Descartes' Machines

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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







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.







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).







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







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







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.)







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.







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







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).







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







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







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







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'







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.

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Descartes' Machines

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