There are certain kinds of explanations, which when
available, are particularly satisfying.
What makes them such is that they not only explain the facts in front of
you, but do so in ways that make the facts inevitable. How do they do this? Well, one way is by
rendering the non-extant alternatives not merely false, but inconceivable. A joke/riddle that I like to tell my students
displays the quality I have in mind.
One physicist/mathematician asks another: why are there
1-humped camels and 2-humped camels, but no N-humped camels, N>2? Answer:
Because camels are convex or concave; no other models available.
I love this
answer. It’s perfect. How so? By shifting the relevant predicates (from natural
numbers to simple curves) the range of possible
camels is reduced to two, both of which are attested! Concave/convex, exhaust the space of options. And once you think of things in this way, it
is clear why 1 and 2 are the only possible values for N.
Let me put this another way: one gets a truly satisfying
explanation if one can embed it in concepts that obviate further why questions. How are they obviated? By
exhausting the range of possibilities. Why are there no 3-humped camels?
Because 3-humped camels are neither concave nor convex and these are the only
shapes camels can come in.
The joke/riddle has a second useful attribute. I displays
what I take to be a central aim of theoretical research: to redescribe the
conceivable alternatives in such as way as to restrict the range of available
alternatives to what one actually sees. The aim of theory is not merely to cover the data, but to explain why the
data falls in the restricted range it does, and this requires carefully
observing what doesn’t happen (what
Paul Pietroski calls ‘negative’ facts (e.g. here)).
So, do we have any of these kinds of explanations within
syntax? I think we do, or at least there have been attempts to provide such.
Let me illustrate.
One current example is Chomsky’s proposed account for why
grammatical operations are structure dependent. This is in Problems of Projection (which I would link to, but it is behind a Lingua paywall with an exorbitant price so I suggest that you just get a copy from
someplace else). Here’s what we want to explain: given that rules that move T-to-C (as in Y/N questions in English)
target the “highest” Ts and not the linearly closest Ts (i.e. leftmost), why must they target these Ts, (i.e. why can’t they target the linearly most
proximate Ts)?
The answer that Chomsky gives is that grammatical operations
cannot use notions like linear
proximity, because linguistic objects
are not linearly specified until Spell Out, i.e. the final rule of the syntax.
So why can’t grammatical operations
be linearly dependent (i.e. non-structure dependent)? Because the syntactic manipulanda
(i.e. phrase markers) contain no linear (i.e. left-right order) information.
Thus, if grammatical rules manipulate phrase markers and these don’t contain
linear information then there is no way to state linearly-dependent rules over
these objects. In other words, why do
such rules not appear to exist? Because they can’t be specified for the objects
over which the grammatical rules operate, and that’s why linear dependent syntax rules don’t exist.
Or, put positively: why are all syntactic rules structure
dependent? Because that’s the only way they can
be. In other words, once the impossible options are eliminated all that’s left
coincides with what we find. In this
way, the actual is explained via the possible and explanatory oomph is
attained. Indeed, I suspect (believe!) that the best way to explain anything is
by showing how the plausible alternatives are actually conceptually impossible
when thought about in the right way.
Here’s another minimalist example. It comes from current
conceptions of Spell Out and how they’ve been used to account for phase
impenetrability (i.e. the prohibition against forming dependencies across a
phase head). Here’s the question: why
are phases impenetrable? Answer: because Spell Out “sends” phase head
complements to the interfaces thereby removing
their contents from the purview of the syntax/computational system. In
effect, dependencies across phase heads are not possible because complements of
phase heads (and hence their contents) are not syntactically “there” to be
related.
Note the similarity to the first account: just as linear
information is not there to be exploited and hence only structure dependent
operations are stateable, so too phase complement information is not there and
so it cannot be exploited. In both cases, the “reason” the condition holds is
that it cannot fail to hold. There really is only one option when properly
conceptualized.
Here’s another example from an earlier era: one of the most
interesting arguments in favor of dispensing with constructions as grammatical
primitives came from considering a conundrum relating to examples like (1c).
(1) a.
John is likely to have kissed Mary
b. John was seen/believed by Mary
c.
John is seen/believed to have kissed Mary
The puzzle is the following in the context of a
construction-based conception of grammatical operations (i.e. a view of FL in
which the basic operations are construction based rules like Passive, Raising
etc).[1]
In (1a), John moves from the post
verbal position to the subject position via Raising. In (1b) the operation that
moves John to the top is
Passivization. Question: what is the rule that moves John in (1c)? Is this
Passive or Raising? There is no
determinate answer.
Eliminating constructions gives a simple answer to the
otherwise unanswerable question: it’s neither, as these kinds of rules don’t exist.
‘Move alpha’ is the sole transformation and it applies in producing both
Raising and Passive constructions. Of course, if this is the only (movement) transformation, then the
question is it Raising or Passive dissolves. It’s move alpha and only move
alpha. As the earlier question (Raising or Passive?) had no good answer, a
conception of grammar where the question dissolves has its charms.
One last example, this one from an undergrad research thesis
by Noah Smith (of CMU fame; yes
he was once a joint ling/CS student). He wrote when Jason Merchant’s work on
ellipsis was first emerging and he asked the following question: Given that
Merchant has shown that ellipsis is deletion and not interpretation, why can’t it be the latter? He rightly (in my view) surmised that this
could not be a data driven fact as the relevant data for determining this was
very subtle. For Jason it amounted to some case and preposition stranding
correlations in sluiced and non-sluiced constructions. On the reasonable
assumption that these fall outside the PLD, the fact that ellipsis was deletion
could not have been a data driven outcome. Say this is correct. Noah asked why
it had to be correct; why ellipsis had to be deletion and could not be
interpretation a la Edwin Williams (i.e. ellipsis amounted to filling in the
contents of null phrase markers with null terminals at LF).[2]
Noah’s answer? Bare Phrase Structure (BPS). BPS replaces the earlier combo of
phrase structure + lexical insertion rules. This has the effect of eliminating
the distinction between the content and position of a lexical item. As such, he
argued, the structures that the interpretive theory of ellipsis presupposed
(phrases with no lexical terminals) were conceptually unavailable and this
leaves the deletion analysis as the only viable option. So why is ellipsis
deletion rather than interpretation? Because the interpretive theories required
structures that BPS rendered impossible. I confess to always liking this story.
One caveat before concluding: I am not here proposing that
the proposed explanations above are correct. I have some questions regarding
the Spell Out explanation of the PIC for example and there are empirical
challenges to Merchant’s evidence in favor of deletion analyses of ellipsis.
However, the kinds of proposals mentioned
above are interesting and important for, if correct, they explain (rather than
describe) what we find. And explanation is (or should be) what scientific
inquiry aims for.
To end: one of the aims of theoretical work is to find ways
of framing questions in such a way that all and only the conceptually possible
answers are actualized. This requires
finding a vocabulary that not only accommodates/describes the actual, but
renders the non-attested impossible, i.e. unstateable. This makes the
consideration of systematic absences (viz. negative data) central to the
theoretician’s task. Explanation lies with the dogs that don’t bark, the things
that though logically possible, don’t occur. Theories explain what happens in
terms of what can happen. This means keeping one’s eyes firmly focused on what
we don’t find, the actual simply being the residue once the impossible has been
pared away.
[2]
There was an interesting and animated debate about ellipsis between Edwin
Williams and Ivan Sag, the former defending an interpretive conception (trees
with null terminals filled in at LF) vs the latters deletion analysis (similar
to Merchant’s contemporary approach).
