I have just finished listening to Chomsky’s fourth lecture and so this will be the last series of posts on them (here). If you have not seen them, let me again suggest that you take the time to watch. They are very good and well worth the (not inconsiderable) time commitment.
In 4, Chomsky’s does three things. First he again tries to sell the style of investigation that the lectures as a whole illustrate. Second, he reviews the motivations and basic results of his way of approaching the Darwin’s Problem. Third, he proposes ways of tidying up some of the loose ends that the outline in 3 generates (at least they were loose ends that I did not understand). Let me review each of these points in turn.
1. The central issues and the Strong Minimalist Thesis (SMT)
Chomsky, as is his wont, returns to the key issues as he sees them. There are two of particular importance.
First, he believes that we should be looking for simple theories. He names this dictum Galileo’s Maxim (GM). GM asserts (i) that nature is simple and (ii) it is the task of the scientist to prove that it is. Chomsky notes that this is not merely good general methodological advice (which it is), but that in the particular context of the study of FL there are substantive domain specific reasons for adopting it. Namely: Darwin’s Problem (DP). Chomsky claims that DP rests on three observations: (i) That our linguistic competence is not learnable from simple data, (ii) There is no analogue of our linguistic capacity anywhere else in the natural world, and (iii) The capacity for language emerged recently (in the last 100k years or so), emerged suddenly and has remained stable in its properties since its emergence. These three points together imply that we have a non-trival FL, that it is species specific and that it arose as a result of a very “simple” addition to ancestor’s cognitive repertoire. So, in addition to the general (i.e. external to the specific practice of linguistics) methodological virtues of looking for simple and elegant theories, DP provides a more substantive (i.e. internal to linguistics) incentive, as simple theories are just the sorts of things that could emerge rapidly in a lineage and remain stable after emerging.
I very much like this way of framing the central aims of the Minimalist Program (MP). It reconciles two apparently contradictory themes that have motivated MP. The first theme is that looking for simple theories is just good methodology and so MP is nothing new. On this reading, MP is just the rational extension of GG theorizing, just the application of general scientific principles/standards of rational inquiry to linguistic investigations. On this view, MP concerns are nothing new and the standards MP applies to theory evaluation are just the same as they always were. The second view, one that also seems to be a common theme, is that MP does add a new dimension to inquiry. DP, though always a concern, is now ripe for investigation. And thinking about DP motivates developing simple theories for substantive reasons internal to linguistic investigations, motivations in addition to the standard ones prompted by concerns of scientific hygiene. On this view, raising DP to prominence changes the relevant standards for theoretical evaluation. Adding DP to Plato’s Problem, then, changes the nature of the problem to be addressed in interesting ways.
This combined view, I think, gets MP right. It is both novel and old hat. What Chomsky notes is that at some times, depending on how developed theory is, new questions can emerge or become accented and at those times the virtues of simplicity have a bite that goes beyond general methodological concerns. Another way of saying this, perhaps, is that there are times (now being one in linguistics) where the value of theoretical simplicity is elevated and the task of finding simple non-trivial coherent theories is the central research project. The SMT is intended to respond to this way of viewing the current project (I comment on this below).
Chomsky makes a second very important point. He notes that our explanatory target should be the kinds of effects that GG has discovered over the last 60 years. Thus, we should try to develop accounts as to why FL generates an unbounded number of structured linguistic objects (SLO), why it incorporates displacement operations, why it obeys locality restrictions (strict cyclicity, PIC), why there is overt morphology, why there are subject/object asymmetries (Fixed Subject Effects/ECP), why there are EPP effects, etc. So, Chomsky identifies both a method of inquiry (viz. Galileo’s Maxim) and a target of inquiry (viz. the discovered laws and effects of GG). Theory should aim to explain the second while taking DM very very seriously.
The SMT, as Chomsky sees it, is an example of how to do this (actually, I don’t think he believes it is an example, but the only possible conceptually coherent way to proceed). Here’s the guts of the SMT: look for the conceptually simplest computational procedures that generate SLOs and that are interpreted at CI and (secondarily) SM. Embed these conceptually simple operations in a computationally efficient system (one that adheres to obvious and generic principles of efficient computation like minimal search, No Tampering, Inclusiveness, Memory load reduction) and show that from these optimal starting points one can derive a good chunk of the properties that GG has discovered natural language grammars to have. And, when confronted with apparent counter-examples to the SMT, look harder for a solution that redeems the SMT. This, Chomsky argues is the right way, today, to do theoretical syntax.
I like almost all of this, as you might have guessed. IMO, the only caveat I would have is that the conceptually simple is often a very hard to discern. Moreover, what Occam might endorse, DP might not. I have discussed before that what’s simple in a DP context might well depend on what was cognitively available to our ancestors prior to the emergence of FL. Thus, there may be many plausible simple starting points that lead to different kinds of theories of FL all of which respond to Chomsky’s methodological and substantive vision of MP. For what it’s worth, contra Chomsky, I think (or, at least believe that it is rational to suggest) that Merge is not simple but complex and that it is composed of a more cognitively primitive operation (viz. Iteration) and a novel part (viz. Labeling). For those who care about this, I discuss what I have in mind further here in part 4 (the finale) of my comments to lecture 3. However, that said, I could not agree with Chomsky’s general approach more. An MP that respects DP should deify GM and target the laws of GG. Right on.
 Chomsky has a nice riff where he notes that though it seems to him (and to any sane researcher) that (i)-(iii) are obviously correct, nonetheless these are highly controversial claims, if judged by the bulk of research on language. He particularly zeros in on big data statistical learning types and observes (correctly in my view) that not only have they not been able to deliver on even the simplest PoS problems (e.g. structure dependence in Y/N questions) but that they are currently incapable of delivering anything of interest given that they have misconstrued the problem to be solved. Chomsky develops this theme further, pointing out that to date, in his opinion, we have learned nothing of interest from these pursuits either in syntax or semantics. I completely agree and have said so here. Still, I get great pleasure in hearing Chomsky’s completely accurate dismissive comments.
 I also discuss this in a chapter co-written with Bill Idsardi forthcoming in a collection edited by Peter Kosta from Benjamins.