18 May 2012
The Mind is Physics - Guest Post by Steve Zara
“I speak the truth”. It’s a brief statement. Imagine yourself saying it. Hear the words. This seems like hardly anything, and yet what you have just done is deep in meaning and has rich and strange implications. I’ll be dealing with just one of those, which is to do with the nature of mind, and the strange business of qualia - qualities of experience - and what they can and can’t be.
How can such a simple act, speaking a phrase and recognising its meaning, have anything significant to reveal about the mind? To see why, we need to think like aliens for a bit.
We are aliens, visiting Earth. We have picked up radio signals broadcast just a little way across the galaxy, just a few tens of light years, and we have traced their origin to this blue planet. We haven’t managed to decode the signals completely, but they seem to contain information about a species of intelligent ape. Some of the earliest signals suggest that the apes are starting to enter the Jazz age, and so we are keen to see how things develop. We arrived at Earth, engaged the appropriate stealth devices, and are now examining these humans. They communicate mainly by vocalisations. Our (undetectable and painless) probes reveal how this happens. We can see how the muscles in the face and neck react to electrochemical signals sent along nerves from a brain. We have started to trace these signals through the millions of neural networks in the human brain so we can reverse-engineer how brain activity results in sounds.
Nothing about this (probably) fictional scenario is beyond science. It’s a kind of thought experiment. We can see where we get with it. This is where I want to try and get: is the project to trace all the signals through the brain feasible? Is it possible to say why we humans move our mouths and make sounds only taking into account what happens in and between brain cells and nerves? It has to be possible, at least in principle. This doesn’t mean it’s going to be easy. This might be like that it’s possible, in principle, to count all the grains of sand on all the beaches on Earth. It doesn’t matter, though, if it’s like that. It just has to be possible in principle. Assume it is, for now. This is a thought experiment after all.
If we assume that we can trace through the brain all the signals that result in our words, then this means that the words we speak have at least two meanings. The first is the meaning of the words, the meaning we put into the words through the act of speaking our minds. The second is that the words are there because of muscle twitches due to patterns of nerve activity resulting from things going on in our brains. The words indicate that brain activity. And so, those aliens wanting to find out why we humans make the noises we call speech can get an answer in terms of nothing more than signals in our brain. It may be a very, very complicated answer because it involves perhaps millions of brain cells doing what brain cells do. As brain cells can have many thousands of connections to other brain cells, it does seem likely that such an answer would be very complicated indeed. Let’s give this assumption a name. Let’s call it the Alien Answer Hypothesis: the suggestion that our speech can have an explanation in terms of only what brain cells do.
Now we have got that out of the way, let’s look at what it means for us to hear our own words (or see them written down) and to believe that they express a truth. When we are used to hearing or reading a language, we don’t have to put much work into getting the meaning. Even though it seems effortless, a lot is going on in our brains, as physical signals are interpreted. That’s the key thing here - physical signals. Something rather amazing happens when we speak, write or express ourselves in other ways, such as through song, or gesture. We are translating what is going on in our minds into the physical world. An entirely physical part of reality contains our meaning. When we recognise that meaning, we are implicitly acknowledging the power of the physical to contain our meaning. (at least those of us who don’t believe that we live entirely in our minds).
Now, on to one of the most discussed aspects of consciousness: qualia. A ‘quale’ is a part of conscious experience: a quality of experience. It is the sweet smell of vanilla, the redness of a red rose, the sound of a musical note, the tingle of a touch. It’s what gives us the experience of being conscious. Well, almost. We can experience qualities of experience (see how language gets rather tied up when dealing with the subject of mind? This is a common.. experience!) in dreams, so we should really use a word other than ‘conscious’. Perhaps ‘awareness’? But anyway, I hope you get the idea. It’s a unit of experience. Qualia seem mysterious once you start to think about them. Why are they there? Why does red look like that, and not like something else? Such questions have been asked by philosophers and scientists for a very long time. Some who have asked them believe that qualia, the qualities of experience, are so different from anything else we know about that they cannot be explained by physics. After all, why should what atomic particles do result in us experiencing the redness of red? It seems quite beyond all possible explanation. What I’m going to try and show is that this opinion of qualia is mistaken. I’m going to try and how something that many may think is mind-blowing (at least it explodes many ideas of what our minds are). What I’m going to try and show is that qualia must be explainable by physics, and that to think that there is some extra aspect of reality involved is wrong. I may not get there, but I’m going to try. (This is an extremely presumptuous thing to do, as qualia remain the subject of intense ongoing debate. But I’m going to try anyway).
Imagine you say ‘I see a red rose’, and you are actually seeing a red rose. Those words are true. Not just that, but you recognise your own words as true. You have accepted that your words are a correct representation of your thoughts and beliefs. Hold onto that fact. It’s important. Now, why are you saying ‘I see a red rose’? It’s because you have the experience of the red colour of what you recognise as a rose, and you have decided to announce that fact. You have announced in the form of sound patterns that you have experienced a quale - the redness of the rose. The explanation for you saying ‘red’ is the experience of red. This sounds quite obvious, but this matters. It matters because we are saying that a quale - the experience of red - causes your speech. All perfectly clear. You have a think about the strangeness of qualia, and as a result you say ‘Qualia can’t be explained by physics’. You would be far from alone in this. You recognise your own words as expressing what you believe to be true. But, things are starting to look pretty weird. In your previous statement, what you said was a result of the experience of redness. That is straightforward. But what is the cause of your second statement, the one about qualia not being explained by physics? This is getting a bit murky. What is it exactly about qualia that leads to this belief? What is the ‘not explainable’ quality of a quale? This is very hard to pin down, and many have tried. It’s confusing because we are trying to describe the quality of a quality, and we don’t have anything to compare it with. If you don’t believe that qualia can be explained by the physical, have a think about this question - what would qualia be like if they could be explained by the physical?
But now, let’s go back to the Alien Answer Hypothesis. If we accept it, then the words ‘I see a red rose’ have an explanation only in terms of physical brain cell activity, and nothing else. It’s going to be a vast and complex explanation, but it exists, if we accept the hypothesis. But if such a purely physical explanation for the words exists, then qualia must be physical. That seems a huge leap, but it really isn’t. If there exists a purely physical explanation for the words, then there seems to be no room for any non-physical extras. That purely physical explanation seems to contains everything about why the words were spoken. Of course, the Alien Answer need not be the only answer as to why we spoke. This may seem contradictory, but it isn’t. We don’t consider thoughts and speech in terms of individual brain cell activity and individual sounds, just as we don’t consider waves on the sea in terms of individual water molecules. More than one reason for something physical happening can be true, but once you have found one of those reasons and what is going on in terms of the substance, you have pretty much excluded any other ingredients. Once we discovered water molecules, there was no more room in the world for water sprites, no matter how strangely the waves may dance. The sound waves of our speech are composed of the movement of air molecules, moved around by the actions of our muscles, triggered into movement by electrochemical signals from our nerves. The nerves trigger because of signals from the vast networks of cells in our brains. Is this a proof that there is nothing but physics going on? No, it isn’t. There could be more than physics, but it would have to be a strange extra factor, because it would have to have no overall effect as compared to the answer consisting of only physics. There could be something extra, but the presence of your spoken words cannot be taken as evidence for such extra thing, because that extra thing doesn’t change the words from what they would be if there was only physics.
So, if you accept the possibility of the Alien Answer, then you have problems if you continue to think that there must be more to mind than physics, if you insist that there really must be more. The first of these problems is how you would convince the aliens of this. You can say that there is some extra quality of the experience of colour that is beyond physics, but the aliens could respond that they have looked hard at their analysis of what is happening in your brain, and see nothing but physics there. Nothing but physics. Now, here is where it gets really interesting. The Alien Answer Hypothesis asserts that all speech can be traced back through the brain purely in terms of physics. That means ALL speech. You, still a believer that something extra is involved in mind, respond to the aliens by saying “You don’t understand, there is some special quality of experience that your analysis doesn’t capture”. But the speech of this very statement can itself be explained by physics alone. No matter how much you protest, no matter how much you might argue, every single statement you make has a physical cause. The more you talk, the more evidence you get back from the aliens that there is nothing but brain cell physics going on.
Now let’s move things on. I chose to use aliens as the beings who would analyse our brains because they would (in my scenario) initially not understand our language, so they could analyse what causes speech without any assumptions that it was anything but raw noise. They might even find it surprising when they discover that the noises are sonic codes for thoughts. I wanted to highlight the dual meaning of the sounds. But now, let’s get rid of the aliens (in a polite way, of course). They have left their technology behind, and we can use it. You can use it. Every time you speak, you can get a full report of why those noises were produced from their machines. How would you react if you said “I see a red rose” and you could see that there was a purely physical explanation? How would you react if you said “there is something strange about qualia” and you could also see that there was a purely physical explanation? You might still have a feeling that something is missing somewhere, but it’s hard to see where this could be. You have the intention to say the words based on what is in your mind, you say the words, which, on hearing them, you can be sure are the words you spoke, and these words contain the meaning you wanted to put into them, and at the same time you can see that there is a purely physical explanation for why you made those sounds. No matter what you say about what you know, what you feel, what you experience, all those words have at least one explanation which involves only brain cells interacting. And so, if you believe in physics, nothing you ever say can be considered as evidence for there being anything more than physics in the mind. No matter what arguments you put forward for how things must be more than material, or what it feels like to be conscious and have subjective experience, none of those arguments work if you accept that you can express the truth of your arguments as words.
If you really wanted your mind to be more than physics, you could always reject the Alien Answer Hypothesis. However, that hypothesis isn’t making any unreasonable assumptions. The hypothesis is based on the findings of centuries of science, including the discovery that we are biochemical beings: our bodies are made up of the same particles that exist elsewhere in the universe. Indeed, as Lawrence Krauss has pointed out, our bodies are made up of atoms in close to the same proportions as those atoms exist in the universe. There is no life force, just biochemistry and physics working it’s own purely natural kind of magic. The hypothesis is also based on the discovery that we are evolved beings, having been shaped by our environment and our fellow organisms for billions of years. We are built from ordinary stuff. Our bodies don’t involve interactions with exotic particles, or strange quantum mechanical behaviour on anything but molecular scales. We are biological systems working using the physics of the every-day, there is no room for strange phenomena to infiltrate our bodies and provide a ghost in the machine.
And so, if you accept science and what it has found out about the world for the past few centuries, then you can’t be consistent and insist that our minds are more than matter, that the queerness of qualia points to something non-physical. It just doesn’t work!
The position of those who want minds to be more than the material world reminds me of one of my favourite M. C. Escher works:
The dragon is struggling to pull itself out of flatness, to become three-dimensional. But no matter how much the paper on which it is drawn is cut and folded, the dragon remains trapped on it.
There is probably little about our minds that is as we think it is. That should be no surprise. We aren’t born experts about what goes on in our bodies. So why should we gain much insight about what it is like to be mind in brain from being that mind?