Wood Paths: Articles

Pathways to Philosophy


truth and subjective knowledge

Geoffrey Klempner


minds and biology

why I cannot be turned into stone or into a zombie

Why can't a stone think?

Let me start by telling a story. I am going to describe a thought experiment, to test our intuitions concerning selfhood, consciousness and physical embodiment.

In my story, Adam and Eve were not banished from the Garden of Eden. Instead, they had to give up the power of speech and movement. The Angel of the Lord appeared, and turned Adam and Eve into marble. For all eternity, Adam is condemned to gaze into Eve's face, to see the guilt and sorrow written there. For all eternity Eve is condemned to gaze into Adam's face, to see the sorrow and guilt written there.

It is a powerful image. We feel that we understand what it would mean — what it would be like — to be turned into a stone statue. But the image is incoherent. It cannot be imagined or thought, because it doesn't make any sense, even though it seems to. It is a philosophical illusion. Unless we suppose God's omnipotence to include the power to do what is logically impossible, Adam and Eve could not be Adam and Eve while existing as stone statues.

How can I be so dogmatic? I don't intend to bring subtle metaphysical arguments to bear on this issue. I'm not going to invoke a theory of the mind or consciousness. My approach will be purely dialectical. I will take this image, prise it open, and let you see for yourselves.

Incidentally, I'm not the first to raise this question:

Couldn't I imagine having frightful pains and turning to stone while they lasted? Well, how do I know, if I shut my eyes, whether I have not turned into a stone? And if that has happened, in what sense will the stone have the pains? In what sense will they be ascribable to the stone? And why need the pain have a bearer at all here?!

And can one say of the stone that it has a soul and that is what has the pain? What has a soul, or pain, to do with a stone?

L. Wittgenstein Philosophical Investigations para 283

However, not everyone is impressed by the fact that Wittgenstein thought such-and-such. On the question whether a stone can feel, LW doesn't think it was necessary to give an argument. Instead, he asks a series of seemingly rhetorical questions, and leaves it to us to figure it out for ourselves.

What makes marble Adam and Eve themselves? Each experiences the world around them from a certain point of view, formerly occupied by their living body. Marble Adam looks like the living Adam. Marble Eve looks like the living Eve. Admittedly, the colour has gone from their cheeks and eyes, their hair. On second thoughts, I am forgetting, marble statues do not need to look like marble statues! There is physical evidence that the great sculptures of Ancient Greece were originally painted (as horrifying as the idea might seem to the art historian). If a lick of paint helps, then go ahead and apply it. Imagine the effect to be better than any Madame Tussaud's waxwork. Let's suppose that in the first few moments, as Adam and Eve stand, rooted to the spot, they don't even realize what has happened to them.

But we do. Stone statues do not move because they chose not to, but because they cannot.

Let's continue with the story. After a while, the Almighty tires of this effect. He wants Adam and Eve to see their own agonized expressions. No need for a mirror. Just give Adam the power to see with Eve's eyes, and give Eve the power to see with Adam's eyes. That is an idea we readily understand. We know the eye is connected to an optic nerve, and the nerve to the brain. In principle — though thankfully this has never actually been tried — a surgeon could remove your eyes and attach a few extra yards of optic nerve, or better still, connect the removed eyes to a radio transmitter. I'll leave you to think of possible applications.

Now Adam sees Adam and Eve sees Eve. Does that mean that each sees themself? Before you say, Yes, consider the following thought: We could just as easily have imagined that God gave Adam Eve's body, and Eve Adam's body. Or could we? If you think about it a bit more, you will realize that we are not in fact imagining anything different in these two cases. There is no logical distinction between the hypothesis that Adam now sees himself with Eve's eyes, and the hypothesis that Adam, the new owner of Eve's body now sees Eve, the new owner of Adam's body.

In short, once they cease to exist as living, breathing human beings, there is no longer anything to connect Adam and Eve's unique viewpoints, their thoughts and feelings with any particular physical object in the world. I won't mince words. It follows that the story I told you about Adam and Eve being turned into statues is complete nonsense. I don't just mean physically impossible, inconsistent with the laws of nature. What I mean is that I didn't understand what I was saying, when I said the words that I said, and neither did you. I might as well have said, “Ba ba ba ba.” for all the sense my words made. Take away the causal role played by biology in the aetiology of subjective states, take away the biological structure of sense organs, brain, nervous system, and you take away the only thing that can logically glue a particular set of subjective states to a particular body.

We are now going to think of another punishment for Adam and Eve. (By the time we've finished with them, I reckon they'll be pretty glad to have been cast out into the Wilderness.)

In our new story, Adam and Eve's bodies remain intact. The Angel of the Lord appears and says: “At some time in the future — I won't tell you when — one of you is going to be turned into a zombie. The other will not be able to tell that anything has happened. The zombie's speech, facial expressions, bodily movements will be just as they were when consciousness was inside. Only now all will be darkness within. This is a punishment for both of you. For the one who becomes a zombie, it is equivalent to death. The other will be condemned to live with the dead, empty shell of the person they once loved!”

Every morning, Adam says to Eve, “I'm still alive, but I wonder about you!” Every morning, Eve says to Adam, “I'm still alive, but I wonder about you!” Shocking, terrible. It is difficult to imagine anything worse than not knowing whether your partner is a human being or a zombie.

Until one day, the Angel of the Lord carries out his promise.

Eve is turned into a zombie. Eve's stream of consciousness comes to a halt. There is no longer any self aware of itself as Eve. There are no thoughts or feelings corresponding to the familiar movements of Eve's lifeless hulk. The noises that come out of Eve's mouth are just that, and nothing more. Eve's eyes still see, her ears still hear. Her brain processes the sensory input. On a biological level, nothing has changed. But Eve's mental life is no more. The spark of selfhood has been extinguished.

Yet, every morning, Adam says to Eve, “I'm still alive, but I wonder about you!” Every morning, Eve says to Adam, “I'm still alive, but I wonder about you!”

— In case you missed it, that was my argument. The assumption behind this story is that biological processes are the causal source of mental phenomena. Yet even though we may accept this, we have a powerful intuition that there is something extra, in addition to the physical, which we know from our own case. We know that we have consciousness, thoughts, feelings. We know that we have a point of view. And we conceive this to be a contingent fact. We can imagine the mental phenomena taken away, without any effect on the physical. The inner exists in addition to the outer. The outer can exist in the absence of an inner.

However, if that is so, then we also have to accept that the person who says this, the person who says, “I know that I have consciousness, thoughts feelings. I know that I have a point of view!” might still be a zombie. What we say, the words that we utter that strive to give expression to the belief that there is something extra 'inside', does not make contact with that inner something. The very same words would still come out, whether there was anything inside or not.

What is the moral of our two thought experiments?

As a matter of logic and not merely contingent fact, the biological processes that occur in you and me are necessary for our bodies to be ours. As a matter of logic and not merely contingent fact, the biological processes that occur in you and me are sufficient for our bodies to be us. There is nowhere we can place a self or mind in a body that lacks the requisite biology. That is the point of the first story. Given the biology, there cannot fail to be a self or mind. That is the point of the second story.

the privacy of the mental

how experiences can be private without being 'private objects'

Wittgenstein's private language argument is directed at anyone who is tempted to think that there are subjective, private 'objects' whose very existence is tied to my point of view. Nothing would count as another person's coming to see or know these objects. So far as you are concerned, the mental 'objects' that exist inside my own consciousness are not just hard to see, they're not even invisible. They simply don't exist, they are not in the world that you are in. They have just one side, the side they present to me. Move away, to another point of view, and they're gone.

Examples: the indescribable way that the colour blue looks to me, the indescribable quality that the taste of chocolate has for me, the indescribable sensation in my head and stomach that I have learned to name 'feeling giddy'.

What Wittgenstein's thought experiment with sensation "S" ( Philosophical Investigations para 258 ff.) shows is that the very idea of such one-sided objects is nonsensical. Or in the terminology I prefer, there is no such thing as an object whose appearance constitutes is own reality.

What follows is that my response to blue, or chocolate, or giddiness, my awareness of those experiences, does not exhaust their intrinsic nature. In addition to the side they present to me, there is also a side that is in hidden from my gaze, that points away, out onto the world.

But this is where things get sticky.

Materialists, of the good old-fashioned Australian variety (Armstrong, Smart), used to talk of things like 'stimulation of C-fibres'. The idea was that if you knew enough about the brain and its workings, you could pin-point the part responsible for my experience of blue, or chocolate, or giddiness. One American philosopher, Richard Rorty (in an article on the private language argument which he has subsequently repudiated) once speculated about a device he called a 'Cerebroscope' which could be used to read a person's experiences. So if someone said, 'This tastes like chocolate to me' you could use your cerebroscope to tell if they were telling the truth. It would show up on the dials. It would be impossible to lie.

The idea, in other words is that the event of a chocolate taste has two sides or aspects, the subjective and the objective. There is nothing in the subjective aspect that is not translated into an objective aspect. All we lack — at present! — is a way to crack the code. When we cut open a brain, all we see is grey stuff. (Actually, only brains in glass jars are grey. Living brains, I was surprised to see on TV recently, are pink.) Under a microscope, all we see is a jumble of nerve fibres. If only we had the translation manual — if only we could unlock and decode the program running on a human brain — we could read those fibres like a book.

I don't believe that for one minute.

Let me suggest a more realistic picture. In the amazing complexity of a human brain, information is encoded, encrypted in a way that is, in principle, accessible only to the person whose brain it is. My experience of chocolate, as caused by processes in my brain, is there in the world, not just there for me. It is objective, and not merely subjective. But it is not there for objective knowledge. It slips invisibly through the net of science, however finely that net is cast.

What about language and behaviour? The logical behaviourist reading of Wittgenstein according to which my experiences are capable, in principle of being fully brought to light in what I say and do has long been discredited. Experience is massively undetermined by speech and behaviour. It is undetermined by the totality of possible scenarios that you could put a subject in, that would reveal things about their mental states that are not revealed in the actual world. Inside the black box, things could be different in all sorts of ways, and it would not necessarily show up on the outside.

So there is a very real sense in which knowledge of my subjective experiences is available to me in a way that it is impossible in principle to communicate to others. Not because my subjective experiences are private objects in the sense attacked by Wittgenstein. But because the only adequate way to access what is in a brain, is to be the owner of that brain.

We can share some of what's there. We can talk about our experiences of blue, or chocolate or giddiness and not be talking past one another. But language only goes so far. I look out the window and remark, 'Look at that beautiful sunset!' You call lazily from the TV room, 'Describe it for me, I'm watching X-Files.' I reply, 'I can't describe it, you'll have to see for yourself!' — But when something is happening in me, I can't show you. I have to rely on words.

The point of all this:

In a well-known article, 'What is it Like to be a Bat?' Thomas Nagel raised problems for physicalism, arguing that physicalism could not be reconciled with our strong intuition that there is something it is like to be a bat that we can never know. I do not agree with critics of Nagel's argument who sought to play down the intuition, or even deny it outright. I don't need any convincing that the only thing that can access what is in a bat brain, is to be the bat whose brain it is. Lacking language, the bat cannot be said to 'know' either. But to do the kinds of thing a bat does, knowledge is not required. The purposes, given to it by evolution, are served by its appropriate sensitivity to its surroundings, mediated by its sense organs and nervous system.

subjective knowledge

the contents of brain states are accessible only to the organism whose brain it is

I am going to state dogmatically — because I am not sure of the grounds for this — the principle that the information embodied in a brain state is accessible only to the organism whose brain it is.

If that principle is true, I mean a priori true, not just true because of contingent facts about the way the world is, then many, if not all, of the things that one wanted to say about private objects can be said about the contents of brain states. They are private to the person who has them. They are given to only one perspective, namely mine.

Perhaps the only thing that definitely cannot be said about the contents of brain states is that their reality is equivalent to their own appearance. Obviously, the reality of my brain states, the ever-changing physical configuration of the cells or molecules or electrons that compose my brain is fundamentally different to the way that brain state appears to me. The objectively indecipherable process in my brain that constitutes my feeling a sharp stab of pain is not the same as the subjective feeling. One is a physical object or event, the other is a mental object or event.

Or so it seems.

For it is not as if we are not talking about something like this. Outside my window as I type these words, there is the big red sign for the Honda garage. Then there is my perception of the sign that I see through my study window (partially obscured by the ceiling-high pot plant that is stealthily taking over my work space). The Honda sign can be looked at from different angles, different points of view. You can go up close, or further away. You can walk past the sign, and watch as its appearance changes with differences in perspective.

My inner perception of the sign is something entirely different. As a content-bearing brain state, there is necessarily only one perspective that it can be seen from, I mean, seen for what it is: namely here, now. I cannot get closer to my brain state or further away. I can't walk round it. The physical and mental objects — my brain state and the experience it causes in me — are stuck tightly to one another.

So tightly, in fact, that one begins to wonder what is the force of saying that these are two things rather than one thing with two different aspects.

This is familiar territory. The 'mind-brain identity theory'. But look how we got here. Earlier, I said that when the Australian materialists — Smart, Armstrong — were writing in the 60's, it was generally assumed that one day, not too far in the future, one would be able to open up a person's skull, observe the 'stimulation of C-fibres' and read the content of their brain state. But as is well known this leads to all sorts of trouble for the claim of identity. What is the difference between a claim that A (the mental object) is identical with B (the physical object), and the claim that A and B merely stand in a law-like correlation with one another? What right have you got to claim identity, if all you can prove is correlation? Supposing that we agree to identify the 'stimulation of C-fibres' with something we call 'pain', how can we be sure that what we are talking about is actual pain, the subjective, Nagelian, what-it's-likeness of pain, rather than merely 'pain' so-called, the objectively existing entity or event that scientists observe?

insides and the subjective standpoint

the difference between the inside of the sun and the inside of a person

The conclusion of our thought experiment concerning Adam and Eve was: “There is nowhere we can place a self...in a body that lacks the requisite biology...Given the biology, there cannot fail to be a self.” I cannot be turned to stone. I cannot become a zombie. A logically necessary and sufficient condition for having subjective experiences is that I have a functioning brain, sense organs and nervous system.

I also asserted the principle, “The contents of a brain state are accessible only to the organism whose brain it is.” That makes it look as if subjective knowledge is knowledge of the inside of my brain. But subjective knowledge is not knowledge of any object. Objects belong in the world of truth. Thus, the statement, ‘I am in pain’ is an expression of objective knowledge, not subjective knowledge, in the sense in which I am using the term. It is a statement with truth conditions. In rejecting the notion of a private language, Wittgenstein was rejecting a false theory of the truth conditions for statements about one’s mental states.

If subjective knowledge is not knowledge of some object, what is it? This is where things get more speculative. I want to say that my subjective knowledge is more like a continually changing adjustment between myself qua physical being with the physical world around me. It is the subjective 'side' or 'aspect' of practical knowledge, or knowledge how. My brain and nervous system are constantly tuned and re-tuned to the world around me through sense perception, but also through proprioceptive feedback (the immediate, physical knowledge we get when we manipulate objects — for example, tying a shoelace or hammering a nail).

Reader's of Robert Pirsig will recognize 'Quality perception' here. But right now, I don't have an axe to grind about values.

Another idea that is well worth looking at is the connection between what I'm trying to say and Nietzsche’s perspectival metaphysics of 'centres of power'.

In fact, I'd like to go lean on the metaphysics. It is enough to say, “The world is not all that is the case.” If you are taking an account of all there is — I mean an 'account' in the modest sense of a philosopher accountant's ledger book, rather than a grand 'explanation of everything' — then all that can be said goes in one column. But there is another column, where you can't write anything, because what goes there is the multi-faceted world of each agent's practical knowledge, each agent’s continually changing state of adjustment with the physical world as they alone perceive it. Here is where something like Nietzschean perspective might come in to play.

My practical knowledge is a reality for you only insofar as you can make statements of the form, 'GK knows how to...'. But my subjective knowledge — or adjustment or attunement with the world around me, or whatever you want to call it — is more than could ever be expressed in any number of such statements, more than can be said.

So much for subjective knowledge. What about truth?

The world of truth is all that is the case. But there can be no truth for the isolated agent, qua centre of power at war with all other centres of power. Something can be said, something true, or false, only if it can be said in a common language. That is the upshot of Wittgenstein’s rejection of a private language. To inhabit a world which is not of my making is to recognize a truth that is common, a truth that is the same truth for me as it is for the Other who shares that world with me: the truth as such.

One final jig-saw piece is the concept of insides. I first came across the notion of insides as a philosophical concept in an obscure book which I found in a second-hand book shop, Act and Agent by Douglas Browning (University of Miami Press 1964). (In a final remark Browning refers to Paul Weiss: “Some time after this essay took shape my attention was directed to the discussion of insides in the philosophy of Paul Weiss. Professor Weiss, I have found, has anticipated my remarks in certain respects but not in others... .” As philosophers do.) I am not sure whether my usage is anywhere close to either of these men. I'm simply interested in the contrast between the sense in which the inside of the sun, or an atom is hidden from us, and the sense in which the inside of a person is hidden from us.

When we put forward a theory about the inside of the sun, or an atom, what we aim for is a mechanism that would show how the effects that we observe come about. Nagel argues in an important recent paper 'The Psycho-Physical Nexus' (P. Boghossian and C. Peacocke Eds. New Essays on the a Priori OUP 2000) that mechanism is what is missing in any account of the putative causal link between phenomenological 'inner' and physical 'outer' that could be expressed in the language of physics.

The fatal weakness of Nagel's position, in my view, is that he gives too much credence to the 'zombie' hypothesis. Nagel's gut feeling on this is that the phenomenological blueness of blue, what it is like, subjectively, to look up on a fine day and take in the colour of the sky, cannot be intelligibly connected to any physical description. Take any physical description, and we can imagine the phenomenology to be absent. So we need a 'third term' (readers of Kant will be familiar with this idea!) neither mental nor physical, through which we can grasp the psycho-physical nexus. My gut feeling is that Nagel is babbling. In the article, he vehemently and repeatedly attempts to say what cannot be said. He is not talking about blue. The word 'blue' is a word from our common language. Nagel is talking about this, the unnameable subjective given which I know from my own case. He uses familiar words, but the words have no meaning, in the context in which he wishes to use them. That is babbling.

Subjective knowledge is unique to the individual. With that I agree. I cannot communicate my subjective knowledge to you, and you cannot communicate your subjective knowledge to me. There is an unsurpassable gulf between the subjective and objective sides of practical knowledge, the dual aspects of the agent's attunement with the external world. The indescribable 'blueness' I see inside me when I look up at the sky on a fine day is the hidden, subjective side of the practical ability, which I acquired when I learned the language, to put words to my perceptions, to follow the rule for the word 'blue'. I can utter the words, 'Look at the blue sky' but I cannot utter that which makes it possible for me to use those words. From whichever side you look at it, there is only me, and the sky, and the biologically founded attunement between the one and the other.

© Geoffrey Klempner 2001

Paper given at the Shap Conference, Philosophical Society of England, Cumbria 17 February 2001