On the Concept of a Conceptual Scheme
The phrase “conceptual scheme”, as it is used in philosophy, anthropology, and the history of ideas, is intended to signify a particular conception of the conceptualizing mind, namely that our ways of thinking of the world are contingent, variable, and sometimes non-translatable. That is, as a result of various historical, cultural, and practical facts, the human conceptual apparatus is not an essential invariant attribute of the mind but can vary in ways that prohibit mutual understanding. My conceptual scheme may be radically different from yours, so much so that we cannot communicate with each other; our ways of thinking are “incommensurate”, mutually unintelligible. In the extreme case, there could be aliens whose conceptual scheme is completely disjoint from the human conceptual scheme (itself various) and simply not comprehensible by us. Conceptual schemes can be as various as anatomy: differently shaped bodies, differently shaped minds. This conception of conception is to be contrasted with what might be called the “conceptual system” conception, for want of a better term: the idea that conceiving minds are essentially uniform, fixed either by an unvarying reality or a genetic blueprint, and hence always mutually intelligible. According to this view, there is only one type of conceptual repertoire available to all humans (and perhaps all thinkers if we include possible aliens), while according to the “conceptual scheme” view there could be (and actually are) many radically different kinds of conceptual repertoire. There are multiple conceptual schemes (according to one view) but only one conceptual system (according to the other view)—the system but a scheme (compare: many anatomical schemes but only one cellular system). Notice that we have to insert the word “radically” into this characterization of the distinction, because clearly people can differ in the range of concepts they have learned, use, and understand, according to their education, interests, and occupation. The idea is rather that there are either many non-translatable schemes or a unique translatable system: the distinction depends on whether you think concepts can exist without being available to other concept users or whether they must always be so available. Are concepts parochial or universal, idiosyncratic or shared? Do we live in different conceptual worlds or in the same conceptual world? Is there a multiplicity of incommensurate conceptual standpoints or just a single shared conceptual standpoint? I am going to argue for a limited (but quite strong claim), viz. that the concept of many conceptual schemes is not a possible concept for us. We cannot form such a concept, so the doctrine of many conceptual schemes is not a doctrine we can understand. Maybe there could be many incommensurable schemes but we cannot think such a thing: we cannot have the concept of an alien conceptual scheme. The argument for this takes the form of a dilemma. On the one hand, we might be able to think of another person’s conceptual scheme by having concepts of their concepts; but that would imply also having their concepts, so that the scheme would not be truly alien and incommensurate. On the other hand, the other person’s scheme might be truly inconceivable by us, but then we could not think about it, having no concepts with which to conceptualize it. Therefore, we cannot have the concept of an alien conceptual scheme. The first horn of the dilemma is easy to grasp: for me to have the concept of the concept of red I must have the concept of red. In order to think about the concept of red I need to be able to think about red; I don’t have the concept of that concept unless I have the concept it is a concept of. If I think of you as having a certain concept, I must know what that concept is, but I can only know that by having the concept in question. I don’t know what your concept is unless I know what it is about, but then I have to be able to conceptualize what it is about, which is to say I must have the concept of that thing. Knowledge of someone else’s conceptual scheme presupposes access to that conceptual scheme, but that means that I must share the concepts that constitute it. Having a concept of a concept implies having that concept. So, we are pushed to the second horn of the dilemma, which is less simple to state. I must be thinking of the other person’s conceptual scheme in some less direct way, but what might that way be? I clearly can’t study or investigate the alien conceptual scheme, because that would require me to have concepts of the concepts comprising it; but can I perhaps refer to it without knowing what it is composed of? Can’t I say “That conceptual scheme” pointing at the individual, or “His conceptual scheme”? Here the problem is that mere pointing and referring don’t add up to conceiving: I have no mode of presentation of the other’s conceptual scheme, just a blank act of reference to I know not what. I don’t know what I am talking about—literally. I don’t have any conception of the alien scheme precisely because it is alien. I only have words not genuine content-bearing thoughts. It is a different matter with alien anatomy: here I can see the alien body and make perceptual judgements about it—I am not limited to blind pointing. But I can’t see the other person’s incommensurate conceptual scheme, and I can’t conceive it either (by definition); so, I have no mental representation of it—nothing that could ground the application of the phrase “conceptual scheme”. I know what my conceptual scheme is because I am aware of my own concepts, but I don’t have any insight into his because I have no access to it. The phrase “conceptual scheme” as applied to others with alien conceptual schemes has no sense for me: I have no way of thinking of such schemes precisely because they fall outside of my conceptual capabilities. I can think of alien anatomies without sharing them because I can perceive and conceive them, but I have no way of thinking of alien conceptual anatomies without sharing them (by using concepts of concepts). Likewise, I can think of alien perceptual systems and alien belief systems because I can conceive these things in the usual way: I can observe the senses involved or imagine forming different beliefs from the ones I hold. But I am cognitively cut off from alien conceptual schemes, so I have no means of representing them other than by brute reference without sense or knowledge. I have, as Russell would say, no acquaintance with alien conceptual schemes, so the idea of an alien conceptual scheme has no meaning for me. It only seems to me that I grasp the concept because I tacitly assume that the scheme is not really alien—that I can enter into its “world”. If we are told that Eskimos have a different conceptual scheme from us because they have more conceptual distinctions for snow than we do, we can easily understand the nature of their snow-directed conceptual scheme—but that is simply because it is not really alien to us. The difficult case is that of the radically alien scheme that has no overlap with ours, for then we have no way of entering into the scheme in question. No doubt people exaggerate the variations in human conceptual schemes—they are never that alien—but the rhetoric (the intention) is to claim that there might be radicallydifferent conceptual schemes; and that poses problems of intelligibility. To repeat: we can have no conception of a truly alien conceptual scheme; we cannot conceive of concepts we don’t have, since our concepts limit what we can think about. I can’t conceive of what lies outside of my range of concepts–trivially. Thus, the concept of a conceptual scheme (as opposed to the concept of the conceptual system) has no meaning for me; it isn’t a concept I possess. It has no descriptive or discursive content for me. I can have the concept of a conceptual order—an arrangement of concepts—but I can’t have the concept of a conceptual scheme in the sense intended by that phrase, i.e., the idea of an arrangement of concepts that might be completely unintelligible to me. That is not something I can form a conception of, since (as Ramsey said in another context) I can’t say it and I can’t whistle it either—I can’t directly specify what that alien mind might be like, and I have no indirect way of getting my mind around it either (it can’t be “shown”). This means that I can’t describe my own set of concepts as a conceptual scheme, since that phrase has no sense for me, as it is intended by its users (it is a technical term). I can’t think of my own set of concepts as one scheme among many that may differ dramatically from mine. Maybe there are beings in the universe equipped with completely different concepts from me, but I can’t conceive of what this would consist in, since I am confined to my own concepts. The situation is similar to what Hume envisaged in the case of causal necessity: we can use the words “causal necessity”, and even succeed in referring to something real with them, but we don’t really know what they mean, since causal necessity is not something we grasp (have knowledge of, comprehend). Or as I might put it, we are “cognitively closed” to alien conceptual schemes, trivially so, even if we can use these words to refer to them. The important point is that the case is not at all like so-called incommensurate conceptual schemes that actually overlap with ours—this we can grasp perfectly (Eskimos, the Hopi Indians, historical holders of “paradigms”, etc.). It is really not difficult to understand the ways of thought being contemplated in these cases, as evidenced by the people reporting them; but a genuine case of untranslatability is a very different type of case—here we don’t know what is being contemplated. We really can’t grasp what an alien thought would be, if there were such a thing.
 Davidson discusses translation as a criterion of identity for conceptual schemes in his classic “On the Very Idea of a Conceptual Scheme” (1973).
 Is it even clear that the word “conceptual” can be meaningfully applied to alien forms of cognition (or even the word “cognition” come to that), since that word derives from our own conceptual scheme? Who is to say that what the aliens are doing involves concepts in our sense? Maybe that is a misdescription of what goes on in their heads. Maybe their psychology is so different from ours that the word “concept” is inappropriate. That would mean that even to call what they have a “conceptual scheme” goes beyond what we can know of their inner workings. We don’t even have the right concepts to characterize the most general form of their intellectual make-up. The phrase “conceptual scheme” might itself be too parochial: we can’t say they have a different conceptual scheme from ours (or cognitive, intellectual, thinking scheme).
 Of course, there is a tradition of identifying necessities of thought of various kinds—properties that all possible thoughts must have: obedience to universal logic, the subject-predicate form, categories of space and time, reference to material particulars, indexical devices, dependence on sense-data, etc. I have not discussed these, but they certainly pose a threat to claims of infinite conceptual plasticity and the cultural determination of thought. I would certainly resist the idea of the relativity of truth to a conceptual scheme or suggestions of metaphysical anti-realism arising therefrom. My own view would be that the concepts an individual possesses are mainly a function of genetic endowment and a fixed objective world, so that variations in concept possession are local and minor.