Philosophy 024: Big Ideas

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Philosophy 024 Big Ideas Prof. Robert DiSalle
(rdisalle_at_uwo.ca) Talbot College 408,
519-661-2111 x85763 Office Hours Monday and
Wednesday 12-2 PM Course Website
http//instruct.uwo.ca/philosophy/024/ New Link!
The final exam
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Philosophical questions about the computer What
is intelligence? What is thought? Are these
functions that a machine can have? If machines
can display thought or intelligence, does
this imply that human cognition is a kind of
computational ability? If human cognition is
computation, does that imply that the human mind
in general is a kind of machine?
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Some philosophical background to the
computer René Descartes, 1596-1650 Mathesis
universalis G.W. Leibniz (1646-1716) Universal
characteristic, calculating machine Charles
Babbage (1791-1871) Calculating machines George
Boole (1815-1864) The Laws of Thought Gottlob
Frege (1848-1925) Conceptual Notation Kurt
Gödel (1906-1978) Formally Undecidable
Propositions Alan Turing (1912-1954) The
Turing Machine
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Descartes on how to tell the difference between a
human being and a mechanical imitation They
could never use speech or other signs as we do
when placing our thoughts on record for the
benefit of others. For we can easil understand a
machines being constituted so that it can utter
words, and even emit some responses to actions on
it of a corporeal kind, which brings about a
change in its organsBut it never happens that it
arranges its speech in various ways, in order to
reply appropriately to everything that may be
said in its presence, as even the lowest type of
man can do
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Descartes And the second difference is, that
although machines can perform certain things as
well as or perhaps better than any of us can do,
they infallibly fall short in others, by the
which means we may discover that they did not act
from knowledge, but only from the disposition of
their organs. For while reason is a universal
instrument which can serve for all contingencies,
these organs have need of some special adaptation
for every particular action. It is morally
impossible that there should be sufficient
diversity in any machine to allow it to act in
all the events of life in the same way as our
reason causes us to act.
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1956 Howard Aiken, Harvard University, on the
idea of a universal machine If it should
turn out that the basic logics of a machine
designed for the numerical solution of
differential equations coincide with the logics
of a machine intended to make bills for a
department store, I would regard this as the most
amazing coincidence that I have ever encountered.
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Leibniz When, several years ago, I saw for the
first time an instrument which, when carried,
automatically records the number of steps taken
by a pedestrian, it occurred to me at once that
the entire arithmetic could be subjected to a
similar kind of machinery so that not only
counting, but also addition and subtraction,
multiplication and division could be accomplished
by, a suitably arranged machine easily, promptly,
and with sure results.
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Leibniz on the Universal Characteristic Although
many persons of great ability, especially in our
century, may have claimed to offer us
demonstrations in questions of physics,
metaphysics, ethics, and even in politics,
jurisprudence, and medicine, nevertheless they
have either been mistaken (because every step is
on slippery ground and it is difficult not to
fall unless guided by some tangible directions),
or even when they succeed, they have been unable
to convince everyone with their reasoning
(because there has not yet been a way to examine
arguments by means of some easy tests available
to everyone).
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Whence it is manifest that if we could find
characters or signs appropriate for expressing
all our thoughts as definitely and as exactly as
arithmetic expresses numbers or geometric
analysis expresses lines, we could in all
subjects in so far as they are amenable to
reasoning accomplish what is done in Arithmetic
and Geometry. For all inquiries which depend on
reasoning would be performed by the transposition
of characters and by a kind of calculus, which
would immediately facilitate the discovery of
beautiful results. For we should not have to
break our heads as much as is necessary today,
and yet we should be sure of accomplishing
everything the given facts allow.
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Indeed for a long time excellent men have brought
to light a kind of "universal language" or
"characteristic" in which diverse concepts and
things were to be brought together in an
appropriate order, with its help, it was to
become for people of different nations to
communicate their thoughts to one and to
translate into their own language the written
signs of a foreign language. However, nobody, so
far, has gotten hold of a language which would
embrace both the technique of discovering
propositions and their critical examination -- a
language whose signs or characters would play the
same rôle as the signs of arithmetic for numbers
and those of algebra for quantities in general.
And yet it is as if God, when he bestowed these
two sciences on mankind, wanted us to realize
that our understanding conceals a far deeper
secret foreshadowed by these two sciences.
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Leibnizs Calculating Machine
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George Boole on The Laws of Thought
(1854) The design of the following treatise is
to investigate the fundamental laws of those
operations of the mind by which reasoning is
performed to give expression to them in the
symbolic language of a Calculus, and upon this
foundation to establish the science of Logic and
construct its method.
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They who are acquainted with the present state of
the theory of Symbolic Algebra, are aware that
the validity of the processes of analysis does
not depend upon the interpretation of the symbols
which are employed, but solely upon the laws of
their combination. Every system of interpretation
which does not affect the truth of the relations
supposed, is equally admissible, and it is thus
that the same processes may, under one scheme of
interpretation, represent the solution of a
question on the properties of number, under
another, that of a geometrical problem, and under
a third, that of a problem of dynamics or optics.
... It is upon the foundation of this general
principle, that I purpose to establish the
Calculus of Logic ... (Boole, 1845)
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Boole on the laws of thought Logic is
essentially mathematics with just two values, 0
and 1. The basic logical connections are AND, OR,
and NOT.
AND yields a 1 only if both inputs are 1 0 x 0
0 1 x 0 0 0 x 1 0 1 x 1 1
OR yields a 1 if at least one input is 1 0 0
0 1 0 1 0 1 1 1 1 1
NOT yields the negation of whatever is put in
These correspond to the logic gates of a
computer.
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Alan Turing (1912-1954) On Computable Numbers,
with an Application to the Entscheidungsproblem
(1936) Proposed Electronic Calculator
(1946) Intelligent Machinery (1948) Computing
Machines and Intelligence (1950)
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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. Instead of
attempting such a definition I shall replace the
question by another, which is closely related to
is and is expressed in relatively unambiguous
words. Turing, Computing Machines and
Intelligence (1950) (Available for download at
www.jstor.org)
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The imitation game A a man B a woman C
an interrogator, who knows A and B only as X and
Y, and who gets to ask questions of A and
B.. Cs object is to determine which is which
either X is A and Y is B, or vice-versa. As
object is to make C misidentify A and B. Bs
object is to make C identify A and B correctly.
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Turings new 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? 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.
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Basic elements of a computer Store a store of
information, e.g. the human computers memory or
calculations on paper. Executive unit that
which carries out the operations in a
calculation Control that which constrains the
computer to carry out the instructions
exactly. Discrete state machine A machine
that can be in a finite number of definitely
distinct states, eg. On or Off, Open or
Closed. A simple Turing machine A device
capable of reading, printing, and erasing symbols
at defined places on a strip of paper or tape.
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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 new machines to do various computing
processed. They can all be done with one digital
computer, suitably programmed for each case. It
will be see that as a consequence of this all
digital computers are in a sense
equivalent. (Turing, 1950)
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Objections to Turings account The Theological
Objection Thinking is a function of mans
immortal soul, so machines could never
think. Reply If theological arguments are
allowed, it must be argued that God could not
give a soul to an unthinking thing, or that he
could not give our soul the same machinery for
thinking that a computer uses. But there is no
such argument. In any case, theological
arguments have generally hindered science.
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The Head in the Sand Objection The
consequences of machines thinking would be too
dreadful. Let us hope and believe that they
cannot do so. Reply This is a feeling rather
than a substantial argument requiring refutation.
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The Mathematical Objection There are
non-computable functions, and therefore there are
limits to the powers of discrete-state
machines. Reply It is not proven that humans
are capable of computing the non-computable
functions, either.
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The Consciousness Objection A machine can never
have consciousness, which is a feature of human
thought. Reply We dont know that other people
think, since we cant feel what their
consciousness is like. We only think that they
think because they pass the Turing test.
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The Disability Argument There are too many
things that human thought can do that machines
cant do (e.g. self-reflection, appreciation of
humor, etc.) Reply We are not fully aware of
the capacities of machines or people. It is not
hard to foresee machines that are aware of their
own states.
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The Originality Objection Machines dont have
the capacity to originate anything, or to do
anything other than what they are told. Reply
It is foreseeable that there will be computers
capable of learning. Moreover, it is not clear
how original humans are, since human creativity
is always manipulation of available ideas or
images
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The Continuity Objection The human nervous
system is continuous, unlike a digital
computer. Reply Digital computers can closely
match the behaviour of continuous machines (e.g.
in calculating irrational numbers).
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The Informality Objection Human behavior is
informal, not subject to general rules like the
behavior of a computer. Reply Human behaviour
is more subject to laws than we realize.