Objections to dualism
1) Intuitive appeal to consistency: why should the
world inside our heads be different from everything
outside our heads?
2) Interaction problem
3) No evidence
4) Ockham’s razor
–
–
In explanations, entities should not be multiplied
unnecessarily
i.e. the simplest explanation is generally to be preferred.
5) Lack of explanatory power
Idealism
Bishop George Berkeley (1685-1753)
Everything is mind.
• Advantages: solves the interaction problem and solves the
problem of mere physical things having consciousness,
intelligence, etc.
• Disadvantages: lack of explanatory resources. All explanations
appeal to God. Why do things seem physical? Why do things
persist? Why do things appear to be explicable through
physical laws and reducible to simpler physical objects and
forces? Because that’s the way God imagines it.
Physicalism
Definitions of physicalism
Physicalism: the belief that the only kinds of things are
physical things and the only kinds of properties are
physical properties
Physicalism is the belief that everything in the universe can
be explained in terms of physics (thus, there is no
mysterious non-physical stuff that does not follow
physical laws)
All mental phenomena can be explained in terms of nonmental phenomena
Physicalism with regard to the mind
The mind is a biological machine (maybe like a
computer).
If we understand how the mind works physically, we
can understand thoughts, feelings, consciousness
A computer or robot could theoretically
have a mental life (i.e. consciousness)
The Hard Problem
of Consciousness
Easy and hard problems of consciousness
Distinction proposed by David Chalmers
The easy problems:
• finding the neural correlate of consciousness
• explaining the ability to apply information to thinking and
behavior
• explaining the ability to focus attention, recall items from
memory, integrate perceptions, etc.
The hard problem:
Why does consciousness feel the way it does? Why does it feel
like anything?
Why the problem is hard
“You can look into your mind until you
burst, and you will not discover neurons
and synapses and all the rest; and you
can stare at someone’s brain from dawn
till dusk and you will not perceive the
consciousness that is so apparent to the
person whose brain you are so rudely
eye-balling.“ (McGinn 1999)
“The problem of consciousness, simply put, is that we cannot
understand how a brain, qua gray, granular lump of biological
matter, could be the seat of human consciousness, the source or
ground of our rich and varied phenomenological lives. How could
that ‘lump’ be conscious – or, conversely, how could I, as conscious
being, be that lump?” (Akins 1993
What is it like to be a bat?
Thomas Nagel
One of the most famous
papers in all of philosophy!
(1974)
We can never know what it feels like to be a bat.
Why a bat?
There is something
it is like to be a bat.
Compare:
Cloud, rock, tree – nothing it is to be like
Mosquito, frog, computer – who knows? People have
different intuitions.
Bats are mammals. Most people agree they have experiences –
they are conscious.
But, their consciousness is alien to us:
They “see” by sonar.
They fly and hang upside-down.
They lust for other bats.
We might be able to imagine what it would be like for us to live
and behave like a bat.
But we can’t imagine what it is like for a bat to be a bat.
Problem of privacy?
Nagel: not a problem of privacy
e.g. “no one can catch my catches”
It’s not that we cannot experience bat token
experiences, e.g. Billy the bat’s sonar qualia.
Bat qualia are mental types that other subjects could
also experience. But we cannot learn what these
types are like objectively.
Bat’s experience is subjective.
Consciousness = having a point of view
Scientific knowledge is objective.
“The view from nowhere.”
Example: lightning
– subjective: looks like a flash of light
– objective: electrical discharge
Study of objective science can never reveal the
character of subjective experience.
Is this the same as the problem of other minds?
Not quite.
What is it like to be an eskimo?
What is it like to be Tom Cruise?
Nagel: we can answer these questions fairly well by using our
imagination. But, the answer is accessible to us only because we
base our imagination on our own experiences. We need the
subjective experience of being human to imagine the experience of
others.
Objective science alone could not give us these answers.
A Martian could not learn from objective facts what it is like to be
human.
Science cannot explain consciousness in physical terms.
“I have not defined the term 'physical'. Obviously it does not apply
just to what can be described by the concepts of contemporary
physics, since we expect further developments. Some may think
there is nothing to prevent mental phenomena from eventually
being recognized as physical in their own right. But whatever else
may be said of the physical, it has to be objective.” (Nagel 1974)
Physical facts are objective.
Consciousness is subjective.
So consciousness can never be explained by physical facts.
Question: Is this right? Are only objective facts physical? Are the
objective and the subjective irreconcilable?
Is physicalism about mental states wrong?
Nagel: not necessarily
“It would be a mistake to conclude that physicalism must be false…. It
would be truer to say that physicalism is a position we cannot understand
because we do not at present have any conception of how it might be
true.” (Nagel 1974)
Example: we saying “mind is brain” is like pre-Socratic philosopher saying:
“matter is energy”
“Strangely enough, we may have evidence for the truth of something we
cannot really understand.” (Nagel 1974)
Example: caterpillar  butterfly
Possible responses
1) Agree that is it impossible to understand qualia by investigating
the physical facts, because
a) dualism is true –dualists; or
b) we don’t have the mental capacity to understand it -- the
“New Mysterians”, e.g. Nagel, Colin McGinn
Quote from Colin McGinn:
“consciousness is indeed a deep mystery. . . . The reason for this
mystery, I maintain, is that our intelligence is wrongly designed
for understanding consciousness.” (McGinn, 1999)
2) Refute the claim from a functionalist perspective
– We can know what it is like to be a bat, objectively. By
learning the functional properties of the bat’s qualia, we
understand what the qualia is like.
– We can learn, for example, what size objects the bat can
detect, what kind of detail it can perceive, how well it can
track speeds and orientations of flying objects, etc. We can
learn what the bat’s map of the world is like.
– Is that equivalent to knowing what it is like for the bat to
perceive?
– E.g. Daniel Dennett
3) Deny that physical facts must be objective.
There are subjective physical facts (Max
Deutsch). Some physical facts can only be
learned from the perspective of someone
experiencing them.
Max Deutsch, “Subjective physical facts”
available at: http://consc.net/online/1.3a
Online papers on consciousness website:
also many other interesting papers dealing
with the Knowledge Argument
4) Agree that the hard problem is too hard to solve … for now.
Concentrate on the “easy” problems of consciousness and believe
that the answers to the hard problem will come eventually
The typical cognitive science approach.
Francis Crick, in a work about visual consciousness:
“I have said almost nothing about qualia – the redness of red –
except to brush it to one side and hope for the best” (Crick 1994)
The Chinese Room Argument
Can a machine think?
If we are just biological machines, could we make a
thinking machine?
Would it have to be biological?
How would we know if the machine was intelligent?
How would we know if the machine had
consciousness?
The Turing Test
In 1950, a computer scientist, Alan Turing,
wanted to provide a practical test to
answer “Can a machine think?”
His solution -- the Turing Test:
If a machine can conduct a conversation so well that
people cannot tell whether they are talking with a
person or with a computer, then the computer can
think. It passes the Turing Test.
Sufficient vs. necessary
• The Turing Test is meant to be a sufficient test of
intelligence.
• Not a necessary test.
• In other words, if something can pass the Turing Test,
then that thing is intelligent.
• But something that is intelligent could
still fail the Turing Test.
• E.g. Spock
There are many modern attempts to produce computer
programs that pass the Turing Test.
In fact, in 1991 Dr. Hugh Loebner started the annual
Loebner Prize competition, with prize money offered to
the author of the computer program that performs the
best on a Turing Test.
One winner of the Loebner prize was a program called
ALICE.
You can try her out on this website:
http://alicebot.blogspot.com/
And you can talk to others at:
http://www.pandorabots.com/botmaster/en/~12c23476
ad41c7e1e90d9f6c~/mostactive
A Conversation with Alice
Human: Do you like talking to people?
ALICE: No, I don't care for it.
Human: Then you must be unhappy now.
ALICE: Right now? Interesting deduction. Do you mind if I tell other
people you say I am unhappy.
Human: I don't mind.
ALICE: OK then.
Human: But tell me, are you unhappy now?
ALICE: Oh. Umm. Do I seem like it? I am as happy as ever.
Human: You don't seem unhappy, but you said you don't like talking
to people, so I figured you must be unhappy now.
ALICE: Oh. You don't know me well enough to say that.
Human: It was just a deduction
ALICE: Oh I get it. Very interesting.
Human: So, was my reasoning wrong?
ALICE: Alright then. It depends who you ask.
Human: I'm asking you.
ALICE: OK you can ask me.
Searle’s Chinese Room Argument
John Searle
• Famous philosopher at the
University of California, Berkeley
• Most well-known in philosophy of
language, philosophy of mind and
consciousness studies
• Wrote “Minds, Brains and Programs”
in 1980, which described the
“Chinese Room Argument”
Searle’s Chinese Room Argument
• The Chinese Room argument is one kind of objection to to the
Turing Test
• Also an attack on “strong AI”
• Searle makes distinction between strong AI and weak AI
• Strong AI: “the appropriately programmed computer really is a
mind, in the sense that computers, given the right programs
can be literally said to understand”
• Weak AI: Computers can simulate thinking and help us to learn
about how humans think
• Searle objects only to strong AI.
The Chinese Room
Searle cannot understand any Chinese.
He is in a room with input and output windows, and a list of
rules about manipulating Chinese characters.
The characters are all “squiggles and squoggles” to him.
Chinese scripts and questions come in from the input window.
Following the rules, he manipulates the characters and produces
a reply, which he pushes through the output window.
The Chinese answers that Searle produces are very good.
In fact, so good, no one can tell that he is not a native Chinese
speaker!
Searle’s Chinese Room passes the Turing Test. In other words, it
functions like an intelligent person.
Searle has only conducted symbol manipulation, with no
understanding, yet he passes the Turing Test.
Therefore, passing the Turing Test does not ensure understanding.
In other words, although Searle’s Chinese Room functions like a
mind, it is not a mind, and therefore there is more to
intelligence than mere functioning.
Searle believes that no computer-like system could be truly
intelligent.
Syntax vs. semantics
Searle argued that computers can never understand
because computer programs are purely syntactical with
no semantics.
Syntax: the rules for symbol manipulation, e.g. grammer
Semantics: understanding what the symbols (e.g. words)
mean
Syntax without semantics: The bliggedly blogs browl
aborigously.
Semantics without syntax: Milk want now me.
• Searle concludes that symbol manipulation alone can
never produce understanding.
• Computer programming is only symbol manipulation.
• Computer programming can never produce
understanding.
• Strong AI is false and intelligence cannot be created
in a computer.
What could produce real understanding?
Searle: “it is a biological phenomenon” and “only
something with the same causal powers as brains
can have [understanding]”.
Objections
The Systems Reply
Searle is part of a larger system. Searle doesn’t understand
Chinese, but the whole system (Searle + room + rules) does
understand Chinese.
The knowledge of Chinese is in the rules contained in the room.
The ability to implement that knowledge is in Searle.
The whole system understands Chinese.
Searle’s Response to the Systems Reply
1)
It’s absurd to say that the room and the rules can provide
understanding
2)
What if I memorized all the rules and internalized the whole
system. Then there would just be me and I still wouldn’t
understand Chinese.
Counter-response to Searle’s response
If Searle could internalize the rules, part of his brain would
understand Chinese. Searle’s brain would house two
personalities: English-speaking Searle and Chinesespeaking system.
The Robot Reply
What if the whole
system was put inside a
robot?
Then the system would
interact with the world.
That would create
understanding.
Searle inside the robot
Searle’s response to the Robot Reply
1) The robot reply admits that there is more to
understanding than mere symbol manipulation.
2) The robot reply still doesn’t work. Imagine that I am
in the head of the robot. I have no contact with the
perceptions or actions of the robot. I still only
manipulate symbols. I still have no understanding.
Counter-response to Searle’s response
Combine the robot reply with the systems reply. The
robot as a whole understands Chinese, even though
Searle doesn’t.
The Complexity Reply
• Really a type of systems reply.
• Searle’s thought experiment is deceptive. A room, a
man with no understanding of Chinese and “a few slips
of paper” can pass for a native Chinese speaker.
• It would be incredibly difficult to simulate a Chinese
speaker’s conversation. You need to program in
knowledge of the world, an individual personality with
simulated life history to draw on, and the ability to be
creative and flexible in conversation. Basically you
need to be able to simulate the complexity of an adult
human brain, which is composed of billions of neurons
and trillions of connections between neurons.
Complexity changes everything.
Our intuitions about what a complex
system can do are highly unreliable.
Tiny ants with tiny brains can
produce complex ant colonies.
Computers that at the most basic level are just binary
switches that flip from 1 to 0 can play chess and beat the
world’s best human player.
If you didn’t know it could be done, you would not believe
it.
Maybe symbol manipulation of sufficient complexity can
create semantics, i.e. can produce understanding.
Evaluation of Searle’s Claims
1)
The Turing Test:
Searle is probably right about the Turing Test.
Simulating a human-like conversation probably does not
guarantee real human-like understanding.
Certainly, it appears that simulating conversation to some
degree does not require a similar degree of understanding.
Programs like ALICE presumably have no understanding at
all.
.
2) Machine intelligence
Advocates of machine intelligence can respond that identification
of the of the room/computer and a mind is carried out at the
wrong level.
The computer as a whole is a thinking machine, like a brain is a
thinking machine. But the computer’s mental states may not be
equivalent to the brain’s mental states.
If the computer is organized as a really long list of questions with
canned answers, the computer does not have mental states such
as belief or desire.
But if the computer is organized like a human mind, with concepts,
complex organization and hierarchical layers of functional
systems, the computer can have beliefs, desires, etc.
3) Strong AI:
Could an appropriately programmed computer have real
understanding?
My view: too early to say.
The right kind of programming with the right sort of
complexity may yield true understanding.
e.g.
homuncular modularity
mixing of levels
self-updating
4) Syntax vs. Semantics
How can semantics (meaning) come out of symbol
manipulation? How can 1s and 0s result in real
meaning? It’s mysterious. But then how can the firing
of neurons result in real meaning? Also mysterious.
5) Consciousness
Can a computer have consciousness? Again, it is hard
to understand how silicon and metal can have
feelings. But it is no easier to understand how meat
can have feelings.
If a computer could talk intelligently and convincingly
about its feelings, we would probably ascribe feelings
to it. But would we be right?
5) Searle’s claim: understanding can only occur in
biological systems with the same causal properties
as the brain:
Why? What is special about biological systems? What
evidence is there?
Readings
Required:
• Searle, John. R. (1990), “Is the Brain's Mind a
Computer Program?” in Scientific American, 262,
pgs. 20-25
• Churchland, Paul, and Patricia Smith Churchland
(1990) “Could a machine think?” in Scientific
American 262, pgs. 26-31