Minimalist Physics?

I was recently rereading some essays by Steven Weinberg (here) and was reminded why it is that I have a severe case of physics envy. It is not only the depth of the results, both theoretical and empirical, and not only the fact that when it comes to explanation, what you find in physics is the gold standard, but my envy is also grounded in a respect for the disciplined way that physicists talk about even the most obscure methodological matters. Weinberg, in discussing his reductionist urges, makes three points that should resonate with those who have a minimalist pulse.  He discusses these on pages 37-40.  Here’s “lessons” he draws from “the history of science in the last three hundred years” (btw, I am pretty sure that the last quoted passage is said/written with tongue firmly in cheek).

1.     The aim of fundamental physics is to “explain why everything is the way it is. This is Newton’s dream, and it is our dream.”

2.     “The importance of phenomena in everyday life is, for us, a very bad guide to their importance in the final answer.”

3.     Indeed, whether something is ubiquitous or common is a very unreliable guide to its interest or importance: “We do not know about muons in our everyday life. But as far as we know, muons play just as fundamental a role (which may or may not be very fundamental) as electrons  [which is “ubiquitous in ordinary matter” –NH] in the ultimate scheme of things.”

4.     “We are not particularly interested in our electrons or our muons. We are interested in the final principles that we hope we will learn about by studying these particles. So the lesson is that the ordinary world is not a very good guide to what is important.”

5.     “…if we are talking about very fundamental phenomena, then ideas of beauty are important in a way that they wouldn’t be if we were talking about mere accidents…[P]lanetary orbits don’t have to be beautiful curves like circles because planets are not very important on any fundamental level. On the other hand, when we formulate the equations of quantum field theories or string theories we demand a great deal of mathematical elegance, because we believe that the mathematical elegance that must exist at the root of things in nature has to be mirrored at the level where we are working.  If the particles and fields were working on were mere accidents…then the use of beauty as a criterion in formulating our theories would not be so fruitful.”

6.     “…in the theories we are trying to formulate, we are looking for a sense of uniqueness, for a sense that when we understand the final answer, we will see that it could not have been any other way. My colleague John Wheeler has formulated this as the prediction that when we learn the ultimate laws of nature we will wonder why they were not obvious from the beginning.”

These have more than a passing resemblance to oft quoted minimalist dicta.  (1) is the familiar minimalist credo: the aim is not only to know what is the case but to know why it is the case.

(2) sums up why it is that looking at large collections of surface data are very likely to be irrelevant.  Real explanations lay hidden beneath the surface of things, just as much in the study of FL as in the study of basic physics.

(3) reinforces the point in (2) and also suggests the hazards of concentrating on the common, a feature not unknown to the statistically inclined. Common/frequent does not imply theoretically important unless one has a pretty surfacy/empiricist conception of theory.

(4) is a favorite of mine: think of the distinction between linguistics and languistics. But it goes deeper.  We study languages because we believe that studying these will tell us something about the nature of human cognition and biology.  They are instruments for probing minds/brains, the latter (not languages) being the ultimate objects of inquiry.  In this sense linguistics is not about language any more than physics in Weinberg’s conception, is about electrons or muons. 

(5) starts moving onto very subtle but important territory. Weinberg and Chomsky share the idea that at fundamental levels reality is simple and elegant. The converse of this is that complexity is the result of interacting systems. As fundamental theory describes single (i.e. non-interacting) there is no place within fundamental theories for interaction effects. Thus we expect (and find) simplicity and elegance. So here’s a regulative ideal: simplicity holds at fundamental levels and complexity arises from the interaction of simple systems. Thus, when looking for the fundamental look for the simple and when it eludes you assume that the complexity is a sign of two or more interacting simple systems.  This is, admittedly, murky advice.  However, at times, murky methodological advice can be important and consequential. Weinberg and Chomsky identify two projects where this is likely to be the case.

And last we have (6): it provides a kind of ex post conception of a notion Chomsky has been fond of: “virtual conceptual necessity (VCN)” Ex post, VCN cannot guide research: it simply describes what we are looking for: a theory that when stated will seem both obviously true and inevitable.  We can, however, get an inkling about what kinds of notions such a theory will contain.  For example, FL will have to contain a rule that puts elements together (merge) and it would be very surprising given what we know if its operations were not regulated by natural computational considerations like cyclicity and locality.  These are candidate basic notions for a theory that has VCN. As Weinberg puts it:

That [Wheeler’s conception above -NH] may very well be true. If it is, I suspect it will be because by the time we learn the ultimate laws of nature, we will have been so much changed by the learning process that it will become difficult to imagine that the truth could be anything else…

Note the historical gloss Weinberg gives to Wheeler’s dictum. This is why I added “given what we know” above. Given minimalism’s roots in Generative Grammar research over the last 60 years operations like merge and notions like cyclicity and locality and economy must be part of any reasonable account. That’s Weinberg’s version of VCN, and as we can see, it’s not limited to the dreams of linguists.  All good science, at least all good basic science, appears to share the dream.

Physics Envy

Yes, I suffer, badly. Not only that, but I distrust those that don’t. A good dose of Physics Envy is the sign of good theoretical taste.  That’s why I prize fMRI snaps of frontal lobes awash in green whenever ‘CERN,’ ‘Higgs boson,’ ‘renormalizable,’ ‘Standard Theory,’ ‘SU-3 symmetry,’ etc. are flashed to visual and auditory fields.  It is beyond dispute: Physics is THE science. It provides THE models for explanation.  Its methodological precepts should be stolen and copied at every opportunity. What physics has is what every right-minded science should aspire to. The fact that we are likely to fall short (maybe very short) is no excuse.

I mention this because I had an acute spike in my physics-enviometer recently as I read some old essays by Steven Weinberg (collected here).  Here are four observations he made with suggestions of how these may be relevant to linguistics.

1. Weinberg, aficionados of Chomsky’s philosophical writings might recall, is a strong proponent of the Galilean style (GS), which consists in ”making abstract models of the universe to which the physicists, at least, give a higher degree of reality than they accord the ordinary world of sensations.” GS values a theory’s explanatory reach as well as its empirical coverage. Indeed, at some times, explanatory power outweighs (and should outweigh) empirical coverage and empirical anomalies and (apparently) contradictory evidence is (and should be) set aside for the sake of further theoretical development.   

The relevance of this methodological attitude to linguistics is pretty evident. Linguistics is very data rich. Experiments (acceptability judgments) are cheap and easy. The problem is not finding another “fact” that resists explanation, but putting together a theory that has even a hint of non-trivial deductive explanatory structure. GS values this enterprise and reminds us that theories can be worth pursuing (and discarding) for reasons other than how many data points they (appear) to cover (or miss).

2. Weinberg remarks on what we want from our theories:

…there are explanations and explanations.  We should not be satisfied with a theory that explains the Standard Model in terms of something complicated an arbitrary…To qualify as an explanation, a fundamental theory has to be simple- not necessarily a few short equations, but equations that are based on a simple physical principle…And the theory has to be compelling- it has to give us the feeling that it could scarcely be different from what it is (ch 1).

These desiderata are reminiscent of those endorsed by the Minimalist Program, which, as Chomsky has repeatedly observed, are the in tune with the standard methodological tenets widespread in the successful sciences, viz. physics. Note Weinberg’s gloss on “simple” and “compelling.” Simple theories are based on natural principles, ones that make sense. This is also what makes them compelling. Within linguistics, the Minimalist Program endorses a similar mindset.  What makes for a simple and compelling theory of FL?  What are natural principles of UG?  These are very abstract very hard questions. But, as Weinberg observes for physical theories, they are the questions that any science with explanatory ambitions must confront.  Indeed, we might do worse than evaluate the success of a research program with how well it manages to operationalize these very important concerns.  For what it’s worth, I believe that one of the successes of the Minimalist Program is that it has tried (somewhat successfully in my view) to grapple with these issues. The central motif is that FL/UG is a computational system. We should explore its computational design features and look for natural ones.  Principles like Extension/No-tampering, Inclusiveness, Minimality, and Locality make computational sense. The program is to explore exactly how such notions operate and exactly what computational virtues they reflect.  Natural, simple principles, with great explanatory potential, that’s what we ought to be looking for!

3. Weinberg notes that what basic theory finds is likely to be irrelevant for many concerns:

The discovery of a final theory is not going to help us cure cancer or understand consciousness…We probably already know all the fundamental physics we need for these tasks (Ch 1).

There are many questions within linguistics where the results of minimalist theorizing will likely be irrelevant.  So far as I can tell, if you are interested in how kids acquire their grammatical competence in real time or how people parse sentences in real time or in how exotic language ‘E’ forms questions or relative clauses or how it expresses anaphoric dependencies then GB (and for many questions the Aspects Standard Model) is more than adequate to your task.  This is especially the case if, as I believe, a desirable boundary condition on adequate Minimalist theory (note: theory, not program) is that it preserve the generalizations embodied in these earlier descriptions of FL/UG. At any rate, much of what minimalism aims to accomplish will likely be of little relevance to these other investigations for roughly the same reasons that Weinberg notes above.

4. Weinberg describes the explananda of physics as follows:

…physicists are interested in the explanation of regularities, of physical principles, rather than individual events…Biologists, meteorologists, historians and so on are concerned with the causes of individual events…while a physicist only becomes interested in an event…when the event reveals a regularity of nature…(Ch2).

Another way of putting this is that physicists aren’t interested in what happens but in what could happen.  Linguists, at least those interested in competence, are very similar.  They are not interested in performances (what so and so said at this and this time) but the capacity that underlies these performances (which, to confess, I for one believe we will never be able to explain).  But more than this, linguists of the generative variety are interested in regularities, and high level ones at that. We often describe these as “effects,” island effects, principle C effects, Weak Cross Over effects etc.  These are highly stylized regularities and work in syntax aims to discover such effects and explain why they hold. Gathering linguistic data is worthwhile to the degree that these sorts of effects/generalizations are discovered.  Why? Because understanding the etiology of these effects is the key to unraveling the general properties of FL.  Linguists tend to underappreciate this point.  Effects (and anomalies, which are systematic counter-examples to effects) are what drive theory in the serious sciences.[1] They should do so in linguistics as well. Moreover, just as in physics, the aim should be to deduce these regularities from more and more general principles. As Weinberg puts it:

…we explain a physical principle when we show how it can be deduced from a more fundamental physical principle.

Weinberg has a very interesting discussion of what ‘fundamental,’ ‘deduced,’ and ‘principle,’ mean in the context of physics, which I urge you to look at.[2] In the context of contemporary linguistics, it is equally important to get a bead on the interpretation of these terms, especially given minimalist aspirations.  I have discussed my views of this elsewhere (here) (and I have some papers discussing this that are on the way out that I will link to when they come out) but for now, let’s just note that the ambitions are partially reductive, the aim being to deduce the laws of GB from more general principles.  Reduction does not imply elimination, rather the converse. And finding general accounts for the structure of FL need not imply that the principles of UG are domain general rather than domain specific (see here).  However, looking to deduce principles of UG from more general considerations, most likely of a computational sort, is what physics enviers should be aspiring to and Weinebrg’s examples illustrate the subtleties of this enterprise in a domain far more successful than our own.

There is a lot more in these Weinberg’s essays that I found thought provoking. Physics envy is a great motivator.  If you want to fuel your methodological mirror neurons, Weinberg’s popular writings are not a bad place to go.

---

[1] I will discuss effects and anomalies and their role in linguistics in a future post.

[2] Weinberg notes that “physicists try to explain just those things that are not dependent on accidents, but in the real world most of what we try to understand does depend on accidents.” Compare this to Norvig’s conception of scientific understanding (discussed here).