Nearly thirty years ago I coined the phrase “cognitive closure” to mean “things that can’t be known”. I now want to introduce the phrase “interrogative closure” to mean “questions that can’t be asked”—to be contrasted with “affirmative closure” meaning “answers that can’t be given”. Just as there may be answers to questions that are beyond us to discover, so there may be questions that are beyond us to ask. We can ask some questions about nature, but maybe there are questions that we are not equipped to ask, because of a paucity of concepts or a theoretical blind spot. The human question generator may not be able to output every question that can be coherently formulated. This is a species of cognitive closure because it depends upon a cognitive limitation; it is a lack of knowledge that leads to the inability to ask questions (or the right questions). Questions require concepts and the requisite concepts may be lacking. This is presumably true of many or most animals: they may well be capable of interrogative thought, but they are not capable of asking every possible question. Questions of explanation are likely to be beyond their cognitive capacities: they may wonder what the sun is but they can’t ask what explains the sun’s movements. Nor could they come to be able to ask such questions save by substantial neural reprogramming; they couldn’t do it simply by thinking harder or being forced to sit in a chair while lectured to. They may have the interrogative construction in their cognitive apparatus, but they cannot formulate every meaningful question that can be asked about reality—not by a long chalk.
Humans are adept at interrogation, as every parent of a young child knows. We are always asking questions, thirsting for answers, not letting go of a question. If we are natural thinkers, we are also natural questioners. Descartes questioned whether everything is open to doubt before he came up with his answer—questions precede answers. But despite our prodigious questioning—we can ask infinitely many questions, as we can produce infinitely many affirmative sentences—we are not guaranteed to be able to ask every question that can in principle be asked. It would be biologically anomalous if we were; and it is notorious that asking the right question often takes genius—it isn’t routine. Interrogative omniscience is not to be expected. This is surely obvious. What is not so obvious is that this is not an all-or-nothing matter: it isn’t that every question is such that we can either clearly ask it or clearly not ask it. Let me distinguish extreme interrogative closure from moderate interrogative closure: the extreme kind implies that we cannot ask the question at all, in any form, not even close; the moderate kind implies that we can formulate a question in the neighborhood of a given question but can do so only inadequately, ineptly, inaccurately, and obscurely. We don’t grasp the right question, but we grasp a question that gestures towards the right question, albeit feebly and misleadingly. The question that we ask might involve conceptual confusions that are cleared up by the correct question, or it might have false presuppositions. There are facts that we are asking about, but our way of asking contains conceptual errors. And it may be that this moderate closure is incurable: we can never ask the question in its proper form, only the inferior substitute. But at least we are not completely blocked from asking the relevant question, unlike animals. We are semi-closed to the question.
It is hard to find an example where we can see that this is the situation, since that would require grasping a formulation of a question that we by hypothesis cannot grasp. If this is our position with respect to a certain question, we will not be aware that it is—we will suppose that we are more or less on the right track. We will be like children asking ill-formed questions without realizing it (“When does dreaming become waking?” “Why doesn’t Tuesday follow Sunday?”). Maybe there is some coherent thought in the vicinity of the question, but it is so ineptly put as to be unanswerable. What I want to suggest is that we are in this kind position with respect to the mind-body problem: we suffer from moderate but not extreme interrogative closure. We are on the verge of asking the right question, but we are not really there; or better, we are far from formulating the right question correctly, but we at least recognize that there is a question. We glimpse the question from afar, obscurely, but we cannot get it into focus. Perhaps we can never get it into focus, given our conceptual limitations.
Consider then how we talk about the mind-body problem. We speak of the mind “depending” on the brain, “resulting” from it, being “caused” by it; or we introduce technical terms like “emergence” and “supervenience”. Then we form questions like these: “In virtue of what does the mind depend on the brain?” or “How does the brain cause the mind?” or “Is the mind strongly or weakly emergent on the brain?” or “What makes the mind supervenient on the brain?” Thus we contrive to state the question that encapsulates the mind-body problem—or we think we do. But how solid are these formulations? First, the concepts invoked add to the underlying facts: these are that changes in the brain are accompanied by characteristic changes in the mind. But it is another thing to start speaking of “dependence” and “causation” and “emergence”. That is to import concepts into our description of the case that have their original home elsewhere. We know what we mean when we use these concepts in their usual context, but they become loose and metaphorical when applied to mind and body. This is why people appeal to models drawn from other domains to explain the meaning of the technical term they re-deploy: water and liquidity, crystals and molecules, embryogenesis. But it is far from clear that we can subsume mind and body under such concepts: isn’t this just sheer hand waving? Isn’t it a forced resort to concepts that work elsewhere and are wheeled in just so that we have something definite to say? Maybe the relation between consciousness and the brain is correctly captured in terms quite alien to us (even using the word “relation” here is tendentious); we are forcing it into a conceptual box that suits our actual concepts. A conceptual lacuna is papered over with concepts drawn from elsewhere and quite unsuitable for the task. Instead of asking, “How does the mind depend on the brain?” where the word “depend” is taken from its original home in describing things like architectural forms and weather patterns, we should be asking, “How does the mind stand in relation R to the brain?” where R is a relation alien to our conceptual scheme. Let’s not pretend that we know what we are talking about in invoking these words and admit that they are poor substitutes for more adequate and accurate concepts. They are stopgap measures, crutches.
We say that the brain “generates” the mind, “produces” it, “gives rise” to it, but we have no idea what these labels mean, except the meaning given by their original context, which has nothing to do with the case at hand. We feel there is some general relation between mind and brain, something like causation or generation; but we really don’t have any clear conception of what sort of relation holds between the two—so we just stick a label on it. Then we proceed to formulate a question using the appropriated label hoping thereby to make sense. But that question may be quite inept, confused, and misleading, given its dubious genesis. Of course, we can’t make such a judgment directly by comparing our concocted question to the question as it should be formulated (by God or super-intelligent aliens), since we don’t know what that formulation would look like; so we blunder blindly on, not realizing that our question falls short of capturing the nature of what we are attempting to describe. Interrogative closure, extreme or moderate, never announces itself as such. Still, we may reasonably suspect that something like this is what is going on, given how we set about formulating our question and the peculiar nature of what we are asking about. The general character of the relation between mind and brain is not apparent to us, so we can’t just refer to it directly and ask how it works; instead we postulate a relation and give it a name—“dependence”, “emergence”, “supervenience”, etc. All that warrants the term are the basic facts, namely that changes in the mind are correlated with changes in the brain. It is not that the chosen terms are clearly false or confused, so that the question we ask is simply meaningless; it is rather that the question as formulated falls short of the formulation that best captures the real relation between mind and body. I can’t tell you what that relation is, for obvious reasons, but I have an inkling that it needs to be conceptualized in ways that are unavailable to us. For one thing, it would need to be a relation holding between something inner and private and something outer and public. And it could never be observed: we could never see that mind and brain stand in relation R.
It is difficult to find analogies for the case of mind and body precisely because it is unique. We are asking for an explanation of “dependencies” between mind and body not between bodies or within minds. We can ask about how emotion depends upon belief and about how air currents depend upon temperature, but it is another thing to ask how consciousness “depends upon” neural activity. In what sense does the former “depend on” the latter? All we get in reply is some sketchy business about correlation.  Presumably the relation is much stronger than mere correlation, so we reach for more full-blooded language; but we may be reaching in the wrong direction and seizing upon whatever happens to fit our cognitive grip regardless of suitability (a hammer to do the job of a screwdriver). The standard analogies used to explain what the relation is supposed to be between mind and brain encourage us to be complacent about our capacity to frame the right question; we may be quite far off target. The very fact that our formulations of the question don’t lead anywhere satisfactory suggests that we are not asking the question as it needs to be asked. For a being that knows how to ask the question the answer might not be so elusive. Its elusiveness to us is a sign that we are in the presence of interrogative closure: we can’t find the answer because we can’t ask the question (properly, adequately). There is affirmative closure because there is (moderate) interrogative closure: our inability to get the question right is bound up with our inability to answer the question. In addition, our cluelessness about the inadequacy of our question leads us to false optimism about answering it: if we knew how bad our formulation of the question was, we would be more inclined to think we cannot answer it. But of course if we knew that we would be on the road to answering it. Our predicament is that we are (moderately) closed to the right question but we find it hard to recognize that fact, and so we think we are conceptually on the right track to solving the problem. I believe we are completely closed to the solution and moderately closed to the question, but I have not argued for that composite position here. I have suggested only that it is probable that we suffer from moderate interrogative closure with respect to the correct formulation of the mind-body problem. 
 It may be suggested that we can help ourselves to a very abstract notion of dependence, perhaps defined in terms of counterfactuals, just as supervenience is abstractly defined. But that abstract notion will not do justice to the specific relation that holds between mind and brain—the notion that distinguishes it from other applications of the abstract notion. We want to know how that relation holds between mind and brain. We want to know how the actual specific relationship between mind and brain is set up—how this part of nature operates. This is why people invoke concepts like emergence: because it promises to identify the explanandum clearly and distinctly. But it does so only by means of dubious analogies and assimilations that serve to obscure the proper formulation of the issue. This is why it is more hygienic to express the question as, “What is the explanatory basis of the relation R that holds between mind and brain?” and remain agnostic about the identity of R. Using words like “depends upon” is at best a crude and uninformative description of how mind and brain connect up (and that phrase too is loaded). There is a good way to ask the question out there in interrogative space, but it is not to be found in our formulations heretofore (and perhaps permanently).
 Imagine that we are extremely interrogatively closed to a large number of questions—as every other animal on our planet is. There are thousands of questions about nature that we are not equipped to ask. Then it will not be surprising if there are some questions to which we are partially open—which are only moderately closed to us. These exist on the border between the humanly accessible questions and the humanly inaccessible questions. I have suggested that the question that constitutes the mind-body problem might be one of these borderline cases (other philosophical questions might also belong in this class). Isn’t this a realistic way to look at the human ability to ask questions? Some we can ask clearly, some we can’t ask at all, and some we can ask only unclearly.