Minds=Brains

Minds=Brains

Before We Begin

Counseling and Psychological Services (CAPS):– caps.sa.ucsb.edu– counseling.ucsb.edu– (805) 893-4411

Announcements

• The paper due date is postponed until Friday June 6th.

• Attendance will not be taken at sections this week (though they will be held).

• Office hours will be held as usual this week.

• I will hold extra office hours after lecture on Friday.

Physicalism

The main problem for dualism was that it could not account for the interaction between immaterial and material objects.

Physicalism

Roughly, this was because minds and physical bodies were claimed to be so radically different that they could not interact.

Physicalism

This problem can be easily avoided by a view which claims that minds are physical things with physical properties.

Physicalism: Every mental event is a physical event.

Physicalism

Given the close association of our brains to our mental lives, it is natural to suppose that mental states and events just are states of our brains.

Brain Identity Theory

Brain identity theory claims that every mental state is identical to a physical state of some brain.

For instance:Pain=C-fibers firing.


According this claim is analogous to other sorts of scientific identity claims:

• Lightning=atmospheric electric discharge• Heat=mean molecular motion


Just as heat is nothing over and above mean molecular motion, pain is nothing over and above C-fibers firing.

Pain and the firing of C-fibers are one and the same thing.


In general, the claim that mental states are brain states seems to have an air of scientific respectability.• Avoids positing “spooky” talk of minds or souls.• Keeps everything firmly in the realm of the

physical.• Has the result that we can study minds by

studying the nature of brains.


“It seems to me that science is increasingly giving us a viewpoint whereby organisms are able to be seen as physico-chemical mechanisms: it seems that even the behavior of man himself will one day be explicable in mechanistic terms. There does seem to be, so far as science is concerned, nothing in the world but increasingly complex arrangements of physical constituents…


Except for one place: in consciousness. That is, for a full description of what is going on in a man, you would have to mention not only the physical processes in his tissue, glands, and nervous system, and so forth, but also his states of consciousness: his visual, auditory, and tactual sensations, his aches and pains…I just cannot believe that this can be so. That everything should be explicable in terms of physics, except the occurrence of sensations seems to me to be frankly unbelievable.” (Smart)

The Unity of Science

This may sound like a blind statement of faith (Smart acknowledges this) but think how weird the world would be if:• The laws of physics could successfully explain

everything except minds.• Biology could explain everything having to do

with life, except minds.• Some of the basic laws of the universe had to do

with ridiculously complicated things like minds.


Recall Dawkins’ assertions about complexity.

If minds cannot be reduced to simpler entities and explained scientifically, we would be left with an extraordinary unexplained level of complexity in the universe.


The brain identity theory is especially plausible if one endorses something like:

The Unity of Science: Every observable phenomena can ultimately be explained in terms of some set of fundamental physical laws.

Unity of SciencePhysics

Chemistry

Biology

Neuroscience

Psychology

Political Science

Economics

Medicinal Sciences

Material Sciences

Cosmology

Unity of Science

Adopting the brain identity theory gives us an easy way to fit the mind into this picture.

The nature of minds are to be explained by studying the neurophysiological, biological, and chemical nature of brains.


Brain Identity theory seems to have a lot going for it:• It can easily accommodate interactionism

(minds are brains, which are physical things)• It fits nicely into a scientific worldview.• It allows for the empirical study of minds.


Smart raises and answers a series of objections to this seemingly plausible proposal.

First Objection

An illiterate medieval peasant knew all about pain, but didn’t know anything about C-fibers. So pain is not identical to C-fibers firing.

First Objection

Response:• You could just as well say that heat is not

identical to mean molecular motion because peasants didn’t know anything about molecules!

• The brain identity theory does not say that the concepts of pain and C-fibers are the same.

• Just because someone has two different concepts for something doesn’t entail that it is two different things (e.g. Clark Kent/Superman)

First Objection

A related objection could try to point out that the meanings of our words “pain” and C-fibers” are different, but this makes the same sort of error.

Second Objection

1. The pain is in my arm.2. The C-fibers are firing in my head.3. Therefore, the pain is not identical to the

firing of the C-fibers. (by Leibniz’ law)

Second Objection

Response:• Strictly speaking, the damage is in you arm.

The pain is in your head.– Phantom pains in amputated limbs– Dream pains– Pain produced by exciting C-fibers in the brain

Second Objection

Consider an analogous case: my visual experience of the book on the table:

• I have an experience as of a book right there.• But no one would be inclined to say that my

visual experience itself is on the table.• Why not say the same thing about pain?

Third Objection

Pains and C-fiber firings don’t share other kinds of properties, for instance:

1. Pains can be sharp or dull.2. C-fiber firings cannot be sharp or dull.3. Therefore, pains are not identical to C-fiber

firings.

Third Objection

This seemingly begs the question. If brain identity theory is true, strange as it may sound to say:

• When my C-fibers are firing, it can feel sharp or dull to me.

Third Objection

The oddness of such claims is due to the fact that our concepts of pain and C-fibers differ, but we already shows that this does not bear against the brain identity theory.

Fourth Objection

• Pains, like all mental states are private (in some special way).

• C-fiber firings are not private in this way.– Anyone can detect them using MRIs and FMRIs.

• So pains are not identical to C-fiber firings.

Fourth Objection

Responses:• Before people had MRIs and FMRIs there

wasn’t any way to tell directly whether someone’s C-fibers were firing. Now we have this technology.

• But people don’t carry these things around with them, so whether or not you are in pain is still private in any practical sense.

Fourth Objection

More importantly, even if people did carry around such devices, they wouldn’t know about your pain in the same way.

So even according to brain identity theory, you can still have a special kind of access to your pain that others don’t.

More Serious Problems

Smart does a fair job of addressing a set of initial worries for the brain identity theory.

But there are serious problems on the horizon.

Announcements

Finish reading the Kim selection.

The due date on the paper has been postponed until next Friday.

Both Dillon and I are holding extra office hours today after lecture.

Savannah Okey see me now or after lecture.

More Serious Problems

Before proceeding, we need to get a bit clearer on the nature of the theory we are criticizing.

Tokens and Types

When Smart says that all mental states are brain states he could be referring to tokens of such states or types of such states.

Tokens and Types

How many letters are there in the following word:

Mississippi

There are two correct answers:1. 11 (11 letters of any kind)2. 4 (4 types of letter: “M”, “I”, “S”, “P”)

Tokens and Types

A token is a particular thing.

A type is a kind of thing.

Tokens vs. Types

Using this distinction we can distinguish two different physicalist claims:

1. Token Physicalism2. Type Physicalism

Token Physicalism

Token Physicalism: Every particular mental event is identical to some physical event or other.

Token Physicalism

Token physicalism is a very weak thesis.

For all it says, pain in one case could be C-fibers firing, but later on, pain could be D-fibers or some other neural event.

Type Physicalism

By making claims such as: “pain=C-fibers firing” brain identity theorists like Smart clearly mean something stronger than this.

What they want to say is that every instance of pain, is an instance of C-fiber firing.

Type Physicalism

So brain identity theory is a version of:

Type Physicalism: Every mental event type is identical to a physical event type.

Type Physicalism

This is a much stronger claim. To show that brain identity theory is false all we need are possible cases in which you have a pain but you lack C-fibers.

Objections to Brain Identity Theory

1. Modal objection2. Multiple realizability3. The problem of consciousness

Background on Possibility

When philosophers talk about modality they are usually talking about a domain of metaphysics having to do with possibility and necessity.


Possible World: A way the world might have been that settles every question of fact (for any claim p, either p or not-p is true).


p is necessary if and only if p is true in every possible world.

Necessary truths could not have been false no matter how the world might have been: e.g. 2+2=4.


p is possible if and only if, there is at least one possible world where p is true.

There is a way the world might have been such that p would have been true.


For example:So there is a possible world in which I wore a red shirt today.

There is no possible world in which I (Tim Butzer) was a rock.


As we have seen before (recall the Amnesia case) it turns out that identity claims (if true) are necessary.

So if A=B, there is no possible world where A and B are different things.


So if you can show that it is possible for A and B to be distinct, you have shown that they are not really the same thing.

This is just what Descartes tried to do with the conceivability argument!

The Modal Objection

The brain identity theory says that pain=C-fibers firing. So according to this theory, it is impossible to have pain without C-fibers firing and it is impossible to have C-fibers firing without pain.

The Modal Objection

David Chalmers introduced the case of zombies.

In this context, a zombie is something that is physically identical to me, but lacks conscious experience.

A zombie has C-fiber firing, but no pain.

The Modal Objection

If cases like this are possible then, the brain identity theory is false.

The Modal Objection(1) Zombies are possible.(2) If zombies are possible, then there is a world in which

there are C-fibers firing, but there is no pain.(3) If A can possibly exist without B existing, then A and B

are not identical.(4) Therefore, pain is not identical to C-fiber firing.

The Modal Objection

You can think of this as Descartes’ argument inverted:• Descartes argued that you could have the

mental state without the physical state.• Chalmers thinks you can have the physical

state (C-fibers firing) without the mental state (pain).

Conceivability and Possibility (Again)

It is certainly true that we can conceive of zombies.

But we know from objecting to Descartes that conceivability doesn’t entail possibility.


So a brain identity theorist could try to argue that zombies are conceivable but not possible.


The debate here gets complicated and controversial fast.

If zombies are possible, it seems we have a good objection to brain identity theory.

But it is highly controversial whether or not zombies are possible.


In short, many people take such arguments to be falling into the same trap as Descartes fell into.

But if you think that a zombie case is possible, this might be a reason for you to reject brain identity theory.

Multiple Realizability

Recall that brain identity theory is a version of type physicalism.

That is, the theory claims that every mental event type is identical to a brain event type.


The objection from the multiple realizability of the mental argues: • That there is no single brain or physical state

type that corresponds, without exception to pain.

• So any version of type physicalism is false, including brain identity theory.

Octopi and Aliens

“But (brain identity theory) implies that unless an organism has C-fibers, it cannot have pain. But aren’t there pain-capable organisms, like reptiles and mollusks, with nervous systems very different from the human nervous system? Perhaps in these species the neurons…are not like human C-fibers at all.” (208)

Octopi and Aliens

An octopus nervous system is very different from our own.

It is much more decentralized. They have a brain, but they also have complex information-processing nerve clusters in all of their arms.

Octopi and Aliens

Octopi can clearly feel pain.

But it is unlikely that they have any C-fibers in their radically different nervous systems.

Octopi and Aliens

Looking around the animal kingdom it seems that we share many mental state types with many different animals.• Fear• Physical attraction• Hunger• Stress• Perceptual experiences (seeing green etc.)

Octopi and Aliens

Some more intelligent animals will also have mental states such as:

• Beliefs• Desires• Memories

For Wednesday

Read Nagel’s “What is it Like to be a Bat.”

Start reading Turing’s “Computing Machinery and Intelligence” (online)

Savannah Okey see me now or after lecture.

Octopi and Aliens

According to brain identity theory, if two creatures share a mental state type such as fear or pain, their brains must be identical in that regard.

Octopi and Aliens

But we have no reason to suspect that this is true, and it seems highly improbable that it will turn out to be right for every mental state type across every organism.

Octopi and Aliens

Even worse: consider possible alien creatures that we have not yet discovered.

If we ever find other forms of life not native to earth it is likely that they will be capable of feeling pain.

Octopi and Aliens

The brain identity theory is committed to the implausible claim that every single creature that we ever find that feels pain will also have C-fibers.

Octopi and Aliens

Still worse:• We are carbon-based life-forms. • Silicon is structurally very similar to carbon.• It is generally acknowledged to be possible for

life to be silicon based.• But C-fibers are (partially) composed of carbon.• Therefore any silicon based life-form will not

have C-fibers

Octopi and Androids

The brain identity theory is committed to saying that any such life-form is incapable of feeling pain.

What an amazing claim to make from the armchair!


What all of this seems to show is that mental states like pain are multiply realizable.

That is, they can be realized by many different physical/brain structures.


“If pain is identical with a physical state, it must be identical with some particular physical state, but there is no single neural correlate or substrate of pain. On the contrary, there are indefinitely many physical states that can “realize” pain in all sorts of pain-capable organisms and systems. So pain, as a type of mental state, cannot be identified with a neural state type or with any other physical state type.” (208)


The multiple realizability of mental states entails that no type physicalist theory of the mental can be correct.


But what about token physicalism?

Can it still be true that each mental state is identical to some physical state or other?

Multiple realizability does not say anything about this possibility.

Are Minds Computers?

Consider a computer program like Microsoft Word.

Word can be run on many different kinds of computers.


These computers can vary widely in their physical structure: they have different processors, different kinds of memory, can be made of different materials and so on.


Actually, you can build a computer out of any kind of material:• The first computers made use of vacuum

tubes, gears, tape, and so on.• Now they are made of silicon and other highly

manuctured parts.• You could even build a computer out of

toothpicks or Legos!


In short computers, and computer programs are multiply realizable. You can run the same program on machines that have very different physical structures.


In other words, you can’t get at the nature of a computer program just by looking at the particular physical structure that realizes it.

The actual physical constitution of the computer is (in some sense) irrelevant.


What matters at a certain fundamental level is a certain functional relationship between an input, other internal states of the machine, and the outputs of the machine.

Brief Remarks on Functionalism

But of course, every computer is a physical thing and every time a computer program runs there is a certain series of physical states that realize the program.

Brief Remarks on Functionalism

It is a very rich research project both in the philosophy of mind and cognitive science to understand the mind as something similar to a computer in this regard.


If we can develop a theory along these lines, we can respect:• The multiple realizability of mental states• The claim that minds are physical things.

Documents

Minds=Brains