This was prompted by various replies to Jeff's recent post (see
below), which triggered many memories of déjà vu. But it got too long, in
every relevant sense, for a single comment.
Rightly or wrongly, I think knowledge of language is an
interesting example of knowledge acquired under the pressure of experience, but
not acquired by generalizing from experience. Rightly or wrongly, I suspect
that most knowledge is of this sort. That's one way of gesturing at what it is
to be a Rationalist. So I'm curious how far the current wave of skepticism
regarding POS-arguments goes, since such arguments are the lifeblood of
Rationalism.
Once upon a time, somebody offered an argument that however people
acquire knowledge of the Pythagorean Theorem, it isn't a matter of generalizing
from observed instances of the theorem. This leads me to wonder, after reading
some of the replies to Jeff: is the Platonic form of a POS argument also
unpersuasive because (1) it is bound up in "meaty, theory-internal
constructs," and (2) the input is impoverished only relative to "an
(implicit) superficial encoding and learning algorithm"? If not, what
makes the argument that Jeff offered relevantly different? The classic POS
arguments in linguistics were based on observations regarding what certain
strings of words cannot mean, raising the question of how the relevant
constraints could be learned as opposed to tacitly assumed. What's so
theory-internal about that?
Moreover, sensible rationalists never denied that thinkers can
and often do represent certain "visible things"--drawn on the board,
or in the sand--as right triangles, and hence as illustrations of
theorems concerning right triangles. The point, I thought, was that any such
way of "encoding the data" required a kind of abstraction that is
tantamount to adopting axioms from which the theorems follow. If one uses
experience of an actual drawing to activate and apply ideas of right angles
formed by lines that have no width, then one is using experience in a
remarkable way that makes it perverse to speak of "learning" the
theorem by generalizing from experience. But of course, if one distinguishes
the mind-independent "experienceables" from overtly representational encodings--I
believe that Jeff usually stresses the input/intake contrast--then any
experience-dependent knowledge acquisition can be described as the result of
"generalizing" from encodings, given a suitably rich framework for
encodings. Indeed, given a suitably rich framework, generalizing from a single
case is possible. (It's worth remembering that we speak of both arithmetic
induction and empirical induction. But if knowledge of linguistic constraints
turns out to be more like knowledge acquired via arithmetic induction, that's
hardly a point against Rationalists who use POS arguments to suggest that
knowledge of linguistic constraints turns out to be more like knowledge
acquired via arithmetic induction.)
With enough tenacity, I guess one can defend the idea that (pace
Descartes) we learn from our encodings-of-experience that the world contains
material things that endure through time and undergo change, and that (pace
Leibniz) we generalize from observations of what is the case to conclusions
about what might be or must be the case, and that (see Dyer and Dickinson,
discussed by Gallistel and others) novice bees who were only allowed to forage
a few times in late afternoons still generalized from their
encodings-of-experience in a way that allowed them to communicate the location
of food found on the first (and overcast) morning. Put another way, one can
stipulate that all experience-dependent knowledge acquisition is learning, and
then draw two consequences: (1) POS-arguments show that a lot of learning--and
perhaps all learning--is very very unsuperficial, and (2) a huge part of the
enterprise of studying knowledge of language and its acquisition consists in
(a) repeatedly reminding ourselves just how unsuperficial this
knowledge/acquisition is, and (b) using POS arguments to help discover the
mental vocabulary in terms of which encodings of the relevant experience are
formulated. But (1) and (2) seem like chapter one and verse of Aspects.
So as usual, I'm confused by the whole debate about POS arguments.
Is the idea that with regard to human knowledge of language, but not knowledge
of geometry (or bee-knowledge of solar ephemeris), there's supposed to be some
residual plausibility to the idea that generalizations of the sort Jeff has
pointed to (again) can be extracted from the regularities in experienceables
without effectively coding the generalizations in terms of how the "data
of experience" gets encoded? If so, is there any better form of the
argument that would be accepted as persuasive; or is it that with regard to
knowledge of linguistic generalizations, the prior probability of Empiricism
(in some suitably nonsuperficial form) is so high that no argument can dislodge
it?
Or is the skepticism about POS arguments more general, so that
such arguments are equally dubious in nonlinguistic domains? If so, is there
any better form of the argument (say regarding geometry, or the bees) that
would be accepted as persuasive; or is it that with regard to knowledge of all
generalizations, the prior probability of Empiricism (in some suitably
nonsuperficial form) is so high that no argument can dislodge it?
Of course, nobody in their right mind cares about drawing a sharp
line between Rationalism and Empiricism. But likewise, nobody in their right
mind denies that there is at least one distinction worth drawing in this
vicinity. Team-Plato, with Descartes pitching and Leibniz at shortstop, uses
POS considerations to argue that (3) we encode experience and frame hypotheses
in very interesting ways, and (4) much of what we know is due to how we encode
experience/hypotheses, as opposed to specific experiences that
"confirm" specific hypotheses. There is another team, more motley,
whose roster includes Locke, Hume, Skinner, and Quine. They say that while (5)
there are surely innate mechanisms that constrain the space of hypotheses
available to human thinkers, (6) much of what we know is due to our having
experiences that confirm specific hypotheses.
To be sure, (3-6) are compatible. Disagreements concern cases, and
"how much" falls under (6). And I readily grant that there is ample
room for (6) under the large tent of inquiry into knowledge of language; again,
see chapter one of Aspects. Members of Team-Plato can agree that (6) has
its place, against the background provided by (3) and (4); though many members
of the team will insist on sharply distinguishing genuine cases of
"inductive bias," in which one of two available hypotheses is
antecedently treated as more likely, from cases that reflect knowledge of how the
relevant vocabulary delimits the hypothesis space (as opposed to admitting a
hypothesis but assigning a low or even zero prior probability). But my question
here is whether there is any good reason for skepticism about the use of POS
arguments in support of (3) and (4).
Absent a plausible proposal about how generalizations of the sort
Jeff mentions are learned, why shouldn't we conclude that such generalizations
fall under (4) rather than (6)?
Sidepoint: it's not like there is any good basis, empirical or
conceptual, for thinking that most cases will fall under (6)--or that
relegation to (4) should be a last resort. The history of these debates is
littered with versions idea that Empiricism is somehow the
default/simpler/preferable option, and that Rationalists have some special
burden of proof that hasn't yet been met. But I've never met a plausible
version of this idea. (End of sidepoint.)
I'm asking because this bears on the question of whether or not
linguistics provides an interesting and currently tractable case study of more
general issues about cognition. (That was the promise that led me into
linguistics; but as a philosopher, I'm used to getting misled.)
If people think that POS arguments are generally OK in the
cognitive sciences, but not in linguistics, that's one thing. If they think
that POS arguments are generally suspect, that's another thing. And I can't
tell which kind of skepticism Jeff's post was eliciting.