Are You a Computer?
Is a Science of the Mind possible? According to some people, this question has a simple answer: there is already a Science of the Mind, so of course it must be possible. This is the answer we would get from researchers in a new field, formed from the union of four traditional academic disciplines. The field is Cognitive Science and its four component fields are: philosophy, psychology, linguistics and computer science. It is an extremely active area of research, and it draws some of the brightest people from all four disciplines, along with large amounts of money to fund the research. The one branch of it that has been most in the news lately is Artificial Intelligence, or "AI" for short. There are a lot of reasons it has been in the news. Two of the most widely publicized ones are these.
First, there is competition with Japanese industry. In 1981, the Japanese Ministry of International Trade and Industry (MITI) decided to commit a large block of resources to building what has been dubbed a "Fifth Generation Machine" - a machine capable of thought and language in just the same sense as a human being is capable, only much faster much more reliable and with a much larger memory. Large Japanese corporations gave some of their best, youngest and brightest personnel time off so that they could spend a decade or more on designing and building the first fifth generation machine. MITI does not make such decisions frivolously; billions of dollars were committed. The nation that produces the first fifth generation machine will enjoy an enormous economic advantage during the next century; some believe that it will dominate the world economy for decades to come. American corporations were scared. So they formed a consortium (Microelectronics and Computer Consortium) to pool resources and personnel, and they are likewise committing billions to developing a fifth generation machine. Without government support, the consortium fell apart. But the work continues at other sites. This work is already having an impact on corporate practice and planning. It is not unreasonable to assume that the kinds of lives you live - what economists call "quality of life" - and the kinds of careers you and your children can have, depend heavily on the results of this race for machines that (who?) can think.
The second reason that AI stays in the news is its hoped for role in various weapons systems. Already, hundreds of millions of dollars have been poured into AI research in the hope that it will result in smart weapons and weapons systems, able to cope more effectively with the millions of split second decisions that would need to be made in defending against an all-out nuclear attack on the USA. There is much debate about whether or not the money is well-spent, but it is significant that there are people on both sides of the issue. AI has that much credibility.
Where does AI's credibility come from? Why are so many smart people willing, collectively, to bet billions on it? There are two sources: its past successes, which have been rather meagre, and its driving theory, which is of interest to us.
We can state that theory loosely and metaphorically by saying that we think with our brains, and that the brain is a computer - a meat machine, as some have called it. This metaphor - the computer model of the mind - immediately encounters both misunderstanding and resistance, so we need to be careful about its proper interpretation.
The main misunderstanding that we have to guard against is taking "computer" or "machine" too narrowly, to refer simply to those familiar examples of the things that we often see around us. The objects to which we typically apply those terms are computers and machines, but they do not exhaust the content of the concept as cognitive scientists use it. They have a much broader, more precise and more flexible definition for them, as "interpreted formal systems," and one of our jobs will be to get as clear as we can about the concept's boundaries. The ultimate source of the definition is the mathematical theory that provides the foundations for all computer science, the theory of automata, or, as it is also called, recursive function theory or the theory of computability. Fortunately, there is a very nice analogy between interpreted formal systems and familiar board games that allows us to avoid, or evade, much of the mathematical intricacies.
Three Sources of Resistance to the Computer Model of the Mind
Even before people see the details, they often react negatively to the message that they are machines. Sometimes, the reaction has a rational basis. I'll discuss three of the main sources of resistance to the computer model.
The most powerful and prevalent source is belief in Dualism: many people believe that there is more to us than could be contained in any mere physical object or system, no matter how complex; that there must be a non-physical, spiritual component in us that endows us with the ability to think, feel, deliberate, choose, hope, wish, feel, love, and so on. We met a form of dualism in our discussion of phrenology, namely, Cartesian Dualism. In order to give you a reason for looking beyond dualism, I'll alert you to two serious difficulties that face dualism in the section devoted to it.
A second source of resistance to the computer model of the mind is the belief that you can't make a smart thing out of stupid parts. According to the computer model, it seems that all of our individual nerve cells are organic switches, linked together in complex circuits. How, one might wonder, can one get mental activity by wiring switches together? No one switch can think, and it may be hard to imagine how it could help to hook two of them together - or three, or four, or more. Whence:
Stupid Parts Argument
It's not possible to build a thinking thing from unthinking parts
Every possible computer is built from unthinking parts
Therefore, no computer could think
The first premise seems to be based on the following general principle:
Part/Whole Principle: If the parts of a complex whole, W, do not have property F, then W does not have F.
If this is the basis for the first premise, then it is ill-supported, since the principle is false. One brick does not a building make, but a bunch of them does. One person does not make a society, but a group does. And so on. If Part/Whole Principle is not the source for the first premise, then we are owed some other support for it. Is there something special about thinking that prevents it from emerging once the system reaches a high (enough) level of complexity? What could that be?
A third source of resistance to the computer model of the mind is the belief that the kind of unpredictable seeming complexity of behavior that is the hallmark of living and thinking things simply can't be generated by the simple sorts of rules that govern the basic operations of even the most complicated machines. How, one might wonder, can you get the truly amazing repertoire of highly variable, environment-sensitive behavior out of nothing more than the repeated application of rules so simple they are comprehensible even to those who never did get chummy with high school algebra? To help you overcome this kind of resistance, there is beautiful, recent work in Chaos, fractal geometry and cellular automata. It turns out that even very simple equations and rules may yield truly unpredictable behavior - behavior that is impossible for any physically possible computer that will ever exist ever to predict. So the fractals of Chaos and Paradigms are counterexamples to the claim that unpredictable complexity cannot be generated by the simplest rules.
Dualism and Thinking Things
A very large percentage of the people with whom I've discussed these issues - over 80% - believe that they have a non-physical mind in addition to having a body. I'd be surprised if the percentage were any lower among the wider American population. So I'm pretty confident that the dominant view among you is that our best examples of thinking things have a dual, or two part, nature. A still large though somewhat smaller percentage believe that living things have a vital essence, in addition to their physical constitution. So many are dualists about both living and thinking things. Those of you who have these beliefs have a lot of very good company: most of the best minds of civilization have been dualists of one sort or another, and the view is probably still the majority view among those who have considered the question. We all know, however, that being widely held is no guarantee of truth. Belief in a flat Earth though once nearly universal is now a recognized falsehood; similarly for a geocentric picture of the solar system. So let us take a closer look at these widely held beliefs. In this section, I'll focus on dualism about thinking things. As I explained in the section on the meaning of "life," much of what I say will apply to analogous views about living things. To begin, let's see what the sources of dualism are. Then I can state the view itself more clearly. After I've done that, I will present two serious problems for dualism.
There are at least three sources for dualistic intuitions.
First, dualism certainly has a powerful religious motivation. Many religions have as part of their central doctrines the belief that people are both physical and spiritual beings, with one part for each of those two jobs. For example, one familiar group of religions says that minds are temporarily embodied for a while here on Earth, and then, at death, the body and mind separate, with the body staying here on Earth to be disposed of, and the mind going either Up or Down, depending upon how the mind has behaved while embodied. It seems very difficult to make sense of 'life after death' unless we suppose that the surviving part - which, after all, is what determines your identity and is the subject of ultimate moral judgment - is nonphysical. And I'm not kidding about its being nonphysical: it's not a physical object, it's not a physical process, and it's not a gaseous substance or fluid or energy field. Even if you don't fully understand the most famous formula of the century - E=mc2 - you should know that it entails that 'energy and matter are equivalent, that "energy" and "matter" are two words for the same thoroughly physical subject.
It's worth getting a bit clearer on the contrast between physical and nonphysical, since it's fundamental for dualism. Suppose you were asked to explain "physical" to someone unfamilar with the term. The usual strategy in explaining unfamiliar terms is to give lots of examples and then to point out that they have some defining characteristic in common. In this case, we can easily think of lots of examples: galaxies, stars, mountains, toasters, bacteria, atoms, electrons, etc. They vary considerably in size. But they all have some size, enormous in the case of a galaxy, very small for an electron. By the same token, to say that something is not physical is to say that it doesn't have this defining characteristic of physical things; that is, if something is nonphysical, it takes up no space.
It is possible to be both an atheist and a dualist. Descartes gave a simple, powerful argument for dualism using the concept of a self-evident belief that we met in our discussion of faith and evidence. Minds, we found, are knowable in the self-evident way. But we also found that bodies are not knowable in this way; recall that it's possible for you to be radically mistaken about which parts yours has. So, there is a real difference between minds and bodies. However closely related they may be at times, they must nevertheless be distinct things. If we add the assumption that, as a complex physical object with many parts, bodies are thereby capable of malfunction, we can conclude that minds are not similarly physical. No theology here.
In addition, many truths about ourselves and other people are most straightforwardly interpreted on a dualistic model. A great deal of our common usage seems to presuppose a dualistic picture. To give just three examples, consider three very short stories:
Karla crouched behind the couch, her mind racing with fear, her body motionless.
Stephen's body was weak and diseased, but his mind was strong and healthy.
You love me just for my body, not for my mind!
In each case, the sentence can be used to express a truth (you can fill out the story), and the truth expressed seems in each case to be about one individual who at one time has 'opposite' characteristics - and how could that be unless the individual was comprised of two distinct components, one characteristic for each? I'm sure that you can devise thousands of additional examples. This doesn't prove that dualism is correct, but it ought to be somewhat persuasive. So we have a third source of evidence for dualism.
The clearest and most well-worked out form of dualism was Descartes's, Cartesian Dualism. According to his view,
I. Each person is composed of two things, a body and a mind.
II. Bodies and minds can and sometimes do exist independently of one another (e.g., after death).
III. Minds are necessarily such that they can think but take up no space.
IV. Bodies are necessarily such that they cannot think and do take up some space.
If we were to stop there, we would have an incomplete form of dualism, because we would have said nothing about how the body and mind influence one another. This is a crucial issue for any theory of thought, because our ability to explain people's actions depends on there being such an influence. One kind of purpose-directed explanation explains people's behavior as based on their beliefs and desires: Jack's hungry and wants some food. He believes that the best way to get some is to cross the street to Jill's Bar and Grill. So, Jack crosses the street. Or: The President wants to get re-elected, and he believes the best way to do that is to increase aid to education, so he increases aid to education. Since such explanations are so important for many reasons - any hope of doing psychology, sociology, political science, economics, history, human factors engineering, anthropology, analysis of literature, music and the arts depends on having a secure basis for such purpose-directed explanation - we can't leave the sort of influence out and we can't leave it vague. Descartes, who was after all a genius, was aware of this issue, and so he added a fifth tenet, the
V. (Postulate of Interactionism:) There is two-way causal interaction between a person's body and the person's mind; mental events in the mind can cause physical events in the body, and vice versa.
Here are two examples, one for each direction of causation: (i) Being stuck with a pin causes a complex series of electrochemical events in your peripheral and central nervous system, and the last brain event causes the mental event that is the sensation of pain. A series of events in your body causes an event in your mind. (ii) Wanting to raise your hand is a mental event in your mind which causes electrochemical changes in your brain, and these cause impulses to travel into your arm, chemicals to be released, muscles to contract and, finally, your hand to rise. Of course, not every event in the body causes an event in the mind. There are automatic, biomechanical or biochemical processes, like absorbtion of nutrients in the large intestine, that have no direct effect on train of thought. Nor need we suppose that every event in the mind - perhaps, thinking silently to oneself - causes a bodily event. But, V says, interaction does sometimes occur, and it's of the familiar, every-day sort: cause and effect. So that's Cartesian Dualism. It was designed to respect religious doctrine, it is supported by argument, and it accords well with common usage. But it also faces two very serious problems.
First, how can the motion of electrons in your brain cause changes in your mind which, by its very nature, takes up no space?
In a game of pool, your aim, to put it crudely, is to get ball 1 to bump into ball 2 and so to change the position of ball 2. Unless you are suspended above the pool table and have extraordinarily good vision, you'll typically not be able to see where ball 1 comes into contact with ball 2. But you know that there must be contact, or ball 2's not going anywhere. The same sort of contact is also required in more complex cases. If you see the result of a head-on collision between two cars, it's generally not feasible to determine where, exactly, all the points of contact were, but you can be sure that there were lots of them. Sometimes, causation is mediated by a chain of contacts. If you blow on a page of this book, it will deflect even though your mouth does not touch the page. What's happened is that your mouth has moved some air molecules (think of them as tiny pool balls), and they have bumped into others, and ..., and finally some molecules bump into the piece of paper and push it out of its original position. (Think of a row of dominoes falling down.) Seeing works in much the same way. Particles of light (photons) from the sun or a light fixture bounce off the page, hit your eye and the complex chemical molecules therein, etc. Even the fanciest physics seems to rely on the pool table model: every force of nature is carried by particles; for example, you remain here on Earth instead of floating off into space because your body and the Earth exchange gravitons, particle exchange that constitutes the force of gravity. It's all a cosmic game of pool. So, a good slogan about the very nature of causation is: "all causation requires contact." But, according to Cartesian Dualism, minds take up no space, unlike even the smallest of subatomic particles, and they cannot bump into anything that does take up space, e.g., electrons in the nerve cells in your brain.
No Interaction Argument against Cartesian Dualism
If Cartesian Dualism is true, then souls can interact causally with bodies.
All causal interaction requires contact
It is impossible for a mind to come into contact with a body
Therefore, Cartesian Dualism is not true.
I have heard three replies to this argument. I'll present them and explain why each comes at a high price.
First reply: The second premise is false. Causation can take place even where there is no possibility of contact. This is a possible reply, but it is so hard to think of non-controversial examples where contact is not involved, that whoever replies in this way owes us an alternative analysis of causation. The analysis would have to tell us why it sure looks like all causation requires contact, but really doesn't. A tall order, especially given the constraint that purpose-directed explanation places on us.
Second reply: The second premise is true, but minds can influence and be influenced by bodies without their interacting causally. So influence is possible, even though causal interaction is not. Again, one might reply in this way, but remember that the postulate of interactionism is part of Cartesian Dualism for a good reason: it serves as the foundation for all explanation of human action. So we must insist on clarity here - the issue is too important to rest with vagueness. And it is not particularly easy to think of alternatives to causation. Descartes was a genius, and he thought of nothing better.
The problem here is not merely a technical one that will get resolved with further progress in science. It's a far deeper, conceptual problem. Here's a helpful analogy: suppose I tell you that I've spent a lovely afternoon imagining brightly colored round squares. I'm so edified by my experience that I urge you to join in the pasttime. How would you react? Although the words I've used are all familiar, as are the concepts they express, they simply don't fit together in the way I've said. What could it possibly mean to say, "I've been visualizing round squares"?! And it won't do any good to hope for advances in psychology or geometry. In much the same way, when a Cartesian Dualist says she's been thinking about things that take up no space causing changes in things that do, we ought to be deeply puzzled, to demand a coherent explanation, and to be skeptical about the chances of getting one.
Third reply: Maybe the second premise is false, maybe it's true, but we'll never know which, or why. There is influence of some sort between body and mind, but it is just one of the many mysteries in life how it happens: no matter how hard we try, we will never be able to fathom the mystery; we will never know the answer. This is the desperate Mystery Response, and it exacts the highest price of the three replies, because for fundamental concepts, mystery cannot be quarantined; the disease of ignorance becomes pandemic. (Another metaphor: plunging fundamental concepts into darkness is like dropping a boulder into a small pond - the ripple effect is disastrously large and empties the pond.) In this case, the mystery will infect all explanations of human action. Immediately, we lose our ability to explain human behavior, and with this loss go psychology (pure and applied to, say, education, business management, and therapy), history, political science, literary analysis, sociology, human factors engineering, etc. Not an attractive result. Are you willing to take this plunge into nearly universal ignorance about human beings? Why would anyone buy a theory of mind that deepened ignorance about the mind?
So I think the No Interaction Argument poses a serious problem for dualism.
There is a fourth reaction to the argument that I have often heard. They say that belief in Cartesian Dualism is for them a matter of "blind (religious) faith," and that's the end of it. I call this a "reaction" and not a response because it is a refusal to make specific criticisms of any of the premises of the No Interaction Argument. It is instead a declaration of withdrawal from any attempt to criticize that argument.
While this is a common reaction, it has an extraordinarily high price which, I would have thought, no religiously motivated Cartesian Dualist would want to pay. I'll explain.
Accepting some statements on faith is, as we found in our discussion of Separation by Foundation, necessary for rationality itself. So every rational person "invokes faith" all the time, even if s/he is a stalwart atheist. However, not just any belief deserves to be accepted on faith, i.e., accorded foundational status. Rather, great caution and high standards are called for (and, as Plantinga suggests, some simple religious beliefs may well qualify as foundational). But they, like any other candidate for foundational status, must qualify. It's not: "anything goes, foundationally."
Here's a story to help emphasize the key point:
Suppose that Mr. Reneé believes about himself: "I have a non-physical soul that interacts causally with my body," and that he accepts this on faith in the aforementioned sense (that is, accords it foundational status). Suppose that Mr. R is made aware of the No Interaction Problem and the Problem of Other Minds and that he is then asked what considerations lead him to continue to hold this belief on faith. Imagine that he replies, "I have no considerations to offer - save for the fact that I've been this way for a long time, like those who raised me - so it's just a matter of BLIND faith for me." That tells the questioner what Mr. R's mind-set is, but it gives the questioner absolutely no reason to adopt that belief in any way, no less to accept it on faith. So replying to the question in this way does not give any persuasive reasons for Mr. R's persisting in his belief - he's told us simply that he insists on persisting. And, Mr. R might add, "I don't care at all if anyone else agrees with me about this matter. I don't even want to try to persuade anyone else. After all my faith is BLIND!"
And many students have in the past responded in just this fashion, with words close to these. But:
Later that same day, Mr. R gets into a heated discussion with Ms. Agnosti about the (im)morality of abortion and euthanasia. He vigorously contends that both abortion and euthanasia are morally wrong (at least, almost always), because both what is new in the womb and what is old in the hospital bed are living persons; on Mr. R's dualistic faith, a living person is a human body with a soul. It would be murder, he says, to end a person's life - only the Creator of Souls can properly decide when life ends. And, he insists, there must be laws criminalizing such murders.
Ms. A does not currently believe that persons are ensouled bodies since she does not now believe that there are non-physical souls (though she's keeping an open mind). She reminds Mr. R of the two standard objections to his dualism and asks Mr. R why she should join him in political and social action on these issues. Obviously, it will do Mr. R's cause no good for him to say, "It's just a matter of blind faith for me." That describes his state of mind, but gives no one else any good reason to adopt his attitude.
Of course, it might be that most others believe as Mr. R does and can trounce the minority in a democracy by voting their faith. Or it might be that Mr. R and his fellow believers in souls are in the minority but have a great deal of wealth and power and can force their views on the majority. But unless "might makes right" - a truly repugnant view - none of that would be anything to be proud of. And Ms. Agnosti still shouldn't be persuaded, though she may be forced to behave as if she'd been persuaded.
So, the blind faith response renders dualistic belief politically and socially inert. Typically, however, dualists invest dualism with great moral, political and social significance - it's proposed as a view about the deepest fundamentals of human nature - so they would pay a very high price were they to adopt the blind faith response. And if dualistic views were inert and insignificant in this way, why would anyone take the trouble to maintain and defend them?
What about relying on the Bible or another religious scripture to butress faith? Unless you intend to waste your time "preaching to the converted," two conditions must be met if you relying on religious scripture in this way:
(i) You must justify your proffered interpretation of what it says (something that my colleagues in Religious Studies often find rather difficult, despite being able to read scriptures in their original languages, e.g., Arabic, Chinese, Greek, Hebrew, Hindi, Japanese, Urdu); and
(ii) You must argue that those in your audience who do not already take what the Bible says for granted ought instead to accept it as reliable and authoritative on these questions about dualism. Otherwise, you would be "preaching to the converted."
Another common attempt to support belief in Cartesian souls relies on reports of "near death" experiences. There are many such reports from apparently quite sincere people. Among these people are physicians who have undergone surgery; they claim that their souls temporarily leave their bodies, to observe the surgical scene from a distance. Are such examples helpful in defending dualism?
There are at least a couple of serious problems with such examples.
First, the patients (doctors or non-doctors) may use the word "soul," in their reports, but do they mean by it: "non-physical substance that thinks"? If not, or if it's not clear what they mean, then their reports are not relevant to discussion of dualism. Typically, it is at best unclear whether they use the word with the relevant dualistic meaning.
Second, in every case, the patients are people who are undergoing massive central nervous system disruption, often because they have been given large doses of brain-scrambling chemicals. (Trauma can have similar effects, of course). If such a person were to advise you to buy stock in Red Hat today, or even to assert that it's raining, you'd not likely look for a stockbroker or reach for your umbrella: such people are recognized as highly unreliable about many, many things. Why, then, would one take their reports about what they themselves describe as extraordinary experiences as good guides to Ultimate Reality? Is there something special about these experiences that makes them atypically reliable? What is it? And how would someone else not having those experiences be able to discover that this special quality was present in another's experience at a given moment (no less later, after the other wakes up from surgery or the coma)?
So, even if it's true that you have had a "direct experience" of your own non-physical soul, your report of that experience is irrelevant unless there's something about it that will give other people secure reason for accepting your experience as settling the matter. (It's not entirely clear what "direct experience" means here - but I have often heard people talk this way, and I would not want you to write so very obscurely.)
Sometimes, someone will say in frustration, "Well, that's MY experience, and it convinces ME!" and will then refuse to say any more to convince others. The frustration may be understandable, but simply claiming veracity for one's own experience and doing nothing further to justify it for others cannot be an effective response in the context of this paper. In this context, it is akin to the blind faith response in its defects.
Would it help to distinguish minds from souls? The suggestion seems to be that minds are physical - perhaps the memories, beliefs, desires, sensations, etc. are a product of brain functioning, and hence minds are mortal - but souls are non-physical (and hence can survive even brain death). The point of the suggestion would presumably be to explain 'life after death' (in Heaven, Hell, Elsewhere or through reincarnation, or ...).
This suggestion runs into very serious difficulties:
If souls are subject to Ultimate Judgment (or other sorts of meaningful assessment), then they must carry the person's identity, and the mind is at an essential least part of (if not the whole of!) that identity. So one would still have to explain how physical minds are related to nonphysical souls, and that's the same as explaining brain-soul (causal) interaction. If, however, souls are not the subjects of judgment, what conceptual role do they play in explaining 'life after death'?
And if a soul does not constitute some one person's identity, then it isn't any person in particular. (Who, or what, would it be? someone else?!!). There would be no reason for any person to have any particular interest in that thing's persistence after his/her death.
[Digression: Some theists to whom I've presented the No Interaction Argument have found it the troubling because, they realise, it raises questions about the interaction of divine, as well as human, minds with the physical world. After all, if a nonphysical human mind cannot cause changes in the body it somehow inhabits, how can a purely spiritual, nonphysical being - for example the God of the main Western religious traditions - cause changes in the physical universe? Could such a being even create a physical universe? But what is unsettling in one context might help settle matters in another. Perhaps it is characteristic of religion to suppose that this kind of causation actually takes place. Let's return briefly to the topic of separation.
Separation by Immaterial Causation
Religion says that changes in nonphysical objects cause changes in physical objects, but Science does not.
Unlike Separation by Explanation, this proposal does not imply an essential religious reliance on noncausal explanation; instead the difference between religion and science depends on a difference between two sorts of causal explanation. Science does talk about nonphysical objects, most obviously mathematical objects, such as numbers (and, perhaps, mere possibilities), and such objects are apparently essential ingredients in causal explanations of changes in physical things ("the mass decreased from 200 to 100 grams because the temperature rose from 50 to 800 degrees"), but science does not seem to suppose that changes in the nonphysical objects themselves cause changes in physical things. (Numbers and numerals - number names, which are physical objects - are, of course different: one number may have many names, and names can be erased while the number remains.)
The analogy about imagining round squares still ought to worry us. Is Separation by Immaterial Causation even intelligible? What does it mean to say that changes take place in a nonphysical object? Among the clearest examples of nonphysical objects are numbers, and they seem to lack dynamic qualities. This proposal might then be claiming that there's an impossibility at the heart of religion (-the same impossibility in all possible religions).
Until we know more about the nature of mathematical (and other nonphysical) objects and their role in causal explanations, it will be difficult fully to evaluate Separation by Immaterial Causation.
Apart from the independent value such knowledge would have, there is good reason to reject Separation by Immaterial Causation. Its plausibility comes from a focus on the main Western religious traditions (and, perhaps, from a conflation of purpose-directed explanation with a kind of nonphysical causal explanation). In those traditions, the distinction between spiritual and non-spiritual tracks pretty well with the distinction between physical and nonphysical. But there are other religious traditions that have no obvious use for the latter. It is not just that they hold that the spiritual is essentially embodied, although, no doubt, there are some such religions; rather, they do not suppose that there are nonphysical things to be embodied, or they say that there are no physical things at all, though we often suffer from the illusion that they exist.
One of the most interesting ways in which the world's religions are diverse is in their fundamental, metaphysical presuppositions. It is this aspect of their diversity that weighs against Separation by Immaterial Causation.]
Even if we can take care of the problem posed by the No Interaction Argument, there is another serious problem for dualism.
Before presenting the second problem, I'd like to run a brief sanity check. Consider the following scenario. You arrive home one day to find a loved one deep in anguished thought. She says that she's now convinced that she's the only thinking thing in the world - that all others are merely mindless robots, who act as if they can think, but who engage in no genuine mental activity at all. Wouldn't you take that as an emergency, and try to get help for your loved one? After all, such a belief is obviously crazy. Anyone who takes it seriously does not deserve points for philosophical insight; they need, perhaps, a long rest in a quiet place. Consider a slightly different scenario. This time, your loved one announces excitedly that she has a new, bold, empirical hypothesis, she wants your help in doing the needed experiments: "There are thinking things - people - besides me! How about that! There's a Nobel Prize in this for us!" This, too, is crazy. Our knowledge that there are other minds is not like our knowledge that, say, there are electrons. It is not mediated by a complex, albeit well-confirmed, theory. Instead, knowing "there's another mind," is an excellent candidate for foundational belief, one that is normally beyond challenge. So I hope that we can all agree on this much: any theory of thought that tells us we're rational to take such crazy hypotheses seriously, is itself in serious trouble.
But, of course, Cartesian Dualism is in just such trouble. For minds are invisible, untouchable and in short, undetectable. Perhaps you know 'from the inside' that you have (better: are) a mind, but you have no direct access to others' minds - all you have is access to their bodily noises and motions. Those noises and motions might be produced by a mind, but if Cartesian Dualism is true, then it is just as reasonable to assume that they are not so produced.
The Problem of Other Minds
If Cartesian Dualism is true, then, for all I know, I am the only thinking thing in the world.
I do know that I am not the only thinking thing in the world (since I'm not nuts).
Therefore, Cartesian Dualism is not true.
The second premise is sometimes misread as "If Cartesian Dualism is true, then I am the only thinking thing in the world," without the essential reference to knowledge of particular thinking things. Of course, Cartesian Dualism does not entail such an absurd consequence (whic is sometimes called "solipsism"). Cartesian Dualism does recognize the existence of other minds. But having granted their existence, it then makes knowing which bodies to find them in impossible, thus denying us knowledge of other minds.
This second problem is independent of the first. Even if the first can be solved, the second would remain untouched. And it is of broader scope, since it relies only on the supposed nonphysical nature of the mind - an assumption common to all forms of dualism
If you are sympathetic with dualism, then, I think, you have cause for concern. At least, I hope that you will agree that it is worthwhile to look at some alternatives. And that's what we will do. Next, we will consider a view that is as far from Cartesian Dualism as one can get. It is called "Behaviorism", and it begins by denying the existence of nonphysical minds. After we see Behaviorism's problems - it's got plenty of its own - we will then be in a position to appreciate a way of steering between dualist and behaviorist extremes, the way that drives cognitive science research: Machine Functionalism, aka the computer model of the mind. It is this model that offers the hope of accounting for mental phenomena without using irreducibly purpose-directed explanation.
Behaviorism
Behaviorism developed as a reaction to dualism, and begins by denying everything that the dualist holds dear: There are no (non-physical) minds. But there are (thinking) people. So each person is the very same thing as his/her body, and exists only so long as the body continues to function. No live body, no person.
These are simply denials of dualist doctrine. They relieve the Behaviorist of the No Interaction problem, since there no souls to interact with. But these denials don't amount to a theory of mind. The guts of Behaviorism lies in its claim that certain patterns of bodily motion are definitive of mental states: Bodies can think - mental states and processes are (dispositions or tendencies to exhibit) patterns of stimuli and response.
The Problem of Other Minds vanishes since, according to Behaviorism, we can literally see others think. To see why the latter is so and to appreciate the positive portion of Behaviorism, let us look at the last part.
Behaviorism is a form of materialism about mental processes: every mental process is some physical process or other. Your mental processes are certain physical processes that take place in your body. But that's not all that Behaviorism says. It says something much more specific about how to say which physical processes are mental processes. And what more it says is at the heart of Behaviorism.
The key notion is that of a disposition, or dispositional property. When we say that sugar is soluble in water, we attribute to sugar a certain disposition, roughly:
if the sugar were in water, then the sugar would dissolve.
(Of course, that's not chemically correct, but I hope you get the idea.) This form of expression is so common that it's been labeled a "subjunctive conditional" by linguists and grammarians. It's the ideal linguistic tool for expressing dispositional properties. The most important logical characteristic of such properties is that an object can have them even when they are not being shown off. If you keep your favorite sugar cube in a fluid tight safe until the world ends, it will still be true of it, at every moment of its existence, that it's soluble - because if it were in water, then it would dissolve; but you never give it the chance to realise its potential. In the same way, the fragility of some glassware is a disposition that we may hope is never exhibited:
if the glass were dropped on a hard surface, then the glass would shatter.
But just because it's never dropped, the glass does not stop being fragile. Some dispositional properties are so complex that entire branches of engineering are devoted to their study; for example, there's airworthiness, which you insist that the plane be certified to have before you get on board. Aeronautical engineering is focused on that extremely complex characteristic, which we can describe very roughly and oversimply, with no offense intended to the engineers, as
if the plane were to take off, then the plane would fly.
How does this pertain to mental states and Behaviorism. Let's consider a simple example. Suppose that we decide to investigate the mental process we call "desire" or "wanting". To make the example more definite and to avoid the naughty bits, let's talk about chocolate desire. Our experimental subject is my associate, Mr. Waldo.
What would we do to find out if he wanted some chocolate? That's an easy one: we offer him some and see if he takes it. If he does, he's got the desire, if he doesn't he doesn't. What Behaviorism says is that we should take this sort of pattern of acceptance and refusal as our definition of chocolate desire. So, to a first rough approximation, we have:
Mr. Waldo desires chocolate =def if Mr. Waldo were offered some chocolate, then he would take it.
Behaviorists like to describe this by saying that there is a certain pattern of stimuli and responses that defines chocolate desire. Here, offering Mr. Waldo the chocolate is the stimulus and his acceptance is the response. Notice that this pattern-description can accurately describe Mr. Waldo even at a time when he is not being offered any chocolate. He might have the tendency or disposition described by the definition, even though he's not been sparked into action by the appropriate stimulus. So even in a chocolate-free environment, this Behaviorist definition says that it is possible to desire chocolate.
Notice something important about this definition: it says nothing about what goes on inside Mr. Waldo; it stops, so to speak, at the skin. So far as the Behaviorist definition is concerned, it makes no difference how the pattern is produced; all that matters is the skin-level pattern of stimuli and response. Therefore, so far as Behaviorism is concerned, Mr. Waldo may as well have a black box inside his head, a box that can't be opened by anyone. We can treat Mr. Waldo as a device that gives a certain sort of output for a specified input, and we don't have to concern ourselves with the details of internal processing.
All of this generalises, to give the general form of Behaviorism's definitions of mental states and processes:
P is in mental state M =def if P were stimulated with input I in circumstance C, then P would respond with output O.
In the example we are using now, we are considering just one input and one output. But in general, there will be many inputs and outputs that characterize the relevant pattern - the pattern will typically be quite complex. So we should talk about inputs I1, ... , In, and outputs O1, ... , On, and we'll also need to talk about a variety of circumstances and environments, as well. That's nice for psychologists, because it gives them something to do, namely, figure out the complex patterns. This was no small reason for Behaviorism's popularity among psychologists. It's reassuring to be guided by a doctrine that says you'll have a job for the foreseeable future. Figuring out all the relevant input-output statements would take a long time.
Behaviorism and the Problem of Pattern Poverty
Like many simple views, Behaviorism is guilty of over-simplifying in a rather serious way. To appreciate Behaviorism's main problem, let us take a look at the Behaviorist approach to defining another mental activity. It is a process that Artificial Intelligence (AI) research is very concerned with: conversation. There are many AI researchers who would love to know how to make a machine that would be able to understand English. I will describe a machine that would behave just as if it could understand English, but which is really unable to understand anything. It is a machine that exhibits the behavioral patterns of a conversing human being, but which undergoes no mental activity at all. If we focus on the kind of understanding involved in conversation, we can define it Behavioristically in this way:
P understands conversation =def if P were stimulated with a statement or asked a question, then P would answer sensibly.
Notice two features of this definition that it shares with our first example. First, it does not imply that P is able to understand verbal stimuli only if he is actually listening or talking. S/he can have the ability even when s/he is alone and silent. Second, this definition entails that exhibiting a certain behavioral pattern is sufficient for understanding. So anything that exhibits the pattern is therefore a thinking thing, no matter how the pattern of behavior is produced. Also note that there is no restriction on stimulus subject matter: we can talk with P about anything at all. Of course, we have to allow that among his/her sensible responses might be "I don't know" or "It sounds like nonsense to me", but then those are sensible responses in some contexts. It might even be OK for P to utter nonsense, if we asked him, "Can you make some meaningless sounds?"
Now I'll describe Ned Block's design for a possible machine that gives a perfect simulation of understanding, which meets this Behaviorist definition, but which is clearly not a thinking thing.
Some preliminaries: the conversations of concern will take place over a computer terminal. Plenty of conversations take place in this way. (Anyway, for a few thousand dollars, we could equip our machine with voice synthesis and recognition, and let the conversation take place over the telephone. With a Disneyland budget, we could build a robot.) The conversation is to take a finite period of time; you get to pick the duration in advance. It can be any period of time, but there must be a limit. Let's suppose it's one hour. That's usually more than enough for us to tell if we're being understood under normal circumstances, but if you're more cautious, pick a larger number and let me know what it is. Call something a "typable string" if a person can type it into a terminal during an hour. There are lots of typable strings, but the number is finite. Many typable strings consist of nonsense: random assortments of keystrokes. Call something a "sensible string" if it is a typable string that consists of meaningful sentences. The set of sensible strings will be a relatively small subset of the set of typable strings. Simply to cut down on the number of strings we have to deal with, let's restrict them to a particular conversational style. There are many ways to do this. For convenience, we're going to model the set on the conversational style of Mr. Waldo. That subset will be smaller still, and it will consist of all the possible one-hour long conversations that one might have with Mr. Waldo. Call it the "set of all Waldo-strings". We get a large grant for Project Waldo. Assemble a team of programmers and have them spend a year with Mr. Waldo, following him around to workplace, supermarket, malls, bowling alleys, his kitchen at home, etc. Using their feel for his personality, the programmers put all the Waldo-strings into the memory of a big computer. Now, here's how the software works.
You type in a sentence:
A: Hello, I am glad to meet you.
The machine searches its memory for all those Waldo-strings that begin with A. There will be many of them. It selects one, randomly. It then prints out the second sentence in the string as its response:
B: Have you got any chocolate?
You now respond:
C: No, I'm sorry to say that I don't.
The machine now searches its memory for all Waldo-strings that start with ABC, selects one at random, and prints out its fourth sentence as its response:
D: Please get me some, or I'll die.
Then you respond with E, and the machine searches its memory for Waldo-strings beginning with ABCDE, selects one at random, and prints out its sixth sentence as output. And so it goes for the Unthinking Waldo Simulator. The algorithm that the computer uses to produce outputs for given inputs is a very simple one. It is clearly engaged in no understanding of the inputs: it simply matches input sequences against sequences stored in memory. It functions as a 'sieve for sentences', sorting sentence by their syntactical 'shapes' (written or spoken) rather than their meanings. The software is so simple, it would make a reasonable assignment for a first course in computer programming. Because of the ingenuity that the programmers have exercised, the patterns of inputs and outputs is just like that of a thinking human being. But despite this pattern of behavior, the machine has as much ability to understand English as does a sieve, that is, none at all. As much as we might admire the ingenuity of the programmers, the machine itself cannot think, any more than a TV's thoughts are the programs it transmits.
Unfortunately for Behaviorism, this machine meets the definition of conversational ability - for its behavior matches that of a thinking thing, namely, Mr. Waldo. But the machine is not a thinking thing.
The great virtue of this example is that it does more than merely demonstrate the falsity of Behaviorism. It also yields a diagnosis of the deficiency with which Behaviorism is afflicted. The reason that the Unthinking Waldo Simulator is not a thinking thing is that the sort of internal processing that goes on in it is not of the sort necessary for understanding. This example therefore reminds us of the importance of internal processing. Behaviorism says that internal processing doesn't count. How you get from input to output is, according to Behaviorism, irrelevant to mental processing. But, as we can now see, the 'how' is not only relevant but essential to defining mental activity. Internal processing counts. Behaviorism suffers from pattern poverty precisely because it leaves internal processing out.
Note that only some sorts of internal processing will count as parts of mental processes. Patterns of inputs and outputs - even when they constitute perfect simulation - aren't enough to distinguish the mental sorts of internal processing from the non-mental sorts. We need additional conceptual resources to distinguish mental from non-mental processes.
And that is the central insight of Machine Functionalism, the computer model of the mind. Machine Functionalism tries to overcome the pattern poverty of Behaviorism by adding the third element of internal processing, and by saying exactly what conceptual resources we need to describe such processing.
Machine Functionalism
The official title of the computer model of the mind is "Machine Functionalism." It arises from the ashes of Dualism and Behaviorism, and may be seen as an attempt to steer a reasonable middle course between the extremes that they represent. Let's begin by incorporating the diagnosis of Behaviorism's failure that we ended with in the last section. Patterns of inputs and outputs are part of the story, but there's also what goes on in between. According to Machine Functionalism, to define any mental state or process, one must specify three elements:
(i) stimuli (inputs) that typically cause the mental state or process;
(ii) cause and effect relationships that the given mental state or process typically has to other mental states and processes ("functional role"); and
(iii) responses (outputs) that the mental state or process typically causes.
But that's not yet much of a theory. We need to find out why the view's name is apt.
"Functionalism" derives from the theory's use of functional definition. I'll introduce the basic idea with a simple, non-psychological example and then return to the theory's use of the idea.
It must be nice for you to be out of prison. After an almost entirely successful career as a safecracker, you've been 'rehabilitated' and decided to go straight. You want to make the best use of the skills you've got in making an honest living, and what you're best at is opening locked things. So you open a locksmithing business. You're very good at it, and soon have more work than you can handle, so you hire an apprentice, whom you teach so well that the two of you have more work than you can handle. After a third and fourth apprentice, you decide it would be more efficient to develop a training program for locksmiths (which could also be marketed to trade schools). The first step in developing the curriculum is, of course, to develop a good theory of locks and keys. We're all familiar with those oddly shaped pieces of metal - we carry them in our bags and pockets - that open various doors. But those aren't the only possible lock and key combinations. At the bank, there is a large vault room where the safe deposit boxes are secured. When the manager opens the vault door in the morning, you can bet she doesn't haul out a huge key to turn in the enormous lock; rather, she punches in a sequence of numbers on the electronic keypad built into the vault door, this activates a servomechanism, and motors cause the door to swing slowly open. The geometrical pattern at the back of your eye (the retina) is unique to you. At some high security installations, retinal scanning is used in place of metal keys. You step up to a laser-scanner, your eye is harmlessly scanned, and the pattern compared to the one stored in computer memory; if it's a match, you are admitted; if not, you're turned away (at best). We can conceive of chemical lock/key combinations: pour the right stuff into a little hole in the door, and a chemical reaction triggers opening. And there are other possibilities. Any theory of locks and keys must reflect this diversity of possible materials. The following definitions are a good start:
L is a lock =def L secures a portal for which there is a key.
K is a key =def K opens a lock that secures a portal.
Despite its simplicity, this pair of definitions illustrates two important features of even the most complex functional definitions. First, there is 'indifference to material': neither definition says, "one must make keys or locks out of just the following material;" instead, "lock" and "key" are functional notions - locks and keys are defined by what they do, not what they're made out of. Naturally, the definitions place some constraints on materials. A key made of butter or a lock made of ice won't do. Second, these functional definitions form a (here, tiny) system of interlocking concepts. Each concept's definition makes essential reference to the other concept. It's not possible to say what a key is unless one also says what a lock is; either you take the whole package, or you get nothing at all.
According to Machine Functionalism, a given mental state is defined by what is does as part of a system of mental states, and what it does is to stand in a complex web of cause and effect relations which it's the job of its functional definition to specify. When we talked about Cartesian Dualism's Postulate of Interactionism, we considered the example of the kind of pain you feel when you're stuck with a pin. How would Machine Functionalism define that same mental state? The three-part recipe would yield something like this:
p is pin-prick pain =def p is typically caused by pin-pricks; p typically causes desire for relief, belief that one is in pain, anxiety, ...; and p typically causes wincing, withdrawal, noise ("Ouch!") ....
The ellipses ("...") conceal a great deal here because pain bears many more relations to many other mental states and is expressed at the skin-level in many other ways. The full definition would take more words than in this whole book, or in most libraries since it really can't be given in isolation from the interlocking functional definitions of all the other implicated mental states. Given what we learned from the failure of Behaviorism, that's as it should be.
The word "typically" is doing its fair share of work, too. This kind of pain can occur in a pin-free environment, and can even result from nervous system malfunction, in the complete absence of sharp, pointy objects.
But why is it called "Machine Functionalism?" How does the computer model come into play in describing the complex web of relationships verbally specified in the functional definitions?
"The basic idea of cognitive science is that intelligent beings are semantic engines - in other words, automatic formal systems with interpretations under which they consistently make sense."
John Haugeland, "Semantic Engines: An Introduction to Mind Design" (31).
So sayeth Professor Haugeland. Our mission, should we choose to accept it, is to try to understand what he means. To see what he means, we have to understand what automatic formal systems are and what an interpretation of one is.
Automatic Formal Systems
We begin by characterizing the notion of a formal system. In order to define one, we must specify three things:
(1) what the tokens are
(2) what the starting position is
(3) what moves are allowed in any given position.
From this characterization it follows that any formal system will have three features: (i) it will be self-contained; (ii) it is perfectly definite; and (iii) it is finitely checkable. Let us say that any system with these three features is digital.
Notice how abstract this characterization is. No limitation whatever is placed on what we might call the system's "material realization". Any system that meets the particulars of a specification will be the same formal system, despite any differences in the materials and despite many possible differences in their arrangements. Formal systems are thus to some extent medium independent. They are, in essence, a kind of functional definition and so share indifference to material.
Some of the most familiar examples of formal systems are board games, like chess. Chess, we know, is usually played on a square board marked off in 64 squares, with 32 pieces, 16 of one color and 16 of another. The rules of chess specify a system of abstract relationships which we find it convenient to keep track of with chess sets. It is, however, the relationships that matter. Chess sets can be made out of any material that suits us, and some museums have large collections of chess sets fashioned from a wide variety of materials. We could even substitute live human beings for the pieces and use a building with (at least) 64 rooms as the playing field. That's not something I'd recommend, but the abstractness of the defining rules allows it. Chess, however, is a very complicated game. To get a better feel for the concept of interpreted formal system, let's look at some simpler examples.
(a) Suppose that there are two bathrooms on an airplane, located opposite one another at the head of the long central isle. There is a nearby display panel, for indicating occupancy. If at least one of the bathroom doors is unlocked, then the light indicating vacancy is on. If both are locked, "No vacancy" is illuminated.
(b) Suppose that the display breaks down - some passenger, furious at getting an olive rather than an onion in his drink, has smashed it. So a flight attendant rigs up a board with four squares in it. If a bathroom door is unlocked, he puts a check mark in the "Vacancy" square; if it is locked, he puts a check mark in the "No vacancy" square. If both "No Vacancy" squares are checked, you've got to wait a bit longer. If one of the other squares is checked, relief is moments away. Because of the way the board is positioned, it is hard for the passengers to see it, so the first flight attendant enlists the aid of a second, who runs up and down the aisles, waving a "No Vacancy" sign, or a "Vacancy" sign, depending upon what he sees on the board. (There are other ways the flight attendants might have done things to convey the same information.)
(c) Consider now a computer designer, Ms. A, who wishes to design a circuit to represent the logic of the mathematical use of the word "or". According to such usage, a statement of the form "p or q" is true if and only if at least one of the component statements is true (and not otherwise). She designs a circuit in which the absence of current flow represents falsehood. If both branches of the circuit are open - that is, if both p and q are false - then no current flows, and the whole statement is false. If one or both of the branches is closed, then current flows, and the whole statement is true. The circuit is a parallel circuit.
(d) Suppose on the other hand that computer designer Mr. B decides that the absence of current flow represents truth instead. If both p and q are true, the branches are both open, no current flows, and the statement is true. If one of p and q is false, then one of the branches is closed, current flows, and the whole statement is false. In this way, Mr. B's circuit represents the logic of the word "and": a statement of the form "p and q" is true if and only if both constituent statements are true (and false otherwise).
[tables omitted]
Let me introduce you to one of the dullest 'games' or formal systems you'll ever know. It's the *-game, and it has some very simple rules. Inputs and outputs are of two sorts, X and Y. Two inputs are required, and one output is the result. If both inputs are of sort X, then the output is of sort X; if the inputs are both or sort Y, or are mixed, then the output is of sort Y.
[table omitted]
The marvelous thing about the *-game is that, with the right interpretation, it's very useful. Let X mean NV and Y mean V, and we've got the much desired news about bathroom availability on board the airplane Let X mean false and Y mean true, and we compute the meaning of "or." With X interpreted as true, and Y as false, we compute the meaning of "and."
So despite their obvious differences in these four examples, they are all examples of the same formal system. The game has two tokens and two 'squares'. Of course, we give the squares and the tokens different names and meanings in each example, but that is irrelevant to their identity as formal systems. What makes them formal is precisely the fact that meaning is irrelevant.
When Machine Functionalism analyzes mental states, the number and types of basic components is far greater, and the relationships far more complex - so simple tabular displays are no longer useful or feasible. (It sometimes helps to think of networks of nerve cells.) But the basic idea remains the same. Every mental state can be modeled as some interpreted formal system.
MF is far richer in its resources than is Behaviorism. While Behaviorism is confined to inputs and outputs at the boundary between organism and world, MF allows one to look inside and to keep track of the internal processing. Thus MF adds a third element to the inputs and outputs of Behaviorism: it adds relations among internal mental states of the subject. Mr. Waldo and the Unintelligent Waldo Simulator have the same inputs and outputs (over a rather wide range, anyway), but the computations that occur internally are of very different sorts. The computations that occur in Mr. Waldo produce understanding, and the computations that occur in the Simulator do not. Or so MF would claim. MF thus seems to avoid the problem of pattern poverty: richer patterns are allowed, and we are told, precisely, of what sort the patterns may be. MF seems to make good on the computer model for the mind.
A Dangerous Analogy
Behaviorism was based on a 'black box' model of mental processes: we can treat everything inside the body as if it were in an unopenable black box, and concentrate on the patterns of inputs and outputs that the body might exhibit. MF replaces the one big black box with a series of smaller black boxes, wired together in complicated ways. When we seek to discern the nature of internal processing that MF says is essential to defining mental states and processes, we break the process down into simpler sub-processes, much as one analyses a computer program using a flowchart. And just as we define the boxes in a flowchart by specifying their inputs and outputs, MF tells us to define the sub-processes by their inputs and outputs. We can go all the way down to the level of nerve cells, if we wish. When we talks about nerve cells, though, we must treat them as little black boxes which give a particular kind of output for a specified input: they are functionally specified, as are the pieces in a chess game, as members of a complex formal system. Where ingenuity is required is in figuring out how to wire the little boxes together to produce intelligent mental processing. So, if we are careful not to confuse MF and Behaviorism, it might be helpful to think of MF as a kind of "Internal Behaviorism", which directs us to look not only at skin-level behavior, but also at the behavior of the stuff inside.
It is this similarity between the two views that worries many people. How much good does it really do to increase the number of 'black boxes'?
Two Objections to Machine Functionalism
First Objection: MF versus the Block Heads
Ned Block has given a famous objection to MF. He focuses on a particular sort of mental state: sensations, like pain or pleasure. Unlike, say, belief or knowledge, sensations have a characteristic feel. There is no particular way it feels to believe that 2+2=4, or to know that there is a book in front of you. But having a toothache produces a very definite, all too familiar sort of sensation, toothache pain, and its essential feature is that it hurts. In general, what makes a sensation the mental state that it is, is precisely the way that it feels.
Suppose that at some time in the not too distant future, psychologists have discovered enough about people to draw functionally accurate flowcharts for toothache pain. It is plausible to assume that 1 billion nerve cells are involved in producing that unpleasant sensation. Each of them has a certain array of inputs and outputs that contribute to toothache pain. MF says that all there is to toothache pain is the pattern of inputs and outputs involving the nerve cells wired together. The flowchart for toothache pain is therefore a certain formal system. This system, like any other such system, is capable of many different sorts of physical realizations. There is nothing in the nature of the system that says it must be built out of small, squishy organic parts. Any network of components that obeys the rules will suffice.
Drawing on these features of MF, Block asks us to perform a thought experiment. Imagine that we convince the government of China that it would greatly enhance its international prestige to participate in a great experiment in Cognitive Science. We equip each of the 1 billion or so individual members of the Chinese population with two-way radios, linked via satellite to Cognitive Science Central in Cambridge, MA. Each of them receives instructions about how to play the toothache pain game, each individual playing the role of an individual nerve cell. (It's a game with 1 billion pieces. To avoid costly litigation, we give them all anaesthetic, so that they won't feel anything if they trip and fall during the simulation.) And, for the period of an hour, the Chinese population obediently and flawlessly plays the toothache game, just as it is played by your nerve cells.
About such a situation, MF must say that the Chinese population, considered as a whole, suffers from toothache pain during this time. Just as the flight attendants could substitute for the electrical components in the airplane bathroom status display, the Chinese people can substitute for your nerve cells. But something can suffer toothache pain only if it hurts. So MF entails that during the hour of the simulation, China hurts. That, says Block is absurd. You cannot produce that sensation by such functional simulation. So MF is wrong. We can summarize as follows:
Block's Absent Quality Objection to MF
If MF is true, then China hurts if it runs your toothache pain program
China does not hurt if it runs your toothache pain program
Therefore, MF is not true.
There is a common misunderstanding of this objection that we must avoid. Block is not claiming that participation in the experiment would produce pain in the individual players (-remember that they're full of anaesthetic, anyway!). MF does not say that. Rather, it is the whole system - the group that is the entire Chinese population - that has the pain and hurts. MF does say that the system hurts. And that is what Block finds absurd. Pain (and other sensations), Block says, are partly a matter of functional role, but they also have an essential element of felt quality (sensation = functional role + felt quality), and this latter element is what MF leaves out. If Block is right, MF is bedevilled by pattern poverty, too: both external and internal behaviorism share a failing, if he is right.
MFs have often responded to this argument by claiming that since there is no more to mental activity than functional role, the roles imagined in this odd experiment do produce the sensation of pain. It sounds odd to say, "China hurts" because the whole situation is odd and unfamiliar; sometimes, however, the truth is odd. Some of the oddity can be dispelled by indulging in another science-fictional thought experiment, which I heard described in a talk by one of the best and funniest philosophers of science, Clark Glymour. We already have artificial substitutes for hearts, lungs, kidneys, joints and other organs or body parts. Some of these replacements don't work as well as the originals, but it's a matter of time before better designs are produced. While no neuroscientist would claim to know exactly how brain cells work, a great deal has been learned, and it is similarly a matter of time before we are able to produce artificial neurons; they'll be something like the microchips of today, though much smaller and perhaps more complex ("silicon patches"). What they will do is to replicate the patterns of signal processing in wet, squishy organic neurons; the patches will be functionally identical to biological brain cells, though made of different (perhaps more robust) material. I'd like you to imaginitively project yourself into the future era when such patches are commonplace; I'll bet that younger readers will live in this era. Suppose that after years of hard work, you are ready for a retirement full of the sports you never had time for, say, ping-pong. But your years of alcohol consumption have pickled the brain cells that control parts of your hands, and they no longer work as well as they once did for either pinging or ponging. Your neighborhood neurosurgeon offers you hope: "We can remove the pickled cells and patch in some functionally good-as-old silicon substitutes. It's a quick, virtually no-risk, office procedure done under local anaesthetic, and your health insurance will pay for it. It'd be no worse for you than having a cavity filled by your dental robot. I've done thousands of these procedures myself with no problems at all. You can call my patients to check up on me. Are we going ahead, or are you going to sit by the sidelines and watch enviously while others enjoy themselves at the table?" (When I've presented this thought experiment to people, only about fifty percent say they want to go ahead at first. Then, I reassure them about the safety of the procedure, and the percentage jumps over ninety percent.) Suppose that you have the work done and are once again able to win at ping-pong. Years pass and you pickle more cells, which you also have replaced. Finally, you're a silicon head: all of the old neurons have literally gone down the drain and you have functionally perfect artificial neurons instead. In some ways, you're better off: you used to have to worry about being hit in the head with your partner's paddle, but now, the paddle breaks. From the inside, so to speak, things have remained as always, since the input-output patterns and the pattern of intercellular connections have all been carefully preserved. If all that sounds right to you, then you are having strong machine functionalist intuitions because all that's been preserved are the relevant functional roles, and that seems to be enough.
So the debate may seem to end in a draw. There is another objection that may prove more serious.
An Objection to MF, On Purpose
Even if Block's objection were satisfactorily answered, there is another, even deeper objection that the MF faces. The objection centers on the question of interpretation.
Recall the example of the "and" and "or" circuits, and the Bathroom Availability Display. In a sense we made clear, all of these were physical realizations of the same formal system. But this is not to imply that there is no difference in meaning among "and", "or" and "bathroom available". It is just that these differences do not emerge until we say how the elements of the system are to be interpreted, or assigned meaning. If we let the absence of current mean false, then the circuit represents "or"; if the absence of current mean true, then the circuit represents "and". Without an interpretation, the formal system is, strictly speaking, a meaningless game. It would make no sense to ask about a circuit, "What does its output mean?" if the formal system it realizes had not been given an interpretation.
The same holds for MF in its attempt to give an account of mental processes. They are not just automatic formal systems. They are automatic formal systems with an interpretation. But now an important question arises: what is it about the internal and external behavior of a physical system that determines which interpretation is the correct one? Suppose that Mr. Waldo is doing a proof in a mathematics class and thinking a thought of the form "p or q". He is not thinking of "and" and he is not on his way to the bathroom. Pretend that there is a parallel circuit in his brain that executes the relevant operation. If it is to be that thought, and not "p and q" (or "bathroom status"), then there must be some way of nailing down the interpretation of the physical states of the circuit. But there pretty clearly is nothing about the circuit that decides the matter: just as it is, it could (and does, according to our definition of "physically realizes") equally well realize "p and q" or "bathroom status". Why isn't it doing all three simultaneously?
Such questions are familiar in computer science. And there, they have familiar and reasonable answers: it is relative to the purposes of the designers and the programmers, who decide what the circuits are to represent. One and the same sequence of circuit flip-flops might be used to make weather predictions on Monday, and on Tuesday to simulate battle logistics in WWII. It all depends on what purpose the programmer had.
What happens if we try the same tack with the thinking things that we are? The MF then says that "S believes that p or q" means that S's body (brain) executes the belief program relative to purpose P; or B(S,P). We introduce an extra parameter, as the mathematicians say, and relativize all mental state interpretations to the purpose(s) of the interpreter(s). Now serious trouble arises for MF. Among the mental processes that MF seeks to analyze is that of having a (particular) purpose. And the same problem we had with "or" thoughts arises with the mental activity of having a purpose. So the "P" in "B(S,P)" should be analyzed as P(S,P). But the interpretation of the second "P" also depends on a purpose parameter, so it should be written P(S,P); and so it goes, indefinitely. MF is caught in a trap: it needs the notion of purpose to do any interpreting, and so it needs a notion of purpose to interpret "having a purpose". But it can't interpret "having a purpose" unless it first has the notion of purpose. So it must fix an interpretation of "having a purpose" before it fixes an interpretation of "having a purpose". And the latter is impossible. So MF cannot fix any interpretations, if it needs the notion of purpose to do so. Although this objection may seem like a trick, it is not. It presents a very serious problem for MF.
An Argument against MF, on Purpose
If MF is true, then every mental activity is an interpreted formal system (IFS)
If every mental activity is an IFS, then having a purpose is an IFS (=P*)
Every IFS presupposes P*
No interpretation can presuppose itself
Therefore, MF is false
There are several responses to this argument that are worth considering, mainly because they help to show how deep the problem is.
As long as we confine our view to the inside of the head, so to speak, the objection spells doom for MF. So let's exand our view and look outside the head. Perhaps there's something about the relationship between the head and the wider world that will supply the missing purpose parameter.
Suppose that we say, on behalf of the MF, that it is God, our designer, who determines the interpretations of our brain function. We can call this Theological Functionalism. [As a matter of sociological fact, no proponent of MF is going to want to take this route, since MF is meant as a way of saving a materialistic view of the mind; bringing God in at this point will seem (at best) like a cheat to the proponent.] Anyway, it won't do any good. Presumably, one of God's mental activities is having purposes. If there is significant similarity between his purposiveness and ours, then MF will apply to his as well, and the problem arises all over again (only now we're dealing with an incorporeal being, and it's pretty obscure how the computer model is supposed to apply there). If, on the other hand, God's being in that mental state is entirely dissimilar from any mental state any human being could have, then we will have no idea how to understand such religious claims as "God purposefully designed the Universe". Such claims play an important role in many religions, and in attempting to persuade people to worship God. If making such claims strictly unintelligible is the price of Theological Functionalism, then no believer will want to endorse the view; and that leaves no one else to endorse it.
A second, more popular, response is Evolutionary Functionalism. In a metaphorical sense, human beings are 'designed by Nature': their behavior is shaped by the forces of biological evolution, and this in turn shapes our brain and somehow supplies the missing purpose parameter. Since these forces work on behavior, Evolutionary Functionalism is Behaviorism augmented by a distinction between adaptive and non-adaptive behavior. Given what a miserable failure Behaviorism was, we ought to be skeptical about Evolutionary Functionalism. Is it really plausible to insist that all distinctions in thought must be tied to this distinction? Much of what we value most in human life - advanced science, art, music, literature - seem to have no direct bearing on biological survival, and some of it arguably gets in the way.
One standard objection to this view is the "Swampman [better: Swamperson] Objection." Suppose that a molecule-for-molecule exact replica of you were to form accidentally out of "swamp gas." It seems that s/he would surely be in the same mental states as you were at the time of formation and would even believe, for example, that she was you. But Evolutionary Functionalism says that, lacking an evolutionary history, Swamperson has no mental states at all, a strongly counter-intuitive result, to say the least!
We need to see the details of Evolutionary Functionalism before finding it as much as plausible. For what it's worth, I've seen lots of details, and I don't think it works.
One response to the argument is to reject the first premise and MF with it. We might make an exception for purposiveness, and endorse a version of Purpose-Directed Functionalism instead. We would need to defend that move, but we have the materials for a defense at hand. In effect, our discussion of theories of thought serves as a kind of argument for Purpose-Directed Functionalism.
To be honest - the best policy - Purpose-Directed Functionalism is better described as a kind of Dualism. Dualism comes in two varieties: there's Substance Dualism, according to which mental activity requires a special, nonphysical substance; and there's what I call Conceptual Dualism, according to which there is at least one concept unique to psychology that's needed to state and explain the facts about certain complex physical systems, namely, the fact that they think. Purpose-Directed Functionalism is a brand of Conceptual Dualism. It shares with Cartesian Dualism the insight that physics won't suffice, but it rejects the reliance on soul-stuff.
Although I'm rather attracted to Purpose-Directed Functionalism, I do worry that it might be subject to a version of the Problem of Other Minds: how can I know about a particular physical system (say, my wife) that a basic notion of purpose applies to it - given that this notion cannot be analysed in terms of concepts from physics, chemistry or computer science, useful though their concepts remain? (My wife believes that I worry too much. At least, I think she does.)
These worries aside, our investigation of attempts to reduce biology and psychology to physics provide strong support for the claim that some sort of purpose-directed explanation is needed in each. If that's right, then our last, best separation principle, Separation by Explanation, fails.
The investigation in this book leaves us with no compelling reason to think that there is any fundamental difference between religion and science. We therefore find ourselves on a level playing field where it would make as much sense to criticize a proposal or practice as either pseudoreligious or pseudoscientific. So the next time someone offers you an explanation, no matter what the subject (e.g., "Here's why you should live your life in this way ...."), don't waste your time finding out whether it has a religious or scientific origin, because those labels carry virtually no valuable information. Instead, evaluate the explanation on its own merits, using the universal criteria that embody the highest standards of thought. Why settle for less?
(c)2000 David F. Austin
This page last updated on July 14, 2000