Turing, A.M. (1950). Computing
machinery and intelligence. Mind, 59, 433-460.
COMPUTING
MACHINERY AND INTELLIGENCE
By A. M. Turing
By A. M. Turing
1. The Imitation Game
I propose to consider the question,
"Can machines think?" This should begin with definitions of the
meaning of the terms "machine" and "think." The definitions
might be framed so as to reflect so far as possible the normal use of the
words, but this attitude is dangerous, If the meaning of the words
"machine" and "think" are to be found by examining how they
are commonly used it is difficult to escape the conclusion that the meaning and
the answer to the question, "Can machines think?" is to be sought in
a statistical survey such as a Gallup poll. But this is absurd. Instead of
attempting such a definition I shall replace the question by another, which is
closely related to it and is expressed in relatively unambiguous words.
The new form of the problem can be
described in terms of a game which we call the 'imitation game." It is
played with three people, a man (A), a woman (B), and an interrogator (C) who
may be of either sex. The interrogator stays in a room apart front the other
two. The object of the game for the interrogator is to determine which of the
other two is the man and which is the woman. He knows them by labels X and Y,
and at the end of the game he says either "X is A and Y is B" or
"X is B and Y is A." The interrogator is allowed to put questions to
A and B thus:
C: Will X please tell me the length
of his or her hair?
Now suppose X is actually A, then A
must answer. It is A's object in the game to try and cause C to make the wrong
identification. His answer might therefore be:
"My hair is shingled, and the
longest strands are about nine inches long."
In order that tones of voice may not
help the interrogator the answers should be written, or better still,
typewritten. The ideal arrangement is to have a teleprinter communicating
between the two rooms. Alternatively the question and answers can be repeated
by an intermediary. The object of the game for the third player (B) is to help
the interrogator. The best strategy for her is probably to give truthful
answers. She can add such things as "I am the woman, don't listen to
him!" to her answers, but it will avail nothing as the man can make similar
remarks.
We now ask the question, "What
will happen when a machine takes the part of A in this game?" Will the
interrogator decide wrongly as often when the game is played like this as he
does when the game is played between a man and a woman? These questions replace
our original, "Can machines think?"
2. Critique of the New Problem
As well as asking, "What is the
answer to this new form of the question," one may ask, "Is this new
question a worthy one to investigate?" This latter question we investigate
without further ado, thereby cutting short an infinite regress.
The new problem has the advantage of
drawing a fairly sharp line between the physical and the intellectual
capacities of a man. No engineer or chemist claims to be able to produce a
material which is indistinguishable from the human skin. It is possible that at
some time this might be done, but even supposing this invention available we
should feel there was little point in trying to make a "thinking
machine" more human by dressing it up in such artificial flesh. The form
in which we have set the problem reflects this fact in the condition which
prevents the interrogator from seeing or touching the other competitors, or
hearing -their voices. Some other advantages of the proposed criterion may be
shown up by specimen questions and answers. Thus:
Q: Please write me a sonnet on the
subject of the Forth Bridge.
A : Count me out on this one. I
never could write poetry.
Q: Add 34957 to 70764.
A: (Pause about 30 seconds and then
give as answer) 105621.
Q: Do you play chess?
A: Yes.
Q: I have K at my K1, and no other
pieces. You have only K at K6 and R at R1. It is your move. What do you play?
A: (After a pause of 15 seconds)
R-R8 mate.
The question and answer method seems
to be suitable for introducing almost any one of the fields of human endeavour
that we wish to include. We do not wish to penalise the machine for its
inability to shine in beauty competitions, nor to penalise a man for losing in
a race against an aeroplane. The conditions of our game make these disabilities
irrelevant. The "witnesses" can brag, if they consider it advisable,
as much as they please about their charms, strength or heroism, but the
interrogator cannot demand practical demonstrations.
The game may perhaps be criticised on
the ground that the odds are weighted too heavily against the machine. If the
man were to try and pretend to be the machine he would clearly make a very poor
showing. He would be given away at once by slowness and inaccuracy in
arithmetic. May not machines carry out something which ought to be described as
thinking but which is very different from what a man does? This objection is a
very strong one, but at least we can say that if, nevertheless, a machine can
be constructed to play the imitation game satisfactorily, we need not be
troubled by this objection.
It might be urged that when playing
the "imitation game" the best strategy for the machine may possibly
be something other than imitation of the behaviour of a man. This may be, but I
think it is unlikely that there is any great effect of this kind. In any case
there is no intention to investigate here the theory of the game, and it will
be assumed that the best strategy is to try to provide answers that would
naturally be given by a man.
3. The Machines Concerned in the
Game
The question which we put in 1 will
not be quite definite until we have specified what we mean by the word
"machine." It is natural that we should wish to permit every kind of
engineering technique to be used in our machines. We also wish to allow the
possibility than an engineer or team of engineers may construct a machine which
works, but whose manner of operation cannot be satisfactorily described by its
constructors because they have applied a method which is largely experimental.
Finally, we wish to exclude from the machines men born in the usual manner. It
is difficult to frame the definitions so as to satisfy these three conditions.
One might for instance insist that the team of engineers should be all of one
sex, but this would not really be satisfactory, for it is probably possible to
rear a complete individual from a single cell of the skin (say) of a man. To do
so would be a feat of biological technique deserving of the very highest
praise, but we would not be inclined to regard it as a case of
"constructing a thinking machine." This prompts us to abandon the
requirement that every kind of technique should be permitted. We are the more
ready to do so in view of the fact that the present interest in "thinking
machines" has been aroused by a particular kind of machine, usually called
an "electronic computer" or "digital computer." Following
this suggestion we only permit digital computers to take part in our game.
This restriction appears at first
sight to be a very drastic one. I shall attempt to show that it is not so in
reality. To do this necessitates a short account of the nature and properties
of these computers.
It may also be said that this
identification of machines with digital computers, like our criterion for
"thinking," will only be unsatisfactory if (contrary to my belief),
it turns out that digital computers are unable to give a good showing in the
game.
There are already a number of
digital computers in working order, and it may be asked, "Why not try the
experiment straight away? It would be easy to satisfy the conditions of the
game. A number of interrogators could be used, and statistics compiled to show
how often the right identification was given." The short answer is that we
are not asking whether all digital computers would do well in the game nor
whether the computers at present available would do well, but whether there are
imaginable computers which would do well. But this is only the short answer. We
shall see this question in a different light later.
4. Digital Computers
The idea behind digital computers
may be explained by saying that these machines are intended to carry out any
operations which could be done by a human computer. The human computer is
supposed to be following fixed rules; he has no authority to deviate from them
in any detail. We may suppose that these rules are supplied in a book, which is
altered whenever he is put on to a new job. He has also an unlimited supply of
paper on which he does his calculations. He may also do his multiplications and
additions on a "desk machine," but this is not important.
If we use the above explanation as a
definition we shall be in danger of circularity of argument. We avoid this by
giving an outline. of the means by which the desired effect is achieved. A
digital computer can usually be regarded as consisting of three parts:
(i) Store.
(ii) Executive unit.
(iii) Control.
The store is a store of information,
and corresponds to the human computer's paper, whether this is the paper on
which he does his calculations or that on which his book of rules is printed.
In so far as the human computer does calculations in his bead a part of the
store will correspond to his memory.
The executive unit is the part which
carries out the various individual operations involved in a calculation. What
these individual operations are will vary from machine to machine. Usually
fairly lengthy operations can be done such as "Multiply 3540675445 by
7076345687" but in some machines only very simple ones such as "Write
down 0" are possible.
We have mentioned that the
"book of rules" supplied to the computer is replaced in the machine
by a part of the store. It is then called the "table of
instructions." It is the duty of the control to see that these
instructions are obeyed correctly and in the right order. The control is so
constructed that this necessarily happens.
The information in the store is
usually broken up into packets of moderately small size. In one machine, for
instance, a packet might consist of ten decimal digits. Numbers are assigned to
the parts of the store in which the various packets of information are stored,
in some systematic manner. A typical instruction might say-
"Add the number stored in
position 6809 to that in 4302 and put the result back into the latter storage
position."
Needless to say it would not occur
in the machine expressed in English. It would more likely be coded in a form
such as 6809430217. Here 17 says which of various possible operations is to be
performed on the two numbers. In this case the)e operation is that described
above, viz., "Add the number. . . ." It will be noticed that the
instruction takes up 10 digits and so forms one packet of information, very
conveniently. The control will normally take the instructions to be obeyed in
the order of the positions in which they are stored, but occasionally an
instruction such as
"Now obey the instruction
stored in position 5606, and continue from there"
may be encountered, or again
"If position 4505 contains 0
obey next the instruction stored in 6707, otherwise continue straight on."
Instructions of these latter types
are very important because they make it possible for a sequence of operations
to be replaced over and over again until some condition is fulfilled, but in
doing so to obey, not fresh instructions on each repetition, but the same ones
over and over again. To take a domestic analogy. Suppose Mother wants Tommy to
call at the cobbler's every morning on his way to school to see if her shoes
are done, she can ask him afresh every morning. Alternatively she can stick up
a notice once and for all in the hall which he will see when he leaves for
school and which tells him to call for the shoes, and also to destroy the
notice when he comes back if he has the shoes with him.
The reader must accept it as a fact
that digital computers can be constructed, and indeed have been constructed,
according to the principles we have described, and that they can in fact mimic
the actions of a human computer very closely.
The book of rules which we have
described our human computer as using is of course a convenient fiction. Actual
human computers really remember what they have got to do. If one wants to make
a machine mimic the behaviour of the human computer in some complex operation
one has to ask him how it is done, and then translate the answer into the form
of an instruction table. Constructing instruction tables is usually described
as "programming." To "programme a machine to carry out the operation
A" means to put the appropriate instruction table into the machine so that
it will do A.
An interesting variant on the idea
of a digital computer is a "digital computer with a random element."
These have instructions involving the throwing of a die or some equivalent electronic
process; one such instruction might for instance be, "Throw the die and
put the-resulting number into store 1000." Sometimes such a machine is
described as having free will (though I would not use this phrase myself), It
is not normally possible to determine from observing a machine whether it has a
random element, for a similar effect can be produced by such devices as making
the choices depend on the digits of the decimal for .
Most actual digital computers have
only a finite store. There is no theoretical difficulty in the idea of a
computer with an unlimited store. Of course only a finite part can have been
used at any one time. Likewise only a finite amount can have been constructed,
but we can imagine more and more being added as required. Such computers have
special theoretical interest and will be called infinitive capacity computers.
The idea of a digital computer is an
old one. Charles Babbage, Lucasian Professor of Mathematics at Cambridge from
1828 to 1839, planned such a machine, called the Analytical Engine, but it was
never completed. Although Babbage had all the essential ideas, his machine was
not at that time such a very attractive prospect. The speed which would have
been available would be definitely faster than a human computer but something
like I 00 times slower than the Manchester machine, itself one of the slower of
the modern machines, The storage was to be purely mechanical, using wheels and
cards.
The fact that Babbage's Analytical
Engine was to be entirely mechanical will help us to rid ourselves of a
superstition. Importance is often attached to the fact that modern digital
computers are electrical, and that the nervous system also is electrical. Since
Babbage's machine was not electrical, and since all digital computers are in a
sense equivalent, we see that this use of electricity cannot be of theoretical
importance. Of course electricity usually comes in where fast signalling is
concerned, so that it is not surprising that we find it in both these
connections. In the nervous system chemical phenomena are at least as important
as electrical. In certain computers the storage system is mainly acoustic. The
feature of using electricity is thus seen to be only a very superficial
similarity. If we wish to find such similarities we should took rather for
mathematical analogies of function.
5. Universality of Digital Computers
The digital computers considered in
the last section may be classified amongst the "discrete-state
machines." These are the machines which move by sudden jumps or clicks
from one quite definite state to another. These states are sufficiently
different for the possibility of confusion between them to be ignored. Strictly
speaking there, are no such machines. Everything really moves continuously. But
there are many kinds of machine which can profitably be thought of as being
discrete-state machines. For instance in considering the switches for a
lighting system it is a convenient fiction that each switch must be definitely
on or definitely off. There must be intermediate positions, but for most
purposes we can forget about them. As an example of a discrete-state machine we
might consider a wheel which clicks round through 120 once a second, but may be
stopped by a ]ever which can be operated from outside; in addition a lamp is to
light in one of the positions of the wheel. This machine could be described
abstractly as follows. The internal state of the machine (which is described by
the position of the wheel) may be q1, q2 or q3.
There is an input signal i0. or i1 (position of ]ever). The internal state at
any moment is determined by the last state and input signal according to the
table
(TABLE
DELETED)
The output signals, the only externally visible indication of the internal state (the light) are described by the table
State q1 q2 q3
output o0 o0 o1
This example is typical of
discrete-state machines. They can be described by such tables provided they
have only a finite number of possible states.
It will seem that given the initial
state of the machine and the input signals it is always possible to predict all
future states, This is reminiscent of Laplace's view that from the complete
state of the universe at one moment of time, as described by the positions and
velocities of all particles, it should be possible to predict all future
states. The prediction which we are considering is, however, rather nearer to
practicability than that considered by Laplace. The system of the
"universe as a whole" is such that quite small errors in the initial
conditions can have an overwhelming effect at a later time. The displacement of
a single electron by a billionth of a centimeter at one moment might make the
difference between a man being killed by an avalanche a year later, or
escaping. It is an essential property of the mechanical systems which we have
called "discrete-state machines" that this phenomenon does not occur.
Even when we consider the actual physical machines instead of the idealized
machines, reasonably accurate knowledge of the state at one moment yields
reasonably accurate knowledge any number of steps later.
As we have mentioned, digital
computers fall within the class of discrete-state machines. But the number of
states of which such a machine is capable is usually enormously large. For
instance, the number for the machine now working at Manchester is about 2 165,000,
i.e., about 10 50,000. Compare this with our example of the clicking
wheel described above, which had three states. It is not difficult to see why
the number of states should be so immense. The computer includes a store
corresponding to the paper used by a human computer. It must be possible to
write into the store any one of the combinations of symbols which might have
been written on the paper. For simplicity suppose that only digits from 0 to 9
are used as symbols. Variations in handwriting are ignored. Suppose the computer
is allowed 100 sheets of paper each containing 50 lines each with room for 30
digits. Then the number of states is 10 100x50x30 i.e., 10
150,000 . This is about the number of states of three Manchester machines
put together. The logarithm to the base two of the number of states is usually
called the "storage capacity" of the machine. Thus the Manchester
machine has a storage capacity of about 165,000 and the wheel machine of our
example about 1.6. If two machines are put together their capacities must be added
to obtain the capacity of the resultant machine. This leads to the possibility
of statements such as "The Manchester machine contains 64 magnetic tracks
each with a capacity of 2560, eight electronic tubes with a capacity of 1280.
Miscellaneous storage amounts to about 300 making a total of 174,380."
Given the table corresponding to a
discrete-state machine it is possible to predict what it will do. There is no
reason why this calculation should not be carried out by means of a digital
computer. Provided it could be carried out sufficiently quickly the digital
computer could mimic the behavior of any discrete-state machine. The imitation
game could then be played with the machine in question (as B) and the mimicking
digital computer (as A) and the interrogator would be unable to distinguish
them. Of course the digital computer must have an adequate storage capacity as
well as working sufficiently fast. Moreover, it must be programmed afresh for
each new machine which it is desired to mimic.
This special property of digital
computers, that they can mimic any discrete-state machine, is described by
saying that they are universal machines. The existence of machines with this
property has the important consequence that, considerations of speed apart, it
is unnecessary to design various new machines to do various computing
processes. They can all be done with one digital computer, suitably programmed
for each case. It 'ill be seen that as a consequence of this all digital
computers are in a sense equivalent.
We may now consider again the point
raised at the end of §3. It was suggested tentatively that the question,
"Can machines think?" should be replaced by "Are there
imaginable digital computers which would do well in the imitation game?" If
we wish we can make this superficially more general and ask "Are there
discrete-state machines which would do well?" But in view of the
universality property we see that either of these questions is equivalent to
this, "Let us fix our attention on one particular digital computer C. Is
it true that by modifying this computer to have an adequate storage, suitably
increasing its speed of action, and providing it with an appropriate program, C
can be made to play satisfactorily the part of A in the imitation game, the
part of B being taken by a man?"
6. Contrary Views on the Main
Question
We may now consider the ground to
have been cleared and we are ready to proceed to the debate on our question,
"Can machines think?" and the variant of it quoted at the end of the
last section. We cannot altogether abandon the original form of the problem,
for opinions will differ as to the appropriateness of the substitution and we
must at least listen to what has to be said in this connection.
It will simplify matters for the
reader if I explain first my own beliefs in the matter. Consider first the more
accurate form of the question. I believe that in about fifty years' time it
will be possible, to program computers, with a storage capacity of about 109,
to make them play the imitation game so well that an average interrogator will
not have more than 70 per cent chance of making the right identification after
five minutes of questioning. The original question, "Can machines
think?" I believe to be too meaningless to deserve discussion. Nevertheless
I believe that at the end of the century the use of words and general educated
opinion will have altered so much that one will be able to speak of machines
thinking without expecting to be contradicted. I believe further that no useful
purpose is served by concealing these beliefs. The popular view that scientists
proceed inexorably from well-established fact to well-established fact, never
being influenced by any improved conjecture, is quite mistaken. Provided it is
made clear which are proved facts and which are conjectures, no harm can
result. Conjectures are of great importance since they suggest useful lines of
research.
I now proceed to consider opinions
opposed to my own.
(1) The Theological Objection
Thinking is a function of man's
immortal soul. God has given an immortal soul to every man and woman, but not
to any other animal or to machines. Hence no animal or machine can think.
I am unable to accept any part of
this, but will attempt to reply in theological terms. I should find the
argument more convincing if animals were classed with men, for there is a
greater difference, to my mind, between the typical animate and the inanimate
than there is between man and the other animals. The arbitrary character of the
orthodox view becomes clearer if we consider how it might appear to a member of
some other religious community. How do Christians regard the Moslem view that
women have no souls? But let us leave this point aside and return to the main
argument. It appears to me that the argument quoted above implies a serious
restriction of the omnipotence of the Almighty. It is admitted that there are
certain things that He cannot do such as making one equal to two, but should we
not believe that He has freedom to confer a soul on an elephant if He sees fit?
We might expect that He would only exercise this power in conjunction with a
mutation which provided the elephant with an appropriately improved brain to
minister to the needs of this sort[. An argument of exactly similar form may be
made for the case of machines. It may seem different because it is more
difficult to "swallow." But this really only means that we think it
would be less likely that He would consider the circumstances suitable for
conferring a soul. The circumstances in question are discussed in the rest of
this paper. In attempting to construct such machines we should not be
irreverently usurping His power of creating souls, any more than we are in the
procreation of children: rather we are, in either case, instruments of His will
providing .mansions for the souls that He creates.
However, this is mere speculation. I
am not very impressed with theological arguments whatever they may be used to
support. Such arguments have often been found unsatisfactory in the past. In
the time of Galileo it was argued that the texts, "And the sun stood still
. . . and hasted not to go down about a whole day" (Joshua x. 13) and
"He laid the foundations of the earth, that it should not move at any
time" (Psalm cv. 5) were an adequate refutation of the Copernican theory.
With our present knowledge such an argument appears futile. When that knowledge
was not available it made a quite different impression.
(2) The "Heads in the
Sand" Objection
The consequences of machines
thinking would be too dreadful. Let us hope and believe that they cannot do
so."
This argument is seldom expressed
quite so openly as in the form above. But it affects most of us who think about
it at all. We like to believe that Man is in some subtle way superior to the
rest of creation. It is best if he can be shown to be necessarily superior, for
then there is no danger of him losing his commanding position. The popularity
of the theological argument is clearly connected with this feeling. It is
likely to be quite strong in intellectual people, since they value the power of
thinking more highly than others, and are more inclined to base their belief in
the superiority of Man on this power.
I do not think that this argument is
sufficiently substantial to require refutation. Consolation would be more
appropriate: perhaps this should be sought in the transmigration of souls.
(3) The Mathematical Objection
There are a number of results of
mathematical logic which can be used to show that there are limitations to the
powers of discrete-state machines. The best known of these results is known as
Godel's theorem ( 1931 ) and shows that in any sufficiently powerful logical
system statements can be formulated which can neither be proved nor disproved
within the system, unless possibly the system itself is inconsistent. There are
other, in some respects similar, results due to Church (1936), Kleene (1935),
Rosser, and Turing (1937). The latter result is the most convenient to
consider, since it refers directly to machines, whereas the others can only be
used in a comparatively indirect argument: for instance if Godel's theorem is
to be used we need in addition to have some means of describing logical systems
in terms of machines, and machines in terms of logical systems. The result in
question refers to a type of machine which is essentially a digital computer
with an infinite capacity. It states that there are certain things that such a
machine cannot do. If it is rigged up to give answers to questions as in the
imitation game, there will be some questions to which it will either give a
wrong answer, or fail to give an answer at all however much time is allowed for
a reply. There may, of course, be many such questions, and questions which
cannot be answered by one machine may be satisfactorily answered by another. We
are of course supposing for the present that the questions are of the kind to
which an answer "Yes" or "No" is appropriate, rather than
questions such as "What do you think of Picasso?" The questions that
we know the machines must fail on are of this type, "Consider the machine
specified as follows. . . . Will this machine ever answer 'Yes' to any question?"
The dots are to be replaced by a description of some machine in a standard
form, which could be something like that used in §5. When the machine described
bears a certain comparatively simple relation to the machine which is under
interrogation, it can be shown that the answer is either wrong or not
forthcoming. This is the mathematical result: it is argued that it proves a
disability of machines to which the human intellect is not subject.
The short answer to this argument is
that although it is established that there are limitations to the Powers If any
particular machine, it has only been stated, without any sort of proof, that no
such limitations apply to the human intellect. But I do not think this view can
be dismissed quite so lightly. Whenever one of these machines is asked the
appropriate critical question, and gives a definite answer, we know that this
answer must be wrong, and this gives us a certain feeling of superiority. Is
this feeling illusory? It is no doubt quite genuine, but I do not think too
much importance should be attached to it. We too often give wrong answers to
questions ourselves to be justified in being very pleased at such evidence of
fallibility on the part of the machines. Further, our superiority can only be
felt on such an occasion in relation to the one machine over which we have
scored our petty triumph. There would be no question of triumphing
simultaneously over all machines. In short, then, there might be men cleverer
than any given machine, but then again there might be other machines cleverer
again, and so on.
Those who hold to the mathematical
argument would, I think, mostly he willing to accept the imitation game as a
basis for discussion, Those who believe in the two previous objections would
probably not be interested in any criteria.
(4) The Argument from Consciousness
This argument is very, well
expressed in Professor Jefferson's Lister Oration for 1949, from which I quote.
"Not until a machine can write a sonnet or compose a concerto because of
thoughts and emotions felt, and not by the chance fall of symbols, could we
agree that machine equals brain-that is, not only write it but know that it had
written it. No mechanism could feel (and not merely artificially signal, an
easy contrivance) pleasure at its successes, grief when its valves fuse, be
warmed by flattery, be made miserable by its mistakes, be charmed by sex, be
angry or depressed when it cannot get what it wants."
This argument appears to be a denial
of the validity of our test. According to the most extreme form of this view
the only way by which one could be sure that machine thinks is to be the
machine and to feel oneself thinking. One could then describe these feelings to
the world, but of course no one would be justified in taking any notice. Likewise
according to this view the only way to know that a man thinks is to be that
particular man. It is in fact the solipsist point of view. It may be the most
logical view to hold but it makes communication of ideas difficult. A is liable
to believe "A thinks but B does not" whilst B believes "B thinks
but A does not." instead of arguing continually over this point it is
usual to have the polite convention that everyone thinks.
I am sure that Professor Jefferson
does not wish to adopt the extreme and solipsist point of view. Probably he
would be quite willing to accept the imitation game as a test. The game (with
the player B omitted) is frequently used in practice under the name of viva
voce to discover whether some one really understands something or has "learnt
it parrot fashion." Let us listen in to a part of such a viva voce:
Interrogator: In the first line of
your sonnet which reads "Shall I compare thee to a summer's day,"
would not "a spring day" do as well or better?
Witness: It wouldn't scan.
Interrogator: How about "a
winter's day," That would scan all right.
Witness: Yes, but nobody wants to be
compared to a winter's day.
Interrogator: Would you say Mr.
Pickwick reminded you of Christmas?
Witness: In a way.
Interrogator: Yet Christmas is a
winter's day, and I do not think Mr. Pickwick would mind the comparison.
Witness: I don't think you're
serious. By a winter's day one means a typical winter's day, rather than a
special one like Christmas.
And so on, What would Professor
Jefferson say if the sonnet-writing machine was able to answer like this in the
viva voce? I do not know whether he would regard the machine as
"merely artificially signaling" these answers, but if the answers
were as satisfactory and sustained as in the above passage I do not think he
would describe it as "an easy contrivance." This phrase is, I think,
intended to cover such devices as the inclusion in the machine of a record of
someone reading a sonnet, with appropriate switching to turn it on from time to
time.
In short then, I think that most of
those who support the argument from consciousness could be persuaded to abandon
it rather than be forced into the solipsist position. They will then probably
be willing to accept our test.
I do not wish to give the impression
that I think there is no mystery about consciousness. There is, for instance,
something of a paradox connected with any attempt to localize it. But I do not
think these mysteries necessarily need to be solved before we can answer the
question with which we are concerned in this paper.
(5) Arguments from Various
Disabilities
These arguments take the form,
"I grant you that you can make machines do all the things you have
mentioned but you will never be able to make one to do X." Numerous
features X are suggested in this connection I offer a selection:
Be kind, resourceful, beautiful,
friendly, have initiative, have a sense of humour, tell right from wrong, make
mistakes, fall in love, enjoy strawberries and cream, make some one fall in
love with it, learn from experience, use words properly, be the subject of its
own thought, have as much diversity of behaviour as a man, do something really
new.
No support is usually offered for
these statements. I believe they are mostly founded on the principle of
scientific induction. A man has seen thousands of machines in his lifetime.
From what he sees of them he draws a number of general conclusions. They are
ugly, each is designed for a very limited purpose, when required for a minutely
different purpose they are useless, the variety of behaviour of any one of them
is very small, etc., etc. Naturally he concludes that these are necessary
properties of machines in general. Many of these limitations are associated
with the very small storage capacity of most machines. (I am assuming that the
idea of storage capacity is extended in some way to cover machines other than
discrete-state machines. The exact definition does not matter as no
mathematical accuracy is claimed in the present discussion,) A few years ago,
when very little had been heard of digital computers, it was possible to elicit
much incredulity concerning them, if one mentioned their properties without
describing their construction. That was presumably due to a similar application
of the principle of scientific induction. These applications of the principle
are of course largely unconscious. When a burnt child fears the fire and shows
that he fears it by avoiding it, f should say that he was applying scientific
induction. (I could of course also describe his behaviour in many other ways.)
The works and customs of mankind do not seem to be very suitable material to
which to apply scientific induction. A very large part of space-time must be
investigated, if reliable results are to be obtained. Otherwise we may (as most
English 'Children do) decide that everybody speaks English, and that it is
silly to learn French.
There are, however, special remarks
to be made about many of the disabilities that have been mentioned. The
inability to enjoy strawberries and cream may have struck the reader as
frivolous. Possibly a machine might be made to enjoy this delicious dish, but
any attempt to make one do so would be idiotic. What is important about this
disability is that it contributes to some of the other disabilities, e.g., to
the difficulty of the same kind of friendliness occurring between man and
machine as between white man and white man, or between black man and black man.
The claim that "machines cannot
make mistakes" seems a curious one. One is tempted to retort, "Are
they any the worse for that?" But let us adopt a more sympathetic
attitude, and try to see what is really meant. I think this criticism can be
explained in terms of the imitation game. It is claimed that the interrogator
could distinguish the machine from the man simply by setting them a number of
problems in arithmetic. The machine would be unmasked because of its deadly
accuracy. The reply to this is simple. The machine (programmed for playing the
game) would not attempt to give the right answers to the arithmetic problems.
It would deliberately introduce mistakes in a manner calculated to confuse the
interrogator. A mechanical fault would probably show itself through an
unsuitable decision as to what sort of a mistake to make in the arithmetic.
Even this interpretation of the criticism is not sufficiently sympathetic. But
we cannot afford the space to go into it much further. It seems to me that this
criticism depends on a confusion between two kinds of mistake, We may call them
"errors of functioning" and "errors of conclusion." Errors
of functioning are due to some mechanical or electrical fault which causes the
machine to behave otherwise than it was designed to do. In philosophical
discussions one likes to ignore the possibility of such errors; one is
therefore discussing "abstract machines." These abstract machines are
mathematical fictions rather than physical objects. By definition they are
incapable of errors of functioning. In this sense we can truly say that
"machines can never make mistakes." Errors of conclusion can only
arise when some meaning is attached to the output signals from the machine. The
machine might, for instance, type out mathematical equations, or sentences in
English. When a false proposition is typed we say that the machine has
committed an error of conclusion. There is clearly no reason at all for saying
that a machine cannot make this kind of mistake. It might do nothing but type
out repeatedly "O = I." To take a less perverse example, it might
have some method for drawing conclusions by scientific induction. We must
expect such a method to lead occasionally to erroneous results.
The claim that a machine cannot be
the subject of its own thought can of course only be answered if it can be
shown that the machine has some thought with some subject matter. Nevertheless,
"the subject matter of a machine's operations" does seem to mean
something, at least to the people who deal with it. If, for instance, the
machine was trying to find a solution of the equation x2 - 40x - 11 = 0 one
would be tempted to describe this equation as part of the machine's subject
matter at that moment. In this sort of sense a machine undoubtedly can be its
own subject matter. It may be used to help in making up its own programmes, or
to predict the effect of alterations in its own structure. By observing the
results of its own behaviour it can modify its own programmes so as to achieve
some purpose more effectively. These are possibilities of the near future,
rather than Utopian dreams.
The criticism that a machine cannot
have much diversity of behaviour is just a way of saying that it cannot have
much storage capacity. Until fairly recently a storage capacity of even a
thousand digits was very rare.
The criticisms that we are
considering here are often disguised forms of the argument from consciousness,
Usually if one maintains that a machine can do one of these things, and
describes the kind of method that the machine could use, one will not make much
of an impression. It is thought that tile method (whatever it may be, for it
must be mechanical) is really rather base. Compare the parentheses in
Jefferson's statement quoted on page 22.
(6) Lady Lovelace's Objection
Our most detailed information of
Babbage's Analytical Engine comes from a memoir by Lady Lovelace ( 1842). In it
she states, "The Analytical Engine has no pretensions to originate
anything. It can do whatever we know how to order it to perform"
(her italics). This statement is quoted by Hartree ( 1949) who adds: "This
does not imply that it may not be possible to construct electronic equipment
which will 'think for itself,' or in which, in biological terms, one could set
up a conditioned reflex, which would serve as a basis for 'learning.' Whether
this is possible in principle or not is a stimulating and exciting question,
suggested by some of these recent developments But it did not seem that the
machines constructed or projected at the time had this property."
I am in thorough agreement with
Hartree over this. It will be noticed that he does not assert that the machines
in question had not got the property, but rather that the evidence available to
Lady Lovelace did not encourage her to believe that they had it. It is quite
possible that the machines in question had in a sense got this property. For
suppose that some discrete-state machine has the property. The Analytical
Engine was a universal digital computer, so that, if its storage capacity and
speed were adequate, it could by suitable programming be made to mimic the
machine in question. Probably this argument did not occur to the Countess or to
Babbage. In any case there was no obligation on them to claim all that could be
claimed.
This whole question will be
considered again under the heading of learning machines.
A variant of Lady Lovelace's
objection states that a machine can "never do anything really new."
This may be parried for a moment with the saw, "There is nothing new under
the sun." Who can be certain that "original work" that he has
done was not simply the growth of the seed planted in him by teaching, or the
effect of following well-known general principles. A better variant of the
objection says that a machine can never "take us by surprise." This
statement is a more direct challenge and can be met directly. Machines take me
by surprise with great frequency. This is largely because I do not do
sufficient calculation to decide what to expect them to do, or rather because,
although I do a calculation, I do it in a hurried, slipshod fashion, taking
risks. Perhaps I say to myself, "I suppose the Voltage here ought to he
the same as there: anyway let's assume it is." Naturally I am often wrong,
and the result is a surprise for me for by the time the experiment is done
these assumptions have been forgotten. These admissions lay me open to lectures
on the subject of my vicious ways, but do not throw any doubt on my credibility
when I testify to the surprises I experience.
I do not expect this reply to
silence my critic. He will probably say that h surprises are due to some
creative mental act on my part, and reflect no credit on the machine. This
leads us back to the argument from consciousness, and far from the idea of
surprise. It is a line of argument we must consider closed, but it is perhaps
worth remarking that the appreciation of something as surprising requires as
much of a "creative mental act" whether the surprising event
originates from a man, a book, a machine or anything else.
The view that machines cannot give
rise to surprises is due, I believe, to a fallacy to which philosophers and
mathematicians are particularly subject. This is the assumption that as soon as
a fact is presented to a mind all consequences of that fact spring into the
mind simultaneously with it. It is a very useful assumption under many
circumstances, but one too easily forgets that it is false. A natural
consequence of doing so is that one then assumes that there is no virtue in the
mere working out of consequences from data and general principles.
(7) Argument from Continuity in the
Nervous System
The nervous system is certainly not
a discrete-state machine. A small error in the information about the size of a
nervous impulse impinging on a neuron, may make a large difference to the size
of the outgoing impulse. It may be argued that, this being so, one cannot
expect to be able to mimic the behaviour of the nervous system with a
discrete-state system.
It is true that a discrete-state
machine must be different from a continuous machine. But if we adhere to the
conditions of the imitation game, the interrogator will not be able to take any
advantage of this difference. The situation can be made clearer if we consider
sonic other simpler continuous machine. A differential analyser will do very
well. (A differential analyser is a certain kind of machine not of the
discrete-state type used for some kinds of calculation.) Some of these provide
their answers in a typed form, and so are suitable for taking part in the game.
It would not be possible for a digital computer to predict exactly what answers
the differential analyser would give to a problem, but it would be quite
capable of giving the right sort of answer. For instance, if asked to give the
value of (actually about 3.1416) it would be reasonable to choose at random
between the values 3.12, 3.13, 3.14, 3.15, 3.16 with the probabilities of 0.05,
0.15, 0.55, 0.19, 0.06 (say). Under these circumstances it would be very
difficult for the interrogator to distinguish the differential analyser from
the digital computer.
(8) The Argument from Informality of
Behaviour
It is not possible to produce a set
of rules purporting to describe what a man should do in every conceivable set
of circumstances. One might for instance have a rule that one is to stop when
one sees a red traffic light, and to go if one sees a green one, but what if by
some fault both appear together? One may perhaps decide that it is safest to
stop. But some further difficulty may well arise from this decision later. To
attempt to provide rules of conduct to cover every eventuality, even those
arising from traffic lights, appears to be impossible. With all this I agree.
From this it is argued that we
cannot be machines. I shall try to reproduce the argument, but I fear I shall
hardly do it justice. It seems to run something like this. "if each man
had a definite set of rules of conduct by which he regulated his life he would
be no better than a machine. But there are no such rules, so men cannot be
machines." The undistributed middle is glaring. I do not think the
argument is ever put quite like this, but I believe this is the argument used
nevertheless. There may however be a certain confusion between "rules of
conduct" and "laws of behaviour" to cloud the issue. By
"rules of conduct" I mean precepts such as "Stop if you see red
lights," on which one can act, and of which one can be conscious. By
"laws of behaviour" I mean laws of nature as applied to a man's body
such as "if you pinch him he will squeak." If we substitute
"laws of behaviour which regulate his life" for "laws of conduct
by which he regulates his life" in the argument quoted the undistributed
middle is no longer insuperable. For we believe that it is not only true that
being regulated by laws of behaviour implies being some sort of machine (though
not necessarily a discrete-state machine), but that conversely being such a
machine implies being regulated by such laws. However, we cannot so easily
convince ourselves of the absence of complete laws of behaviour as of complete
rules of conduct. The only way we know of for finding such laws is scientific
observation, and we certainly know of no circumstances under which we could
say, "We have searched enough. There are no such laws."
We can demonstrate more forcibly
that any such statement would be unjustified. For suppose we could be sure of
finding such laws if they existed. Then given a discrete-state machine it
should certainly be possible to discover by observation sufficient about it to
predict its future behaviour, and this within a reasonable time, say a thousand
years. But this does not seem to be the case. I have set up on the Manchester
computer a small programme using only 1,000 units of storage, whereby the
machine supplied with one sixteen-figure number replies with another within two
seconds. I would defy anyone to learn from these replies sufficient about the
programme to be able to predict any replies to untried values.
(9) The Argument from Extrasensory
Perception
I assume that the reader is familiar
with the idea of extrasensory perception, and the meaning of the four items of
it, viz., telepathy, clairvoyance, precognition and psychokinesis. These
disturbing phenomena seem to deny all our usual scientific ideas. How we should
like to discredit them! Unfortunately the statistical evidence, at least for
telepathy, is overwhelming. It is very difficult to rearrange one's ideas so as
to fit these new facts in. Once one has accepted them it does not seem a very
big step to believe in ghosts and bogies. The idea that our bodies move simply
according to the known laws of physics, together with some others not yet
discovered but somewhat similar, would be one of the first to go.
This argument is to my mind quite a
strong one. One can say in reply that many scientific theories seem to remain
workable in practice, in spite of clashing with ESP; that in fact one can get
along very nicely if one forgets about it. This is rather cold comfort, and one
fears that thinking is just the kind of phenomenon where ESP may be especially
relevant.
A more specific argument based on
ESP might run as follows: "Let us play the imitation game, using as
witnesses a man who is good as a telepathic receiver, and a digital computer.
The interrogator can ask such questions as 'What suit does the card in my right
hand belong to?' The man by telepathy or clairvoyance gives the right answer
130 times out of 400 cards. The machine can only guess at random, and perhaps
gets 104 right, so the interrogator makes the right identification." There
is an interesting possibility which opens here. Suppose the digital computer
contains a random number generator. Then it will be natural to use this to
decide what answer to give. But then the random number generator will be
subject to the psychokinetic powers of the interrogator. Perhaps this
psychokinesis might cause the machine to guess right more often than would be
expected on a probability calculation, so that the interrogator might still be
unable to make the right identification. On the other hand, he might be able to
guess right without any questioning, by clairvoyance. With ESP anything may happen.
If telepathy is admitted it will be
necessary to tighten our test up. The situation could be regarded as analogous
to that which would occur if the interrogator were talking to himself and one
of the competitors was listening with his ear to the wall. To put the
competitors into a "telepathy-proof room" would satisfy all
requirements.
7. Learning Machines
The reader will have anticipated
that I have no very convincing arguments of a positive nature to support my
views. If I had I should not have taken such pains to point out the fallacies
in contrary views. Such evidence as I have I shall now give.
Let us return for a moment to Lady
Lovelace's objection, which stated that the machine can only do what we tell it
to do. One could say that a man can "inject" an idea into the
machine, and that it will respond to a certain extent and then drop into
quiescence, like a piano string struck by a hammer. Another simile would be an
atomic pile of less than critical size: an injected idea is to correspond to a
neutron entering the pile from without. Each such neutron will cause a certain
disturbance which eventually dies away. If, however, the size of the pile is
sufficiently increased, tire disturbance caused by such an incoming neutron
will very likely go on and on increasing until the whole pile is destroyed. Is
there a corresponding phenomenon for minds, and is there one for machines?
There does seem to be one for the human mind. The majority of them seem to be
"subcritical," i.e., to correspond in this analogy to piles of
subcritical size. An idea presented to such a mind will on average give rise to
less than one idea in reply. A smallish proportion are supercritical. An idea
presented to such a mind that may give rise to a whole "theory"
consisting of secondary, tertiary and more remote ideas. Animals minds seem to
be very definitely subcritical. Adhering to this analogy we ask, "Can a
machine be made to be supercritical?"
The "skin-of-an-onion"
analogy is also helpful. In considering the functions of the mind or the brain
we find certain operations which we can explain in purely mechanical terms.
This we say does not correspond to the real mind: it is a sort of skin which we
must strip off if we are to find the real mind. But then in what remains we
find a further skin to be stripped off, and so on. Proceeding in this way do we
ever come to the "real" mind, or do we eventually come to the skin
which has nothing in it? In the latter case the whole mind is mechanical. (It
would not be a discrete-state machine however. We have discussed this.)
These last two paragraphs do not
claim to be convincing arguments. They should rather be described as
"recitations tending to produce belief."
The only really satisfactory support
that can be given for the view expressed at the beginning of §6, will be that
provided by waiting for the end of the century and then doing the experiment
described. But what can we say in the meantime? What steps should be taken now
if the experiment is to be successful?
As I have explained, the problem is
mainly one of programming. Advances in engineering will have to be made too,
but it seems unlikely that these will not be adequate for the requirements.
Estimates of the storage capacity of the brain vary from 1010 to 1015
binary digits. I incline to the lower values and believe that only a very small
fraction is used for the higher types of thinking. Most of it is probably used
for the retention of visual impressions, I should be surprised if more than 109
was required for satisfactory playing of the imitation game, at any rate
against a blind man. (Note: The capacity of the Encyclopaedia Britannica,
11th edition, is 2 X 109) A storage capacity of 107,
would be a very practicable possibility even by present techniques. It is
probably not necessary to increase the speed of operations of the machines at
all. Parts of modern machines which can be regarded as analogs of nerve cells
work about a thousand times faster than the latter. This should provide a
"margin of safety" which could cover losses of speed arising in many
ways, Our problem then is to find out how to programme these machines to play
the game. At my present rate of working I produce about a thousand digits of
progratiirne a day, so that about sixty workers, working steadily through the
fifty years might accomplish the job, if nothing went into the wastepaper
basket. Some more expeditious method seems desirable.
In the process of trying to imitate
an adult human mind we are bound to think a good deal about the process which
has brought it to the state that it is in. We may notice three components.
(a) The initial state of the mind,
say at birth,
(b) The education to which it has
been subjected,
(c) Other experience, not to be
described as education, to which it has been subjected.
Instead of trying to produce a
programme to simulate the adult mind, why not rather try to produce one which
simulates the child's? If this were then subjected to an appropriate course of
education one would obtain the adult brain. Presumably the child brain is
something like a notebook as one buys it from the stationer's. Rather little
mechanism, and lots of blank sheets. (Mechanism and writing are from our point
of view almost synonymous.) Our hope is that there is so little mechanism in the
child brain that something like it can be easily programmed. The amount of work
in the education we can assume, as a first approximation, to be much the same
as for the human child.
We have thus divided our problem
into two parts. The child programme and the education process. These two remain
very closely connected. We cannot expect to find a good child machine at the
first attempt. One must experiment with teaching one such machine and see how
well it learns. One can then try another and see if it is better or worse.
There is an obvious connection between this process and evolution, by the
identifications
Structure of the child machine =
hereditary material
Changes of the child machine =
mutation,
Natural selection = judgment of the
experimenter
One may hope, however, that this
process will be more expeditious than evolution. The survival of the fittest is
a slow method for measuring advantages. The experimenter, by the exercise of
intelligence, should he able to speed it up. Equally important is the fact that
he is not restricted to random mutations. If he can trace a cause for some
weakness he can probably think of the kind of mutation which will improve it.
It will not be possible to apply
exactly the same teaching process to the machine as to a normal child. It will
not, for instance, be provided with legs, so that it could not be asked to go
out and fill the coal scuttle. Possibly it might not have eyes. But however
well these deficiencies might be overcome by clever engineering, one could not
send the creature to school without the other children making excessive fun of
it. It must be given some tuition. We need not be too concerned about the legs,
eyes, etc. The example of Miss Helen Keller shows that education can take place
provided that communication in both directions between teacher and pupil can
take place by some means or other.
We normally associate punishments
and rewards with the teaching process. Some simple child machines can be
constructed or programmed on this sort of principle. The machine has to be so
constructed that events which shortly preceded the occurrence of a punishment
signal are unlikely to be repeated, whereas a reward signal increased the
probability of repetition of the events which led up to it. These definitions
do not presuppose any feelings on the part of the machine, I have done some
experiments with one such child machine, and succeeded in teaching it a few
things, but the teaching method was too unorthodox for the experiment to be
considered really successful.
The use of punishments and rewards
can at best be a part of the teaching process. Roughly speaking, if the teacher
has no other means of communicating to the pupil, the amount of information
which can reach him does not exceed the total number of rewards and punishments
applied. By the time a child has learnt to repeat "Casabianca" he
would probably feel very sore indeed, if the text could only be discovered by a
"Twenty Questions" technique, every "NO" taking the form of
a blow. It is necessary therefore to have some other "unemotional"
channels of communication. If these are available it is possible to teach a
machine by punishments and rewards to obey orders given in some language, e.g.,
a symbolic language. These orders are to be transmitted through the
"unemotional" channels. The use of this language will diminish
greatly the number of punishments and rewards required.
Opinions may vary as to the
complexity which is suitable in the child machine. One might try to make it as
simple as possible consistently with the general principles. Alternatively one
might have a complete system of logical inference "built in."' In the
latter case the store would be largely occupied with definitions and
propositions. The propositions would have various kinds of status, e.g., well-established
facts, conjectures, mathematically proved theorems, statements given by an
authority, expressions having the logical form of proposition but not
belief-value. Certain propositions may be described as "imperatives."
The machine should be so constructed that as soon as an imperative is classed
as "well established" the appropriate action automatically takes
place. To illustrate this, suppose the teacher says to the machine, "Do
your homework now." This may cause "Teacher says 'Do your homework now'
" to be included amongst the well-established facts. Another such fact
might be, "Everything that teacher says is true." Combining these may
eventually lead to the imperative, "Do your homework now," being
included amongst the well-established facts, and this, by the construction of
the machine, will mean that the homework actually gets started, but the effect
is very satisfactory. The processes of inference used by the machine need not
be such as would satisfy the most exacting logicians. There might for instance
be no hierarchy of types. But this need not mean that type fallacies will
occur, any more than we are bound to fall over unfenced cliffs. Suitable
imperatives (expressed within the systems, not forming part of the rules of the
system) such as "Do not use a class unless it is a subclass of one which
has been mentioned by teacher" can have a similar effect to "Do not
go too near the edge."
The imperatives that can be obeyed
by a machine that has no limbs are bound to be of a rather intellectual character,
as in the example (doing homework) given above. important amongst such
imperatives will be ones which regulate the order in which the rules of the
logical system concerned are to be applied, For at each stage when one is using
a logical system, there is a very large number of alternative steps, any of
which one is permitted to apply, so far as obedience to the rules of the
logical system is concerned. These choices make the difference between a
brilliant and a footling reasoner, not the difference between a sound and a
fallacious one. Propositions leading to imperatives of this kind might be
"When Socrates is mentioned, use the syllogism in Barbara" or
"If one method has been proved to be quicker than another, do not use the
slower method." Some of these may be "given by authority," but
others may be produced by the machine itself, e.g. by scientific induction.
The idea of a learning machine may
appear paradoxical to some readers. How can the rules of operation of the
machine change? They should describe completely how the machine will react
whatever its history might be, whatever changes it might undergo. The rules are
thus quite time-invariant. This is quite true. The explanation of the paradox
is that the rules which get changed in the learning process are of a rather
less pretentious kind, claiming only an ephemeral validity. The reader may draw
a parallel with the Constitution of the United States.
An important feature of a learning
machine is that its teacher will often be very largely ignorant of quite what
is going on inside, although he may still be able to some extent to predict his
pupil's behavior. This should apply most strongly to the later education of a
machine arising from a child machine of well-tried design (or programme). This
is in clear contrast with normal procedure when using a machine to do
computations one's object is then to have a clear mental picture of the state
of the machine at each moment in the computation. This object can only be
achieved with a struggle. The view that "the machine can only do what we
know how to order it to do,"' appears strange in face of this. Most of the
programmes which we can put into the machine will result in its doing something
that we cannot make sense (if at all, or which we regard as completely random
behaviour. Intelligent behaviour presumably consists in a departure from the
completely disciplined behaviour involved in computation, but a rather slight
one, which does not give rise to random behaviour, or to pointless repetitive
loops. Another important result of preparing our machine for its part in the
imitation game by a process of teaching and learning is that "human
fallibility" is likely to be omitted in a rather natural way, i.e.,
without special "coaching." (The reader should reconcile this with
the point of view on pages 23 and 24.) Processes that are learnt do not produce
a hundred per cent certainty of result; if they did they could not be unlearnt.
It is probably wise to include a
random element in a learning machine. A random element is rather useful when we
are searching for a solution of some problem. Suppose for instance we wanted to
find a number between 50 and 200 which was equal to the square of the sum of
its digits, we might start at 51 then try 52 and go on until we got a number
that worked. Alternatively we might choose numbers at random until we got a
good one. This method has the advantage that it is unnecessary to keep track of
the values that have been tried, but the disadvantage that one may try the same
one twice, but this is not very important if there are several solutions. The
systematic method has the disadvantage that there may be an enormous block
without any solutions in the region which has to be investigated first, Now the
learning process may be regarded as a search for a form of behaviour which will
satisfy the teacher (or some other criterion). Since there is probably a very
large number of satisfactory solutions the random method seems to be better
than the systematic. It should be noticed that it is used in the analogous
process of evolution. But there the systematic method is not possible. How
could one keep track of the different genetical combinations that had been
tried, so as to avoid trying them again?
We may hope that machines will
eventually compete with men in all purely intellectual fields. But which are
the best ones to start with? Even this is a difficult decision. Many people
think that a very abstract activity, like the playing of chess, would be best.
It can also be maintained that it is best to provide the machine with the best
sense organs that money can buy, and then teach it to understand and speak
English. This process could follow the normal teaching of a child. Things would
be pointed out and named, etc. Again I do not know what the right answer is,
but I think both approaches should be tried.
We can only see a short distance
ahead, but we can see plenty there that needs to be done.
