might have hoped for from a formalism that is used to describe the behavior of what we tend to think of as the basic constituents of physical reality, the various elementary particles or better, quantum fields.  But if someone, say Nagel, did believe that this all flies in the face of common sense, it would be open to him to say that in this case, we are permitted, encourage, or perhaps even required to fly in said face by the weight of scientific evidence.

As I've said, I disagree on two counts with Nagel's skepticism about an evolutionary explanation of mind and reason: it doesn't fly in the face of my common sense, and I weigh the evidence as favoring it more strongly than does Nagel. Part of my disagreement may be that what Nagel has in mind is an evolutionary explanation that is commited to a "reductive materialism that purports to capture life and mind through its neo-Darwinian extension." Whereas I have in mind a less reductive approach, in which consciousness and reason are evolutionarily favored because they have survival value, but we do not necessarily reduce these concepts themselves to physical terms. In my view, biology is rife with concepts that are not physical, nor likely to be usefully reduced to physical terms--- like, say, "eye". As with "eye", there may be no useful reduction of "consciousness" or "perception" or "thought" or "word" or "proposition", etc.., to physics, but I don't think that implies that the appearance of such things cannot have an evolutionary explanation. (Nor, just to be clear, does it imply that these things are not realized in physical processes.) So I might share Nagel's incredulity that such things could have a "materialist" explanation, if by this he means one in terms of physics, but not his incredulity about evolutionary explanations of the appearance of mind and reason. To me, it seems quite credible that these phenomena form part of the mental aspect of structures made of physical stuff, though we will never have full explanations for all the phenomena of consciousness and the doings of reason, in terms of this physical structure.

(David Deutsch's recent book The Beginning of Infinity is one excellent source for understanding such non-reductionism---see in particular its Chapter 5, "The Reality of Abstractions".)

I'll likely make several more posts on this business, both on other ways in which I think Brad and others have mischaracterized Nagel's arguments or misplaced the emphasis in their criticisms, and on why this matters because some important points that Nagel has made on matters closely related to these, that I think have value, are in danger of being obscured, caricatured, or dismissed under the influence of the present discussion by Brad and others.

Skim away (Long run return to equities...)

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Everybody who makes any investment decisions (like what to do with the money in your IRA or other retirement account) needs to understand something that Bill Gross, managing director at PIMCO and involved in the running of the PIMCO Total Return bond fund (PTTRX), the world's largest, with a market capitalization of $263 billion as of the market close yesterday, apparently does not.  Namely, that one should not expect the long run rate of return on ownership of stock to be equal to the growth rate of GDP, or even of the economy's capital stock.  Gross (quoted by CNBC online):

The 6.6 percent real return belied a commonsensical flaw much like that of a chain letter or yes - a Ponzi scheme," he says. "If wealth or real GDP was only being created at an annual rate of 3.5 percent over the same period of time, then somehow stockholders must be skimming 3 percent off the top each and every year."

"If an economy's GDP could only provide 3.5 percent more goods and services per year, then how could one segment (stockholders) so consistently profit at the expense of the others (lenders, laborers and government)?"

It's remarkable that someone in finance is conceptualizing the returns to capital as "at the expense of others (labor, lenders, and the government)".  (I'm not implying that that's never the case...) I guess it is part of his main misconception, that returns beyond the rate of growth of the capital stock must be somehow at the expense of other sectors, rather than any kind of return to capital based on its productivity, or scarcity, or similar economic factors.    What Gross fails to understand is that the economy does not necessarily invest all of the returns to capital in growing the capital stock, and thus growing potential GDP; some of these returns are, if you like, "skimmed off the top" and consumed.  For publicly traded companies, for example, this can take the form of dividends returned to shareholders.  Doing a more precise accounting of where firms' profits go, in terms of new capital formation, dividend payouts and other ways of getting cash to investors, and so forth, and comparing it to long-run stock market returns, seems like a worthwhile exercise.  It's one I'm not especially well-equipped to do although I suspect it would begin with a (salutary for any investor) review of financial accounting---in particular, how to interpret corporate income statements and balance sheets.   And I suspect many economists have done versions of it.  [Added Aug. 2nd 2012:  I think that dividends and distributions are not really the key here:  investors might reinvest dividends (supporting the stock price, and tending to increase market returns), or sell stocks and consume some of the proceeds without reinvesting (reducing overall market returns).  The main point is as stated above, that economy-wide, all of the returns to capital should not be assumed to be reinvested.] But it's shocking that someone managing money at this scale (or any scale, actually!), even if it's mostly not equities, doesn't have their mind around this basic fact.

That doesn't mean I necessarily endorse the 6.6% real returns mentioned by Gross for US equities over the last century, as a reasonable expectation of (very) long-run returns to US stocks...I would need to see how the calculation is done, and of course, past performance is no guarantee of future returns...    But when I saw Gross' statements linked on major financial information websites, I felt like I had to say something.  Brad DeLong explains in more detail.  He also makes the point that the earnings yield of the S & P 500 is currently around 7.7%, and in a further post, points out that the yield using the past 10 years' earnings, smoothed, is around 4.5%, which together with an (historically reasonable) assumption of 2% real earnings growth, suggests to him that around 5% real returns to equity is a reasonable expectation (unless you expect a collapse in earnings, or price-to-equityearnings ratio).

A spear carrier's view of the 1994 health care reform debacle (DeLong)

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I get annoyed by blogs that are mostly just links to other people's stuff... but I had to link this great post from Brad DeLong on his inside view of the 1994 debacle in health care...

I"ve been wondering for the last few weeks or months... why can't Obama be more like LBJ?  Still, everyone has to operate from their own strengths... he may yet pull off health care reform in his own style, and for those who care about the horse-race aspect of this (and I certainly do inasmuch as it affects the Democrats' chances in the next two elections): by now, anything decent (or even apparently decent) by way of a health care bill will be viewed as a victory for Obama.

I'm worried, though, that although there are apparently European models for well-functioning healthcare that don't involve a public option, they involve nongovernmental nonprofit entities, or high levels of regulation.   Such models may be very difficult to replicate in this country where they may be easily co-opted or weakened by the money and influence big insurance can put behind things, and by the continual possibility of politically motivated medldling/sabotage.  Ironically, I fear our politics and culture may make a public option more workable than a semiprivate one.

Niall's back with an extra dose of Keynes-bashing, but now Brad's on the case

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In an LA times editorial, Niall Ferguson augments his Feb. 2 Financial Times piece, which I commented on earlier, with much more explicit Keynes-bashing and fiscal-stimulus-dissing.  This time, Brad's on the case.

Long Treasury yields did rise a bit (roughly from just under 3, to just over 3.5, percent over the last few weeks), and there was similar if less pronounced movement across the longer end of the curve, so maybe we shouldn't count on financing the whole stimulus at todays low rates---though I couldn't tell you if this is a response to the clear likelihood of a stimulus package, which I would have thought would have been priced in for a while now.  But if we're getting output closer to potential, sooner, with the stimulus, we're increasing the overall stream of real output that the Treasury will have avaible to tax to pay these things back---increased indebtedness being met with increased debt-servicing capability.  Maybe not one-for-one, although that cuddly, big-eyed multiplier sure helps.  The cuddly reference:  "Uneasily aware that their discipline almost entirely failed to anticipate the current crisis, they seem to be regressing to macroeconomic childhood, clutching the Keynesian "multiplier effect" -- which holds that a dollar spent by the government begets more than a dollar's worth of additional economic output -- like an old teddy bear."---Ferguson from the LA Times piece.)  Among the most multiplier-besotted economists would seem to be Paul Krugman;  here is a fairly random sample of him failing to anticipate the current crisis (you can go back much further with him on the dangers --- and let's not forget, the existence --- of the housing bubble).  As for regression to childhood, there seems to be a more serious epidemic among some (but far from all!) politically conservative economists, of regression to being macroeconomically unborn.  What's Ferguson's argument here: If they teach it in Econ 1 in every halfway respectable university in the country, there can't be anything to it?

Blowin' Hot and Cold---Niall Ferguson on recapitalization versus stimulus

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Niall Ferguson seems to agree with Paul Krugman and the Axis of Smart on nationalizing, er, sorry, recapitalizing the banks:

"First, banks that are de facto insolvent need to be restructured – a word that is preferable to the old-fashioned “nationalisation”. Existing shareholders will have to face that they have lost their money. Too bad; they should have kept a more vigilant eye on the people running their banks. Government will take control in return for a substantial recapitalisation after losses have meaningfully been written down. Bond­holders may have to accept either a debt-for-equity swap or a 20 per cent “haircut” (a reduction in the value of their bonds) – a disappointment, no doubt, but nothing compared with the losses when Lehman went under."

He even cites the Swedish case as a sensible model while, of course, noting the need to avoid "the nightmare of a state-dominated financial sector".  I don't think Larry Summers will let that come to pass... let's just hope the soon-to-be-announced overhaul of the rescue package for financial institutions involves an effective temporary takeover, if perhaps in some form of ---voting, please--- preferred equity stake by the government, rather than the perhaps more efficient outright purchase of the big banks on the open market.

Now, where does Ferguson think the money for this takeover and recapitalization will come from, if not government borrowing?   Substituting government debt for private may indeed stimulate demand, through the wealth effect and lower debt servicing costs, especially because the government can borrow at bargain-basement rates right now, so even if the--somewhat, but only somewhat, mythical---rational taxpaying consumer is factoring in the need for higher taxes in the future to pay this off, it's a net gain.  Of course, if the rational taxpaying consumer is a Keynesian and believes output will be closer to potential because of this stimulus, the anticipation of the higher lifetime income stream that will generate is still more impetus to spend---an argument that applies to government-expenditure-based stimulus, too.

Forcing renegotiation of mortgages, and the making of new mortgages, at lower rates is another interesting idea of Ferguson's;  noises from the Obama administration suggest they may have something in mind along these lines---and with the noise about helping out homebuyers coming from Republicans in Congress, maybe there could even be bipartisan support.  (Naah, they'll back off on principle.)

But what about the rest of Ferguson's piece:

"...the western world is suffering a crisis of excessive indebtedness. Many governments are too highly leveraged, as are many corporations. More importantly, households are groaning under unprecedented debt burdens. Worst of all are the banks. The best evidence that we are in denial about this is the widespread belief that the crisis can be overcome by creating yet more debt.

The US could end up running a deficit of more than 10 per cent of gross domestic product this year (adding the cost of the stimulus package to the Congressional Budget Office’s optimistic 8.3 per cent forecast). Today’s born-again Keynesians seem to have forgotten that their prescription of a deficit-financed fiscal stimulus stood the best chance of working in a more or less closed economy. But this is a globalised world, where unco-ordinated profligacy by national governments is more likely to generate bond market and currency market volatility than a return to growth."

Well, the last bit sounds more like an argument for the US providing leadership in co-ordinated, global fiscal stimulus policy than for giving up on stimulus.  (It's also the argument for buy-domestic provisions in stimulus plans, though that's definitely a second-best option to co-ordinated, unrestricted stimulus, and perhpas somewhat silly in that much of what a stimulus package will get spent on will be nontraded goods in any case---although some good public transportation infrastructure would be highly welcome, and might well involve a lot of European-made equipment.)

It's hard to think of a better time than now, with the lowest borrowing rates in years available to the US Treasury, to make some serious public investments.   So Ferguson's ideas on the financial sector and mortgage loans seem reasonable, and may well provide fiscal stimulus themselves, but his argument against government expenditure for additional stimulus seems weak.  Co-ordinated profligacy with your restructuring, anyone?