JOHN SEARLE'S CHINESE ROOM ARGUMENT
John Searle begins his (1990) ``Consciousness, Explanatory Inversion and Cognitive Science'' with
``Ten years ago in this journal I published an article (Searle, 1980a and 1980b) criticising what I call Strong AI, the view that for a system to have mental states it is sufficient for the system to implement the right sort of program with right inputs and outputs. Strong AI is rather easy to refute and the basic argument can be summarized in one sentence: {it a system, me for example, could implement a program for understanding Chinese, for example, without understanding any Chinese at all.} This idea, when developed, became known as the Chinese Room Argument.''
The Chinese Room Argument can be refuted in one sentence:
Searle confuses the mental qualities of one computational process, himself for example, with those of another process that the first process might be interpreting, a process that understands Chinese, for example.
Here's the argument in more detail.
A man is in a room with a book of rules. Chinese sentences are passed under the door to him. The man looks up in his book of rules how to process the sentences. Eventually the rules tell him to copy some Chinese characters onto paper and pass the resulting Chinese sentences as a reply to the message he has received. The dialog continues.
To follow these rules the man need not understand Chinese.
Searle concludes from this that a computer program carrying out the rules doesn't understand Chinese either, and therefore no computer program can understand anything. He goes on to argue about biology being necessary for understanding.
Here's the refutation in still more detail.
Assume the process is a good participant in an intelligent Chinese conversation, i.e. behaves as though it understands Chinese. What is required for that we'll discuss shortly. The so-called Berkeley answer is that the system, consisting of the man and the book of rules, understands Chinese.
Our answer is an elaboration of the Berkeley answer. A computer interprets computer programs, i.e. carries them out instruction by instruction. Indeed a program can interpret other programs, e.g. a Lisp or Java interpreter interprets, i.e. carries out, Lisp or Java programs. We speak of the interpreter as carrying out the Lisp program, although this could be elaborated to saying that the computer carries out the Lisp interpreter which is carrying out the Lisp program step by step.
Indeed a time-shared operating system can carry out many different programs at once, some may be in machine language, others may be in Lisp, C, Fortran or Java. Suppose one of these programs is a Lisp program carrying out an intelligent Chinese conversation with someone at a terminal. Suppose another program is carrying out an intelligent French conversation or a different Chinese conversation with someone at a different terminal. Assume that these conversations are normally considered to require an understanding of Chinese or French. What understands Chinese?
We don't want to say that the computer understands Chinese and French but rather that the respective programs understand Chinese and French respectively. Indeed if we have two Chinese conversation programs, one may understand Chinese well and the other hardly at all.
Returning to the man in the room. He can be carrying out a conversation in English or playing chess while he is interpreting the book of rules for a Chinese conversation. Indeed he may have memorized the book of rules and be carrying them out in his head. As with the computer programs, it's the process that understands Chinese well or badly.
Let's consider some practicalities that may help us understand the question better. There are two extreme levels on which the man may be carrying out the Chinese conversation. One level is that of Joseph Weizenbaum's 1965 program ELIZA. It makes sentences by re-arranging and transforming the words in the input sentence. Thus one version, called DOCTOR, and included in the Xemacs editor, replies to "My mother hates me?" with "Why do you say mother hates you". According to Weizenbaum (personal communication), ELIZA requires so little computation that it can be carried out by hand. Thus an ELIZA level Chinese room is entirely feasible.
Does an ELIZA level Chinese room understand Chinese? It depends on what you mean by "understand", but I would prefer to say that a Chinese ELIZA does not understand Chinese. We'll see why?
Now consider a Chinese room that passes the Turing test, i.e. the Chinese interlocutor cannot be sure whether he is conversing with an intelligent fellow Chinese speaker. This is not feasible with a man and a book of rules. In fact it is beyond the present state of the art in artificial intelligence. While the book of rules probably needn't be bigger than an ordinary encyclopedia, I doubt that a human could carry out the rules at better than $10^{-9}$ of the speed required for conversation.
What is required for a Chinese room that passes the Turing test?
- A knowledge base of facts about the world, e.g. about 3-dimensional objects and the fact that they fall when unsupported and end up on the floor or ground.
- A knowledge base of facts about Chinese life and the Chinese language.
- A representation of the conversational purpose of the program.
- A program that translates the sentences into some internal form and responds appropriately, given the motivations we have given the program.
- A program that translates the output sentences into Chinese, prints the result, and pushes it back under the door.
These requirements can, at least in principle, be implemented in a variety of ways, e.g. by a sequentially operating neural net or by a logic based reasoner. I think the latter approach can do more now and will approach the goal of a human level conversation sooner.
So what is it to understand Chinese?
Understanding Chinese involves being able to translate Chinese sentences into some internal representation and to reason with the internal representation and some knowledge base. Thus understanding "Tom is an airplane pilot." requires being able to correctly answer, "Does Tom know how rotating the control column left affects the ailerons?"
More about understanding is discussed in my Making Robots Conscious of their Mental States.
More Searle arguments
``Once we get out of that confusion, once we escape the clutches of two thousand years of dualism, we can see that consciousness is a biological phenomenon like any other and ultimately our understanding out it is most likely to come through biological investigation'' John Searle - New York Review of Books, letter pp 58-59, 1990 June 14.
My view is that consciousness is an abstract phenomenon, currently best realized in biology, but causal systems of the right structure can also realize it. See Making Robots Conscious of their Mental States.
The discussion of the Chinese Room has remained at an excessively high level on both sides. I propose to discuss what would actually be involved in a set of rules for conducting a conversation in Chinese, independently of whether these rules are to be carried out by a human or a machine.
First we must exclude various forms of cheating that aren't excluded by Searle's formulation of the problem.
1. We need to exclude a system like Weizenbaum's Eliza that merely looks for certain words in the input and makes certain syntactic transformations on each sentence to generate an output sentence. I wouldn't count such a program as understanding Chinese, and a fortiori Searle wouldn't either. The program must respond as though it knew the facts that would be familiar to an educated Chinese.
2. If the rules are to be executed by a human, they must not involve translating what was said into English, e.g. by giving the dictionary entries for the characters. If this were done, the English speaker could use his own understanding of the facts of the world to generate English responses that he then translates into Chinese. The database of facts must not be in English. We also suppose that the human is not allowed to do cryptanalysis to translate the inputs or the database into English.
This eliminates the forms of cheating that I can think of, but I don't guarantee that there aren't others.
How shall we construct our program? Artificial intelligence is a difficult scientific problem, and conceptual advances are required before programs with human level intelligence can be devised. Here are some considerations.
1. In discussing concrete questions of intelligence, it is useful to distinguish between a system's algorithms and its store of facts. While it is possible in principle to consider the facts as built into the algorithm, making the distinction is practically essential for studying both human and machine intelligence. We communicate mainly in facts even when we are trying to tell each other algorithms.
2. The central problem of AI is, in my opinion, achieving goals in the commonsense informatic situation See my What is artificial intelligence? for more on this.
Searle offers four axioms.
1. Brains cause minds.
"Cause" makes me a little nervous. If he only means that the human mind is an abstraction of part of the operation of the brain, I'll agree.
2. Syntax is not sufficient for semantics.
This purported axiom is slippery. Does he just mean that defining a language, whether a natural language, first order logical language, or a programming language, requires defining what the expressions of the language mean? If that's what he means, I agree.
3. Computer programs are entirely defined by their formal, or syntactic structures.
This is ok provided we remember that the programming language has a semantics, and the data structures used by the program must have semantics if the program is to be intelligent.
4. Minds have mental contents; specifically they have semantic contents.
That's ok with the above provisos.
Conclusion 1. No computer program by itself is sufficient to give a system a mind. Programs, in short, are not minds, and they are not by themselves sufficient for having minds.
The conclusion doesn't follow from the axioms, not even informally.
I should remark that Searle's Chinese room argument hasn't convinced very many of his fellow philosophers.
In his Scientific American article on the Chinese room Searle makes an interesting mistake, though not a new mistake. He writes that a transcript of the Chinese conversation could equally well represent the score of a chess game or stock market predictions. This will only be true if the Chinese conversation is very short; perhaps it would have to be less that 20 characters - or maybe it's 100 characters.
We have to haggle about what equally well means. We can get a 1-1 correspondence between Chinese dialogs and chess scores by enumerating Chinese dialogs and enumerating chess scores and putting thenth dialog correspond to the nth score. This isn't good enough. Both Chinese dialogs and chess scores have meaningful substructures, and the previously described correspondence does not make the substructures correspond. One structure is that of initial segments. The initial segment of a Chinese dialog is meaningful to a Chinese, and an initial segment of a chess score is meaningful to a chess player, and these meanings related to the meanings of the whole dialog and the whole score respectively.
All this relates to the notion of unicity distance in cryptography. A simple substitution cryptogram that has less than 21 letters is likely to have several interpretations. With more than 21 letters the interpretation is extremely likely to be unique. That's why people can solve cryptograms.
I think there is a mathematical theorem stating that meaningful strings in a structured language have unique interpretations if their lengths exceed some rather small bound. I don't know how to formulate such a theorem.
I don't know whether this mistake of Searle's is related to his Chinese room mistake. It seems to me that Quine's assertions about "the indeterminacy of radical translation" are based on too small examples. However, I may be misunderstanding what Quine was claiming.
===============
Practical applications of Philosophy in Artificial Intelligence
Karim Oussayef
Among the sciences, Artificial Intelligence holds a special attraction for
philosophers. A.I. involves using computers to solve problems that seem to require
human reasoning. This includes computer programs that can beat human opponents at
games, automatically find and proof theorems and understand natural language. Some
people in the AI field contend that programs that solve these types of problems have the
possibility of not only thinking like humans, but also understanding concepts and
becoming conscious. This viewpoint is called strong AI
1
. Many philosophers are
concerned with this bold statement and there is no shortage of arguments against the
metaphysical possibility of strong AI. If these philosophical arguments against strong AI
are true then there are limits to machine intelligence that cannot be surpassed by better
algorithms, faster computers or more clever ideas.
Hilary Putnam in his paper Much Ado About Not Very Much asks “AI may
someday teach us something about how we think, but why are we so exercised about it
now? Perhaps it is the prospect that exercises us, but why do we think now is the time to
think decide what might in principle be possible?” The reason we are so exercised about
A.I. is because knowing whether true intelligence is a possibility will change the goals of
researchers in the field. If strong AI is not possible then the best we can hope for is a
program that acts humanly but doesn’t think humanly. Even this goal is a very difficult
and many programs seek to achieve it. Cycorp
2
is a company whose software attempts to
1
Coined by John Searl in Minds, Brains and Programs.
2
Information from Cycorp’s website. mimic human intelligence by creating a huge database of common sense facts. Their
website gives some examples: “Cyc knows that trees are usually outdoors, that once
people die they stop buying things, and that glasses of liquid should be carried right side
up.”
To illustrate how a fact-based program such as Cycorp’s would try to solve a
simple problem let us turn to the Turing test
3
. Turing reasoned that a computer could
prove that it was artificially intelligent by fooling a person into thinking it was another
human being. His test was modeled from this reasoning: A human would type questions
to either another human or a computer (he or she wouldn’t know which) for a certain
amount of time. If that person couldn’t tell at the end of the time which of the two he or
she was talking to, the computer would pass the test (and therefore Turing reasoned, be
artificially intelligent). Let me stress that I am not arguing that the Turing test is a good
one for determining if a computer can think; I am simply using it to demonstrate how a
program might go about solving a problem. The fact-based program mentioned above
might try to answer the simple question “What is a car?” by supplying the information
that was in its code: “A car is a small vehicle with 4 wheels”. A harder question might
have to do with a description a car object followed by “What am I describing?” This
could be answering by going down a tree of facts as follows: The description is of a
vehicle, search for all the objects under the vehicle topic. It has four wheels; discard the
possibility of the motorcycle. It is light; discard the possibility of the truck. Conclusion:
It must be a car.
A program like this could pass the Turing test if it was given enough data.
However it has many disadvantages. First it requires someone to input a vast amount of
3
Introduced by Alan Turing’s article Computing Machinery and Intelligence in 1950. information manually. Although the program is capable of making some extensions of
the given information, it still needs millions of hard facts. Cycorp’s database has been
painstakingly entered using over 600 person-hours of effort since 1984. The list of facts
now stands at 3 million (Anthes). Second the machine doesn’t seem to work like a
human, it looks up rules and then gives an answer instead of figuring out what the
question means.
Searle’s Chinese room analogy shows why this program isn’t an example of
strong AI. Imagine an English speaking person inside of a small room. This person has
access to a large rulebook, which is written in English. Other people outside the room
can pass notes written in Chinese to him through a small hole in the wall. Although the
person inside the small room cannot speak Chinese, he uses the complex rulebook to give
back an appropriate response to the Chinese writing in Chinese. Also imagine that this
rulebook is so well written that the answers the person inside the room gives back are
indistinguishable from the answers that a native Chinese speaker might give back. This
“man in a room” system would be able to carry on a written conversation with a native
Chinese speaker on the other side of the wall. In fact the Chinese person might assume
he was speaking to another person who understands Chinese. We can plainly see
however, that the person does not.
This analogy is disastrous for fact-based AI. In the same way that the computer
passes the Turing test by fooling humans into thinking it is another human, the English
speaker can fool native Chinese speakers into thinking that he understands Chinese. To
further explain, the person inside the room is analogous to the computer CPU; they both
know how to interpret instructions. The rulebook is analogous to the program; they supply the instructions to obtain the intended result. The computer programmed with this
fact-based knowledge does not understand English any more than the English speaker
understands Chinese. Both of them are following rules instead of understanding what is
being asked and responding based their interpretation.
The defeat of the fact-based program poses problems for strong A.I. supporters. It
shows that any program that relies on pre-made a set of rules (no matter how complex)
cannot understand in the same way that a human mind does. In fact Searle argues: “… in
the literal sense the programmed computer understands what the car and the adding
machine understand, namely, exactly nothing” (Searl 511). However Searle’s argument
doesn’t rule out all programs. A program that learns from scratch, without the use of a
rulebook or a prefabricated fact database, can understand in the same way that a human
can. I will now go about describing such a program.
To construct the fact-based program we attempted to record facts about the world.
The learning program takes an orthogonal approach. It attempts to program the computer
to learn these facts for itself. To see how to go about this let us examine how a small
child learns. A child comes into the world knowing very little. She does not know how
to talk, walk or understand English. She goes about learning these abilities with three
tools. First she has basic goals or needs. Some of a child’s needs are food, water and
shelter. Second she can observe the world. A child can tell that when she is eating, she is
getting less hungry. Finally she can remember what has happened to her. Let me
demonstrate how these three tools allow her to learn something. Imagine that this child is
hungry. She observes that when she cries her mother brings her food. She remembers what has happened to her and finally her need for food causes her to cry again the next
time she’s hungry. Her tools have allowed her to learn that crying results in getting food.
These three tools are the core of the learning program. However, the goals of a
computer will differ from the goals of a human. A computer has no need for food or
water so they are not appropriate goals. Instead these goals can be anything that A.I.
programmers think are important. Isaac Asimov proposed three such goals (or laws) in
his fictional stories
4
:
1. A robot may not injure a human being or, through inaction, allow a
human being to come to harm.
2. A robot must obey the orders given it by human beings, except where
such orders would conflict with the First Law.
3. A robot must protect its own existence, as long as such protection does
not conflict with the First and Second Laws.
In short a robot’s goals are human well-being, human will and its own well-being. These
goals can be implemented in the form of variables linked to actions that the computer
might perform. Whenever the computer does something that accomplishes one of its
goals it might raise the value of the variables connected with its current state or action.
Similarly it would lower the values of these action-variables when it did something
against its goals. These variables also represent the computer’s memory. This is where
the computer remembers what to do the next time it is in a similar situation. Finally the
computer needs a console, sensors or some other form of input so it can observe what is
happening around it. Let me demonstrate how it works with a simple example.
Imagine a robot equipped with a camera, a flashlight and wheels. The robot is put
in an environment and given the extra goal of reaching a certain spot. If the robot had
4
First published in Runaround in 1940. never been in this situation before it might have no idea of how to reach the goal in much
the same way that the child does not know how to get food. So it might begin by doing
any number of things. Perhaps it would turn on its flashlight. This would not help it
reach it’s goal so would try something different. Maybe it starts driving towards the goal.
The robot would observe that it is accomplishing a goal so the “going forward” action
might get a “+ 1 points” in the “trying to reach an object” context. Perhaps there is a wall
in front of it halfway to the flag. It runs into the wall and damages itself. This is bad for
the “well-being of self” goal so the “driving forward” action might get “–1 points” in the
“wall in front of me” context. These point value will help it remember what to do next
time it is trying to get from one point to another. When it sees a wall infront of it in the
future, the robot will see that “driving forward” has less points than, say, “driving
sideways” and might pick that option. The fact that it wants to reach its goals will teach
the robot through trial and error. Eventually it will learn how do drive around objects
(instead of into them).
I argue that a robot constructed in this fashion would actually understand how to
accomplish goals. To support this belief, let’s see if it does any better with the Chinese
room example. Remember that for the fact-based program the person inside the room is
analogous to the computer CPU and the rulebook is analogous to the program. However,
for the learning program there is no rulebook. The person inside the room is analogous to
both the CPU and the program. Instead of people asking questions and having him
answer back, imagine that the input through the slot in his room is the information he
receives from the outside world. At first he has no idea what this input means. He sends
random symbols back but after a while he notices a correlation between what he sends out and what he gets back. He starts to write his own rulebook in his head from this
information that allows him to translate Chinese input into English. When he writes back
he translates the answers that he thought of in English back to Chinese.
The way the “learning-program person” can communicate in Chinese is
drastically different than the way the “fact-based person” does. The “learning-program
person” learns what the Chinese means by association. From his knowledge he knows
the sense of the words. Some people may point out that he does not actually think in
Chinese so he must not understand the language. However, there are many people who
converse in a non-native tongue. We cannot claim that these people’s understanding of
the world is different than our own.
Searl might respond to this learning-program by saying that the person inside the
Chinese room would simulate the entire learning process and that the learning is not
internal but external. This means that the person inside of the room is following
directions that correspond to learning but he himself is not learning. But if such a
program falls victim to the Chinese room, wouldn’t a human brain fall victim as well?
Let us imagine a modified Chinese room for the human brain. Instead of the man inside
of the Chinese room simulating a computer program, he simulates the neurons in
someone’s brain. When he receives input, he would keep track of what neurons get
excited and calculate whether or not they fire. He would know from his rulebook (a
compendium of the laws of physics, chemistry and biology that would allow him to
completely simulate the inner workings of the brain) that when certain neurons fired that
he should output an answer. The person simulating the brain doesn’t understand Chinese
any better than the one simulating a computer program. Why would one be different than the other? Searl’s opinion is that “actual human mental phenomena might be dependant
on actual physical-chemical properties of actual human brains” (Searl 519). Penrose’s
“The emperor’s new mind” provides insight as to why this may be the case.
Penrose mentions many physical processes that are not computable. He first
examines the Mandelbrot set. The Mandelbrot set is created by mapping a formula using
the combination of real and complex numbers. The result is an Argand Plane. Here is
where Penrose brings up an important comment: “We might think of using some
algorithm for generating the successive digits of an infinite decimal expansion, but it
turns out that only a tiny fraction of the possible decimal expansions are obtainable in this
way: the computable numbers” (Penrose 648). In other words, the exact notion of the
Mandelbrot set cannot be computed with a computer. Penrose also mentions quantum
mechanical principles. Tiny sub-atomic particles do not follow the same laws of physics
that larger objects do. The superposition principle states that a particle can be in many
different states at the same time. These states are defined by factors of complex numbers
and thus are another example of a physical law that cannot be simulated in a computer.
These two examples may show why the Chinese room cannot simulate the human
brain. When the person inside of the room was following the directions for simulating a
computer the steps he took were explained by a well-defined algorithm. This is because
computers are Turing machines, a concept that was formalized elegantly by Alan Turing.
All Turning machines can be thought of as a device that reads and writes from an
infinitely long tape. On the tape is a sequence of partitions that are either blank or
marked. The device operates by moving either left or right on the tape. It can change the
current section to either “marked” or “blank” and read its current state. It does this by following a finite set of instructions. This simple abstraction is enough to run any
computer program no matter how complex. It is easy to think of the human inside of the
Chinese room controlling a Turing machine.
The brain may, however, rely on non-algorithmic processes than the person inside
the Chinese room will not be able to follow. If, for example, neuron X would fire only
because of a certain arrangement of subatomic particles, there would be no hard set
directions for what the Chinese-room-person should do. Perhaps the next instruction has
a random chance of occurring, if so the person will be confused and unable to complete
the instruction. It is important to find out whether the brain makes use of these processes
because if it does, it would explain why the Chinese room works for computers but not
for the human brain.
In the chapter “Where lies the physics of the mind,” Penrose argues that the brain
does indeed make use of non-computable phenomenon. He contends that expressions
that deal with consciousness such as “understanding” and “judgment” and those that do
not such as “mindlessly” and “automatically”, suggest a distinction between two parts of
the brain: algorithmic and non-algorithmic (Penrose 653). Penrose brings up Godel’s
incompleteness theorem as an example of how the brain makes use of non-algorithmic
part of the brain. Godel encoded first order predicate calculus into normal arithmetic
using prime numbers. By breaking down F.O.P.C. in this way, he could write out
arithmetic formulas that would equate to either true or false. He used this trick to
demonstrate that there are some statements that cannot be proven or disproved. One such
sentence would be: "A computer which knows the answer to all questions will never prove that this sentence is true.”
5
Human beings know that this sentence is true without
actually going through the process of proving it. If, however, a computer attempts to
assess the validity of the state through a formal proof it will be confused because the
statement remains true until the proof is complete.
Penrose argues that these types of sentences, which humans can reason about,
would be impossible for a computer to understand. What Penrose doesn’t notice is that
even if some statements could not be proved or disproved using FOPC logic, there are
other ways for computers to approach these problems. There is no reason that computers
couldn’t use higher logic to solve puzzles just like a human does. Penrose’s goal of
proving strong A.I. impossible fails because he doesn’t make the link between the nonalgorithmic/non-computable physical phenomenon and the human brain. If in the future
neuroscientists discovered that the brain relies on such processes then his argument
would hold more weight. Still, it would be possible for a program to simulate the
workings of the brain without simulating the actual physical processes.
In fact, computers and human brains excel at different tasks, a fact which makes
literal simulations wasteful. A computer can remember things for an infinite amount of
time (assuming the file isn’t deleted). It can also compute complicated mathematical
expressions in milliseconds. Even a human with the best eidetic memory or an
extraordinary mathematical talent couldn’t rival a computer in these tasks. On the other
hand, computers have a very hard time recognizing objects such as human faces. In dark
or light, different clothes or dyed hair, we can still recognize our best friend. Similarly
the human ability to understand language is amazing. We can utter sentences that we
have never said or heard before and understand a variety of accents and slang. These
5
Adapted from Denton “human algorithms” which require almost no effort for us are very difficult for a
computer. To throw away a computer’s advantages in mathematics, memory and many
other tasks seem a waste. Yet attempting to create a model of human neurons seems to
do exactly that. Instead, it would be better to attempt to simulate the way a human brain
solves problems instead the actual physical processes behind human thinking.
In this paper I have shown how various arguments against strong A.I. interact.
These arguments do not show that it is impossible but do restrict what kind of programs
can be thought of as “truly intelligent”. Searl’s Chinese room argument shows that factbased programs are incapable of understanding things in the same way as humans do. It
also excludes programs that have all their information hard coded in. Learning is
essential to programs that wish to support strong A.I. because information has to come
from the program, not from the programmer. Penrose has suggested that the brain is
unable to be simulated by a computer. If this is true than computers must be a simulation
of how the brain thinks not how the brain works. Finally Godel’s incompleteness
theorem shows that programs must use higher reasoning to achieve its goals. Philosophy
is often criticized for being un concerned with real world implications but in this case it
has shown the best direction for A.I. researchers to explore. References
Books
Clancey, William J. 1997. Situated Cognition. Cambridge, UK: Cambridge University Press.
Dreyfus, Hubert. 1992. What Computers Still Can't Do: A Critique of Artificial Reason. Cambridge, MA:
MIT Press.
Kim, Jaegwon. 1998. Philosophy of Mind. Boulder Colorado: Westview Press Inc.
Penrose, Roger. 1989. The Emperor's New Mind: Concerning Computers, Minds and the Laws of Physics.
Oxford: Oxford University Press.
Russell, Smart and Norvig, Peter. 1995, Artificial Intelligence: A Modern Approach
Smith, Brian Cantwell. 1996. On the Origin of Objects. Cambridge, MA: MIT Press/Bradford Books.
Papers
Dennett, Daniel C. 1988. When Philosophers Encounter Artificial Intelligence. The Artificial Intelligence
Debate: False Starts, Real Foundations: 283-296.
Fodor, J.A. 1980. Searl on What Only Brain Can Do. The Nature of Mind: 520.
Fodor, J.A. 1998. After-thoughts: Yin and Yang in the Chinese Room. The Nature of Mind: 524.
LaForte, Geoffrey, Patrick J. Hayes, and Kenneth M. Ford. 1998. Why Godel's Theorem Cannot Refute
Computationalism. Artificial Intelligence: 211-264.
McCarthy, Daniel C. 1988. Mathematical Logic in Artificial Intelligence. The Artificial Intelligence
Debate: False Starts, Real Foundations: 297-311
Putnam, Hillary. 1988. Much Ado About Not Very Much. The Artificial Intelligence Debate: False Starts,
Real Foundations: 269-282.
Sokolowski, Robert. 1988. Natural and Artificial Intelligence. The Artificial Intelligence Debate: False
Starts, Real Foundations: 45-64.
Searl, John R. 1980. Minds, Brains and Programs. The Nature of Mind: 509-519.
Searl, John R. 1980. Author’s response. The Nature of Mind: 521-523.
Searl, John R. 1998. Ying and Yang Strike Out. The Nature of Mind: 525.
Turing, A.M. (1950). Computing machinery and intelligence. Mind, 59, 433-460.
Journals
Gary H. Anthes, Computerizing Common Sense. Computerworld. 4/8/02.
Electronic
Cycorp: Company Overview. http://www.cyc.com/overview.html
Denton, Willaim. 2000. Godel’s Incompleteness Theorem http://www.miskatonic.org/godel.html
