The Many Minds Problem
When it comes to other minds we are notably weak from an epistemic point of view. We are just not very good at knowing about them. Epistemic inadequacy is our standing condition. This comes out in two ways: first, we find it difficult to justify our ascriptions of mental states to others—the traditional other minds problem; second, we come up short in trying to grasp the nature of minds different from our own—the alien minds problems (bats and the like). We don’t have these problems with our own minds or with other bodies: it is not mind as such that presents epistemic challenges, because we know our own mind remarkably well; and we have no special problem describing the bodies of other beings. But other minds strike us as private, elusive, inscrutable. They seem like an area of reality we are prohibited from entering: we can’t see them, touch them, or smell them. And why are they so hidden from us? Not because they are too far away or too small: we can’t even explain our ignorance of them. Nor is the problem purely philosophical: the inscrutability of others is part of normal human life. It sometimes feels as if the whole effort is a complete waste of time: why not just accept that we are incurably ignorant of other minds? But then social relations would grind to a halt, so we blindly soldier on.
I want to draw attention to another epistemic problem of other minds—what I am calling the many minds problem. We also have difficulty with the notion of another mind—one that isn’t mine. How is this different from my mind in someone else’s body? How can I imagine another center of consciousness? Don’t I model it on my own consciousness–but then how is it different from my own consciousness elsewhere? How do I form the concept of a mind distinct from my own? I can easily form the concept of a body distinct from my own: it exists at a different position in space, over there, and can’t occupy the same place as my body. I don’t model the idea of another body on my body: I just see other bodies—even bodies quite different from mine. But this epistemic resource is not available to me in thinking about other minds: here I can’t form the idea of a plurality of minds laid out in space at specific distances from each other and precluding co-occupation. All I have to go on is my own mind and my perception of bodies, but these are insufficient to give me what I need. Do I really have the idea of other minds? The skeptic thinks not: sure, I can talk that way, but I don’t really grasp what I mean by such talk. This is a case of reference without understanding: naming without describing. I can say “George’s mind”, but I can’t form an adequate conception of what I am referring to (compare Hume on causation). Maybe I even know that there are many minds; what I don’t know is what it is to be a mind other than my own. Even if I recognize that other people have minds, I can’t conceive of what that state of affairs amounts to. I am like a blind man trying to understand colors: I can talk about them and assert their existence, but their nature escapes me. I am condemned to solipsism in the sense that I only really understand my own existence. I understand the concept of a plurality of bodies but not the concept of a plurality of minds.
It might be thought that this is an exaggeration (though exaggerations are often useful in philosophy) since we can conceive of minds under causal and functional descriptions. In a roomful of people I can see their bodies laid out in space, nicely distinguished, but I can also see that different physical inputs and outputs apply to different people. Thus I can distinguish one mind from another by the fact that people perceive different objects and perform different actions. I see the different ways the minds are laid out in the physical world—as a plurality of causal loci. But this doesn’t supply what we need, because it doesn’t add up to a conception of minds as such: it doesn’t help us form the idea of a separate mind from ours that is analogous to our conception of our own mind. It doesn’t give us a conception of a plurality of those private inscrutable things of which I am one. Isn’t this just putting myself in the place of others, not forming the idea of genuine others? The problem is that we have no conceptual framework—better, no conceptual surrounding—in which to situate our conception of many minds. We have nothing like the apparatus of space and perception to give content to our talk of other minds. Thus our thinking is hazy, unformed, and merely heuristic. Animals show awareness that others have minds too, but they surely have no articulate grasp of what they are aware of: they don’t have clear and distinct ideas of a plurality of minds. But neither do we, because we lack any conceptual scaffolding that would hold such an idea in place. We certainly can’t obtain that idea from a combination our own mind and the general notion of body. Maybe if we could literally see other minds we would have a clear and distinct idea of their plural existence, but this is precisely what we lack. We don’t perceive other minds laid out before us like peas in a pod.
It is hard to find a good parallel for our epistemic position in this regard. Not in abstract objects like numbers, because here the plurality is generated by an operation such as the successor function: we form the idea of a totality of discrete numbers by constructing them from an initial basis by iterations of this operation. To do anything analogous for the concept of mind or self we would need an operation that generates the idea of distinct selves from a basis beginning in our own mind or self: but there is no such operation. The same goes for propositions and sentences, or for points in space and time. The plurality of minds is an empirical and contingent plurality governed by no such logical operations. Perhaps the closest analogy would be the idea of a plurality of universes, as in the “many worlds” hypothesis in physics. Here too there is no prospect of a perceptual basis for the totality in question, as there is for objects within a universe, and indeed we have trouble with the idea of such a plurality of universes. For what makes it the case that these alleged universes (cut off from us as they are) form a real plurality: aren’t they just parts of the original universe? Likewise, what makes it the case that other minds are really distinct from my mind: what grounds this idea? Do we really know what we mean when we speak of a plurality of universes? We might think of each mind as a subjective universe in its own right, distinct from our own subjective universe, but again how do we perform the necessary individuation? How do I form the thought, he is not me? I am not thinking of his body when I think this, nor of his causal embedding in the world, but of his mind as such: but what is this thought exactly? Isn’t this talk just a necessary device for negotiating the social world not a well-grounded cognitive representation? I can talk about a bat’s echolocation experience and attribute such experiences to bats, but I have no real conception of what I am talking about; similarly, my talk of multiple selves is not tethered to any intelligible substantive conception. Thus I don’t know what it is for many minds to exist, though I am convinced that such a thing is a fact. To put it differently, I have a cognitive bias in favor of my own mind and think of other minds in the light (or dark) of this bias. I am thinking most clearly when I project my own mind into other bodies, but of course that is not the concept of other minds. My own mind thus exerts a gravitational pull on my thinking about other minds, occluding their independent reality. Hence that sense of puzzlement you feel when you find yourself suddenly wondering what it is to be another person—confronted by a distinct self as real as the self you are confronted by all the time. Don’t you feel like you are facing a complete blank when you try to form an idea of that other self? You grasp what her thoughts and feelings might be, because you have such thoughts and feelings yourself, but you never have any experience of being another person. You never get into an epistemic state in which you are someone else; you are always just boring old you. Hence the difficulty we have of conceiving (really conceiving) of another person’s existence. At least you can see and touch someone else’s body, so you can appreciate its distinctness from your own body, but you can’t see and touch someone else’s mind—so you are stuck with your own mind as a model for everyone else’s. And that is a terrible model, because you are not by definition someone else. Conceptual solipsism is thus forced on us by our very constitution; we can’t transcend ourselves to form a clear idea of other minds. So we must add the problem of many minds to the traditional problem of other minds and the problem of alien minds—we are just unavoidably inept when it comes to knowing minds other than our own. This is not full cognitive closure perhaps, but it is at least partial cognitive blockage.
 Wittgenstein was exercised by this question: “If one has to imagine someone else’s pain on the model of one’s own, this is none too easy a thing to do: for I have to imagine pain which I do not feel on the model of the pain which I do feel” (Philosophical Investigations, 302). As he says, thinking of the pain of another person is not the same as thinking of a pain in one part of my body as in another part of my body.
 It would be possible to imagine intelligent beings that explicitly lack the concept of other minds despite grasping their own minds. They just accept that they have no idea what another mind might be, happily or unhappily. Perhaps the thought has occurred to them that their own minds might not be the only ones, but they freely admit that they have no idea what it would be for another mind to exist: the idea of a plurality of minds is beyond their comprehension. They don’t even talk this way, limiting their psychological remarks to self-attributions. At the other end of the spectrum we can imagine godlike beings whose grasp of minds is as solid and extensive as our grasp of bodies, perhaps more so. Humans lie somewhere between these two extremes, possessing language for other minds and a hazy grasp of what might be involved; but this grasp is inchoate and shaky, a mere sketch of a possible concept. Other minds are like missing shades of blue as far as we are concerned: we can recognize their possibility but we can’t give the idea any color (so to speak).
 The binary open-closed picture of human knowledge is no doubt oversimplified: in many cases we have partial cognitive closure combined with a modicum of openness. Mystery comes in degrees or layers or shades of grey. Thus we might say that there is a high degree of mystery where other minds are concerned, i.e. a serious amount of cognitive closure (epistemic boundedness). We have an inkling, but that’s all we have.