I admit it: until very recently when I heard “morphology” I reached for my pillow. I knew that I was supposed to find it all very interesting, but like cod liver oil, knowing this did not make ingesting it any more pleasant. Moreover, I even developed a spiel that led to the conclusion that I did not have to be interested in it for it was at right angles to those questions that gripped me (and you all know what these are, viz. PP and DP and Empiricism/Rationalism, and FL and UG etc.). Morphology was not as obviously relevant to these questions because much of it dealt with finite (often small) exception-full paradigms. So many rules, so many exceptions, so many data points. Is there really a PoS problem here? Not obviously. So, yes morphology exists and is abundant, but does language really need morphology or is it just an excrescence? At any rate, despite some questions at a very general level (here and here), I was able to divert my gaze and convince myself that I had reason to do so. Then along came Omer thrusting Bobaljik into my hands and I am here to admit that I was completely wrong and that this stuff is great. You may know all about it, but partly as penance, let me say how and why I was wrong and why this stuff is very interesting even for someone with my interests.
Those of you that are better read than I am already know about Jonathan Bobaljik’s (JB) work on the morphology of superlatives. He has a book (here) and a bunch of papers (e.g. here). I want to talk a little about one discovery that he has made that provides a novel (as JB himself notes) take on the classic PoS argument. It should be part of anyone’s bag of PoS examples that gets trotted out when you want to impress family, friends, students, and/or colleagues. It’s simple and very compelling. I have road tested it, and it works, even with those that know nothing about linguistics.
The argument is very simple. The fact concerns morphological patterns one finds when one examines morphological exceptions. In other words, it rests on the discovery that exceptions can be regular. A bunch of languages (though by no means all) can form comparatives and superlatives from base adjectival forms with affixes. English is a good example of one such language. It provides trios such as big, bigg-er, bigg-est and tall, tall-er, tall-est. Note that in these two examples, big and tall are part of the comparative er form and the superlative est form. This is the standard pattern in languages that do this kind of thing. Interestingly, there are exceptions. So in English we also find trios like good bett-er, be-st and bad, worse, wor-st where the comparative and superlative forms are not based on the same base as the simple adjectival form. In other words, the comparative and superlative are suppletive. There’s lots of technical ways of describing this, but for my purposes, this suffices. Here’s what JB established (of course, based on the work of others that JB copiously cites): that if the comparative is suppletive, then so is the superlative. More graphically, if we take the trio of forms as Adj/Comp/Super, we find AAA patterns, ABB patterns and even ABC patterns but we find no ABA patterns and very very few (maybe no?) AAB patterns. JB’s question is why not? And a very good questions this is.
JB argues that this follows from how superlatives are constructed and how suppletion reflects the Elsewhere Principle. The interested reader should read JB, but the basic proposal is that superlatives have comparatives as structural subparts. How one pronounces the subpart then has an effect on how one can pronounce the larger structure. So, in effect, if the comparative is suppletive and it is part of the structure of the superlative, then the superlative must be suppletive as well given something like the Elsewhere Principle. This accounts for the absence of the ABA pattern. Explaining the absence of the AAB pattern takes a few more assumptions concerning the locality of morphological operations.
All of this may or may not be correct (I am no expert) but it is all very interesting and very plausible. Let’s return to the PoS part of the argument. JB notes several very interesting properties of these patterns.
First, the pattern (especially the *ABA) is linguistically very robust. It occurs in languages where the morphology makes it clear that comparatives are part of superlatives (Czech) and those where this is not at all evident on the surface (English). Thus, whatever is responsible for the *ABA pattern cannot be something that is surface detectable from inspecting morphologically overt morphemic forms. Thus, that it holds in languages like English does not follow from the fact that the comparative-within-superlative structure is evident in English forms. It isn’t. So that *ABA holds quite generally, even when there is no surface evidence suggesting that the superlative contains a comparative subpart, suggests that the postulated nested relationship between comparatives and superlatives drives the overt morphology, rather than the other way around. And this, JB notes, strongly suggests that this gap in the possible patterns points to *ABA implicating some fundamental feature of FL/UG.
Note, incidentally, this is an excellent example where the G of language A can ground conclusions concerning the G of language B, something that only makes sense in the context of a commitment to some form of Universal Grammar. The G of Czech is telling us something about the G of English, which borders on the absurd unless one thinks that human Gs as such can have common properties (viz. a commitment to UG in some form).
Second, suppletion of the relevant sort is pretty uncommon within any single language. So, in English there are only two such suppletive trios (for good and bad). So too in other languages (e.g. Hungarian, Estonian, Persian, Sanskrit, Modern Greek and Portuguese have one suppletive form each). Consequently, the *ABA pattern only emerges if one takes a look across a large variety of languages and notes that the rather suppletive *ABA pattern never appears in any.
Let me stress these two points: (i) the pattern is surface invisible in many languages (e.g. English) in that the words that are relevant to finding it do not wear the pattern on their morphological sleeves. (ii) Moreover, the absent pattern occurs in an exceptional part of the language, suppletions being exceptions to the more clearly rule governed part of the morphology. And (iii) suppletions are rare both within a language and across languages. The numbers we are looking at are roughly 200 forms over 50 or so languages. Nonetheless, when all of these exceptions from across all of these languages is examined, the absence of ABA patterns shines through clearly. So, there is a kind of three fold absence of relevant data for the child: the pattern is surface invisible in many languages, suppletion triplets are rare in any given language and the pattern is only really well grounded when one considers these small number of exceptional cases across a good number of languages. The PoSity (haha) of relevant evidence is evident. As JB rightly concludes, this begs for a FL/UG explanation.
Third, as JB notes, the absence really is the absence of a pattern. Here’s what I mean. Even among languages in close contact the pattern cannot be accounted for by pointing to roots and morphemes that express these patterns shared across the languages. The reason is that the relevant roots and morphemes in language A are not those that express it in language B even in cases where A and B are geographical and historical neighbors. So there is no plausible account of *ABA in terms of borrowing forms across Gs either geographically or historically local to one another.
As JB eloquently sums things up (here: p 16):
…a growing body of research…finds…order in chaos – robust patterns of regularity that emerge as significant in their cross-linguistic aspect. Systematic gaps in these attested patterns…point to the existence of grammatical principles that abstract away from the peculiarities of individual words in specific languages and restrict the class of possible grammars.
This argument combines classic PoS themes with one important innovation. What’s classic is zeroing in on the absence of some grammatical possibility. UG is invoked to explain the gaps, exceptions the observed general patterns. UG is not generally invoked to explain what is visible, but what fails to bark. What is decidedly new, at least to me, is that the relevant pattern is only really detectable across Gs. This is the data the linguist needs to establish *ABA. There is no plausible world in which this kind of data is available in any child’s PLD. Indeed, given the rarity of thee forms overall, it is hard to see how this pattern could be detected by linguists in the absence of extensive comparative work.
As noted, JB provides a theory of this gap in terms of the structure of superlatives as containing comparatives plus the Elsewhere Principle. If UG requires that superlatives be built from the comparative and UG adopts the Elsewhere Principle then the *ABA hole follows. These assumptions suffice to provide an explanatorily adequate theory of this phenomenon. However, JB decides to venture into territory somewhat beyond explanatory adequacy and asks why this should be true. More particularly, why must superlatives be built on top of comparatives? He speculates, in effect, that this reflects some more general property; specifically a principle
… limiting the (semantic) complexity of functional morphemes. Perhaps the reason there can be no true superlative (abstract) morpheme combining directly with adjectives without the mediation of a comparative element is that the superlative meaning “more X than all others” contain two semantically rich elements: the comparative operator and a universal quantifier. Perhaps UG imposes a condition that such semantically rich elements must start out as syntactic atoms (i.e. X0 nodes). (herep. 6)
It is tempting to speculate that this proposal is related to the kind of work that Hunter, Pietroski, Halberda and Lidz have done on the semantic structure of most (discussed here). They note that natural language meanings like to use some predicates but not others in expressing quantificational meanings. Their analysis of most critically involves a comparative and a universal component and shows how this fits with the kinds of predicates that the analog number + visual system prefer. One can think of these, perhaps, as the natural semantic predicates and if so this might also relate to what JB is pointing to. At any rate, we are in deep waters here, just the kind of ideas that a respect for minimalist questions would lead one to explore.
Let me end with one more very interesting point that JB makes. He notes that the style of explanation developed for the *ABA gap has application elsewhere. When one finds these kind of gaps, these kinds of part-whole accounts are very attractive. There seem to be other morphological gaps of interest to which this general kind of account can be applied and they have very interesting implications (e.g. case values may be highly structured). At any rate, as JB notes, with this explanatory schema in hand, reverse engineering projects of various kinds suggest themselves and become interesting to pursue.
So let me end. To repeat, boy was I wrong. Morphology provides some gorgeous examples of PoS reasoning, which, moreover, are easy to understand and explain to neophytes. I would suggest adding the *ABA MLG to your budget of handy PoS illustrations. It’s great stuff.
 I also have a copy of an early draft of what became part of the book that I will refer to here. I will call this JB-draft.
 Is Latin the only case of an ABC pattern? JB probably said but I can’t recall the answer.
 This is a classical kind of GG explanation: why do A and B share a property? Because A is a subpart of B. OR why if B then A? Because A is A is part of B. Note that this only really makes sense as an explanatory strategy if one is willing to countenance abstract form that is not always visible on the surface. See below.
 David Pesetsky made just this point forcefully in Athens.
 See JB-draft:15.
 JB-draft (15-16) notes that neither roots nor affixes that induce the suppletion are preserved across neighboring or historically related languages.