加载中…卷三：近代哲学
第一篇 从文艺复兴到休谟 From the Renaissance to Hume
RENE DESCARTES ( 1596-1650) is usually considered the founder of modern philosophy, and, I think,
rightly. He is the first man of high philosophic capacity whose
outlook is profoundly affected by the new
physics and astronomy. While it is true that he retains much
of scholasticism, he does not accept
foundations laid by predecessors, but endeavours to construct a
complete philosophic edifice de novo. This had not happened since
Aristotle,and is a sign of the new self-confidence that resulted
from the progress of science. There is a freshness about his work
that is not to be found in any eminent previous philosopher since
Plato. All the intermediate philosophers were teachers, with the
professional superiority belonging to that avocation. Descartes
writes, not as a teacher, but as a discoverer and explorer, anxious
to communicate what he has found. His style is easy and unpedantic, addressed to intelligent men
of the world rather than to pupils. It is, moreover, an
extraordinarily excellent style. It is very fortunate for modern
philosophy that the pioneer had such admirable literary sense. His
successors, both on the Continent and in England, until Kant,
retain his unprofessional character, and several of them retain
something of his stylistic merit.
Descartes's father was a councillor of the Parlement of
Brittany, and possessed a moderate
amount of landed property. When Descartes inherited, at his
father's death, he sold his estates,
and invested the money, obtaining an income of six or seven
thousand francs a year. He was
educated, from 1604 to 1612, at the Jesuit college of La Flèche,
which seems to have given
him a much better grounding in modern mathematics than he could
have got at most
universities at that time. In 1612 he went to Paris, where he found social life boring, and
retired to a secluded retreat in the
Faubourg Saint Germain, in which he worked at geometry. Friends
nosed him out, however, so, to secure more complete quiet, he
enlisted in the Dutch army
( 1617). As Holland was at peace at the time, he seems to have
enjoyed two years of
undisturbed meditation. However, the coming of the Thirty Years'
War led him to enlist in the
Bavarian army ( 1619). It was in Bavaria, during the winter
1619-70, that he had the experience
he describes in the Discours de la Méthode. The weather being
cold, he got into a stove * in
the morning, and stayed there all day
meditating; by his own account, his philosophy was
half
finished when he came out, but this need not be accepted too
literally. Socrates used to meditate
all day in the snow, but Descartes's
mind only worked when he was warm.
In 1621 he gave up fighting; after a visit to Italy, he settled
in Paris in 1625. But again friends would call on him before he was
up (he seldom got up before midday), so in 1628 he joined the army
which was besieging La Rochelle, the Huguenot stronghold. When this
episode was finished, he decided to live in Holland, probably to escape the risk of
persecution. He was a timid man, a
practising Catholic, but he shared
Galileo's heresies. Some think that he
heard of the first (secret) condemnation of Galileo, which had
taken place in 1616. However that may be, he decided not to publish
a great book, Le Monde, upon which he had been engaged. His reason
was that it maintained two heretical doctrines: the earth's rotation and the infinity of the
universe. (This book was never published in its entirey, but
fragments of it were published after his death.)
He lived in Holland for twenty years ( 1629-49), except for a
few brief visits to France and one to England, all on business.
It is impossible to exaggerate the importance
of Holland in the
seventeenth century, as the one country where there was freedom of
speculation. Hobbes had to
have his books printed there; Locke took refuge there during the
five worst years of reaction in
England before 1688; Bayle (of the Dictionary) found it necessary
to live there; and Spinoza
would hardly have been allowed to do his work in any other
country.
I said that Descartes was a timid man, but perhaps it would be
kinder to say that he wished to be
left in peace so as to do his work undisturbed. He always courted
ecclesiastics, especially Jesuits--not only while he was in their
power, but after his emigration to Holland. His psychology is
obscure, but I incline to think that he was a sincere Catholic, and
wished to persuade the Church-- in its own interests as well as in
his--to be less hostile to modern science than it showed itself in
the case of Galileo. There are those who think that his orthodoxy
was merely politic, but though this is a possible view I do not
think it the most probable.
Even in Holland he was subject to vexatious attacks, not by the
Roman Church, but by Protestant
bigots. It was said that his views led
to atheism, and he would have been prosecuted but for the
intervention of the French ambassador and the Prince of Orange.
This attack having failed,
another, less direct, was made a few years later by the authorities
of the University of Leyden,
which forbade all mention of him, whether favourable or
unfavourable. Again the Prince of Orange intervened, and told the
university not to be silly. This illustrates the gain to Protestant
countries from the subordination of the Church to the State, and
from the comparative weakness of Churches that were not
international.
Unfortunately, through Chanut, the French ambassador at
Stockholm, Descartes got into
correspondence with Queen Christina of
Sweden, a passionate and learned lady who thought
that,
as a sovereign, she had a right to waste the time of great men. He
sent her a treatise on love, a
subject which until then he had somewhat neglected. He also sent
her a work on the passions of
the soul, which he had originally composed for Princess Elizabeth,
daughter of the Elector
Palatine. These writings led her to request his presence at her
court; he at last agreed, and she sent a warship to fetch him (
September 1649). It turned out that she wanted daily lessons from
him, but could not spare the time except at five in the morning.
This unaccustomed early rising, in the cold of a Scandinavian
winter, was not the best thing for a delicate man. Moreover
Chanut
became dangerously ill, and Descartes looked after him. The
ambassador recovered, but Descartes
fell ill and died in February 1650.
Descartes never married, but he had a natural daughter who died at the age of five; this
was, he
said, the greatest sorrow of his life. He always was well dressed,
and wore a sword. He was not
industrious; he worked short hours, and read little. When he went
to Holland he took few books
with him, but among them were the Bible and Thomas Aquinas. His
work seems to have been done with great concentration during short
periods; but perhaps, to keep up the appearance of a gentlemanly
amateur, he may have pretended to work less than in fact he did,
for otherwise his achievements seem scarcely credible.
Descartes was a philosopher, a mathematician, and a man of
science. In philosophy and mathematics, his work was of supreme
importance; in science, though creditable, it was not so
good as that of some of his contemporaries.
His great contribution to geometry was the invention of
co-ordinate geometry, though not quite
in
its final form. He used the analytic
method, which supposes a problem solved, and examines the
consequences of the supposition; and
he applied algebra to geometry. In
both of these he had had
predecessors--as regards the former, even among the ancients. What
was original in him was the use of coordinates, i.e., the determination of the
position of a point in a plane by its distance from two fixed
lines. He did not himself discover all the power of this method,
but he did enough to make further progress easy. This was by no
means his sole contribution to mathematics, but it was his most
important.
The book in which he set forth most of his scientific theories
was Principia Philosophiae,
published in 1644. There were however some other books of
importance: Essais philosophiques
( 1637) deals with optics as well as
geometry, and one of his books is
called De la formation du
foetus. He welcomed Harvey's discovery of the circulation of the blood, and was always
hoping
(though in vain) to make some discovery of importance in medicine.
He regarded the bodies of
men and animals as machines; animals he regarded as automata,
governed entirely by the laws of
physics, and devoid of feeling or consciousness. Men are different:
they have a soul, which resides in the pineal gland. There the soul
comes in contact with the "vital spirits," and through this contact
there is interaction between soul and body. The total quantity of
motion in the universe is constant, and therefore the soul cannot
affect it; but it can alter the direction of motion of the animal
spirits, and hence, indirectly, of other parts of the body.
This part of his theory was abandoned by his school--first by
his Dutch disciple Geulincx, and
later by Malebranche and Spinoza. The physicists discovered the
conservation of momentum,
according to which the total quantity of motion in the world in any
given direction is constant.
This showed that the sort of action of mind on matter that
Descartes imagined is impossible.
Assuming--as was very generally assumed in the Cartesian
school--that all physical action is of
the nature of impact, dynamical laws suffice to determine the
motions of matter, and there is no
room for any influence of mind. But this raises a difficulty. My
arm moves when I will that it shall move, but my will is a mental
phenomenon and the motion of my arm a physical phenomenon.
Why then, if mind and matter cannot interact, does my body behave
as if my mind controlled it?
To this Geulincx invented an answer, known as the theory of the
"two clocks." Suppose you have
two clocks which both keep perfect time: whenever one points to the
hour, the other will strike, so that if you saw one and heard the
other, you would think the one caused the other to strike. So it is
with mind and body. Each is wound up by God to keep time with the
other, so that, on occasion of my volition, purely physical laws
cause my arm to move, although my will has not really acted on my
body.
There were of course difficulties in this theory. In the first
place, it was very odd; in the second place, since the physical
series was rigidly determined by natural
laws, the mental series, which ran parallel to it, must be
equally deterministic. If the theory was valid, there should be a
sort of possible dictionary, in which each cerebral occurrence
would be translated into the corresponding mental occurrence. An
ideal calculator could calculate the cerebral occurrence by the
laws of dynamics, and infer the concomitant mental occurrence by
means of the "dictionary." Even without the "dictionary," the
calculator could infer any words and actions, since these are
bodily movements. This view would be difficult to reconcile with
Christian ethics and the punishment of sin.
These consequences, however, were not at once apparent. The
theory appeared to have two merits.
The first was that it made the soul, in a sense, wholly independent
of the body, since it was never acted on by the body. The second
was that it allowed the general principle: "one substance cannot
act on another." There were two substances, mind and matter, and
they were so dissimilar that an interaction seemed inconceivable.
Geulincx's theory explained the appearance of interaction while
denying its reality.
In mechanics, Descartes accepts the first
law of motion, according to which a body left to
itself
will move with constant velocity in a straight line. But there is
no action at a distance, as later in Newton's theory of gravitation. There is no such thing as a
vacuum, and there are no atoms; yet all interaction is of the nature of
impact. If we knew enough, we should be able to reduce chemistry
and biology to mechanics; the process by which a seed develops into
an animal or a plant is purely mechanical. There is no need of
Aristotle's three souls; only one of them, the rational soul,
exists, and that only in man.
With due caution to avoid theological censure, Descartes
develops a cosmogony not unlike
those
of some pre-Platonic philosophers. We know, he says, that the world
was created as in Genesis,
but it is interesting to see how it might have grown naturally. He
works out a theory of the
formation of vortices: round the sun there is an immense
vortex in the plenum, which carries the planets round with it. The
theory is ingenious, but cannot explain why planetary orbits are
elliptical, not circular. It was generally accepted in France,
where it was only gradually ousted by the Newtonian theory. Cotes,
the editor of the first English edition of Newton's Principia,
argues eloquently that the vortex theory leads to atheism, while
Newton's requires God to set the planets in motion in a direction
not towards the sun. On this ground, he thinks, Newton is to be
preferred.
I come now to Descartes's two most important books, so far as
pure philosophy is concerned.
These are the Discourse on Method ( 1637) and the Meditations ( 1642). They largely overlap,
and
it is not necessary to keep them apart.
In these books Descartes begins by explaining the method of
"Cartesian doubt," as it has come to
be called. In order to have a firm basis for his philosophy, he
resolves to make himself doubt
everything that he can manage to doubt. As he foresees that the
process may take some time, he
resolves, in the meanwhile, to regulate his conduct by commonly
received rules; this will leave his mind unhampered by the possible
consequences of his doubts in relation to practice.
He begins with scepticism in regard to the senses. Can I doubt,
he says, that I am sitting here by
the fire in a dressing-gown? Yes, for sometimes I have dreamt that
I was here when in fact I was
naked in bed. (Pyjamas, and even nightshirts, had not yet been
invented.) Moreover madmen
sometimes have hallucinations, so it is possible that I may be in
like case.
Dreams, however, like painters, present us with copies of real
things, at least as regards their
elements. (You may dream of a winged horse, but only because you
have seen horses and wings.)
Therefore corporeal nature in general, involving such matters as
extension, magnitude, and
number, is less easy to question than beliefs about particular
things. Arithmetic and geometry,
which are not concerned with particular things, are therefore more
certain than physics and
astronomy; they are true even of dream objects, which do not differ
from real ones as regards
number and extension. Even in regard to arithmetic and geometry,
however, doubt is possible. It
may be that God causes me to make mistakes whenever I try to count
the sides of a square or add
2 to 3. Perhaps it is wrong, even in imagination, to attribute such
unkindness to God, but there
might be an evil demon, no less cunning and deceitful than powerful
employing all his industry in misleading me. If there be such a
demon, it may be that all the things I see are only illusions of
which he makes use as traps for my credulity.
There remains, however, something that I cannot doubt: no demon,
however cunning, could deceive me if I did not exist. I may have no
body: this might be an illusion. But thought is different. "While I
wanted to think everything false, it must necessarily be that I who
thought
was something; and remarking that this truth, I think, therefore I am, was so
solid and so certain that all the most extravagant suppositions of
the sceptics were incapable of upsetting it, I judged that I could
receive it without scruple as the first principle of the philosophy
that I sought."
This passage is the kernel of Descartes's theory of knowledge,
and contains what is most
important in his philosophy. Most philosophers since Descartes have
attached importance to the
theory of knowledge, and their doing so is largely due to him.
"I think, therefore I am" makes
mind more certain than matter, and my mind (for me) more certain
than the minds of others.
There is thus, in all philosophy derived from Descartes, a tendency
to subjectivism, and to
regarding matter as something only knowable, if at all, by
inference from what is known of
mind. These two tendencies exist both in Continental idealism and
in British empiricism--in the
former triumphantly, in the latter regretfully. There has been, in
quite recent times, an attempt
to escape from this subjectivism by the philosophy known as
instrumentalism, but of this I will
not speak at present. With this exception, modern philosophy has
very largely accepted the
formulation of its problems from Descartes, while not accepting his
solutions.
The reader will remember that Saint
Augustine advanced an argument closely similar to the
cogito. He did not, however, give prominence to
it, and the problem which it is intended to
solve occupied only a small part of his thoughts. Descartes's
originality, therefore, should be
admitted, though it consists less in inventing the argument than in
perceiving its importance.
Having now secured a firm foundation, Descartes sets to work to
rebuild the edifice of
knowledge. The I that has been proved to existhas been inferred
from the fact that I think, therefore I exist while I think, and
only then. If I ceased to think, there would be no evidence of my
existence. I am a thing that thinks, a substance of which the whole
nature or essence consists in thinking, and which needs no place or
material thing for its existence. The soul, therefore, is wholly
distinct from the body and easier to know than the body; it would
be what it is even if there were no body.
Descartes next asks himself: why is the cogito so evident? He
concludes that it is only because it
is clear and distinct. He therefore adopts as a general rule the
principle: All things that we
conceive very clearly and very distinctly are true. He admits,
however, that there is sometimes
difficulty in knowing which these things are.
"Thinking" is used by Descartes in a very wide sense. A thing
that thinks, he says, is one that
doubts, understands, conceives, affirms, denies, wills, imagines,
and feels--for feeling, as it occurs in dreams, is a form of
thinking. Since thought is the essence of mind, the mind must
always think, even during deep sleep.
动物一样也持有；但是现在我剥下了蜂蜡的衣裳，凭精神感知它赤裸的本相。我通过感官看见蜂蜡，由这件事确实断定我自己存在，但不能断定蜂蜡存在。认识外界事物不可靠感官，必须凭精神。
Descartes now resumes the question of our knowledge of bodies.
He takes as an example a piece
of wax from the honeycomb. Certain things are apparent to the
senses: it tastes of honey, it smells of flowers, it has a certain
sensible colour, size and shape, it is hard and cold, and if struck
it emits a sound. But if you put it near the fire, these qualities
change, although the wax persists; therefore what appeared to the
senses was not the wax itself. The wax itself is constituted by
extension, flexibility, and motion, which are understood by the
mind, not by the imagination. The thing that is the wax cannot
itself be sensible, since it is equally involved in all the
appearances of the wax to the various senses. The perception of the
wax "is not a vision or touch or imagination, but an inspection of
the mind." I do not see the wax, any more than I see men in the
street when I see hats and coats. "I understand by the sole power
of judgement, which resides in my mind, what I thought I saw with
my eyes." Knowledge by the senses is confused, and shared with
animals; but now I have stripped the wax of its clothes, and
mentally perceive it naked. From my sensibly seeing the wax, my own
existence follows with certainty, but not that of the wax.
Knowledge of external things must be by the mind, not by the
senses.
This leads to a consideration of different kinds of ideas. The
commonest of errors, Descartes says, is to think that my ideas are
like outside things. (The word "idea" includes sense-perceptions,
as used by Descartes.) Ideas seem to be of three sorts: (1) those
that are innate, (2) those that are foreign and come from without,
(3) those that are invented by me. The second kind of ideas, we
naturally suppose, are like outside objects. We suppose this,
partly because nature teaches us to think so, partly because such
ideas come independently of the will (i.e., through sensation), and
it therefore seems reasonable to suppose that a foreign thing
imprints its likeness on me. But are these good reasons? When I
speak of being "taught by nature" in this connection, I only mean
that I have a certain inclination to believe it, not that I see it
by a natural light. What is seen by a natural light cannot be
denied, but a mere inclination may be towards what is false. And as
for ideas of sense being involuntary, that is no argument, for
dreams are involuntary although they come from within. The reasons
for supposing that ideas of sense come from without are therefore
inconclusive.
Moreover there are sometimes two different ideas of the same
external object, e.g., the sun as it
appears to the senses and the sun in which the astronomers believe.
These cannot both be like the
sun, and reason shows that the one which comes directly from
experience must be the less like it
of the two.
But these considerations have not disposed of the sceptical
arguments which threw doubt on the
existence of the external world. This can only be done by first
proving the existence of God.
Descartes's proofs of the existence of God are not very
original; in the main they come from
scholastic philosophy. They were better stated by Leibniz, and I
will omit consideration of them
until we come to him.
When God's existence has been proved, the rest proceeds easily.
Since God is good, He will not
act like the deceitful demon whom Descartes has imagined as a
ground for doubt. Now God has
given me such a strong inclination to believe in bodies that He
would be deceitful if there were
none; therefore bodies exist. He must, moreover, have given me the
faculty of correcting errors. I
use this faculty when I employ the principle that what is clear and
distinct is true. This enables me to know mathematics, and physics
also, if I remember that I must know the truth about bodies by the
mind alone, not by mind and body jointly.
The constructive part of Descartes's theory of knowledge is much
less interesting than the earlier destructive part. It uses all
sorts of scholastic maxims, such as that
an effect can never have more perfection than its cause, which have
somehow escaped the initial
critical scrutiny. No reason is given for accepting these maxims,
although they are certainly less
self-evident than one's own existence, which is proved with a
flourish of trumpets. Plato's
Theaetetus, Saint Augustine, and Saint Thomas contain most of what
is affirmative in the
Meditations.
The method of critical doubt,
though Descartes himself applied it only half-heartedly, was of
great philosophic importance. It is clear, as a matter of logic,
that it can only yield positive results if scepticism is to stop
somewhere. If there is to be both logical and empirical knowledge,
there must be two kinds of stopping points: indubitable facts, and
indubitable principles of inference. Descartes's indubitable facts
are his own thoughts--using "thought" in the widest possible sense.
"I think" is his ultimate premiss. Here the word "I" is really
illegitimate; he ought to state his ultimate premiss in the form
"there are thoughts." The word "I" is grammatically convenient, but
does not describe a datum. When he goes on to say "I am a thing
which thinks," he is already using uncritically the apparatus of
categories handed down by scholasticism. He nowhere proves that
thoughts need a thinker, nor is there reason to believe this except
in a grammatical sense. The decision, however, to regard thoughts
rather than external objects as the prime empirical certainties was
very important, and had a profound effect on all subsequent
philosophy.
In two other respects the philosophy of Descartes was important.
First: it brought to completion,
or very nearly to completion, the dualism of mind and matter which
began with Plato and was
developed, largely for religious reasons, by Christian philosophy.
Ignoring the curious transactions in the pineal gland, which were
dropped by the followers of Descartes, the Cartesian system
presents two parallel but independent worlds, that of mind and that
of matter, each of which can be studied without reference to the
other. That the mind does not move the body was a new idea, due
explicitly to Geulincx but implicitly to Descartes. It had the
advantage of making it possible to say that the body does not move
the mind. There is a considerable discussion in the Meditations as
to why the mind feels "sorrow" when the body is thirsty. The
correct Cartesian answer was that the body and the mind were like
two clocks, and that when one indicated "thirst" the other
indicated "sorrow." From the religious point of view, however,
there was a grave drawback to this theory; and this brings me to
the second characteristic of Cartesianism that I alluded to
above.
In the whole theory of the material world, Cartesianism was
rigidly deterministic. Living
organisms, just as much as dead matter, were governed by the laws
of physics; there was no
longer need, as in the Aristotelian philosophy, of an entelechy or soul to explain the
growth of
organisms and the movements of animals. Descartes himself allowed
one small exception: a
human soul could, by volition, alter the direction though not the
quantity of the motion of the
animal spirits. This, however, was contrary to the spirit of the
system, and turned out to be
contrary to the laws of mechanics; it was therefore dropped. The
consequence was that all the
movements of matter were determined by physical laws, and, owing to
parallelism, mental events
must be equally determinate. Consequently Cartesians had difficulty
about free will. And for those
who paid more attention to Descartes's science than to his theory
of knowledge, it was not difficult to extend the theory that
animals are automata: why not say the same of man, and simplify the
system by making it a consistent materialism? This step was
actually taken in the eighteenth century.
There is in Descartes an unresolved dualism between what he learnt from contemporary
science
and the scholasticism that he had been taught at La Flèche. This
led him into inconsistencies, but it also made him more rich in
fruitful ideas than any completely logical philosopher could have
been. Consistency might have made him merely the founder of a new
scholasticism, whereas
inconsistency made him the source of two important but divergent
schools of philosophy.
(待续）
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