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.