Re: Descartes and the Mind

From: Harnad, Stevan (
Date: Fri Oct 20 1995 - 18:33:15 BST

> From: "Parker, Chris" <>
> Date: Fri, 20 Oct 1995 08:36:13 +0100 (BST)
> I found [Descartes'] eventual reconstruction of God and the
> external world difficult to understand.

That part was not Cartetius at his best. He's on much more solid (indeed
eternal) ground when he is doubting than when he is reconstucting. (And
as for his resurrection of St. Anselm's ontological proof for the
existence of God -- [Part of the concept of God is that He is perfect.
Part of perfection is existence {He wouldn't be perfect if He did not
exist}. Therefore He exists] -- that's Descartes at his worst....)

> If you can't prove axioms, isn't anything that follows cheating?

Not at all, because there are still facts, indeed immutable, eternal
facts, about what is and is not COMPATIBLE with a particular set of
axioms. It is not possible to CO-suppose axioms and the denials of
their theorems. And most of maths is that. (The method of reductio ad
absurdum is explicitly that.) That's why 1 + 1 is necessarily = 2. Not
because someone has "proven" the axioms of arithmetic. What they have
proven is that you cannot affirm the axioms yet deny 1 + 1 = 2.

Moreover, if there is anything (like, say, physical quantity) that
happens to obey the axioms, then it must obey the theorems too.

> Couldn't you say that scientific parameters are a bit like axioms. Eg the
> melting point of a specific substance is always x if it's purity is y and
> the pressure is z? Couldn't scientific theory one day explain and exactly
> predict this kind of data form crystal structures etc which are fixed?

You could SAY they are like axioms, but that does not bring you much,
since axioms are assumed to be true, whereas scientific laws have to be
discovered, tested, and supported by evidence.

> Is this all saying that doubting can not be doubted because
> doubting is experience; therefore all experience cannot be doubted
> but all experience isn't doubt?

That experiences are going on cannot be doubted. And that's something --
rather than the nothing there would have been (apart from the truths of
mathematics) if experience too had succumbed to Descartes' method of doubt.

(It's not just doubting you can't doubt -- when you're doubting -- it's
any experience: headache, toothache, seeming to see blue, etc.)

And experience is mental, rather than physical. So whereas the reality
of the physical world is open to doubt (that doesn't mean it doesn't
exist; just that you can't be sure), the reality of the mental is not
open to doubt. Kind of puts the shoe on the other foot, since we tend to
think the physical is somehow more real or substantial than the mental.

And it also puts the mental in a central position, along with maths,
in the pantheon of certainty...

> sh> So where did dualism and the mind/body problem come from? Well, how can
> sh> you possibly equate something as certain and immediate as experience with
> sh> something as uncertain and remote as a physical substance? How, in other
> sh> words, can you give a PHYSICAL explanation of experience?
> I have always felt it was the other way round in practice. How can a mind,
> if it has no physical explanation, operate in a physical world.

That's just restating the same problem.

> I don't
> believe there is an homunculus or in the pineal gland interface (was that
> Descartes?), or is there a virtual homunculus in a virtual reality?

Descartes' pineal-gland hypothesis was again not an instance of him at
his best.

The idea of a virtual homunculus in a virtual reality is incoherent.
Think about it: it's like my thinking I'm a figment of YOUR
imagination: that's getting the appearance/reality/doubt equation all
mixed up!

> I'm worried that doubt and certainty are just two constructs or categories.

Nothing wrong with being a (member of a) category. And mathematics may
be a construction, but a construction in which we are not free to do
everything. Mathematical truth is about the CONSTRAINTS on that
construction, and the constraints are not constructed by us.

The fact that it makes sense to doubt that, say, I have a toothache, when
I have one, is construction-independent. I can doubt I have a tooth, but not
that it's aching...

> In practice don't we absolutely have to assume a physical world whatever
> philosophy we seem to believe?

Not at all. That's what the Cogito shows. The only thing we "absolutely
have to assume" is the truths of mathematics and the reality of our own

> Doesn't the idea of conscious experience as
> a property, a currently unexplainable by-product of neuronal processes,
> fit best in the real world, even if we don't like the implications?

Perhaps, but we were in the 17th century just now...

> Now I have a horrible feeling I've missed the point saying things like real
> world.

It might not be a bad idea to to reflect a bit more about the
appearance/reality distinction before hurrying on to neurons and virtual

> Some quotes (based on patients incapable of emotion)
> in case they are interesting:
> "pure reason is a self-defeating ideal"
> "pure reason is a pathological rather than an ideal form of reason"
> "Cogito ergo sum is neurophysiologically wrong, since human thinking
> cannot exist as pure thinking without bodily experience"
> from:
> All in the mind. Sven Ove Hansson. Review: of Descartes' Error:
> Emotion, Reason and the Human Brain. Antonio R Damasio. Picador, 1995.
> in The Skeptic, Vol 9, No 4, p 26, 1995.

If you want, we can read and discuss Damasio's book. In my view, it is
Damasio who is in error, and Descartes got it right! The first two
quotes are beside the point and the third one misses it completely!


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