[comp.ai.philosophy] how many distinct thoughts can a person have?

mlevin@jade.tufts.edu (06/19/91)

   I was just reading Z. Pylyshin's "Computation and Cognition", and
at one point, he states something like: "the number of distinct human
thoughts is uncountable." Does anyone have any arguments for or
against the idea that the number of possible distinct human thoughts
(or mental states) is uncountably infinite? Note I do not mean
"astronomicallly large" - I mean infinite (and perhaps uncountably so)
in the strict mathematical sense. It seems plausible to me; does
anyone have a good argument either way?

Mike Levin

erwin@trwacs.UUCP (Harry Erwin) (06/19/91)

mlevin@jade.tufts.edu writes:


>   I was just reading Z. Pylyshin's "Computation and Cognition", and
>at one point, he states something like: "the number of distinct human
>thoughts is uncountable." Does anyone have any arguments for or
>against the idea that the number of possible distinct human thoughts
>(or mental states) is uncountably infinite? Note I do not mean
>"astronomicallly large" - I mean infinite (and perhaps uncountably so)
>in the strict mathematical sense. It seems plausible to me; does
>anyone have a good argument either way?

The number of distinct human thoughts isn't even countably infinite
in a quantum-mechanical universe, let alone uncountable. However,
if we ignore that argument, the question boils down to whether the
state of the brain is sensitively dependent to its state on a
cauchy surface. I believe Paul Rapp has evidence that it is. So,
although the number isn't infinite, it looks like it's uncountable.

-- 
Harry Erwin
Internet: erwin@trwacs.fp.trw.com

mlevin@athena.mit.edu (Mike Levin) (06/20/91)

In article <314@trwacs.UUCP> erwin@trwacs.UUCP (Harry Erwin) writes:
>mlevin@jade.tufts.edu writes:
>
>
>>thoughts is uncountable." Does anyone have any arguments for or
>>against the idea that the number of possible distinct human thoughts
>>(or mental states) is uncountably infinite? 
>
>The number of distinct human thoughts isn't even countably infinite
>in a quantum-mechanical universe, let alone uncountable. However,
>if we ignore that argument, the question boils down to whether the
>state of the brain is sensitively dependent to its state on a
>cauchy surface. I believe Paul Rapp has evidence that it is. So,
>although the number isn't infinite, it looks like it's uncountable.
>
>-- 
>Harry Erwin
>Internet: erwin@trwacs.fp.trw.com

  I am sorry - I didn't specify the following in my original message.
I am not looking for arguments from physics or neurobiology (but if
you have an interesting one, let's hear it). I am specifically
interested in arguments which do not assume a specific substratum for
the mind, nor a specific theory of cognition.  I am looking for
people's ideas on this question from the point of view of philosophy or
perhaps non-physiological psychology. An example of the kind of thing
I have in mind: "there are an infinite number of possible objects, and
upon considering each one, a person will/will not have a distinct
mental state because ...". So I am more interested in arguments
stemming from the higher-level concepts of "idea" or "thought" rather
than the bottom-up approcah of trying to figure out how many states
the brain can have, etc. In asking this question I realize that I am
disregarding the behaviorist objection, and also (in trying to make
this substratum- and theory-independent) appealing to each person's
knowlege of what an idea or thought is.

Mike Levin

yanek@panix.uucp (Yanek Martinson) (06/20/91)

In <1991Jun19.033316.18773@athena.mit.edu> mlevin@jade.tufts.edu writes:


>at one point, he states something like: "the number of distinct human
>thoughts is uncountable." Does anyone have any arguments for or
>against the idea that the number of possible distinct human thoughts
>(or mental states) is uncountably infinite? Note I do not mean
>"astronomicallly large" - I mean infinite (and perhaps uncountably so)
>in the strict mathematical sense. It seems plausible to me; does
>anyone have a good argument either way?

If you assume that all thoughts or mental states are physical events, states
and connections of molecules in the brain then, because the number of molecules
in your brain is finite, and states of every individual molecule (it's position
charge, orientation, chemical bonding, whatever) are finit, then the number of 
possible permutations is very large, but finite. Most likely uncountable using
today's technology, but not infinite.

alphonce@cs.ubc.ca (Carl Alphonce) (06/20/91)

In article <314@trwacs.UUCP> erwin@trwacs.UUCP (Harry Erwin) writes:
>mlevin@jade.tufts.edu writes:
>
>
>>   I was just reading Z. Pylyshin's "Computation and Cognition", and
>>at one point, he states something like: "the number of distinct human
>>thoughts is uncountable." Does anyone have any arguments for or
>>against the idea that the number of possible distinct human thoughts
>>(or mental states) is uncountably infinite? Note I do not mean
>>"astronomicallly large" - I mean infinite (and perhaps uncountably so)
>>in the strict mathematical sense. It seems plausible to me; does
>>anyone have a good argument either way?
>
>The number of distinct human thoughts isn't even countably infinite
>in a quantum-mechanical universe, let alone uncountable. However,
>if we ignore that argument, the question boils down to whether the
>state of the brain is sensitively dependent to its state on a
>cauchy surface. I believe Paul Rapp has evidence that it is. So,
>although the number isn't infinite, it looks like it's uncountable.
>
>-- 
>Harry Erwin
>Internet: erwin@trwacs.fp.trw.com

A minor point: if something is uncountable, it is infinite.  In fact,

    finite < countable (countable infinite) < uncountable (uncoutably infinite)

at least as far as I can recall from my logic / set theory courses.

costello@DEC-Lite.Stanford.EDU (Tom Costello) (06/20/91)

In article <1991Jun19.173307.10704@athena.mit.edu>, mlevin@athena.mit.edu (Mike Levin) writes:
|> In article <314@trwacs.UUCP> erwin@trwacs.UUCP (Harry Erwin) writes:
|> >mlevin@jade.tufts.edu writes:
|> >
|> >
|> >>thoughts is uncountable." Does anyone have any arguments for or
|> >>against the idea that the number of possible distinct human thoughts
|> >>(or mental states) is uncountably infinite? 
|> >
|> >The number of distinct human thoughts isn't even countably infinite
|> >in a quantum-mechanical universe,
||> >[stuff deleted]
|> >-- 
|> >Harry Erwin
|> >Internet: erwin@trwacs.fp.trw.com
|> 
|>   I am sorry - I didn't specify the following in my original message.
|> I am not looking for arguments from physics or neurobiology (but if
|> you have an interesting one, let's hear it).
|
|> mental state because ...". So I am more interested in arguments
|> stemming from the higher-level concepts of "idea" or "thought" rather
|> than the bottom-up approcah of trying to figure out how many states
|> the brain can have, etc. In asking this question I realize that I am
|> disregarding the behaviorist objection, and also (in trying to make
|> this substratum- and theory-independent) appealing to each person's
|> knowlege of what an idea or thought is.
|> 
|> Mike Levin


This sounds like Russell's quote, that ``there is a simple
arithmetical proof that there are less things in heaven and earth than 
are dreamt of in my philosophy''.  This is based on the cardinality
of the power set of all things being greater than the set of all things.

To say the number of possible thoughts is uncountable is stretching
the idea of countability from math to philosophy.  In mathematics the 
term means there exists no one to one correspondence in the system,
of the set to the set of natural numbers.  The term is relative to
the system doing the correspondence, a set can be countable to 
one system and uncountable to another.

  The fact that we have the
concept of uncountable is not enough to prove we have uncountable thoughts.
This follows simply from the fact there are countable models of ZFC.


In fact given that there is presumably a model of all possible thoughts,
of some infinite cardinality,that is there is 
a model of all concepts and all relations on concepts
, there must therefore be a model of cardinality aleph 0, by
the downward Lowen Skolem theorem, this of course assumes that
the language of thought is countable, but this seems reasonable even to
dualists on purely behavourialist grounds.

The great danger in using concepts like uncountable in philosophy,
or ai, is that the person using them usually has an agenda.
That is something along the line of, ``there are an uncountable number of
possible thoughts therefore the physical symbol hypothesis is false.''

Using uncountable for arguments like this is pure rhetoric, and shows
a lackl of understanding of the term.  In fact I cannot think of any
particular use of uncountable in ai that wuld not be entirely equivalent
to its use in pure logic, or formal systems, and thus its use
in describing thoughts assumes rather than rejects the
physical symbol hypothesis.

Tom.

chalmers@bronze.ucs.indiana.edu (David Chalmers) (06/20/91)

In article <1991Jun19.033316.18773@athena.mit.edu> mlevin@jade.tufts.edu writes:
>   I was just reading Z. Pylyshin's "Computation and Cognition", and
>at one point, he states something like: "the number of distinct human
>thoughts is uncountable." Does anyone have any arguments for or
>against the idea that the number of possible distinct human thoughts
>(or mental states) is uncountably infinite? Note I do not mean
>"astronomicallly large" - I mean infinite (and perhaps uncountably so)
>in the strict mathematical sense. It seems plausible to me; does
>anyone have a good argument either way?

It's arguable that the number of distinct thoughts an individual can have
is finite, but the number of distinct *beliefs* is at least countably
infinite.

e.g. I believe "1 < 2", "1 < 3", "1 < 4", and so on.

The difference being that thoughts presumably have to be explicit, while
beliefs can be implicit (tacit).

One might argue that even a tacit belief has to be finitely specifiable,
in which case there can't be an uncountable number of them.

-- 
Dave Chalmers                            (dave@cogsci.indiana.edu)      
Center for Research on Concepts and Cognition, Indiana University.
"It is not the least charm of a theory that it is refutable."

me@csri.toronto.edu (Daniel R. Simon) (06/20/91)

In article <1991Jun19.033316.18773@athena.mit.edu> mlevin@jade.tufts.edu writes:
>   I was just reading Z. Pylyshin's "Computation and Cognition", and
>at one point, he states something like: "the number of distinct human
>thoughts is uncountable." Does anyone have any arguments for or
>against the idea that the number of possible distinct human thoughts
>(or mental states) is uncountably infinite? Note I do not mean
>"astronomicallly large" - I mean infinite (and perhaps uncountably so)
>in the strict mathematical sense. It seems plausible to me; does
>anyone have a good argument either way?
>
>Mike Levin

And can they all dance on the head of a pin?


"There *is* confusion worse than death"		Daniel R. Simon
			     -Tennyson		(me@theory.toronto.edu)

dave@tygra.Michigan.COM (David Conrad) (06/20/91)

In article <1991Jun19.033316.18773@athena.mit.edu> mlevin@jade.tufts.edu writes:
>   I was just reading Z. Pylyshin's "Computation and Cognition", and
>at one point, he states something like: "the number of distinct human
>thoughts is uncountable." Does anyone have any arguments for or
>against the idea that the number of possible distinct human thoughts
>(or mental states) is uncountably infinite? ... It seems plausible to me;
>does anyone have a good argument either way?
>
>Mike Levin

I think the argument would rest on the analog, as opposed to digital, nature
of the brain.  Since the potential across a synapse when it fires can be at
any value, i.e. it is not quantized, then one could make use of the
uncountably infinitely many real numbers between any two points on the
number line.  The question is, is our intelligence dependant on the analog
nature of the brain, or can it be simulated on a finite state machine?
This question has sparked much debate, as you might well imagine.

David R. Conrad
dave@michigan.com
-- 
=  CAT-TALK Conferencing Network, Computer Conferencing and File Archive  =
-  1-313-343-0800, 300/1200/2400/9600 baud, 8/N/1. New users use 'new'    - 
=  as a login id.  AVAILABLE VIA PC-PURSUIT!!! (City code "MIDET")        =
   E-MAIL Address: dave@Michigan.COM

erwin@trwacs.UUCP (Harry Erwin) (06/21/91)

alphonce@cs.ubc.ca (Carl Alphonce) writes:

. . . . 
>> The number of distinct human thoughts isn't even countably infinite
>>in a quantum-mechanical universe, let alone uncountable. However,
>>if we ignore that argument, the question boils down to whether the
>>state of the brain is sensitively dependent to its state on a
>>cauchy surface. I believe Paul Rapp has evidence that it is. So,
>>although the number isn't infinite, it looks like it's uncountable.
                                         -----
>>
>>-- 
>>Harry Erwin
>>Internet: erwin@trwacs.fp.trw.com

>A minor point: if something is uncountable, it is infinite.  In fact,

>    finite < countable (countable infinite) < uncountable (uncoutably infinite)

>at least as far as I can recall from my logic / set theory courses.

You're correct, which is why I said "it looks like it's uncountable."
There is some very recent work that indicates you can simulate chaos
satisfactorily with a 16-bit word size. For all practical purposes,
there are an uncountable number of thoughts, but if you look at it
carefully, there are probably only a finite (but very large) number.

-- 
Harry Erwin
Internet: erwin@trwacs.fp.trw.com

thomas@ckgp.UUCP (Michael Thomas) (06/21/91)

Hi everyone:

         Okay, how about this, you must agree that a number is a
thought and a floating point number is a thought. So as long as you can 
count (produce numbers) then you are producing a countable number of thoughts
well I will start and count a number every second from now. You count
the numbers that I'm saying, when you stop, The Brain/mind will have
reached an uncountable number of thoughts. (and if you didn't catch it:
If you want to know how many thoughts is uncountable I will tell you
because I'm counting.... 8^)

	If you think a number isn't a thought/idea, why not? a number
is a symbol for something in the world there are three apples and four
chairs. So If I'm counting say the number of different names in the world
and any possible name I could come up with then I could go on forever
and ever and ever (until I died.)

Yes the mind can conceive an uncountable number of thoughts/ideas...


-- 
Thank you,
Michael Thomas
(..uunet!ckgp!thomas)

thomas@ckgp.UUCP (Michael Thomas) (06/21/91)

In article <1991Jun19.195149.19583@panix.uucp>, yanek@panix.uucp (Yanek Martinson) writes:
> In <1991Jun19.033316.18773@athena.mit.edu> mlevin@jade.tufts.edu writes:
> 
> 
> >at one point, he states something like: "the number of distinct human
> >thoughts is uncountable." Does anyone have any arguments for or
> >against the idea that the number of possible distinct human thoughts
> >(or mental states) is uncountably infinite? Note I do not mean
> >"astronomicallly large" - I mean infinite (and perhaps uncountably so)
> >in the strict mathematical sense. It seems plausible to me; does
> >anyone have a good argument either way?
> 
>If you assume that all thoughts or mental states are physical events, states
>and connections of molecules in the brain then, because the number of molecules
>in your brain is finite, and states of every individual molecule (it's position
>charge, orientation, chemical bonding, whatever) are finit, then the number of 
>possible permutations is very large, but finite. Most likely uncountable using
>today's technology, but not infinite.

Wait a second, 8^) did you say that all thoughts or mental states are 
physical events? You didn't really say that states and connections of 
molecules in the brain are thoughts then? I'm sorry but there is no
way on earth that you are going to be able to make me believe this.
YES, I understand what you are saying, but to directly tie thought&&
idea directly to connections of molecules in the brain, is not going
to "fly."  I am sorry 8^) but since the brain works with stimulus
and all stimulus is a wave/frequency you will have a hard time turning
a frequency into a single molecule. Plus the brain is a "living",
"moving", "growing", "breathing" thing. It is always in motion and
not sitting still in molecules. And even if you are correct mathmatically
the combination of those molecules activity and their pattern of
activity. Thought isn't a single event but an on going one. so when
you count up the growing combinations of molecules and add there activity
across the spectrum of their pattern of activity you get an infinite
number of thoughts still.

thanks for listening....

-- 
Thank you,
Michael Thomas
(..uunet!ckgp!thomas)

dagmar@brainiac.raidernet.com (Greble Dagmar) (06/21/91)

mlevin@jade.tufts.edu writes:
> 
>    I was just reading Z. Pylyshin's "Computation and Cognition", and
> at one point, he states something like: "the number of distinct human
> thoughts is uncountable." Does anyone have any arguments for or
> against the idea that the number of possible distinct human thoughts
> (or mental states) is uncountably infinite? Note I do not mean
> "astronomicallly large" - I mean infinite (and perhaps uncountably so)
> in the strict mathematical sense. It seems plausible to me; does
> anyone have a good argument either way?

You might want to try to define 'distinct human thoughts' a little 
further (and then bring world peace, too :) ), but as I see it what 
Pylyshin has put forth is undeniably true, althought I wouldn't go so far 
as to say infinite in that manner you did, simply because we humans are a 
finite number, composed of a finite number of atoms, etc...  I would say 
that they are completely uncountable unless one wishes to classify, and 
sub-classify, and sub-sub-classify as to make even the Dewey Decimal 
System seem like a breeze.  Hence, you've got to define the 
'distinctness' of the thought itself, or you end up 'combing spaghetti'.  
I think that we could possibly put an upper limit to them (big maybe) on 
a sheerly chemical/biological basis, but it still wouldn't give us much 
of an analysis of what's going on in one's head.

-- _-----_ -------------------------------------------------------------------
  =  \:/  =  Save Mother Earth or Die! :  Greble Dagmar... Occult Theologian
  =_  :  _=    (This is not a joke.)   :...!uunet!mjbtn!raider!brainiac!dagmar
--  -----  -------------------------------------------------------------------

dirish@csc-sun.math.utah.edu (Dudley Irish) (06/21/91)

I am sure that that you have all heard the old saw, "You can never
step into the same river twice."  I would similarly argue that you can
never have the same thought twice.  Thus, for as long as you live you
are constantly having different thoughts.  There are two questions
here.  First, does this sequence map to the integers or to the real
numbers, in other words, is the sequence of brain states countably
infinite or uncountably infinite.  The other question is whether
because people only live a finite time we want to accept that the
sequence of thoughts has an end or whether we want to take a
theoretical stance where we don't view the sequence as ending.

Now, be careful.  Remember the number of real numbers from zero to one
is uncountably infinite.  If you believe that thoughts map to the
real numbers rather than the integers this still leaves you with an
uncountable number of thoughts.  Also, the number of rational numbers
from zero to one is countably infinite.  Thus if between every pair of
thoughts there is another thought, then even if we take the sequence
as ending, it still is countably infinite.

So you simply must decide whether thoughts are continuous or not.  I
don't have a clue as to how to decide this issue.

Now, before you think to flame me for a screwup in my understanding of
cardinal number theory, I will warn you that my favorite mathematics
professor taught a set theory class two quarters ago that I sat in on.
I seriously believe that I remember all this stuff correctly.  Though
what it has to do with AI, I don't know.

--
Dudley Irish / dirish@math.utah.edu / Manager Computer Operations
Center for Scientific Computing, Dept of Mathematics, University of Utah

The views expressed in this message do not reflect the views of the
Dept of Mathematics, the University of Utah, or the State of Utah.

erwin@trwacs.UUCP (Harry Erwin) (06/22/91)

dave@tygra.Michigan.COM (David Conrad) writes:

>>...previous article...
>I think the argument would rest on the analog, as opposed to digital, nature
>of the brain.  Since the potential across a synapse when it fires can be at
>any value, i.e. it is not quantized, then one could make use of the
>uncountably infinitely many real numbers between any two points on the
>number line.  The question is, is our intelligence dependant on the analog
>nature of the brain, or can it be simulated on a finite state machine?
>This question has sparked much debate, as you might well imagine.

Judy Dayhoff (U. Md) is looking at this issue. Based on some similar
things that I've seen in multiprocessing systems, I suspect the
instantaneous state of the brain is sensitive to _when_ individual
synapses fire, so my personal belief is that the analog nature of
the brain is an important component of intelligence. No proof, tho.
Bernardo Huberman has been involved in some research that seems to
indicate that chaotic processes are particularly efficient at
pattern recognition (via rapid phase-locking), which may be why
Paul Rapp has seen chaos in brainwaves. Sander van der Leeuw was
interested in my point that a deterministic system controlled by
a chaotic pattern detector is chaotic as a whole. That is a good
description of the way many cultures operate. 
-- 
Harry Erwin
Internet: erwin@trwacs.fp.trw.com

vu0208@bingvaxu.cc.binghamton.edu () (06/25/91)

In article <1991Jun19.033316.18773@athena.mit.edu> mlevin@jade.tufts.edu writes:
>   I was just reading Z. Pylyshin's "Computation and Cognition", and
>at one point, he states something like: "the number of distinct human
>thoughts is uncountable." Does anyone have any arguments for or
>against the idea that the number of possible distinct human thoughts
>(or mental states) is uncountably infinite? Note I do not mean
>"astronomicallly large" - I mean infinite (and perhaps uncountably so)
>in the strict mathematical sense. It seems plausible to me; does
>anyone have a good argument either way?
>
>Mike Levin

If not infinite then multiple thoughts DO occur concurrently in a
human brain!!

1) I remember reading somewhere about a poet who could
write with both left and right hands, and at times he was writing two
different poems simultaneously!

2) A personal experience: I have had many times NESTED-DREAMS! That
is, Dream in a dream at most to 3 levels. At each level I have
communicated from the nth-level to (n-1)th level of the nested-dreams.

-------

This is purely my theory:

Human brain may be strongly-processing one thought (on which it is
concentrating) but in the back-ground lots of thoughts are being
processed (weakly) (here I use strong and weak thoughts to define the
degree if concentration). Now once the current thought-process is
completed or require more information then one/or more  of the
back-ground process-thoughts share/send the information to/from the
strong-thought. And this thinking process goes on until fewer thoghts
are left (resulting in a conclusion or action) or all the thoughts are
connected together to reach some new discovery/invention by the brain.

sena@infinet.UUCP (Fred Sena) (06/26/91)

>In article <1991Jun19.033316.18773@athena.mit.edu> mlevin@jade.tufts.edu writes:
>>   I was just reading Z. Pylyshin's "Computation and Cognition", and
>>at one point, he states something like: "the number of distinct human
>>thoughts is uncountable." Does anyone have any arguments for or
>>against the idea that the number of possible distinct human thoughts
>>(or mental states) is uncountably infinite? ... It seems plausible to me;
>>does anyone have a good argument either way?
>>
>>Mike Levin

I think that there is some confusion here between "uncountable" and "infinite".
I don't believe that they are the same thing at all because I think that
there are many things that are uncountable yet finite.

For example, if I were to ask you the number of cars that are running on the
roads at a particular instant, the number would be uncountable because you
can't be everywhere at once to count them and the number of cars would change
as you were in the process of counting.  I think that everyone would agree
that the number would be finite as well, since there are a finite number of
cars.

I think that the reason why thoughts in the brain are uncountable is because
the brain is an uncertainty machine.  You cannot measure the number of
thoughts because all forms of measurement will cause the actual state to
change.  As soon as you ask someone how many thoughts they are having, you
are changing the number of thoughts that they have because they have to start
to think about you question instead of whatever they were spontaneously
thinking before you asked them.

Besides, what do we consider to be a "thought" anyways.  It's not exactly
something that you can really measure.   Do you count words, symbols, or both?
The subconscious speaks to the conscious through symbols.

	--fred

-- 
--------------------------------------------------
Frederick J. Sena                sena@infinet.UUCP
Memotec Datacom, Inc.  N. Andover, MA

alphonce@cs.ubc.ca (Carl Alphonce) (06/26/91)

In article <2773@infinet.UUCP>, sena@infinet.UUCP (Fred Sena) writes:
|> 
|> I think that there is some confusion here between "uncountable" and "infinite".
|> I don't believe that they are the same thing at all because I think that
|> there are many things that are uncountable yet finite.
|> 
|> For example, if I were to ask you the number of cars that are running on the
|> roads at a particular instant, the number would be uncountable because you
|> can't be everywhere at once to count them and the number of cars would change
|> as you were in the process of counting.  I think that everyone would agree
|> that the number would be finite as well, since there are a finite number of
|> cars.
|> 

I agree that there is some confusion about this.  The terms finite, infinite,
countable, and uncountable, all have precise mathematical definitions.  However,
they are also used in contexts where it is not clear whether the mathematical
meaning or the "common" meaning is the one which was meant to be conveyed.

Maybe some attempt can be made to indicate when a "technical" meaning of a
word is what is to be conveyed, so that these (fruitless) discussions can be
avoided in future.

For those who are familiar with the mathematicaal definitions of these terms,
feel free to stop reading here.  For those unfamiliar, here is a (hopefully)
non-technical (hopefully) brief summary:

Without getting technical, we may loosely define the terms as follows:

A set is finite if there are n elements in the set (where n is a natural
	number).

(Alternately, where one defines 0 to be {} (ie: the "empty" set - the set with
						no members)
				1 to be succ(0) = {0} = {{}}
				2 to be succ(1) = {0,1} = {{},{{}}}
				. . .
			      n+1 to be succ(n) = {0,1,...,n},

one can say that a set A is finite if there is a one-to-one mapping from
A to some natural number n.)

A set A is infinite if there is no natural number n such that there is a 
one-to-one mapping from A to n.

If we let N, the set of natural numbers, be the set {0,1,...,n,...},
then a set A is said to be countable if there is a one-to-one mapping
from A to N.

Note that (obviously) the set natural numbers is countable.  Furthermore,
the set of even numbers is countable (take the one-to-one mapping to be
f:x -> 2x), and the set of prime numbers is countable (let f be the 
function mapping n to the n-th prime number).  Even the rational numbers
are countable.

However, there are some uncountable sets also.  The set of real numbers,
for example, is uncoutable.  Thus, there is no one-to-one mapping from
the set of natural numbers to the set of real numbers.  For a proof of
this, see any good logic or set theory book.

Carl.
alphonce@cs.ubc.ca

gin001@cdc835.cdc.polimi.it (Mauro Cicognini) (06/27/91)

vu0208@bingvaxu.cc.binghamton.edu () writes:

>In article <1991Jun19.033316.18773@athena.mit.edu> mlevin@jade.tufts.edu writes:
>>   I was just reading Z. Pylyshin's "Computation and Cognition", and
>>at one point, he states something like: "the number of distinct human
>>thoughts is uncountable." Does anyone have any arguments for or
>>against the idea that the number of possible distinct human thoughts
>>(or mental states) is uncountably infinite? Note I do not mean
>>"astronomicallly large" - I mean infinite (and perhaps uncountably so)
>>in the strict mathematical sense. It seems plausible to me; does
>>anyone have a good argument either way?
>>
>>Mike Levin

>If not infinite then multiple thoughts DO occur concurrently in a
>human brain!!

>1) I remember reading somewhere about a poet who could
>write with both left and right hands, and at times he was writing two
>different poems simultaneously!

>2) A personal experience: I have had many times NESTED-DREAMS! That
>is, Dream in a dream at most to 3 levels. At each level I have
>communicated from the nth-level to (n-1)th level of the nested-dreams.

>-------

>This is purely my theory:

>Human brain may be strongly-processing one thought (on which it is
>concentrating) but in the back-ground lots of thoughts are being
>processed (weakly) (here I use strong and weak thoughts to define the
>degree if concentration). Now once the current thought-process is
>completed or require more information then one/or more  of the
>back-ground process-thoughts share/send the information to/from the
>strong-thought. And this thinking process goes on until fewer thoghts
>are left (resulting in a conclusion or action) or all the thoughts are
>connected together to reach some new discovery/invention by the brain.

I think very interesting the experience of having nested dreams, although it
never occurred to me.
I think also very reasonable that many thoughts be carried on at once, since 
a vast number of processes surely go on inside the brain simultaneously: 
just think of all the self-supporting systems and the self-regulation systems.
So, as the autonomous nervous system is able to do many things at once, also thecentral nervous system (that is, the conscious part) is likely to be able to do so, too. The rest is experience.
As for the number of thoughts (that is, mind processes) that can go on at once,
I think that we need first a more precise definition of what we mean with the 
word. Of course, if the definition is loose enough, we may end up as well
saying that we have uncountably infinite thoughts going on in a single moment,
just because we cannot really measure them, or identify them well enough. 
Personally, I think that their number may be very large, but not infinite, due
to the finite number of neurons in the brain. Of course, this is only an idea, 
that comes to me quite natural. But common sense is often wrong.

Let's not forget we are dealing with living things.
And a network that can change itself as it needs.

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Sapere aude! Habe mut dich die einige verstanden zu bedienen! (I. Kant)

t-rmason@microsoft.UUCP (Richard MASON) (06/29/91)

Newsgroups: comp.ai.philosophy
Subject: Re: how many distinct thoughts can a person have?
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In article <1991Jun20.083708.13355@tygra.Michigan.COM> dave@tygra.Michigan.COM (David Conrad) writes:
>In article <1991Jun19.033316.18773@athena.mit.edu> mlevin@jade.tufts.edu writes:
>>Does anyone have any arguments for or
>>against the idea that the number of possible distinct human thoughts
>>(or mental states) is uncountably infinite? ... It seems plausible to me;
>>does anyone have a good argument either way?
>>
>I think the argument would rest on the analog, as opposed to digital, nature
>of the brain.  Since the potential across a synapse when it fires can be at
>any value, i.e. it is not quantized, then one could make use of the
>uncountably infinitely many real numbers between any two points on the
>number line.  The question is, is our intelligence dependant on the analog
>nature of the brain, or can it be simulated on a finite state machine?
>This question has sparked much debate, as you might well imagine.

It seems to me very unlikely that a synapse has an uncountably infinite
number of relevant states, i.e. that any difference in the potential
across a synapse results in a different synapse state and therefore a
different overall thought.

Doesn't this imply that as a voltage-measuring device, a synapse is
an instrument of infinite accuracy, infinitely superior to any voltmeter
we could ever construct?  This seems an absurdity.

So it seems to me more likely that there is some limit on the accuracy
of a synapse potential, therefore synapse potential is in effect
quantized.  If we add to this statement an upper limit on the maximum
potential that can exist across a synapse, it would seem that the
number of distinct possible brain-states is finite.

Very large, but finite.
=========================================================================
Richard Mason      t-rmason@microsoft.com        All opinions are my own.