# Re: Descartes and the Mind

From: Harnad, Stevan (harnad@cogsci.soton.ac.uk)
Date: Thu Oct 19 1995 - 23:57:58 BST

> From: "Baden, Denise" <DB193@psy.soton.ac.uk>
> Date: Thu, 19 Oct 1995 16:10:02 GMT
>
> With regard to our metaphysical debate, the main concept that struck
> me, was how mathematical truths and that sort of 'logic/grammar' was
> given the special privilege of not being open to doubt. Let me explain.
> As far as I understand it, these sorts of truths are formal truths,
> they are by definition true. Surely though, this means they are
> circular and therefore meaningless i.e. 1 plus 1 is 2 because they are
> so defined.

Not quite. It's not all just definition. Remember that a lot of
mathematics has to do with axioms and theorems that "follow" from them.
Now the axioms we don't prove. We simply suppose they are true: "If these
axioms were true, what would FOLLOW from them?" Then we start proving
theorems. And the proofs (if you take them apart) turn out to be of the
form: If you try to suppose that the axioms are true and the theorem is
false then that leads to a contradiction.

That's not just definition any more. (When I define something, I know
what I've said, but when I define a set of axioms, I don't know which
theorems do and do not follow from them. It takes a lot of thinking and
ingenuity to figure it out. There are some famous theorems -- like
Fermat's Last Theorem -- whose truth we did not know until very recently
(and it's still not sure that the Fermat proof is correct!).

So it's true mathematical truth is formal, but that's not quite the same
as definitional -- or if it is, then there's a lot more to definition
than one would have thought!

> If one tries to give real meaning to these definitional
> truths, then other difficulties arise.

Well, in mathematics, anything that obeys the axioms, must obey the
theorems too, on pain of contradiction. So attaching meaning to the
formal symbols is informative, and again not just circular or
definitional.

> For example, one could say that
> to state that something is a chair, but yet is not a chair, is a
> contradiction and so has no meaning. I think however that statement has
> more meaning than a mathematical truth.

If what you mean is that a statement about a chair is not JUST formal,
you are right. But it is ALSO formal, so it is bound, as everything is,
by the law of contradiction.

> When I sit on a chairlike
> piece of furniture, I regard it as a chair, but when my young son sees
> it, its properties become more like those of a table, or climbing
> frame. Maybe I'm just playing word games, but then again, maybe so is
> Descartes.

Not word-games: Rather, you are changing the subject. The chair may or
may not exist (that is a matter that is open to doubt, unlike the
formal fact that if it is true that it exists, then it is not true that
it doesn't exist, which is NOT open to doubt). Let's assume the chair
exists. It is a second matter that you and your son see it or
understand it differently. That may well be true too, but it has no
direct bearing on the earlier issues you raised, about either formality or
meaning.

It has indirect bearing, though, and we will eventually discuss what
might behind you and your son seeing the chair differently, and of the
word having a different meaning for each of you.

> I personally believe that whether one believes in 'the ghost in the
> machine' or mind/body dualism, depends on how one defines 'mind' eg,
> by function, location, structure etc.

Ah, you're not going to reduce the mind/body problem to a matter of
definition as easily as that. The Cogito notes that you cannot doubt
that you are having experiences. Let's call that "the mind." The
mind/body problem then becomes: who can experiences (the mind) be
related to or explained by something physical (the body)?

The "ghost-in-the-machine" dualist's answer is simple: The mind obviously
controls the body. But that would cause big problems for the
conservation laws of physics, in which there is overwhelming evidence
that there is no room in the world for forces emanating from small blobs
on the planet earth that countervene the conservation of energy. Physics
says that anything you do your brain MAKES you do: There's no room for
you to "will" it.

So dualism won't work. What's left is some version or other of the
theory that the mind (= experience, remember) doesn't CONTROL the body,
it somehow IS the body. And the trouble we have understanding how that
could be is called the mind/body problem!

> I can also draw an analogy
> between the problems one has in defining key concepts (i.e.
> categories always tend to merge with each other at the edges, as
> most/all? things are interrelated to some degree) to the structure of
> the brain where millions of neurones interconnect, some clustering
> together in nuclei, others linking distant parts of the cortex. In
> other words, everything is interrelated, but some is more interelated
> than others.

Alas, ecumenical words about how everything is interrelated don't solve
this problem. If I don't see how mental experiences can be physical
things, how does saying everything is interrelated help me?

> I would like to tie all this in to cognitive psychology
> by saying that I don't think the concept of 'mind' is necessary to
> understanding how we think. In some ways, it might even be a
> hindrance, as it implies a separate entity that acts as a conductor,
> in the sense that we picture it as our will/consciousness
> manipulating all the bits of the brain to some end.

I agree that it might well be a hindrance. So does that mean there is no
such thing as a mind? Does it mean I don't really have experiences after
all? Is the Cogito wrong? Can I doubt it after all?

For is I cannot doubt it, then it won't go away, even if it is a
hindrance!

> There are not
> many characteristics of the concept of 'mind' that cannot be shown to
> have been lost or impaired due to injury, trauma or chemical
> imbalances. I include in these things such abilities as planning,
> memory, sense of self, spirituality etc which can be lost, e.g.
> through frontal lobe, temporal lobe or hippocampal lesions. This
> suggests that the mind certainly cannot be thought of as distinct
> from the body.

Yes, it's certainly true that what happens to my brain affects my
experiences. But does that make the problem go away? Does the fact that
a clunk on the head causes the experience of a headache explain how
experiences can be physical things? These relations between experience
and the brain are correlations: They are very real, but correlations
are not explanations. You don't like a ghost in the machine, controlling
the brain. Fine. Do you prefer a brain controlling the ghost in the
machine?

The point of Descartes' insight (an insight I think we all can and do
experience for ourselves) is that experience seems to be some other
kind of "stuff" -- not the same stuff that neurones, or their
chemicals, or their electrical activity are made out of. Finding that
they are so closely correlated only deepens the mystery of what the real
relationship between them is.

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