Produced by Al Haines.
[Illustration: Immanuel Kant]
*THE PHILOSOPHY OF
IMMANUEL KANT*
BY A. D. LINDSAY, M.A.
FELLOW AND TUTOR OF BALLIOL COLLEGE, OXFORD
LONDON: T. C. & E. C. JACK, LTD.
35 PATERNOSTER ROW, E.C., & EDINBURGH
NEW YORK: DODGE PUBLISHING CO.
*FOREWORD*
There is a story that Schopenhauer used to begin his lectures on Kant by
saying: "Let no one _tell_ you what is contained in the _Critique of
Pure Reason_." The writer of this little book hopes that no one will
imagine that he has disregarded this warning. There are no short-cuts
to the understanding of a great philosopher, and the only way to
appreciate the greatness of a philosophic system is to study the
philosopher's own writings. All that the writer of a book like this can
hope to do is to persuade others to undertake that study by interesting
them in the problems with which it deals, and by offering a few
suggestions which may help to an understanding of it. I have said
nothing about the numerous other works which Kant wrote. For the three
_Critiques_ contain his system, and the understanding of that is
all-important.
*CONTENTS*
CHAP.
I. THE IDEA OF CRITICISM
II. KANT'S STATEMENT OF THE PROBLEM. SYNTHETIC A PRIORI JUDGMENTS
III. KANT'S IDEALISM. TIME AND SPACE
IV. THE CATEGORIES AND THE PRINCIPLES OF PURE UNDERSTANDING
V. THE ANTINOMIES AND CRITICISM OF THE PROOFS OF THE EXISTENCE OF GOD
VI. KANT'S MORAL THEORY
VII. THE "CRITIQUE OF JUDGMENT"
BIBLIOGRAPHY
*THE PHILOSOPHY OF KANT*
*CHAPTER I*
*THE IDEA OF CRITICISM*
"It is a difficult matter," says Heine, "to write the life history of
Immanuel Kant, for he had neither life nor history. He lived a
mechanically ordered, abstract, old bachelor kind of existence in a
quiet, retired alley in Koenigsberg, an old town in the north-east
corner of Germany." The times he lived in were stirring enough. He was
born in 1724, and died in 1804. He lived through the Seven Years' War
that first made Germany a nation, he followed with sympathy the United
States War of Independence, he saw the French Revolution and the
beginning of the career of Napoleon. Yet in all his long life he never
moved out of the province in which he was born, and nothing was allowed
to interrupt the steady course of his lecturing, studying, and writing.
"Getting up," continues Heine, "drinking coffee, lecturing, eating,
going for a walk, everything had its fixed time; and the neighbours knew
that it must be exactly half-past four when Immanuel Kant, in his gray
frock-coat, with his Spanish cane in his hand, stepped from his door and
walked towards the little lime-tree avenue, which is called after him
the Philosopher's Walk." "Strange contrast," reflects Heine, "between
the man's outward life and his destructive, world-smashing thoughts."
As the political history of the eighteenth century came to an end when
the French Revolution spilled over the borders of France and drove
Napoleon up and down Europe, breaking up the old political systems and
inaugurating modern Europe, so its opposing currents of thought were
gathered together in the mind of a weak-chested, half-invalid little man
in Koenigsberg, and from their meeting a new era in philosophy began.
There are some philosophers to whom truth seems to come almost unsought,
as an immediate authoritative vision. Kant was not one of these. His
greatest work, the _Critique of Pure Reason_, was conceived when he was
forty-eight, and published in 1781, when he was fifty-seven. It was the
outcome of half a lifetime's patient study and thought. Heine says of
him: "He was the perfect type of the small shopkeeper. Nature had meant
him to weigh coffee and sugar, but fate willed that he should weigh
other things and put a God on his scales, and his weighing was exact."
The sneer is unjust, but there is something in the simile; for Kant's
philosophy was a kind of taking stock, a survey of the great movement of
thought from the time when the Renaissance and the Reformation made
thought free, an attempt to estimate the achievements of the new
sciences, to deal with their conflicting claims and ideals and say what
it all came to. In Kant modern science, which began with Descartes and
Galileo, first became conscious of itself.
This taking stock Kant called _Criticism_. His great books are all
called Critiques--the _Critique of Pure Reason_, the _Critique of
Practical Reason_, the _Critique of Judgment_. He called his philosophy
the Critical Philosophy or Critical Idealism. Essential to an
understanding of Kant is an understanding of what he meant by criticism,
and why he opposes it to dogmatism and scepticism; for the necessity and
possibility of such a criticism was his great philosophical discovery.
We have called Kant's work a survey of the achievements of the thought
of his times, but it was very much more than that, and has a much more
universal significance than could belong to any history of the thought
of one epoch. For these achievements of thought, though great, were
conflicting and partial. They contrasted with failure and barrenness in
other directions, and they seemed to be due to different methods. This
success of thought in one direction and its failure in another, and this
uncertainty about the true method of science, were problems which at
once presented themselves to an impartial observer, and Kant held that
they could be answered only by taking stock of actual attainments, and
by criticism of the powers and range of human thought in general.
The problem that presented itself to him will be understood if we look
for a moment at the history of thought in the seventeenth and eighteenth
centuries. One thing that Kant noted in it was the steady and sure
progress of physics. "With the experiments of Galileo and Torricelli,"
he says in the preface to the second edition of the first _Critique_, "a
new light flashed on all students of nature." The continued success of
physics meant the successful application of mathematics to the concrete
world, and along with it a remarkable development of mathematics itself.
This sudden success inspired men to feel that they had discovered a way
of explaining the universe; they contrasted the fertility of their new
methods with the barrenness of scholastic speculation in morals and
theology; they felt confident that all that was wanted to the attainment
of certain knowledge in all spheres of human interest was the extension
of these methods. If men would only set to work the right way, they
were sure that all difficulties would be overcome; and, by reflection
upon their own success, they hoped to explain what the right way was.
Unfortunately this was not easy, for the advance from pure mathematics
to physics, from a study of the nature of pure mathematical conceptions
to an inquiry into the laws of falling bodies, implied a change whose
nature was not clear to the men who had themselves made the advance. A
conflict arose between those who thought more of the fact that
knowledge, to be certain, must be capable of mathematical expression,
and those who thought more of the basis of experiment and observation on
which the new sciences depended, who remembered that these sciences
began when Galileo, instead of thinking in the abstract how bodies ought
to fall, dropped bodies of different weights from the top of the leaning
tower of Pisa and observed what actually happened. Descartes was the
great representative of the first school. He began by insisting on the
difference between mathematical truth which could be, as he said,
clearly and distinctly conceived, and ordinary opinion about things
which was full of guesswork and imagination. Scientific knowledge was
possible, he thought, only by apprehending the real or primary qualities
of things which were mathematical, in contradistinction to their
secondary qualities--their colour, smell, &c.--which were less real.
Thence he came to think that the real world was mathematical in nature,
like a huge, intricate geometrical figure. The elements of mere fact,
in our present knowledge, its dependence on observation and experiment,
he thought of as temporary defects which the progress of science would
remove. What we ordinarily call perception, indeed, in the sense of
awareness of things in time and space, was described by Descartes'
successors as confused thinking. Our knowledge of the world would, it
was hoped, become a vast mathematical system, all the detail and
complexity of which would be rigorously deducible from a few central
truths.
This general way of thinking was called Rationalism. Kant ordinarily
calls it Dogmatism. It was attacked by other scientists for its view of
the nature of space and time. No one who reflects at all can fail to
distinguish a difference between the way in which we see the truth of a
geometrical proposition--that, _e.g._, the three angles of a triangle
are equal to two right angles--and the way in which we judge that such
and such a figure drawn on a board is a triangle, or make judgments
about the way in which things are actually arranged in space or succeed
in time. Judgments of the latter kind involve words like "here" and
"there," "now" and "then," words which are all a kind of pointing. It
seems impossible from considering the nature of a triangle to deduce why
any existing thing should be called triangular, and all statements about
the position of things in space and time seem to be derived not from a
consideration of the general nature of space and time, but from
observation. Now the science which had made perhaps the most striking
progress in the time we are speaking of, physical astronomy, involved
any number of statements about the position of bodies in space. The
Rationalist school admitted this, but held that that was due to the fact
that science was not sufficiently thought out. In time, they hoped, all
statements about position in space would disappear. To think of things
in spatial order was to think confusedly. Newton, on the other hand,
held that space could not be explained away, that astronomy implied an
absolute space in which things existed, that the spatial relations of
things could not be explained by the nature of the things themselves,
but only by a reference to absolute space in which they all were. This
meant that observation or perception was something of which you could
not hope and should not wish to get rid, and that an ideal of knowledge
in which all applied mathematics should have been transmuted into pure
mathematics was a vain one. Astronomy implied both mere observation and
apprehension of necessary relations. Here was a science which seemed to
employ both methods together. Galileo, in fact could not have made his
discovery without observation but men had observed bodies falling for
ages without discovering the laws of motion. Further, the laws of
motion, once discovered, made men in some degree independent of
observation, made them able to say of actual concrete things not only
what had happened, but what must happen.
Such difficulties as these arose from reflection on the aims and methods
of the mathematical sciences, but there was much genuinely scientific
inquiry in the seventeenth and eighteenth centuries, which showed no
signs of taking mathematical form; chemistry and biology, for example,
were still almost entirely empirical. Furthermore, thinkers were not
concerned with science alone. These centuries saw a great revival of
interest in speculation on human affairs, history, politics, morals and
theology. England, which was the home of free discussion on questions
of politics and morals, and where, more than in most other countries,
there was free discussion on theology, became also the home of
empiricism. The empirical movement, indeed, drew much of its impetus
from a reaction against Hobbes, the only great English thinker who
unhesitatingly applied the mechanical and deterministic assumptions of
the new sciences to morals and politics, and arrived by this
uncompromising method at results so obviously repellent that no man of
any sense could accept them, and so consistently presented that they
could not be refuted save by a refutation of the assumptions upon which
they were founded. Such a refutation was, in fact, undertaken by Locke,
the first great representative of the empirical school. He was
interested alike in the more obviously empirical sciences of chemistry
and biology, and in politics. He was not a very consistent or
systematic thinker, but he had other gifts perhaps as valuable. He was
a man of great common sense and breadth of view, and was able thereby to
take a conspectus of the general situation in the various spheres of
inquiry, to notice the obvious differences in our knowledge of
mathematics, of chemical and biological fact, and of theology, and to
see that these constituted a problem. We find in him the first
statement of the necessity of philosophical criticism. It is contained
in his account of the origin of the _Essay concerning Human
Understanding_. "Were it fit to trouble thee with the history of this
_Essay_, I should tell thee that five or six friends, meeting at my
chamber, and discoursing on a subject very remote from this" (they were
discussing the "principles of morality and revealed religion"), "found
themselves quickly at a stand, by the difficulties that rose on every
side. After we had awhile puzzled ourselves, without coming any nearer
a resolution of those doubts which perplexed us, it came into my
thoughts that we took a wrong course; and that, before we set ourselves
upon inquiries of that nature, it was necessary to examine our own
abilities, and see what _objects_ our understandings were, or were not,
fitted to deal with."
We have here the same general starting point of inquiry as we shall
afterwards find in Kant. There are certain, obstinate puzzles which we
meet with in discussion which can only be solved by going back and
inquiring into the nature of knowledge and the powers of our minds.
Unfortunately, as Kant points out, Locke went the wrong way about his
task. He describes it as "a plain historical inquiry." He thought that
he had only to look into his mind and see what was in it, as he might
open a door and look into a room. The result is that he thinks of all
knowledge as consisting simply in looking at what is present to the
mind. We can know, therefore, whatever can be present to the mind, and
the limitations of knowledge are discovered by asking what can be so
present to the mind. The conclusions to which he comes as to different
spheres of human inquiry are roughly these: We can have knowledge of
mathematics because there we are concerned only with ideas present to
the mind, and with noting their agreement and disagreement. We can have
no knowledge of such questions as the immortality of the soul, or the
nature of spirits, for they are beyond our observation. As regards
existing things, we can have knowledge of them, in so far as they are
present to our minds, and no further. The meaning of "present to the
mind" was never clearly analysed by Locke; but he meant, for example,
that we can observe that an object which is yellow, and which we call
gold, is also heavy, and can be dissolved by Aqua Regia, but we cannot
say why that is so, and we ought not, on Locke's principles, to have any
ground for supposing that these qualities will go on co-existing.
The element of truth in Locke's position is this. When we are examining
concrete things like pieces of gold or any chemical substance, we find
in them a number of varying qualities whose connection we cannot
understand. We do not know why a metal of a certain specific gravity
should also be yellow; we can only note the fact. Hence in chemistry
our method must be quite different from the method of mathematics. In
mathematics we start from the definition, and we can understand the
connection of the properties of a geometrical figure, and see that they
all follow necessarily from the definition. But in sciences like
chemistry a definition does not take us any further; we can only find
out the properties of a substance by observation and experiment. Locke
explains this difference by saying that in the former case we are only
concerned with agreement among our own ideas, in the second place we are
concerned somehow with things outside us. This explanation will not
stand. It is not true that mathematics is simply analysis of an
arbitrary definition, as Locke seems to suggest. It involves
construction, or, as Kant calls it, synthesis. It is a process of
discovering new truths. Secondly, our statements about concrete objects
are not statements of qualities we see co-existing at the moment. They
are statements about all gold or all men; in other words, they are
universal, and Locke found it impossible to explain the universality of
such propositions--what we mean, _e.g._ when we talk about the nature of
gold or of man, not of this gold or this man that I see before me.
Lastly, this distinction of mathematics and the empirical sciences by a
distinction of spheres does not allow, as we saw, for a science like
astronomy, which builds on mathematics and yet applies to the concrete
world.
These difficulties were seen more clearly by Hume, at once the greatest
and the most thorough-going of empiricists. He cut the knot in regard
to mathematics by asserting that geometry, just because it has clearly
an application to the existing world, had no more certainty than any
other empirical inquiry, while arithmetic and algebra, he agreed, were
certain, but confined their application to the sphere of our own ideas.
Both positions are almost obviously inconsistent with the facts. In
considering the nature of our judgments about concrete existences he
raised a more profound problem. All such judgments, as he said, imply
the principle of causation, or of what is called, in modern times, the
principle of the uniformity of nature. That principle we take with us
in our investigation of the existing world. Yet, as Hume saw, we do not
observe causes; we only observe succession and change. We seem,
therefore, to put into the world we see a necessity and uniformity which
the observed facts do not warrant. How is this to be explained?
Hume's answer is ingenious. The principle of causation cannot be
rationally justified, and the necessary connection we predicate of
changes in the outside world is not in the things; it is only a feeling
in ourselves, and is the result of custom. After seeing the same
succession several times, we come somehow to feel differently about it,
and that feeling of difference we express by saying that we have before
us an instance not of simple succession, but of cause and effect.
This is not the place to discuss the difficulties of Hume's position; it
is enough to notice how entirely passive it makes the mind, and how
alien such an explanation is from the spirit of inquiry and discovery.
If cause is simply the effect of custom on the mind, then the facts
either produce that effect or they do not. In neither case is there
anything to find out. But the scientist, in investigating causes,
however strongly he may hold that he has to observe the facts, knows
also that he has a problem to solve, that he has to discover the right
way to go about it, must adopt some principle in dealing with the facts.
Pure passivity will help him little.
Hume's account of causation, then, is really a denial of even empirical
science, and yet it helped to make clear an important truth; for,
although we do not get the _principle_ of causation from experience, we
have to go to experience to discover causal laws. We do not discover
causation by analysing a cause and seeing that it is such that, from its
nature, it must produce a certain effect. All knowledge of causation
goes back to observed succession, though all cases of observed and even
repeated succession are not cases of causation. Hume, therefore, was
right in saying that where there could be no observed succession there
could be no knowledge of causation.
Both the rationalistic and the empirical explanations of science had
failed, the one because it could find no room for observation of facts,
the other because it could find no room for principles governing that
observation; and we shall see that Kant started with a consciousness of
this double failure. He saw that Hume's criticism of causation raised
problems for which the rationalist had no answer, and yet that the
position reached by Hume was incompatible with the existence of science.
The same failure of both rationalism and empiricism had become evident
in another sphere--that of morals and religion. The relation of
philosophy to science is always twofold. Philosophy is partly concerned
with analysing and reflecting on the methods of the different sciences,
partly with seeking to adjust the rival and conflicting claims of the
two great departments of man's life--science and religion.
It might seem, at first sight, as though in morals and religion
rationalism were the only possible method to be approved by philosophy,
for, inasmuch as morals are concerned with what ought to be, not with
what is, they cannot depend on observation, but must be deduced from
some principle above experience; nor are objects of religion, God and
the soul, objects of observation. No man can "by searching find out
God."
It was natural, therefore, that both on the Continent and in England
morality and religion began by being rationalistic. Descartes believed
that his mathematical method could be applied with success to
demonstrate the truths of religion, while Locke includes morality along
with mathematics among the a priori and certain sciences. But the
history of eighteenth century controversy showed that, in spite of
rationalist methods, neither morality nor religion could attain that
certainty and general agreement which marked the mathematical sciences.
Spinoza, applying the same method as Descartes, but with more
consistency, arrived at a conception of God which most of his
contemporaries regarded as "horrid atheism," and the general result of
rational theology is well described by one of Kant's correspondents when
he says that the more proofs of the existence of God he learnt, the more
his doubts increased. In England the attempts made to found morality
upon rationalist principles produced systems too barren to withstand the
attack of empiricism fortified by the growing interest in history and
anthropology. The Deist movement, an attempt to free religion from the
incrustations of faith and deduce it from pure reason, showed that a
religion founded on pure reason contained nothing worth believing. In
Hume we have the final discrediting of reason in these spheres. He
shows ingeniously that "the good Berkeley's" argument for the existence
of God could be turned round to disprove the existence of the soul, and
he concluded that religion was a sphere with which reason had no
concern. In the sphere of morals the distinction between what ought to
be and what is, the distinction on which rationalistic morals are based,
had been discredited by a reduction of all conduct to Utilitarianism, a
search for pleasure and a flight from pain mediated by sympathy. The
consequences are described by Kant in his preface to the _Critique of
Pure Reason_: "At present, after everything has been tried, so they say,
and tried in vain, there reign in philosophy weariness and complete
indifferentism, the mother of chaos and night in all sciences," though
he hopefully continues, "but at the same time the source, or at least
the prelude, of their near reform and of a new light, after an
ill-applied study has rendered them dark, confused, and useless."
The earlier of the modern thinkers--Descartes among the rationalists,
and Bacon among the empiricists--are full of hope. They have confidence
in the human spirit. But increased reflection seemed only to bring
distrust with it. The history of rationalism in theology showed that,
in such matters, reason could prove absolutely opposing positions. Most
men were ready to accept Hume's dictum that any one who follows his
reason must be a fool and take refuge in an indifferentism which accepts
whatever happens to be there.
The remedy for this state of affairs, Kant finds, is the critical
method; for disbelief in reason is the reaction from overconfidence in
it. Men had thought that reason could prove everything. Because these
hopes had been frustrated, they now thought that it could prove nothing.
Philosophy, he was convinced, would oscillate between overweening
confidence and unwarranted distrust in itself until it had criticised
human reason and discovered what it could do and what it could not.
This is the task he set before himself. As the failure of eighteenth
century philosophy, which had led to distrust of all philosophy, had
been twofold--failure to give an intelligible explanation of the
processes of scientific thought, and failure to find any standard by
which to mediate between the conflicting claims of science and
religion--the task of the critical philosophy is twofold. It attempts
to explain and to justify the methods and assumptions of the sciences,
and to find some solution of the conflict between theories of the world
which seem to be based upon these methods and the assumptions and claims
of morality and religion.
*CHAPTER II*
*KANT'S STATEMENT OF THE PROBLEM. SYNTHETIC
A PRIORI JUDGMENTS*
In the preface to the second edition of the _Critique of Pure Reason_
Kant finds the necessity of criticism in the contrast between certain
rational sciences and metaphysics. Mathematics and physics, he
observes, are obviously certain sciences. They are not empirical, they
make steady progress, the results they have reached are secure and
unanimously accepted, and have a certainty which no mere empirical
investigation could attain. Metaphysics, on the other hand, though as
ancient an inquiry, seems incapable of any settled results. Its history
is a record, not of steady progress, but of bewildering marches and
countermarches. The confident conclusions of one philosopher are as
confidently denied by another, and the endless indecisive conflict
produces in the minds of most men the conviction that in philosophy one
doctrine is as good as another, and therefore none are worth very much.
In the sphere where reason might be expected to be most at home, reason
is impotent; yet the achievements of reason in those other spheres of
the a priori sciences should preserve us from any general scepticism of
the powers of reason. The task of criticism will be to examine the part
played by reason in science, and to ask how far its failure in
metaphysics is due to mistakes in method, and how far to the different
nature of the objects of the a priori sciences and of metaphysics. Kant
points out that it was some time before either mathematics or physics
followed the secure path of a science. The contrast between the
haphazard and empirical observations of the Babylonians or Egyptians and
the science of the Greeks was due to the discovery of a new method. The
discovery by Galileo and Torricelli of modern physics came about by a
similar revolution in method. The _Critique_, therefore, is to be a
treatise on method. It will examine the method of reason in the
sciences, and ask what conclusions can be drawn as to the proper method
of metaphysics.
In the _Prolegomena_, a work in which he summarises the results of the
first _Critique_, Kant describes the _Critique_ as an answer to three
questions: How is mathematics possible? How is pure science of nature
or physics possible? and, How is metaphysics possible? Something of the
nature of his answer to the third, and for him the most important,
question, may be gathered from the fact that he explains that the third
question should not be put in the form, How is metaphysics as a science
possible? That question can only be answered by saying that it is not
possible. But it is still allowable and necessary to ask, How is
metaphysics possible as a natural disposition of the mind? For the main
result of his inquiries into the place of reason in the sciences is to
show that reason is successful in the sciences only because of the
presence of certain conditions which are wanting in metaphysics. At
first sight we might think it natural that the objects of metaphysics
which Kant enumerates as God, Freedom, and Immortality should be
understood by reason, and find it more difficult to explain how reason
should apply to the world of ordinary experience. The knowledge of
everyday things is thought of as empirical, a matter of observation;
while we are inclined to think that, if there is rational knowledge, it
is knowledge of something else, of the mere agreement or disagreement of
ideas (as Hume thought), or of the essences of things, known
independently and apart from perception, as Plato thought. Kant argues
that the combination of a priori reasoning and empirical observation,
which earlier thinkers had found so puzzling in the exact sciences,
exhibits the only possible use of reason, that reason, divorced from and
with no reference to the world of experience, is barren, and that
consequently metaphysics, if that be taken to mean a rational knowledge
of objects which are outside of our experience, does not exist. We are
left with metaphysics as a natural disposition; for Kant holds that the
questions which metaphysics seeks to answer arise from the nature of
reason and its relation to experience, though their answer is to be
sought not in knowledge but in action.
This last point must be elucidated later. In the meantime we must see
how this inquiry into the nature of reason crystalises itself into a
seemingly abstract and trivial question: How are synthetic a priori
judgments possible? It is baffling at first to find an inquiry of the
scope we have indicated suddenly take such a narrow form, but a little
consideration will show the importance of the question. Knowledge may
be regarded as either analysis or synthesis, as a puzzling out or
unravelling of what we somehow know already, or as a putting together of
what had previously been known or observed separately. The rationalist
school, whom we described in the last chapter, were inclined to regard
all knowledge as analytical. They thought of progress in knowledge as
an advance from obscure to clear apprehension, and as a thinking out or
making clear of something which had always been known somehow.
Mathematics, the typical form of knowledge for the rationalists, had
been thought of as the analysis of what was implied or given in the
definitions. The conception of analytic a priori knowledge was thus
familiar and simple. On the other hand, the empiricists had thought of
knowledge as primarily synthesis--or, as they called it, association--a
connecting together of ideas in their nature separate. Knowledge of a
thing was thought of as the observing together of several ideas.
Judgments about objects were regarded as judgments about the
co-existence of separate ideas, ideas which were not thought of as being
bound by any logical necessity. We do not understand why a substance
with the specific gravity of gold should be yellow; we only observe the
co-existence of certain qualities. The judgment, then, gold is yellow,
is synthetic; it is an assertion of the co-existence of separate
qualities. It is also empirical; it does not express a reasoned insight
into the necessary connection of gold and yellow. It seems rather a
record of observation. Synthetic knowledge, then, was thought of as in
its nature empirical and a posteriori. Hume, who thought of all
knowledge of the world in experience as synthetic, denied to such
knowledge any necessity or certainty.
Hume, however, had noticed that the principle of causation, the judgment
that every event has a cause, is both a priori and synthetic. It is
not, he held, derived from experience; rather it is a principle which
guides our investigation of experience. It is not got from analysis of
the notion of causation, nor is it simply concerned with the agreement
or disagreement of our ideas. It asserts the necessary connection of
two perfectly separate existing things. Hume himself, as we saw, tried
to explain away these uncomfortable facts. He was too wedded to his
belief that all knowledge was derived from passively received
impressions to face them rightly. Kant, coming to the problem with
different prepossessions, with the belief that most knowledge was
analytic, was impressed with Hume's proof that the principle of
causation could not be derived from analysis. The very basis of all
science of nature, then, contradicted the belief that knowledge was
analytical. Kant was also, with Hume, convinced that the principle of
causation was not derived from experience, for he saw that experience
assumed it. At the same time, he was not prepared, like Hume, to
explain it away. Further, he saw that the problem raised by the
principle of causation was a wide one. For other judgments, he held, are
both synthetic and a priori, among them mathematical judgments. As we
shall see afterwards, Kant proved the impossibility of arriving at
knowledge of God or the soul by mere analysis of concepts. The
judgments of metaphysics, about God or the soul, are also synthetic.
But the validity of the judgments of metaphysics is under dispute. If we
examine the synthetic a priori judgments of mathematics and of science
whose validity is certain, we may then discover whether such judgments
in metaphysics can or can not have similar certainty. We may thus see
that the problem of the possibility of synthetic a priori judgments is a
restatement in logical terms of the problem of the relation between the
a priori sciences and metaphysics.
Something more must be said of the importance of synthetic a priori
judgments in Kant's account of knowledge. Their existence, we have
seen, exposes the shortcomings of both rationalism, which allowed only
for analytic a priori judgments, and empiricism, which allowed only of
synthetic a posteriori judgments. Both these theories tended to regard
knowledge as an analysis or description of what was present to the mind,
and differed really only in their view of what was present. For, though
the empiricist thought of empirical knowledge as synthesis, the
synthesis was not ascribed to the mind, but to associating ideas; the
mind only observed, and knowledge was merely the apprehension of objects
by the senses. We see what is before our eyes, and notice the
differences and similarities in what is before us. The rationalist
conceived of thought as simply apprehending the nature of the real,
freed from the illusions of sense perception. The mathematician has
before his thought the nature of a triangle, and sees intellectually
what that nature implies. We may try to mediate between the two by
saying that while all knowing is observing, some is observing of objects
of thought and some of objects of sense, the one being called
understanding, the other perception. In most scientific judgments,
however, we are not simply observing objects either of thought or of
sense. Scientific judgments are more than descriptions of what is
present to the mind or to the senses; they are essentially
anticipations. They go beyond what is immediately given. This is shown
by the fact that it is the characteristic of a scientific proposition
that it can be verified. If we understand it rightly, we see that it
implies that, under such-and-such conditions, such-and-such things will
be experienced. Hence the importance of experiment to science. A
scientific proposition is, of course, grounded on observation of
perceived fact and understanding of universal connection, but it is an
assertion of something beyond that.
If, then, all scientific judgments are synthetic, and if both
rationalism and empiricism failed to account for the manner in which
such judgments go beyond what is immediately given to the mind, ought we
not to say that the real problem for Kant is to show not merely how
synthetic a priori judgments are possible, but how any synthetic
judgments are possible? This seems at first sight plausible, but the
suggestion must be rejected; for, when Kant asks how a judgment is
possible, he is not asking how we come to make it, but how we know that
it is valid. Now, if we consider any empirical judgment about the facts
of nature, we must recognise that Locke and Hume were right in denying
certainty to such judgments. In all general statements about concrete
facts we to a certain extent go beyond our evidence. Empirical
scientific statements are not theoretically certain. They may, of
course, be certain enough for all practical purposes. They are
reasonable expectations of what will happen, but reasonable expectation
is a very different thing from the certainty of mathematical insight.
Now Kant maintained that, while such empirical judgments are not
certain, they all imply the certainty of a number of general principles
on which they depend. These general principles are the synthetic a
priori judgments with which he is especially concerned. When we apply
the principles of trigonometry to an engineering problem, we know that
our measurements are only approximate, and that the result also will
only be approximate; but the possibility of arriving at such approximate
results depends on the absolute truth of the trigonometrical principles,
and on the assumption that they express not simply the agreement or
disagreement of ideas, but hold of the real. When we apply the rules of
arithmetic to counting objects, there may be a certain arbitrariness in
deciding on our unit. There is no such arbitrariness in the rule. All
scientific judgments of causation are only approximately certain, but
they all imply the certainty of the principle of causation, and are
based on the assumption that such a principle is of universal
application. This and the other principles assumed in our empirical
judgments are, then, the synthetic judgments with which Kant is
concerned. Now, it is of the nature of our empirical knowledge that it
is fragmentary and not uniform, that we are concerned with an indefinite
number of things whose connections we do not wholly understand, and
which we cannot therefore anticipate. Yet we assume that all these
objects will obey the rules of arithmetic and geometry, and will all be
subject in their changes to the principle of causation. On such
assumptions all the sciences of applied mathematics depend. How are
they justifiable? That is Kant's question.
Kant, when he considers mathematics, is concerned with the assumptions
of applied mathematics, of those sciences which, though mathematical,
make statements about existing objects, and in which the old distinction
between understanding and perception which was based on the difference
in the objects of these two faculties breaks down. The sciences which
Kant is investigating imply that principles which are clearly not
derived from mere observation are yet the basis on which we order and
arrange what we observe. Now, if we held that the objects of
mathematics were independent entities quite separate from the things we
perceive, it would be impossible to explain how we might assume that the
things we perceive would be subject to the rules of mathematics. If, on
the other hand, we held that in mathematics we were simply concerned
with the various objects of the senses, it would be impossible to
explain how mathematics can have a generality and necessity which no
statements can have which rest on observation of the various things we
see. The existence of applied mathematics implies firstly that
understanding and perception are distinct, and that neither of them can
be reduced to the other, for that would mean that we should have to give
up either the element of observation and experiment or the element of
necessity and a priority, and secondly, that understanding and
perception are combined, and must be combined for any advance in
science.
Now, Kant finds his answer to the problem he has raised by concentrating
his attention on the fact that, while understanding and perception are
distinct, they are both present in all knowledge. His argument is that
we are necessarily in a difficulty if we think of understanding and
perception as having each its separate objects, and then try to explain
their combination. If we begin with their combination, we may see that
the reference of principles of thought to objects of sense is not an
accident, but that these principles of thought or of understanding, as
Kant calls them, are only concerned with objects of sense, and have no
other meaning. If we object, But how can principles of thought be
universal if they are concerned with the many and varying objects of
sense? Kant's answer is that they are not concerned directly with these
objects, but with the conditions under which these objects can be
understood. They are therefore not statements about objects, but
statements of the conditions of possible experience. If we find out that
all perceiving and thinking imply certain conditions, then we can affirm
the validity of principles based upon these conditions, so long as we do
not try to apply the principles beyond our perceiving.
We may put the point in another way by asking by what right the mind can
prescribe to or anticipate experience. Kant's answer is just in so far
as we can determine the conditions under which alone objects can be
known. If that can be done, we can say, These principles will hold of
objects in so far as they are known. In the preface to the second
edition of the _Critique of Pure Reason_ Kant reverts to the discoveries
of Galileo and Torricelli, and points out that their success was due to
their asking of nature the right question, and the right question was
that which reason could understand. "When Galileo let balls of a
particular weight, which he had determined himself, roll down an
inclined plane, or Torricelli made the air carry a weight, which he had
previously determined to be equal to that of a definite volume of water,
a new light flashed on all students of nature. They comprehended that
reason has insight into that only which she herself produces on her own
plan, and that she must move forward with the principles of her
judgments, according to fixed law, and compel nature to answer her
questions, but not let herself be led by nature, as it were in
leading-strings. Otherwise accidental observations, made on no
previously fixed plan, will never converge towards a necessary law,
which is the only thing that reason seeks or requires. Reason, holding
in one hand its principles, according to which alone concordant
phenomena can be admitted as laws of nature, and in the other the
experiment which it has devised according to those principles, must
approach nature in order to be taught by it, but not in the character of
a pupil who agrees to everything the master likes, but as an appointed
judge, who compels the witnesses to answer the questions which he
himself proposes."
Kant, here, is concerned with reason in its application to experience,
and he makes it clear that there is much in all such inquiries which
cannot be anticipated a priori. "Reason must approach nature in order
to be taught by it." The answer to the questions and experiments cannot
be known beforehand. The empirical element in science cannot be
explained away. Reason dictates not the answer but the question, and so
far the form of the answer. Reason, then, it is suggested, is concerned
with the principles or conditions, according to which we can understand
things. It is not a method of observing or analysing objects; rather it
states the methods and principles according to which objects must be
observed if they are to be understood. The principles are not
statements about the nature of objects, but principles of the
possibility of experience. This new attitude to reason Kant describes
as the Copernican change in philosophy. It constitutes Kant's idealism.
Its nature and importance we must examine in the next chapter.
*CHAPTER III*
*KANT'S IDEALISM. TIME AND SPACE*
The great discovery which Kant considered he had made as to the nature
of reason was that reason was not a method of observing objects as they
really exist, but was concerned directly only with our ways of
understanding objects. This discovery is the essence of Kant's
idealism, and its main purport is expressed in the distinction Kant so
often makes between things in themselves and phenomena. This
distinction is used as the key to the solution of all his difficulties.
But the doctrine it implies is very easy to misunderstand, partly
because idealism is generally used in a very different sense from that
in which Kant uses it, partly because Kant's statement of the
distinction between things in themselves and phenomena depended on a
view of knowledge which he was very much concerned to refute, but with
which we are not now familiar. If we are to understand Kant's
philosophy, we must know what he means by idealism, and wherein his
idealism differs from that of his predecessors.
The word idealism is, naturally, contrasted with realism. It suggests
an assertion that something is not real, but only an idea. If we know
it to be combined with a distinction between things in themselves, and
phenomena, or appearances, it seems to suggest that the objects of
knowledge are somehow illusions, or only appearances in the mind, as
contrasted with real things. Something like this had been held by Kant's
predecessors. For the fundamental principle of the idealism on which
most of Kant's predecessors had been agreed, and which is sometimes
called Cartesian, and sometimes subjective idealism, is that the mind
somehow knows itself and its own actions and states, with more
directness and certainty than it knows external objects. The doctrine
is commonly based upon a confused view of sense perception.
Sense perception is obviously possible only through processes in the
sensory organs, and objects were thought of as producing impressions
through the sensory organs in the brain, and the mind as then becoming
aware of them in the brain. Hence, when Locke says that the mind only
knows its own ideas, he tends to mean (though the facts are sometimes
too much for him and he is nobly inconsistent) that the mind only knows
objects inside the brain. The main objection to this doctrine, apart
from the fact that it is based on a confusion, is that it makes it quite
inexplicable how the notion of an outside world ever arises. For if we
know, and must eternally know, only ideas inside our head, why should we
ever imagine that there an outside world exists. Yet if nothing
_outside_ us were observed--if we knew of no process which went on
between outside objects and the brain, the doctrine would have no basis
on which to rest. There cannot be any meaning in saying something is
"only an idea," if we do not know what is real in the sense of its
having an existence independent of our minds.
Locke supposed that, although we knew only ideas, we could somehow refer
from our ideas to an outside world. For he thought that truth was
concerned with the agreement of our ideas with reality. This form of
the doctrine, the commonest, is sometimes called Representationism. For
it thinks of the mind as concerned with representations, or pictures, or
images which it may compare with the real objects. Its futility is
obvious enough. We can only compare a picture with the thing it
represents, if we can know both. If we can only know ideas, we can
never know that they are only ideas, and can never compare them with
anything else.