The Other Minds Question

We all know that subjective experience exists. It is the realm of colors, sounds, touches, tastes, etc. The existence of this realm need not be proved, since the evidence is directly accessible. In other words, if a swimmer is not convinced that water exists, from direct contact with it, how could she be more convinced any other way? We can all be fooled as concerns the true nature of things. But the very existence of something that gives rise to the ostensible properties cannot be reasonably doubted. So we can debate the true nature of water. But at the very least, we cannot reasonably debate the sensation of wetness.

It's also useful, if not provable, to think that objects in the material world continue to possess their properties, independent of our consciousness of them. A clock does not stop ticking when we look away, and then rapidly advance to the current time when we glance back. It's simpler to think that the clock continued as a steady rate, whether we are looking or not. Hence we come to think of things in the material world as being outside of ourselves, obeying principles that we can discern, and with these principles, we can anticipate the behaviors of things in the world around us. Motivated by the utility of such reasoning, and with a lot of spare time, we can refine a method for deriving such principles, and this is the nature of scientific reasoning.

Yet with modern science, we cannot prove the existence of subjective experience. In fact, in modern neuroscience, not only is there is no physical proof that subjective experience exists — there is no need to posit its existence in order to get a complete description of the behavior of the neural mechanism in question. And by rigorous scientific standards, if there is no evidence of the presence of something, and if the phenomena can be completely described without it, then it does not exist.

So Cartesian dualism persists, as robustly as ever thanks to modern neuroscience. There is the internal realm of thoughts and sensations, and then there is the material world, made of mechanisms devoid of internal states. The existence of both of these worlds is hard to deny, but the relationship between the two is impossible to define. If material things do not possess internal states, and if internal states are not material, it would be a category error to think that they could ever interact. This has led many philosophers to think of these two realms as parallel universes, moving through time in lock-step, where the one does not influence the other, but the two stay synchronized for a reason that we may never know.

What then is the relationship between two minds? Do all minds exist within the same mental realm, while all material things exist in the same material realm? Or does each mind constitute its own internal universe, there being as many of them as there are people, while all people share the same material universe? Or are we all universes to ourselves, each with our own internal states and our own objective realities, where other people are just machines within our mechanistic worlds, and perhaps their minds are guests within ours? Every possible answer to these questions carries along with it a different way in which multiple minds could interact, and within the dualist framework, as the link between mental and material cannot be demonstrated, it is all completely mystical.

But we should not be too quick to jump to mystical conclusions about the full and true nature of reality, giving up the possibility that there could be a simpler way of representing reality. It is indisputable that there is a fundamental difference of kind between subjective experience and the material world, but it's also possible that parallel (or multiple) universes do not constitute the best framework for describing the difference. They are fundamentally different, but they are also fundamentally related. If we can nail down the relationship between these two types of universes, without invoking any mysticism, we should arrive at a much deeper understanding of both of them. Let mysticism answer only those questions that science cannot.

This paper explores the possibility that there is just one universe, but that there are as many different perspectives as there are people (i.e., neural mechanisms to measure the material world), and that internal states are simply among the properties of neural mechanisms.

Suppose you were born and raised in a house. Now suppose that you had never actually left this house — that you have never actually been outside. And suppose the same is true of everybody who lives on your street — they were all born and raised in their houses, and have never been outside. And suppose that you can call your neighbors and talk on the phone with them, and listen to reports of their experiences from inside their houses.

Now let's consider the concept of "houseness" in this context. On the one hand, you have your house. It has properties such as carpet, paintings on the walls, furniture, staircases, the smell of what's cooking in the kitchen, the sound of the stereo, etc. On the other hand, if you look out the window, you see a totally different type of houseness. Your neighbors live in these architectural monuments, with the properties of siding, roof lines, landscaping, etc. These two property sets have nothing in common.

Now suppose that you happen to know that if you dial a certain phone number, you'll get the person living in the house across the street. You know this because if you ask her, she'll come to the window and wave, and you'll wave back. She describes the interior of her house, and it has distinct similarities with the interior of your house. There is a kitchen, a dining room, a living room, etc. So OK, she lives in a house that's different but not totally unlike your house. Of course, you can't see the inside of her house, and she can't see the inside of yours. But her reports seem reasonable to you, and yours seem reasonable to her.

If you get to thinking about it, you realize that you have a metaphysical problem. On the one hand, you have a concept of "interior design-ness" that you get from experiencing your house. On the other hand, you have a concept of "architectural monument-ness" that you get when you look out the window. Now you are starting to get the idea that these are the same thing. And yet, in what sense are they the same?

Interestingly, some of the properties can be mapped across the datasets. When your neighbor describes her house, some of the interior features that she describes match up with features of her house that you can see from the outside. So the two types of reports are related. But the relationship does not merge the property sets — they are still quite distinctly different, and cannot be reconciled with any form of logic.

Your formal description of the world as you see it must then state that there are two types of houseness, that they are partially related, but that they are irreconcilably different. In conversations with your neighbors, you come to refer to this as "The Other Furniture Problem." There's one guy down at the end of the street who actually maintains that carpet and furniture do not exist — they only seem to exist when you're not looking at a true house, which is an architectural monument that cannot be shown to possess the properties of carpet, furniture, etc. The guy across the street from him, who always takes the opposite position just for the aggravation factor, maintains that it's a shame that his neighbor spends so much time at the window, because it is the architectural monuments that only seem to be real, while in fact they are just different types of paintings that can be affixed to a wall.

Then one day you figure out how your front door works, and decide to exit your house, march across the street, knock on your neighbor's front door, and have a look inside. In fact, her house is similar on the inside to yours, but different in some respects. And those features about the inside of her house that seemed to map to features on the outside of the house are exactly as you imagined them.

So OK, architectural monuments have now been proved to be capable of hosting the creature comforts of home on the inside. But what of the metaphysical issue? They're still diametrically opposed definitions of houseness, right?

You find it interesting to note that as you approach the front door from the outside, the apparent dimensions of the exterior wall are reduced, until finally, as you cross the threshold into the house, the exterior wall actually disappears. Then, one step inside the house, the interior view of the same wall has emerged out of nothingness to become a substantial object. In the transition from exterior to interior, the exterior disappears and the interior appears. Exterior and interior are oil-and-water properties.

So indeed, there are fundamentally different concepts of houseness, and the one cannot be derived from the other, nor does the one reduce to the other in any way. But this is not a metaphysical problem. Once we have entered and exited a number of houses, we come to understand that there are simply different perspectives from which a house can be viewed. The interior view cannot be derived from the exterior view, any more than the back of the house can be derived from the front.

But that doesn't mean that each different possible view of a house constitutes a different universe, because that would be just ridiculous. With the concept of variable perspectives, we can greatly reduce the theoretical framework necessary to explain all of the reports. There are not multiple universes — one for each view of each house. There is only one universe, with multiple perspectives. This provides a single framework with room for all of the reports, and with a built-in way of mapping information from one perspective to another. We still have fundamentally different views, and in maintaining their true natures, they are as different as ever. But instead of isolated datasets with a few details in common, we now have one dataset and very well-defined relationships among the different views. And we need no longer ask how furniture can be derived from siding. It just doesn't work that way.

With objective reasoning, we cannot prove the existence of internal states in other human beings. They might all be mindless robots that say that they have internal states, but actually have none. This issue has vexed many an able mind. But if we take the perspective of the observer into account, we know better than to ask such a silly question as to why we cannot prove the existence of other minds. Something would be wrong if we could. We are on the inside of our own mental houses, and we sense our own internal states directly. But we are on the outside of other people's mental houses, and can only observe their behavior, and guess at what internal states they might possess. We are biological measuring instruments. We sense our own measurements, as qualia, and among these measurements are images of the external aspects of other humans. But no matter how we mix and match our qualia, we cannot derive their qualia. Yet this is what we should expect.

Think of two cameras sitting on a hilltop, looking at a sunset. The one camera turns to the other and asks, "Are you seeing what I'm seeing?" And the other responds, "Yup." So the first camera says, "Prove it." So the second camera opens up its back and lets the first camera peer inside. But the first camera then only sees the innards of a camera — it does not see a sunset. But then, why would we ever expect that it would? Something would be wrong with the principles of optics if it did. The only way for the one camera to see what the other camera is seeing is to be in the exact same position, looking in the exact same direction, with the same type of lens set to the same focal distance. But to do this, it would have to push the other camera out of the way. So the one camera will never be able to prove that the other camera is seeing the same thing. Cameras are measuring instruments. They can take pictures of sunsets, and they can take pictures of the insides of other cameras. They cannot take pictures of what another camera is seeing in the metaphysical sense. This is simply how it works.

Yet psychophysicists have opened up the crania of defenseless patients and poked around, looking for the green, red, loud, and sweet neurons. And they were surprised when all that they found was grey matter and white matter. And yet, why did they ever expect to share the subjective experiences of the patients by electrically stimulating their neurons? If one camera inserted an electric prod into another, would it expect to see a sunset? If you want to see green or red, or hear loudness, or taste sweetness, and if you want this to come about with an electric prod, you insert the prod into your own brain!

It's easy to demonstrate that mechanistic reasoning is made of qualia. If you do not have a sense organ, you cannot think in that sense. For example, imagine the solar system. You are probably conjuring up visual imagery. Now imagine the solar system assuming that you are blind. You cannot visualize the solar system, but you still can imagine the spatial relationships if you had been exposed to a physical model of the solar system, and with tactile and proprioceptive senses had built up a concept of the size and location of the planets. Now imagine the solar system as a blind paraplegic, without tactile senses in your hands and proprioceptive senses in your muscles and joints. Having a hard time, huh?

All thoughts, including mechanistic constructs, are made of qualia. But qualia are not made of mechanistic constructs, nor can they be generated by or derived from them. That would be just wrong. Qualia can only be generated by direct sensory stimulation, or by the re-activation of secondary recognitions via associative connections built by coincidence of direct stimulation. A quale generated by mechanistic reasoning would not validate the existence of qualia, but would rather invalidate the mechanistic reasoning. Attempting to prove the existence of other minds with mechanistic reasoning is self-defeating. Positing the existence of other minds accomplishes such a vast reduction in the explanandum that it is truly the only reasonable representation of reality. But it is a construct, made of qualia, and will never be capable of explaining qualia. This is not the failure of mechanistic reasoning to explain the human condition. It's just the mechanistic properties of the relevant measuring instruments.

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