CPSC 533
Philosophical Foundations of Artificial
Intelligence
Presented by: Arthur Fischer
Philosophical Questions in AI
How can mind arise from nonmind? (This is the mind-body
problem.)
How can there be “free will” in the mind, if the brain is
subject to the laws of nature?
What does it mean to “know” or “understand” something.
Can we mechanise the discovery of knowledge.
More Questions
Is there such a thing as a priori knowledge?
What is the structure of knowledge?
Can mind exist in something other than a brain?
What do we communicate when we communicate with
language?
Alan M. Turing
Computing Machinery and
Intelligence
The Imitation Game
If a computer can “fool” a human interrogator into
believing that it is human, then it may be said that the
machine is intelligent, and thinks.
The scope of questions that may be asked is virtually
unlimited.
An Interrogation
Q: Please write me a sonnet on the subject of the Forth Bridge.
A: Count me out of this one. I never could write poetry.
Q: Add 34957 to 70764.
A: <Pause about 30 seconds> 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: <Pause about 15 seconds> R-R8 mate.
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.”
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.”
The Mathematical Objection
“[T]here are limitations to the powers of discrete
state machines” therefore there are questions
that humans can answer, but not machines.
The Argument from
Consciousness
“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.”
Arguments from Various
Disabilities
“I grant you that you can make machines do all
the things that you have mentioned but you will
never be able to make one to do X.”
Lady Lovelace’s Objection
”The Analytical Engine has no pretensions to
originate anything. It can do whatever we
know how to order it to perform.”
“[A] machine can ‘never do anything really
new’.”
Arguments from Continuity in
the Nervous System
“The nervous system is certainly not a discretestate 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 machine.”
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. … To
attempt to provide rules of conduct to cover every
eventuality… appears to be impossible.”
The Argument from ExtraSensory Perception
Using ESP, one could conceivably route around
the issue in the Imitation Game, asking questions
that would require telepathy or clairvoyance in
order to be frequently answered correctly.
J. R. Lucas
Minds, Machines and Gödel
Incompleteness in a Nutshell
In any consistent formal system which is strong enough
to produce simple arithmetic there are formulae which
cannot be proved-in-the-system.
Even if you add these formulae as axioms to the formal
system, there exist other formulae that cannot be provedin-the-system.
This is a necessity for any such formal system.
How do we do it?
Create a formal statement which says, under interpretation, “I
cannot be proven in this formal system”. This statement is called
a Gödel-statement.
If the statement were provable in the system, it would be false,
and thus the system would be inconsistent.
If the statement cannot be proven in the system, it is true, and
therefore there are true statements that cannot be proven in the
system, meaning that the system is incomplete.
The Argument
Since a machine is a concrete representation of a formal system, a
human mind can find the system’s Gödel-statement, and the
machine would be unable to correctly determine that the statement
is true.
The human interrogator can (trivially) determine that the statement
is true, therefore there is something that the human mind can do,
that the machine cannot. Ergo, the human mind is not a machine.
And in no possible way can a machine be equivalent to a human
mind.
Objections
This assumes that the human mind is not a formal system
itself. The argument “begs the question.”
“Lucas cannot consistently assert this sentence.” could be
seen as Lucas’ Gödel-statement.
[C.H. Whitely]
Lucas imagines that machines must necessarily work at
the “machine level” of gears, switches, transistors, etc,
while implicitly assuming that the human mind works at a
higher level.
John Searle
Minds, Brains, and Programs
Into the Chinese Room
If a computer’s answers is indistinguishable from a
human’s, then that computer is said to have “understood”
the questions as well as a human. This is a Strong AI
position.
Therefore, Searle must understand Chinese (writing) as
well as any native speaker of Chinese.
A Possible Instruction
Conclusions
The Turing Test is not a suitable test for intelligence.
Could something think, understand, and so on solely in
virtue of being a computer with the right sort of
program? Could instantiating a program by itself be a
sufficient condition of understanding? NO.
The Systems Reply
“While it is true that the individual person… does not
understand [Chinese], the fact is that he is merely part of
a whole system, and the system does understand the
story.”
The Brain Simulator Reply
“Suppose we design a program that … simulates the
actual sequence of neuron firings at the synapses of the
brain of a native Chinese speaker…. … Now surely in
such a case we would have to say that the machine
understood the stories; and if we deny that, wouldn’t we
also have to deny that native Chinese speakers
understood the stories?”
The Other Minds Reply
“How do you know that other people understand Chinese
or anything else? Only by their behavior.”