TheMindBodyProblem

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The mind-body problem is the problem of determining the relationship between the human body and its mind. Are our minds something different from our physical bodies? Suppose we think that the mind is a substance of some sort--a MentalSubstance?. We might still ask: Is there some way to explain what the mind, a mental substance, is, in terms of physical substance? Or will we maintain that the mind is something totally different from physical bodies, and that we cannot explain what the one is in terms of the other at all?

Suppose instead that we deny that the mind is some mysterious substance, and we hold instead that there are only MentalEvents and that "the mind" designates no more than a series of mental events? We can still inquire about the relation between mind and body a different way, in terms of the relation between MentalEvents and PhysicalEvents. We can ask: Are mental events totally different from physical events, so that you can’t explain what mental events are in terms of physical events; or are mental events somehow explainable as being the same as physical events? For example, when John feels a pain, a mental event is occurring; now is that pain even possibly the same as something that occurs in John's brain, such as the firing of some special group of NeuroNs? Now this question we will examine.

The mind-body problem can be introduced more fully with an example. Suppose John decides to walk across the room, whereupon he does in fact walk across the room. John's decision is a MentalEvent and his walking across the room is a PhysicalEvent. On anyone’s accounting, there is another physical event involved, namely, something happens in John's brain, which tells John's legs to start walking. This BrainEvent is closely connected with John's decision; the brain event happens at about the same time, or right after, John decides to walk across the room. We might ask: How is it possible that a decision, which is something mental, resulted in something in your brain, which is something physical? If we say that the mental and the physical are totally different sorts of things, then how can one have any causal impact on the other? How can a mere mental event, a decision, actually cause neurons in my brain to start firing? The very idea might seem absurd.

On one view (see PhilosophicalView), a better description of the situation is this: John's decision is itself a physical event. When John decides to take my trip across the room, a group of NeuroNs fire in his brain. He is not aware of those neurons; but the firing of those neurons is itself just the same as his decision. There isn’t any more to the decision than that physical event. So, on the view in question, there’s no trouble thinking about how a mental event can have a physical effect; mental events are themselves physical. Ultimately, everything is physical.

To many people it sounds really strange to say that a mental process is no more than a special kind of physical process. The mind, they say, is more spiritual, ethereal, and so it simply is not the sort of thing that can be physical. And they have other reasons as well for rejecting this reduction of the mental to the physical.

So in fact what some philosophers have believed instead--but hardly anyone anymore--is that the ReducTion goes the other way. We should explain what bodies are in terms of mental goings-on; so the physical can be reduced to the mental. When John walked across the room, really that was happening only in John's mind and perhaps also in each of our minds individually at the same time. There is, on this view, nothing more to John's walking across the room than our having the thought, or the perception, that that happens. This view would also solve the problem of how the mental can affect the physical. Since physical events are themselves nothing more than a special kind of mental event, then of course there is no trouble about how a decision, which is obviously a mental event, can result in our bodies moving, which is also a mental event, although less obviously so.

The three above-described views about the relationship between the mental and the physical have names:

DualIsm is the view that mental events and physical events are totally different kinds of events.

PhysicalIsm, or materialism, is the view that mental events are nothing more than a special kind of physical event.

PhenomenalIsm?, or subjective idealism, is the view that physical events are nothing more than a special kind of mental event.

The mind-body problem, to put it as generically and broadly as possible, is this question: What is the basic relationship between the mental and the physical? For the sake of simplicity, we can state the problem in terms of mental and physical events. I could put it just as well in terms of processes, or of consciousness. So the problem restated is: What is the basic relationship between mental events and physical events?

There are, then, three basic choices: mental and physical events are totally different, and cannot be reduced to each other (which is DualIsm); mental events are to be reduced to physical events (which is PhysicalIsm); and physical events are to be reduced to mental events (which is PhenomenalIsm?). To put it in terms of what exists "ultimately," we could say that according to dualism, both mental and physical events exist ultimately; according to physicalism, only physical events exist ultimately; and according to phenomenalism, only mental events exist ultimately. Physicalism and phenomenalism are both varieties of MonIsm; of monism there is one further variety, namely NeutralMonism.

If you are thinking that this is far too many possible positions to consider, just wait -- it gets worse -- because within each category there are further refinements to be made. So we’re going to have to spend the rest of the day trying to come to grips with the refinements and the basic objections that can be made to these different theories. But we are going to focus almost all of our energies on just two theories, namely, dualistic interactionism, and type physicalism.

See also DualIsm and PhysicalIsm.

C. Other theories of mind.

We concluded last time on an upbeat note for physicalism. I had given you some ways that the physicalist could reply to the dualist’s objections; in so doing, I tried to make it plain how some people can hold what, on first glance at least, looks like an absurd claim, that mental events are simply a type of physical event -- brain or neural events. Now I should note that this is just one kind of physicalism; we may call it neural type physicalism, because it says that mental event types are types of nervous system events. It is more commonly called "the type-type identity theory."

I’m going to present an objection to neural type physicalism. But first I’m going to present another kind of physicalism; I’m going to discuss it very quickly, because mainly I want to use it to make quite clear how neural type physicalism is only one kind of physicalism. In the middle of this century, it was very fashionable to try to reduce mental events to behavior. This view is called analytical behaviorism, because the idea is that we can ultimately analyze, or reduce, talk of mental events and processes in terms of things that humans say, express, and do. In other words, analytical behaviorism says that what a mental event is, is a propensity, a tendency, to display a certain set of behaviors -- words, facial expressions, bodily postures, and actions. If you want to see whether someone believes that God exists, you look at what he says, how he reacts when you say "God exists," whether he goes to church, and so on. And his belief is constituted by those behaviors; in other words, there isn’t any more to his belief that God exists than those behaviors. Or to take another example, the good old example of pain. Analytical behaviorism would say that pain is nothing more than the tendency to wince, to grimace, to pull back quickly from the source of something causing bodily damage, to say "ouch" and "that hurts," and similar behaviors. That’s all there is to pain!

Well, I’m not going to discuss the merits of analytical behaviorism. Hardly anyone believes it anymore. Good riddance, I say. But this theory is an example of another kind of physicalism. Why? Because it does say that mental events are reducible to physical events; behaviors are physical events, and behaviorism says that mental events are reducible to behaviors. So how does behaviorism different from the sort of physicalism I was talking about last time, neural type physicalism? Well, it’s a different type of physical event that mental events are being reduced to. On the one hand, neural type physicalism says that mental events can be reduced to types of neural or brain events. On the other hand, analytical behaviorism says that mental events can be reduced to types of behavioral events. So basically here’s a question we might ask: If types of mental event can be reduced to types of physical event, then which types of physical event? Neural type physicalism gives one answer; analytical behaviorism gives a different answer.

This leads me, finally, to that objection to neural type physicalism that I said I was going to give. The objection is this: we have construed the types too narrowly. Maybe there are types of physical events that mental events might be reducible to, that are nothing like neural states. I’d better give you an example if you’re to see what I’m talking about. Suppose after some years, superscientists were to build a robot that was given sensory receptors, could talk intelligently on a wide variety of subjects, could carry out a variety of difficult tasks, and even had what appeared to be emotional reactions to its surroundings -- and so forth. In short, somehow, scientists had created what appeared to be a conscious, intelligent machine. Now, there is considerable debate over whether such a machine is possible -- whether it is possible to, as it were, build a mind from scratch. But just assume, for the sake of argument, that such a machine is possible, and that it does have thoughts, perceptions, feelings, and so on. So then mental events are occurring in this machine.

Now let’s say our superscientists did not use anything much like the human nervous system to build this robot. They used some sort of special circuitry -- very high-tech microchips and whatnot. In that case, it is not any type of neural or brain event to which we would reduce the robot’s mental events. It would be a -- what should we call it? -- a circuitry event! And then in that case mental events could be reducible not just to neural events, but also to circuitry events. So here then is the objection to neural type physicalism: the types we’re reducing mental events to is too narrow. To include the mental events of high-tech conscious robots, we should describe the physical events in some way that would include both neural events and circuitry events. Not just neural events.

Or suppose that there is intelligent life elsewhere in the universe. So there might be some alien species that does not have anything quite like our brain or nervous system. Say this species is intelligent, and conscious, and has a mind, but its mental events are identical to a different type of physical event; instead of neurons, they have schmeurons, say. Well then, if we want to be physicalists, then we should allow that mental events can be reduced to neural events, or circuitry events, or to schmeural events! As you can see, the list might go on.

In any case, I think that this neatly refutes neural type physicalism. Neural type physicalists are biased in favor of the physical types that the human species has. So philosophers of mind, trying to be clever, have named this bias species chauvinism. That means that neural type physicalists are irrationally disposed in favor of their own species, when it comes to describing the physical types that mental events reduce to, or are identical to.

Suppose after all this, I still think that dualism is wrong, and I admit that neural type physicalism is wrong; but I still think that some kind of physicalism is still basically right. I think that everything basically has to reduce to the physical; only the physical exists ultimately. So then what are my options? Is there a way for me to hold onto physicalism, so I can get around the species chauvinism accusation? Well, there are basically two ways. The first way is find an even broader type of event, which describes all the different specific physical event types that different species, or robots, might have. This is called functionalism. The second way is to deny that we are reducing mental event types, and talk instead of reducing mental event tokens. This I will call token physicalism. I’m not going to talk about either theory in much depth, because I’ll tell the truth -- by now we have gotten quite far away from any issues that were talked about throughout most of the history of philosophy. All of these issues about the different kinds of physicalism have arisen in the last fifty or sixty years or so.

So first I will briefly explain functionalism. Functionalism asks: what do neural events, and circuitry events, and schmeural events all have in common? The answer: it can’t be any particular type of physical hardware that they have in common. It’s not neurons, microchips, or schmeurons. So what do they have in common? What they have in common is that they are all structurally similar, or functionally similar. What do I mean by that? Well, to similar sorts of inputs, each of these physical types gives a similar sort of output. Let me give a simple example. The human, the robot, and the alien are all going to feel pain when you damage their bodies; and they are all going to have roughly similar reactions, such as announcing that they’re in pain, avoiding the source of the damage, and perhaps striking back or getting angry.

So here is a simple definition of "functionalism":

Functionalism is the view that mental events are the same as functional states; and a functional state is a state a physical system is in, when it has a set of sensory and other inputs, together with a set of potential behavioral outputs.

So say I’m thinking about bananas. That mental event is, according to functionalism, a functional state; and that just means a state described by various inputs and outputs. For example, an input would be that someone has said the word "bananas" to me and off I go thinking about bananas; and then a potential output would be to go get a banana and eat it. So my mental event, thinking about bananas, is just a functional state, and the functional state is specified by the inputs of the event and the outputs of the event.

Well of course there is a lot we could say about functionalism. For one thing, if all we have at our disposal, to describe mental events, is their inputs and outputs, then have we really described the mental event itself adequately? It would be a little like saying that an oak tree could be adequately described like this: "Oak trees result from acorns (that’s the oak tree input) and they are cut up to make tables (that’s the oak tree output)." Yeah, but (you might ask) what is an oak tree itself? You might ask a similar thing of functionalists. "OK, so mental events have certain inputs and outputs; I can accept that; but what is a mental event itself?" Unfortunately, we don’t have time to go into it. But for what it is worth, functionalism is probably the most popular theory of mind today. So obviously a lot more can be said about it.

I said there is a second way to get around the species chauvinism objection. This can be called token physicalism. More commonly called "the token-token identity theory." Whatever you want to call it, I’ll define as follows:

Token physicalism is the view that tokens of mental events may be reduced to tokens of physical events.

The idea here is that we are giving up trying to give general accounts of mental event types. So for example we won’t try to reduce the whole category of pleasure, or the whole category of pain, to any single mental event type. We’ll focus in on individual, single, pleasures and pains. And we say, of those mental event tokens, that each one is identical to, and reducible to, some physical event token. In our case, we might say that an individual pain is the same as an individual instance of my C-fibers firing. But we might say something quite different about the pain of an alien from Alpha Centauri. The point in either case, though, is that it’s tokens of mental events that are reduced to tokens of physical events.

I’m just going to give one little objection to this theory. Namely, what does the following phrase mean? -- "Token of a mental event." Token physicalism can’t tell us. I mean, suppose a scientist had reduced a slew of mental event tokens to physical event tokens. So I’d say, "Great work! But just what do all of those mental event tokens have in common, that makes us say that they are tokens of mental events, as opposed to any other kind of event?" What distinguishes the mental event tokens from tokens of other kinds of events? That’s the question: What distinguishes mental event tokens? Dualism, remember, says that the mental is an ultimate, fundamental category of being; it can’t be explained in terms of anything nonmental. So dualism doesn’t have to answer this question. And neural type physicalism at least promises to answer the question; it says that we will discover just exactly what all the different mental events have in common, which makes them all mental events; and it’s going to be some special type of event in the brain.

But token physicalism can’t answer this question; it can’t tell us what mental event tokens have in common; and why not? Because if any theory tells us what mental event tokens have in common, then the theory is describing mental event types. Just think: that is precisely what mental event tokens have in common: they are all tokens of mental event types. What do human pain and alien pain in common? They are both tokens of the type, pain. So, if we describe what all mental event tokens have in common, then we have for that very reason described a mental event type! And then the token physicalist would have to talk about mental event types; and that means we’ve basically given up token physicalism. Well, that’s the only thing I’m going to say about token physicalism. My usual disclaimers apply.

In the interests of mercy, let me say that I’m not trying to make you believe that we can’t know which theory of mind is correct -- I don’t want you to leave class being skeptics about philosophical questions about the mind. Generally, in the interests of objectivity and general intellectual responsibility, I feel it is my duty to tell you about most of the leading philosophical theories of the different subjects we’re studying, and some arguments for and against them. So, the mere fact that I’m not telling you that one theory is The Truth doesn’t mean that I have no views about what The Truth is. In fact, I do think that one particular theory of mind is better than the others -- I’m just not telling what it is! And the mere fact that I’m presenting objections to all of the theories I’ve stated doesn’t mean that I think we can’t know which one is correct, or that they are all false; all I’m trying to do is to introduce you to the issues. Philosophical issues are more complicated than you might have thought when you came into this class. So if you want to have really well-informed views on these issues, it’s just the same as having really well-informed views on issues in chemistry, or in political science, or in computer programming. It’s going to take research and long hard thinking.