On his blog, Norbert Hornstein had the following exchange. The original Hagoort post is here.
NH: " If Sprouse and Alemeida are right (which I assure you they are; read the papers) then there is nothing wrong with the data that GGers use."
SV: One should never be 100% sure of anything. There is always uncertainty and we should openly discuss the range of possibilities whenever we present a conclusion, not just argue for one position. That has been a problem in psychology, with overly strong conclusions, and that is a problem in linguistics, experimentally driven or not. But this is specially relevant for statistical inference. We can never be sure of anything.
NH: But I think that I disagree with your second point about being sure. One way of taking your point is that one should always be ready to admit that one is wrong. As a theoretical option, this is correct. BUT, I doubt very much anyone actually works in this way. Do you really leave open the option that, for example, thinking takes place in the kidneys and not the brain? Is it a live option for you that you see through the ears and see through the eyes? Is if a live option for you that gravitational attraction is stronger than electromagnetic forces over distances of 2 inches? We may be wrong about everything we have learned, but we this is a theoretical, not what in the 17th century was called a moral possibility. Moreover, there is a real down side to keeping too open a mind, which is what genuflecting to this theoretical option can engender. I find refuting flat earthers and climate science denialists a waste of intellectual time and effort. Is it logically possible that they are right? Sure. Is it morally possible? No. Need we open our minds to their possibilities? No. Should we? No. Same IMO with that GGers have found out about language. There are many details I am willing to discuss, but I believe that it is time to stop acting as if the last 60 years of results might one day go up in smoke. That's not being open minded, or it this is what being open minded requires, then so much the worse for being open minded.
Let me say this another way: there are lots of things I expect to change over the course of the next 25 years of work in linguistics. However, there are many findings that I believe are settled effects. We will not wake up tomorrow and discover that reflexives resist binding or that all unbounded dependencies are created equal. These are not established facts, though there may be some discussion of the limits of their relevance. But they won't all go away. But this is precisely what Hagoort thinks we should do, and on one reading you are suggesting as well. Maybe we are completely wrong! Nope, we aren't. Bding open minded to this kind of global skepticism about the state of play is both wrong and debilitating.
Last point: you are of course aware that your last sentence is a kind of paradox. Is the only thing we can be sure of is that we can never be sure of anything? Hmm. As you know better than I do, this is NOT what actually happens in statistical practice. There are all sorts of things that are held to be impossible. In any given model the hypothesis space defines the limits of the probable. What's outside has 0 probability. The real fight, always, is what is possible and what not. Only then does probably mean anything.
Since Norbert's blog doesn't allow comments beyond a particular length, I post my response here:
Norbert, I agree that my statement, taken literally, if obviously absurd. When I said that we can't be sure of anything, I didn't mean that we can't be sure that we don't think with our kidneys etc. I fully agree (and I would have to be really, really stupid not to agree! ;) that there are many things we can easily rule out as impossible; no experiments needed there (also not in syntactic investigations). I was talking specifically about results using rating studies. Take Sprouse et al's work, which is excellent in my opinion. More work like that should be done, and I'm fully for it, whatever the outcome. My comment was directed at your statement that we can be sure of Sprouse et al's results. I agree that syntacticians have a finely honed ability to sift through data by just using intuition. So I find the Sprouse et al conclusions plausible. My skepticism is of the following nature: it's entirely possible that the things syntacticians have studied so far were, relatively speaking, low hanging fruit. The Sprouse et al results may be convincing for the items studied so far, but they may have limited validity for future work, where judgements could be a lot more variable and unstable. Or they may not replicate (replication is the acid test). Maybe we can take some of the work on negative polarity; we might find that the judgements diverge from expert NPI researchers (where judgements get pretty unstable---Van der Wouden once told me that we shouldn't even consult "ordinary" speakers of a language for NPI, since they won't even have reliable judgements, one has to consult a syntactician). Once we had an NPI specialist over at Ohio State when I was a grad students, and he presented his expert judgements as the basis for his theory; it was easy to find counterexamples in corpora. Or, if we move to a language like Hindi, which has inherently unstable and variable judgements, the judgements of linguists vs a sample from the population of native speakers may differ quite a bit. For example, I was really surprised by the key example in Mahajan's dissertation; it is very hard to "get" the judgement that Mahajan got. Initially I thought I just didn't get it because I wasn't a refined enough individual syntactically, but that was not the case. Simialrly, we have done several rating studies on word order variation in Hindi, with completely unclear and unstable results. But syntacticians working on Hindi are pretty sure about what's OK and what's not OK in these cases (just take monoclausal word order with and without negation: here's a syntactician holding forth on this topic: http://www.ling.uni-potsdam.de/~vasishth/pdfs/VasishthRLC04.pdf. The situation is much less clear than this guy suggests in the paper, if you do a rating study).
What I was commenting on was the certainty expressed in the statement "If Sprouse and Alemeida are right (which I assure you they are; read the papers)". Neither you nor I can know whether they are right. They have some evidence for their position, which may or may not replicate or generalize when we go beyond the language and phenomena covered there.
PS You said that "One way of taking your point is that one should always be ready to admit that one is wrong. As a theoretical option, this is correct. BUT, I doubt very much anyone actually works in this way." I know at least one person. Take a look at some of my papers:
We have more stuff in the works in which we try to break our own favorite story. Ted Gibson has also published against his favored positions. I think more people need to push against their own positions. People don't do that. I am highly suspicious of people who *only* find (or only publish) results favoring their own position.