From the archive
In this post, Alan touches on a longstanding disagreement between us on “reasonableness.” To be a little reductive, he is (like most of my friends) a firm believer in self-improvement, intuition pumps, Science, and the like; I am a nihilistic slob, with considerable sympathy for irrationalism. Part of this is, no doubt, due to differences in temperament (this is the only way I can explain the fact that I’m not a vegetarian), but differences in intellectual history also have something to do with it.
I should distinguish between contemplative and instrumental rationality: the former is about getting facts right, not believing false arguments, etc.; the latter is about getting what one wants, whatever that might be. (The former is a limiting case of the latter.) Given a list of desires and beliefs, instrumental rationality tells you what actions are (in some pretty obviously meaningful sense) “rationally binding.” In certain very specific contexts (e.g., a prisoner trying to escape), what one wants is clear, and instrumental rationality is a useful tool.
Perhaps some cases in the historical core material of economics — purely profit-maximizing regimes of endeavor — resemble this; however, whether any of it applies to everyday life is much less clear, as it is not evident that people have fixed desires in any meaningful sense. (I wholeheartedly agree with Andrew Gelman’s aphorism that “the utility function is the epicycle of social science,” which I probably consider to be more broadly true than Gelman does.) In order to adapt instrumental rationality to everyday life, one is forced to do a sort of three-step: (a) assume that a utility function exists, (b) use a combination of survey data, “revealed preference,” behavior, and intuition-pumping to figure out what the utility function says, © accuse people of being irrational when the “best” utility function doesn’t do a good job of predicting their behavior.[…]
I’ll restrict myself to a brief note on “ideology” as the term is used in physics. An “ideology” is a widely believed but vague and/or unprovable rule of thumb that can be applied to prove various specific results. It is, in general, a rule about what questions to ask and what kinds of answers to look for. The “renormalization group“ idea in physics is an ideology that plays a role that’s roughly like that played by evolution in biology: one cannot reduce it to a precise, true, non-vacuous statement, but it guides the field. Ideologies are what Weinberg refers to as the “soft” parts of theories:
There is a “hard” part of modern physical theories (“hard” meaning not difficult, but durable, like bones in paleontology or potsherds in archeology) that usually consists of the equations themselves, together with some understandings about what the symbols mean operationally and about the sorts of phenomena to which they apply. Then there is a “soft” part; it is the vision of reality that we use to explain to ourselves why the equations work. The soft part does change; we no longer believe in Maxwell’s ether, and we know that there is more to nature than Newton’s particles and forces. … But after our theories reach their mature forms, their hard parts represent permanent accomplishments.This distinction exists to some degree outside particle physics — a great deal has been learned about the lineages of various species, etc., even if the ideology that led to these discoveries turns out to be false. But it’s worthwhile to distinguish between the predictions of a theory — i.e., predictions that come out of the “hard part” — and those of an ideology, which come from the soft part. The latter cannot be disproved in any straightforward way — they are just patterns we impose on selected agglomerations of fact — and change, as often as not, because the community becomes interested in other problems where the ideology is less useful.