Philosophy

6

LECTURE: More on the identity theory

Types versus tokens

The mind just is the brain. Mind and brain are one and the same thing. Mind = brain. Pretty simple idea, right?

Not so much, as it turns out. There are at least two different ways one could spell out the mind/brain identity theory. To understand them requires understanding what philosophers call the type-token distinction. Consider the sentence:

The cat is on the mat.

How many words are in this sentence? It depends on how you count them. You could say that there are, in one sense, six words: “the,” “cat,” “is,” “on,” “the,” and “mat.” But you might also say that, in another sense, there are only five: “the,” “cat,” “is,” “on,” and “mat.” In this case, we don’t count “the” twice because it is the same one word that simply occurs in two places in the sentence.

We can describe the difference in terms of the difference between a type or general category of thing, and a token or specific individual example of that general type of thing. When we count five words, we are counting word types. There are five word types or categories, one of which is repeated. When we count six words, we are counting word tokens. There are six tokens or individual instances of the various words. And there are two tokens of the word type “the.”

An 80s band. How many words are in their name?

Now, we can draw the same distinction where mental states are concerned. For example, consider the mental state of believing that it is raining. There is the specific individual token instance of Lucy believing that it is raining, on some Thursday morning in February; the specific individual token instance of Ricky believing that it is raining, on some Monday evening in March; and so on. Then there is the general type of mental state of believing that it is raining, which Lucy, Ricky, and countless other people have all been in at some point or other. And we can draw a similar distinction for every other possible kind of mental state (believing that it is sunny, fearing that the stock market will crash, having a headache, and so on).

We can draw a similar distinction where brain states are concerned. Take the brain state of having heightened activity in the hippocampus. There is the individual token instance of Fred’s having heightened activity in the hippocampus, the individual token instance of Ethel’s having heightened activity in the hippocampus, and so on. And then there is having heightened activity in the hippocampus as a general type of brain state that Fred, Ethel, and countless other people might have in common.

Type identity theory

Suppose we gave labels to each possible general type or kind of mental state, as follows:

M1 = believing that it is raining

M2 = believing that it is sunny

M3 = fearing that the stock market will crash

M4 = having a headache

etc.

The list would be absolutely gigantic. But suppose we could do it. Suppose also that we gave a label to each possible general type or kind of brain state – every possible general type of firing pattern in the neurons, every possible general type of chemical secretion, etc., in every different part of the brain. We could label them: B1, B2, B3, B4, etc. This list too would be absolutely gigantic. But suppose we could do it. This gives us a way of stating two possible versions of the identity theory. The first would be:

Type identity theory: holds that every kind or type of mental state or process can be identified with some kind or type of brain state or process

The idea here is that, once we identify and label each possible type of mental state and each possible type of brain state, we should, at least in theory, be able to match them up in a strict one-to-one way. For example, we should be able to determine that there is an exact, law-like correlation between M2 and B14, i.e. between believing that it is sunny and having such-and-such a particular kind of firing pattern in the neurons.

This is a very ambitious version of the identity theory. It entails a connection between types of mental state and types of brain state that is as tight as the connection between, say, water and H2O. Every time you have water, you have H2O, and vice versa; and every time people are in mental state type M2, they are in brain state type B14, and vice versa. The implication is that, at least in theory, we should be able to read off people’s thoughts from what is going on in their brains. If someone exhibits brain state type B14, then we could know that he or she must be in mental state type M2.

“Marty, I’m going to read your thoughts!”

Token identity theory

Token identity theory says that this is too ambitious. For it turns out that there is not, in fact, a one-to-one matchup between mental state types and brain state types. The connection is not in fact as tight as the connection between water and H2O.

A better analogy would be the relationship between having twenty dollars and having paper money. Sometimes when you have $20, it’s because you have a twenty dollar bill; sometimes it’s because you have four five dollar bills; sometimes you have $20 in coins; sometimes you have no currency at all, but have $20 in the bank (recorded electronically); and so on. Going from the other direction, sometimes a certain piece of paper with a certain kind of printing on it counts as genuinely having twenty dollars, but sometimes it does not, because it is counterfeit.

So, there is no exact or one-to-one matchup between having twenty dollars, and having some particular kind of currency. The connection is much looser. Still, having twenty dollars will always involve some kind of physical state, whether having paper currency, or coins, or even just a bank record stored electronically.

Now, mental states and brain states are, according to the token identity theory, like this. There is no strict, law-like matchup between types of mental states and types of brain states. Maybe M2 is sometimes associated with B14, but maybe at other times it is associated instead with B5 or B128. Maybe B14 is sometimes associated with M2, but maybe sometimes instead with M1 or M433. A token mental state will always be associated with some token brain state or other, but not in a law-like or completely predictable way.

Token identity theory: holds only that any particular instance or token of a mental state type is identical to some particular physical state or other

One implication of this is that, on token identity theory, it is not possible even in theory to read off a person’s thoughts from what is going on in his or her brain, at least not in any great detail. The connection between various types of mental states and brain states is too loose for that.

“It means this thing doesn’t work!”

Token identity theory is also called anomalous monism. It’s a kind of “monism” (as opposed to dualism) because it says there is only one kind of stuff, namely matter. But it is “anomalous” (in the sense of “not regular or law-like”) because it denies that there is a regular, law-like, exact connection between types of mental state and types of brain state.

Smart’s defense of the identity theory

The sorts of considerations that led materialists to move from type identity theory to token identity theory ultimately led them to give up the identity theory altogether in favor of functionalism, which has long been the most popular version of materialism. We’ll look at it next week. But to understand the transition, it will be useful to consider some of the views of the materialist philosopher J. J. C. Smart (1920-2012). (Great last name for a philosopher!)

“I’m Smart. So I must be right!”

Smart’s article “Sensations and Brain Processes” defends the identity theory against objections that claim that the theory cannot explain what we have called the qualia associated with bodily sensations and other conscious experiences. Smart uses the term “phenomenal properties” rather than qualia, but it’s the same idea. Qualia or phenomenal properties are the subjective aspects of a conscious experience that seem to be knowable only “from the inside,” as it were. I’ve given the feel of pain as an example.

Smart focuses instead on the example of a yellowish-orange afterimage – the kind you might experience if, say, someone flashes a camera bulb in your face. You might rub your eyes and be unable for a moment to get rid of the appearance of the afterimage. But if people looked inside your eyes or your brain, they wouldn’t see some yellowish-orange image floating around. So, it’s a good example of what is meant by a quale (“qualia” being the plural of “quale”). The yellowish-orange character of the afterimage seems directly knowable only to you, from inside your consciousness.

“Smile! C’mon, show us those qualia!”

Now, Smart considers the objection that, precisely for that reason, experiencing such an afterimage cannot be identical with some process going on in your brain. For if it were identical to that, then shouldn’t anyone be able to see the afterimage, just by looking at your brain? Shouldn’t something in your brain have the yellowish-orange color that the afterimage does?

Topic-neutral analysis

Smart’s response is to say that the way to answer this objection is to give what he calls a “topic-neutral” analysis of what it is to have a certain mental state, such as the experience of an afterimage. To understand what a topic-neutral analysis is, suppose you are startled by a bang on the window. Someone comes in the room, sees you looking nervous, and asks what’s wrong. You say: “Whatever banged on the window startled me.”

Now, what was it that banged on the window? It could have been a person knocking on the window, or a falling tree branch, or a bird flying into the window, or something else. Your expression “whatever banged on the window” does not say which, and you may not know which. But you can still talk about it by using such a phrase. The phrase is a topic-neutral description – a description that is neutral about exactly what the thing is that we’re talking about (the topic of our discussion).

Now, Smart claims that if we properly understand descriptions of various mental states, we will see that these descriptions too are topic-neutral. For example, to say “I am in pain” means something like “There is something going on in me that is the kind of thing that is typically caused by damage to the body, typically causes behavior like screaming and flinching, and so forth.”

What exactly is that “something” that is going on in me? The description doesn’t tell us. It could in theory be something going on in a non-physical res cogitans. But it could instead just be neurons firing in the brain. The description is neutral between these dualist and materialist interpretations.

And the same thing is true of a statement like “I’ve got a yellowish-orange afterimage.” All that statement really means, according to Smart, is something like “There is something going on in me now that is the kind of thing typically caused by light flashing in the eyes, produces behavior like rubbing the eyes, and so on.” And that is an entirely topic-neutral description. It makes no reference to any features (like a certain color) that brain events don’t have but which a res cogitans might have. It is neutral between a dualist reading and a materialist reading, so that the “something” in question could just be neurons firing. And so, Smart claims, properly understood, examples like afterimages don’t really pose a problem for the identity theory.

Stuck in neutral.

Well, that’s all pretty abstract and perhaps so dry that you might wonder what the fuss is about. But there are at least two crucial issues here. The first is that whether Smart is right about this is a crucial part of the question of whether materialism really can explain qualia and consciousness. We’ll come back to that in a couple of weeks.

The second is that Smart’s type of analysis led to functionalism, and through functionalism to the currently extremely popular idea that the mind is really a kind of program or software and the brain a kind of computer that runs the software. We’ll see how beginning next time. In the meantime, here are some optional YouTube videos going into greater depth on some of the topics we’ve been discussing:

Philosophy of Mind: Identity Theory:

https://www.youtube.com/watch?v=VIzsZmAV4yk

Reading Smart: Sensations and Brain Processes, Part 1:

https://www.youtube.com/watch?v=m6TltHbD12I

Reading Smart: Sensations and Brain Processes, Part 2:

https://www.youtube.com/watch?v=EKHfcWbwoX8