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The Aristotelian Society and Wiley are collaborating with JSTOR to digitize, preserve and extend access to Proceedings of the
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Descartes' MachinesAuthor(s): Betty PowellSource: Proceedings of the Aristotelian Society, New Series, Vol. 71 (1970 - 1971), pp. 209-222Published by: on behalf ofWiley The Aristotelian SocietyStable URL: http://www.jstor.org/stable/4544809Accessed: 30-04-2015 12:29 UTC
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XII*-DESCARTES'
MACHINES
by
Betty Powell
The
view of
man
which emerges
from
Descartes'
philosophical
writings
is that of an
amalgam
of two substances: one
material,
and the
other immaterial.
Man has both
body
and
mind.
These
two substances interact
in
some
way
that remained
mysterious
even for Descartes.
The mind
is
a
spiritual
substance,
which
is immortal
and the source of man's freedom. Man's
body
is a
machine, although
a
very
complicated
one.
In
Cartesianstudies it is the mind which receivesmost attention,
and
Descartes
is
regarded as
the
natural
enemy
of
contem-
porary
mechanists.
In
this
paper,
I
want to
take
a
somewhat
different
view
of
Descartes
and
stress
his
mechanism
instead of
his
anti-mechanism.
I
shall
suggest
that
Descartes
considered
the
possibility
of a
science
of
man;
that
he found
(or thought
he
had
found)
such a science
to
be
untenable,
and that he
intro-
duced
mind
because
he
found
it
to
be
untenable.
I
do
not,
of
course, wish to suggest that this was Descartes' only reason
for
thinking
of man
as
both
mind and
body,
but one
reason for
the introduction
of mind was
in
defence of his
scientific
interests.
There
is
no
doubt
whatsoever
that Descartes
considered man
to be both
mind
and
body,
for
he
nowhere
speaks of man in
any
other
way.
Man is alone
in
being
mind
as well
as
body.
Animals have bodies but do not have minds. Animals can be
regarded
as
machines,
to
be
explained
in
mechanical
terms.
Men's bodies too
are
machines, although
highly complicated
ones.
They are,
as
a
matter of
fact,
much more
complicated
than
any
machine
which man can
make,
which is not
surprising,
since
they
are machines
made
by
God. But
however
complicated
a
machine
might be,
and however similar it
might be to a
man,
it
will
not be
a
man if
it lacks
a
mind.
It may be that Descarteshad always thought of man in this
way.
But it is at
least
conceivable
that he
considered
the
possibility
of
explaining
man
mechanically,
that
is, man
as
such and not
merely
man's
body,
and that
he had some
reason
*Meeting
of the Aristotelian
Society
at
5/7, Tavistock Place, London,
W.C.I,
on
Monday,
ioth
May
197I,
at
7.30
p.m.
209
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210
BETTY POWELL
for
rejecting
this
possibility.
I want
to
offer
a kind of
rational
reconstruction of Descartes'
position
on
mechanism,
and in
particularof his reasons for rejecting it. First, however, I shall
try to show that it is
at
least
plausible
that Descartes was
at
some
point
a mechanist.
By
'mechanism' I
mean the
doctrine
that
man can be
fully explained
in
mechanical
terms.
Descartes was
a
scientist, and among his
scientific
interests
was
physiology.
If
Descartes
held
that
man
was
a
machine,
then he
did
so
as a
scientist,
not
as a
philosopher.
His
physiology
is
outdated,
but this does not matter
here.
What is
important
is
that
he does consider that
many,
if not
all,
features of man
can be
explained
in
mechanistic
terms. Descartes had
been
interested
in
physiology
for
many years
before
he wrote the
Discourse.According
to a letter to
MIersenne
20th
Feb.
I639,
K.63)1
he had
spent
much
time
dissecting
for
the
previous
eleven
years,
that
is,
for nine
years
before the
publication
of
the Discourse. Nor were
his
dissections
confined to
animals.
He had also, so he saysin anotherletter to Mersenne (ist April,
I640,
K.
7I)
dissected
human
bodies.
According
to
Part
V of the
Discourse,
is
progress
n
explain-
ing
man
mechanically
was not
inconsiderable.
Besides
ex-
plaining
the
workings
of the
heart,
he
says
he had
explained
many
other features
of
man. His
explanation of
the
heart
is the
only
one
he
gives
in
detail
and
most of
the
Discourse
s taken
up
with it.
The account
is
prefaced by
an
invitation to
the
reader who is 'not versed in anatomy' to procure and cut up
the heart
of some
large
animal
which
has
lungs,
for such a
heart
is
similar
to the
heart of
man.
By
doing so,
the
reader
will
be
better
able
to follow the
explanation
of
its
workings
that
Descartes offers.
We
are,
I
suppose,
to
take this
as
a
para-
digm
of
the
kind of
explanation
he
has
in
view-a
detailed
description
of the
workings.
He claims to have
explained
other
features of man, but he
does not
give
details
of these
explanations
in
the Discourse.
They
were
given,
so
he
says,
in
some
detail
in
the
Treatise
which
he intended to
publish,
but
which
he
suppressed.
He
claims
to have
explained
there the
causes
of
wakefulness,
1
'K'
refers
throughout
to: Descartes
Philosophical
Letters,
ranslated and
edited
by
Anthony
Kenny, Oxford,
I970.
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DESCARTES'
MACHINES
2II
sleep
and dreams,
as
well
as the
way
in which external objects
cause changes
in
the brain. (H.R.
I
15.)2
Unlike
the
heart,
these are not so obviously features of the body. Dreams, for
instance,
might
well be
regarded
as
part
of
mental,
as
opposed
to physical life, yet
Descartes
claims to have given
an
account
of the changes necessary
in
the brain to cause
them.
And
his
claim to have given
a
causal
account of wakefulness might
be
regarded as
at least a partial account of
consciousness.
In
addition to
features such as these, he claims
to have explained
much of
man's overt behaviour
in
mechanical terms.
In fact,
he offersa purely causal account of much of man's behaviour.
This behaviour
he regards
as a response to external stimuli,
via
the
mediation
of the animal
spirits, without any inter-
vention of the mind.
H.R.
I
I5:
I had
explained
all these
matters
in
some detail
in
the Treatise
which
I
formerly
intended
to
publish.
And
afterwards
I
had shown there, what must be
the fabric of the human body in order that the
animal
spirits
therein
contained should have the
power
to
move the
members, just
as the
heads of
animals,
a
little
while after
decapitation
are
still
observed
to move
and bite the
earth,
notwith-
standing
that
they
are
no
longer animate;
what
changes
are
necessary
in
the brain
to cause
wake-
fulness, sleep
and
dreams;
how
light, sounds, smells,
tastes, heat and all other qualities pertaining to
external
objects
are able to
imprint
on it
various
ideas
by
the intervention
of
the
senses;
how
hunger,
thirst
and other internal affections
also
convey
their
impressions
upon
it
....
(how
the
distribution
of
the)
animal
spirits through
the
muscles
can
cause
the members
of such
a
body
to move
in
as
many diverse ways, and in a manner suitable to
the
objects
which
present
themselves
to its senses,
and to its internal
passions
as can
happen
in our
own case
apart
from the
direction
of
our
freewill.
2
'H.R.' refers
throughout
to: Descartes hilosophical
Works,Haldane-Ross,
Vol. I, Cambridge
(also
Dover).
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212 BETTY
POWELL
And
this
will
not seem
strange to
those,
knowing
how
many different
automata
or
moving
machines
can be made by the industry of man, without
employing
in
doing
so more
than a
very
few
parts
in
comparison
with the
great
multitude of
bones,
muscles,
nerves,
arteries, veins or
other
parts that
are found
in
the
body
of
each
animal.
From
this
aspect, the
body
is
regarded
as
a
machine,
which,
having
been
made
by
the hand
of
God, is incom-
parably
better
arranged,
and
possesses
in
itself
movements which are much more admirable, than
any of those
which
can
be
invented
by
man.
Descartes' claim
to have
given
an
account of
these
movements
of the
body
as can
happen
in
our
own
case
apart
from
the
direction of
our
freewill
may
be read in
either of
two
ways.
He
may
mean that he can
explain
in
this
fashion
only
some
move-
ments
of the
body,
namely
those
involuntary
reflex
actions
which can be compared with those made by the heads of
animals which still move
and bite
the
dust even
when
they
are
no
longer animate.
But it can
also
be read
as a claim
to be
able
to
explain
all of the
actions of
men
(or
of
the
human
body)
without reference to
freewill.
In
favour
of
the
latter
inter-
pretation,
it
is
to be
noticed that
the
actions he
is
concerned
with are those which
are
performed
in
response
to
some
stimuli ...
in a
manner
as
suitable to the
objects
which
present
themselves to its
senses ;
in
other
words,
they
are
not
purely
reflex actions. And
secondly,
we know
from
the
Discourse
at
least, that he
thought
it
possible
that
there
should be
machines
which could do
everything
that a
man
could
do,
except
think.
His tests
for
distinguishing
between men
and
machines
are
not
whether machines
respond
appropriately
to their
environment.
Not
only
does Descartes
tell us
in
the
Discourse
of the
dis-
coverieshe has made and of the explanationshe has given, he
also
records
a
resolve to
continue
his
search
for
further
ex-
planations
(H.R.
I50).
He
envisages
a
science
of
man
which
will
be
of tremendous
value
in
improving
man
both
in
mind
and
body.
H.R.
i20:
I
am
sure
that there
is no
one,
even
among
those
who make
its
study
a
profession, who
does
not
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DESCARTES'
MACHINES
213
confess that all that men
know
is almost nothing in
comparison
with
what
remains
to be
known; and
that we could be free of an infinitude of maladies
both
of
mind
and
body,
and even also
possibly
of
the
infirmities
of
age,
if
we
had
sufficient
knowledge
of their
causes, and of
all
the remedies
with
which
nature has
provided
us.
Descartes'
faith in the
possibility,
and in the immense
practical
value of a
science of man, as
exemplified
in
this
passage, is
hardly less than that of many a present day scientist.
Even if we restrict
ourselves to
Descartes'explicit
assertions
in
the
Discourse, here can
be
no
doubt
that he was
interested
in
mechanism.
So
much so that it is
surely unreasonable
to
represent him as the
enemy of
mechanism or as terrified
by
'the bogy of
mechanism'. Whilst
he ultimately held that
man
was
composed
of both
mind and
body,
there is no
reason to
suppose that he ruled out, right from the start, the possibility
that man
was
just a
machine. It would not,
I
think,
have been
particularly
surprising
had Descartes
believed, qua
scientist,
and
particularly as a
result of his
scientific
investigations,
that
man
was a
machine. It does seem
to me
that the passages
I
have
quoted lend
plausibility to the
assumption
that he
did
hold
this
view, but
they
do not, of course,
constitute
evidence
that
he did
so.
Moreover, it has to
be
admitted that there is not,
as far as I have been able to discover, any direct evidence
for it.
There
is
none that I can find in
that part
of Le Mondewhich
is
concerned
with man.
The
account of his scientific
discoveries
given in
Part
V of the
Discourses,
Descartes says, a
summary
of Le
Monde,
which certain
considerations prevented him
from
publishing. Descartes
begins the
Traite'de
l'hommeby
saying that he
will tell
us about
the body, then
about the soul,
and finally about the way in which the two are conjoined. In it
Descartes
writes not of men but
of
machines which
resemble
men, and it
is
the workingsof these
machines
which he
explains.
When
the
soul is
added,
they will be men,
and able
to judge.
The
machines
resemble
men in
everyrespect, both in
behaviour
and in
appearance.
They can do
everything that
men can do
(exceptofcourse, think)
and all
their actionscan be
mechanically
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214 BETTY
POWELL
explained. Their
responses
to
their
environment
are
exactly
the
same
as those
of men, and
Descartesexplainsthe
mechanism
by which they act. The focal point of all the mechanism is the
pineal
gland,
which is
movable by
the animal
spirits,
and
which in
its
turn, gives movement
to
the
animal
spirits.
This
is
the
place
where,
ultimately, the soul
will be.
It is
difficult
to avoid the
conclusion
that the
Traite'de
l'homme
published
posthumously is
not
the same as
that
which
was
summarized
in
the
Discourse.
For if
we take that
summary as a
guide, there are
omissions
n
the
published
version
of the Traite.Although Descartes says in the summary in the
Discourse hat he
has explained the
changes
necessary
in
the
brain
to cause
wakefulness,
sleep
and
dreams ,
there are no
details
of
these in
the
Traite, although vision is treated
at
length. Certainly
this
work is
not the slightest
help
in
deciding
whether
Descartes at
any
time believed
that
men were
machines, or
whether
he
always held the
view
that man was
both mind and body.
Yet,
according
to the
summary,
the
Traite'ought to
have
been
of great
help.
There is,
from my
point of
view, a
parti-
cularly important
omission. In
the
Discourse
Descartes says:
I
had described
after
this the
rational soul,3
and
shownthat it
could not
be
in
any way
derived from
the
power of
matter, but
that
it
must be
expressly
created . As far
as
I
can
see, there is
no
mention of
this in
the Traite'.It
would have been
most
instructive to see why Descartes thought that the rational
soul
could
not
be
derived from
the
power
of
matter,
but no
doubt we
shall
never know.
Nevertheless,
that
Descartes
says
he
has
shown
his, does
indicate
that
he
had
some
reasons for
his
view. It
is
perhaps
not too
much of
an
exaggeration to
3
There is
some
reference to
this
topic in a letter
(3
Oct.
i637, K.36) in
which
Descartes
remarks
on
the distinction
between the souls
of
animals
and those of men:
...
the
souls of
animals are
nothing but their
blood,
the
blood which
is turned
into
spirits
by the
warmth of
the heart
and
travels
through
the
arteries to the
brain and
from
it to the
nerves and
muscles.
This
theory
involves
such an
enormous
difference
between the
souls
of animals and
our
own that it
provides
a
better
argument
than
any
yet
thought of to
refute the
atheists
and
establish
that human minds
cannot be drawn out of
the
potentiality of
matter.
(I do
not
understand how this
establishes it.)
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DESCARTES'
MACHINES 2I5
interpret this
passage as
indicating that
Descartes
had
at
least
considered the
possibility that man was a
machine,
and
that
he had some argumentdesignedto show that there is something
about man which could not be
explained
in
mechanical terms.
I
take
it
that at
least one of the
things Descartes
thinks
cannot
be so
explained, is man's
ability
to
distinguish
between
truth
and
falsities.
This,
I
assume, is what he is
referring
to when
he
says that the men-machines
cannot judge or
think
until
the
soul
is added.
The passage in
the Discourse
s the only piece of
textual
evidence that
I
have been able to
find
which
might
be
inter-
preted to indicate that Descartes,
at any time,
consideredthat
man was a
machine. One can, of course, explain
the
lack of
evidence.
If
Descartes had ever held that man was
a
machine,
it
is likely that
he would not
have said so
in
print.
He
was
anxious not to fall foul of the
authorities, and
he admits to
having prudently
suppressed some of his work.
He
was
not
even prepared, as we shall see, to divulge all the reasons for
his
doubt. La
Mettrie
apparently regarded
Descartes
as the
intellectual ancestor of L'Homme
Machine.4
n
fact,
La
Mettrie
claims
that
Descartes' views
about the
immortal soul were
a
sop
to the
theologians.
There is then, no
real
evidence that Descartes believed that
man,
not
just man's
body, was
a
machine. Nevertheless it
seems
to me
that the
assumptionthat he did
so is
not
completely
outrageous. I shall assume that he did, at one point, wish to
hold as a
scientific thesis that man is a machine and that
he
had
great hopes of a
science of
man. Since he
ended by holding
that
man
is
both mind
and body, he abandoned
or modified
his
mechanistic
view of man.
Since he says that
he has shown
that the
rational soul could not
be derived from
the power of
matter,
he had
reasons for
rejecting mechanism.
That is to say,
he
does
not simply reject
mechanism out of hand,
on some such
presupposition as
that matter cannot think.
What
reason
could
Descartes have had for rejecting
mechanism? His
religion need
not have been a bar to his
acceptance
of
mechanism on
scientific
grounds. There need
4La
Mettrie's
I'Homme
Machine':
A
Study
in the
Origins
of
anIdea,
Aram
Vartanian,
Princeton, I960.
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2I6
BETTY POWELL
be no
impiety
in
the
view that
man
is a
machine,
if
Descartes
were prepared
to
allow
that
men are machines
made
by
God.
Moreover, he sees a need to keep separate religious and
scientificbeliefs.
This is evident from
a letter
(Aug.
i638, K.6o)
in which
he complains that
he cannot
approve
the
work of
some
young
man who
seems
to want to combine
religion and
revealedtruths
too
closely
with the sciences
which are
acquired
by
natural
reasoning .
It is true
that
we are
obliged
to take care
that
our
reasonings do not lead us to any conclusions which
contradict what God
has
commanded us
to
believe;
but
I
think that
to try to derive
from
the
Bible
knowledge
of
truths which
belong only
to human
sciences,
and
which
are useless
for our
salvation is
to apply the holy
scripture
to
a
purpose
for which God did not
give it,
and so to
abuse
it.
I
suggest that his reason for
abandoning mechanism
and
introducing
mind
may have been, paradoxicalas
it
may
seem,
in
the interest of sciences and
especially in the interest
of
his
physiology.
To see this it is
necessary briefly to consider the
doubt.
Descartes'
doubt of the senses is
supposed to
lie in
his
realisa-
tion
of the
possibility of illusion. He gives the
slenderest of
reasons for
his doubt, saying
simply (H.R. I45) that it is
some-
times proved to me that these senses are deceptive and that it
is wiser not
to trust to any thing
by which we have
sometimes
been
deceived . Two
objections have been raised at this:
first,
that
because we have sometimes
been deceived, it
does not
follow
that we are
always
deceived,
and
second,
that
we can
only
have
grounds
for saying that
we
are
sometimesdeceived
if
we take
it that we are
sometimes not deceived. I am by no
means
sure however, that
Descartes is unaware of the
pos-
sibility of the first criticism, and had he revealed his real
reasons for
doubt,
the second would have been met.
In
The
Searchafter Truth,he
has Polyander refuse to
agree
that
it is
wiser
not to
trust the senses
because they have
some-
times
deceived us:
H.R.3I3:
I
am
well aware that the senses sometimes
deceive
us
when
they are
ill
affected, just as a sick person
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DESCARTES'
MACHINES
217
thinks that all food is bitter; when they are too
far
from the object this is also so, just as when
we look
at the starsthey never appear to us as large as they
really are;
and
in
general when they do
not act
freely
according
to
the constitution of their
nature.
But all
their errors are easily known, and
do not
prevent my being now perfectly persuaded
that
I
see you,
that we walk
in a
garden,
that the sun
gives light, and,
in
a word, that all
my
senses
usually offer
to
me is
true.
This suggests that
Descartes realises that to point out
that the
senses sometimes
deceive us provides insufficient
reason for
supposing that they
may always do so, for he has
Eudoxus
agree, and offer as in
the Discourse, irst the example of the
madman, and then point out that sometimeswe dream.
How ,
he
then
asks, can
you be
certain
that your
life is
not
a
perpetual
dream
and that all
that you imagine you
learn
by
means
of
your senses
is not
as false now as it is when you
sleep?
To
pose
a
question is
hardly to provide
a more
cogent
reason
for
doubt.
But Descartes, on his
own admission, is not honest
about
his
grounds for doubting
the senses. In a letter to
Mersenne
(I5th
April, I630, K.3i),
replying to an objection that he
has not
sufficiently explained
how
he
knows that
the soul is distinct
from the body and that its nature is nothing but thought, he
says:
But
I
could not deal any better with this topic
without
explaining
in
detail
the
falsehood
or
uncertainty
to be
found
in
all the
judgements that depend
on
the senses
and
the
imagination,
so as to
show
in
the
sequel
which
judge-
ments depend on
the pure understanding
and
what
evidence and certainty they possess. I left this out on
purpose
and
after
deliberation, mainly because
I
wrote
in
the vernacular.
I
was afraid that weak minds might
avidly
embrace the
doubts and
scruples
which
I
would
have had to
propound.
He
says much the same
in a letter to Vatier (22nd
Feb. I638,
K.46).
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218
BETTY
POWELL
What then are
his reasons for
doubting
the deliverances of
the senses?
I
suggest that
his real reasons for doubt
lie
in
his
scientific works. It is not the fact that illusions occur which
gives rise to his doubt, but his
explanations of the way
in which
the mechanism of the senses work.
It is
not
merely
that
for
example he has:
H.R.
I89:
learned from some persons
whose
arms
or
legs
have been cut off,
that they
sometimes
seemed
to
feel
pain
in
the
part
which
had been
amputated,
which made me think that I could not be quite
certain
that
it was
a
certain
member which
pained
me, even though
I felt pain
in
it.
Rather, it
is
that he has (or thinks
he
has)
an
explanation
of
why it is that such people seem to feel pain. His physiology
and
his
physics teach him, so he
says in MeditationVI (H.R.I
967)
that
when he feels
a
pain in
his foot:
this sensation is communicated by means of nerves dis-
persed through the foot,
which, being extended
like
cords
from
there to the brain,
when they
are
contracted
in the
foot,
at the same
time
contract the inmost
portions
of
the
brain which is their extremityand place of origin,
and then
excite a certain movement
which nature has established
in
order to cause
the
mind to be affected by a sensation
of
pain represented as existing
in the foot. But because these
nerves must pass through the tibia, the thigh, the loins,
the
back
and the neck,
in order to reach from the leg
to
the
brain, it may happen that although their extremities
which are in
the foot
are not affected, but only certain
ones of
their intervening parts (which pass by the loins
or
the
neck), this action will excite the same movement
in
the
brain that
might
have
been excited there by
a
hurt
received
in
the foot, in consequenceof which the mind
will
necessarily feel in the foot the same pain as if it had
received a
hurt.
And
the
same holds good of
all
the other
perceptionsof our senses.
If
the same
kinds of movementsgo on in my brain when I have
a
pain
in
my foot,
as
when
I
simply seem to have a pain in
my
(non-existent) foot, then
I
do
have reason to doubt the deliver-
ances
of
the
senses.
If
the
same kinds of movements go on in my
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DESCARTES'
MACHINES
2I9
brain
when
I
am
dreaming
as when
I am
awake,
then this
is
a
reason for asking how one
can tell one is
not
dreamingnow.
If Descartes retained his physiological explanations, and
indeed
found
in
them
reason to doubt the
deliverances
of
the
senses, he
can hardly,
as
he
claims,
have
rid himself of all
the
opinions
he formerly
possessed.
Yet he
was
supposed
to
be
submitting to doubt
everything
he
possibly
could.
It is
worth noting that there are
other scientific beliefs
which
he
does
not submit to
doubt.
He
does
not
doubt
his beliefs
about the workings of the heart, nor his belief that the sun is
many timeslarger than
the earth, for
instance. On
the contrary,
he relies on
beliefs like
the latter in order to
give examples of
illusions.He assumes
that his physics
and
physiology are basic-
ally sound.
It is true
that he doubts
all that he has believed to
have
come
to him by
way of the
senses, but
he does
not doubt
his
scientific beliefs as
such.
However, since the doubt,
and
the
search for
a
criterion of truth were
undertaken
in
the
interests
of science, it is not to be expected that he should submit his
scientific
findings to
doubt.
Moreover,
if
he wishes to give
some grounds
for his
doubt,
as
indeed he does, then
there must be
something that he
accepts
without question. And
indeed there
is something, even if
we
take
his
writings at face value. He
accepts the
fact of
illusion,
as is
evident from his
assertionthat
the senses sometimes
deceive
us. Had
he added that
perhaps he
was mistaken
in
thinking
that the senses ever deceive us, his doubt would have appeared
to be
completely
without reason.
We are
now
in
a
position
to
see
why Descartes
rejects
the
possibility of
mechanism
and
introduces mind. Descartes
wishes to
defend
the scientific
discoveries
he has thus
far
made.
He
wishes
to be in a
position to expound as
true his
scientific
explanations
including
his physiological
explanations of
man.
It is for this reason that he searches for a criterion of truth
which
he
finds
ultimately
in
the
mind.
He
is
then able
to
expound his
explanations, as he doesat the end
of the
Discourse.
His
causal account of
perception
is in
itself insufficient
to
explain why
he
needs
to
introduce a
mind
in
order
to
account
for our
ability
to
distinguish
between true and
false
beliefs.
Even if the
same
movements go on
in
the brain in
veridical
as
in
non-veridical
perceptions,
it
does not follow
that we can
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220
BETTY
POWELL
never make
distinctions between
veridical
and
non-veridical
perceptions by means
of
the senses.
He
might
have
offered
some
sort of coherence theory of our ability to distinguish between
truth and falsity by means
of
the senses.
There are
other
possibilities too that
one
might
have
expected
Descartes
to
explore. For
example,
he
might
have considered
the
possibility
that we
learn
by experience,
that we
are
'taught
by
nature'
as
his men-machines were.
He
might
have
given
an
account
in
terms of
repeated stimuli
and
response.
He
does
none
of
these things. Nothing
he has thus
far
discovered
about
the
machine rules out the possibility of giving a mechanical
account of the way in
which
we
distinguish between
truth
and
falsity.
He
was far
from thinking
that he
had
given
all
possible
explanations, for
he looked forward to the
developing
science
of man. Many
things,
as he
says
himself,
remain to be
dis-
covered. Yet
he
says
that the
ability
to
distinguish
between
truth and
falsity-the rational soul-cannot
be derived
from
the
power of matter. But if it cannot be, why cannot it be?
I
suggest that Descartes considered that
any
attempt
to
explain
in
mechanical terms our ability to
distinguish between
true and
false
beliefs
would involve
an
infinite
regress.
Since
mechanism would
then involve an
infinite regress it
could not
be
a
science. For,
if it
involved
an
infinite
regress,
then it could
not
be
a
science,
because,
according to Descartes,
a science
must
be
completeable. Mechanism is thus
untenable in the
light of what he considered a science should be. His relevant
views on science
are to be found in
the Rules.
i. Science is the work of man.
( the sciences
taken all
together are identical
with human
wisdom
H.R.
i.)
This is not
the trivial point it
may seem
in
the
context.
2.
In
science we
are
concerned with
truth
as
opposed to
opinion. ( Science in its entirety is true and evident
cognition H.R.3.)
3. In matters of
truth, unlike
matters of opinion, it must be
possible
to
give grounds for
holding that the
belief is true.
( But whenever two men come
to opposite
decisions about
the
same
matter one of them
at least must
certainly be
in
the
wrong,
and apparently
there is not even
one of them
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DESCARTES
MACHINES
221
who
knows;
for
if the
reasoning
of the second
was
sound
and
clear he would be
able so
to
lay
it
before the other
as
finally to succeed in convincinghisunderstandingalso.
H.R.3.)
4.
Descartes
required of
a
science that it should be
possible
to
complete
it.
Here
I
refer
to
Descartes'
optimism
in
scientific matters,
to
his
belief that
there is
nothing
beyond
our reach
if
we but
use the
right
method.
(See
H.R.9
and
H.R.92.)
H.R.92: ... provided only that we abstain from
receiving anything
as
true
which is not
so,
and
always retain the
order
which is
necessary
in
order to deduce the one
conclusion from
the
other,
there can
be
nothing
so
remote that
we cannot reach
it,
nor
so recondite
that we
cannot
discover t.
Mechanism fails to satisfy the completeness requirement.
That
is
to
say, mechanism,
regarded
as the
science
of
man,
as
opposed
to
a
science
of man's
body
is untenable as a
science
because it can
never be
completed.
Descartes
might have
argued
in
the
following way.
Suppose
he, quascientist,
were to
give
an explanation of
the
way the man-machine
distinguishes
between veridical and
non-veridical
perceptions. Then,
according
to
(3)
above, he,
Descartes
the
scientist,
must be
able
to give grounds for holding that this explanation is true. But
by
hypothesis,
Descartes is also
a
man-machine,
so there is
something
about
the machine
that he has
not
yet
explained.
The
man-machine
has now given
grounds for
holding
that the
explanation
is
true,
and
the
giving
of these
grounds
remains to
be
explained. Suppose
he, qua
scientist
gives
an
explanation of
the
way
the
machine
distinguishes
between true
and false
beliefs.
Again,
he
must be able to
give
grounds
for
holding
that
his
explanation
is
a
true
(the correct)
one. And
again,
if
he can
do
this,
then there is
something
about man
the
machine
that
he,
qua
scientist
has
not
yet
explained. Since he
the
scientist is
also
a
machine,
he can
never
complete
his
explanation of the
machine.
Mechanism can
never be a
complete
science; there
is
always
some
bit of
possible
knowledge
out of
his
reach.
It
is
to
remedy
this
that
Descartes
introduces mind.
The
'I'
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222
BETTY POWELL
that thinks-that
offers and assesses
explanations
is
the
mind.
That
which
is explained,
the body,
is the
machine.
The science
of the body, at least, can be complete.
The first
thing to
notice about
this infinite
regress
argument
is that
it is
not concerned
with things,
but with
explanations.
It is not concerned
with
machines, but
with
explanations
of
machines.
Now there
are two things
that might
be meant by
'mechanism'-one,
that
men are
machines;
and
two,
that
men
can be fully explained
in
mechanical
terms. These
two claims
are
not
equivalent,
on the
grounds
that
p may
be
true,
although
no one may know it. It may be true, that men are machines,
but
false that
men
may
be
fully
explicable
in mechanical
terms.
In
maintaining
that men
are
mind and body,
Descartes
denies
that
men
(as
such) are
machines.
But
all
the
infinite
regress
argument
warrants is
that men cannot
be
fully explicable
in
mechanical terms.
From
the fact-if it
is
a
fact-that
men
cannot
be
completely
explained
in mechanical terms
it does
not follow that men are not machines, yet it appears that
Descartes
thinks that
it does.
Much
depends
on
the
nature
of
the
regress.
In
a
way
it is
concerned with
Descartes'
inability to give
a
complete
ex-
planation
of the workings
of the
machine.
This
inability,
however,
is
not the
result
of
supposing
that
he himself is a
machine,
but
of
his
own
epistemological
requirements.
Given
any explanation,
it must
always
be
possible
to assess it
as
correct or incorrect. Given any belief, it must always be
possible
to assess
it as true or
false. It is
not
the
kind
of
thing
Descartes is,
which
engenders
the
regress,
but the
kind
of
requirements
for
explanation.
All
that
the
regress
shows
in
fact,
is that
any
assessment
of
an
explanation
must be
separate
from that explanation.
No
explanation
can
contain
within
itself its
own assessment-or
it would
be an untestable
explana-
tion. And
this
seems
to be
a
regress
of an innocuous kind.