main question of the _Critique of Pure Reason_: How are synthetic judgments
_a priori_ possible?
The philosophy of experience had overestimated sense and underestimated the
understanding, when it found the source of all knowledge in the faculty of
perception and degraded the faculty of thought to an almost wholly inactive
recipient of messages coming to it from without. From the standpoint of
empiricism concepts (Ideas) deserve confidence only in so far as they can
legitimate themselves by their origin in sensations (impressions). It
overlooks the _active_ character of all knowing. Among the rationalists,
on the other hand, we find an underestimation of the senses and an
overestimation of the understanding. They believe that sense reveals
only the deceptive exterior of things, while reason gives their true
non-sensuous essence. That which the mind perceives of things is deceptive,
but that which it thinks concerning them is true. The former power is the
faculty of confused, the latter the faculty of distinct knowledge. Sense is
the enemy rather than the servant of true knowledge, which consists in the
development and explication of pregnant innate conceptions and principles.
These philosophers forget that we can never reach reality by conceptual
analysis; and that the senses have a far greater importance for knowledge
than merely to give it an impulse; that it is they which supply the
understanding with real objects, and so with the content of knowledge.
Beside the (formal) activity (of the understanding), cognition implies a
passive factor, a reception of impressions. Neither sense alone nor the
understanding alone produces knowledge, but both cognitive powers are
necessary, the active and the passive, the conceptual and the intuitive.
Here the question arises, How do concept and intuition, sensuous and
rational knowledge, differ, and what is the basis of their congruence?
Notwithstanding their different points of departure and their variant
results, the two main tendencies of modern philosophy agree in certain
points. If the conflict between the two schools and their one-sidedness
suggested the idea of supplementing the conclusions of the one by those of
the other, the recognition of the incorrectness of their common
convictions furnished the occasion to go beyond them and to establish a
new, a higher point of view above them both, as also above the eclecticism
which sought to unite the opposing principles. The errors common to both
concern, in the first place, the nature of judgment and the difference
between sensibility and understanding. Neither side had recognized that
the peculiar character of judgment consists in _active connection_. The
rationalists made judgment an active function, it is true, but a mere
activity of conscious development, of elucidation and analytical inference,
which does not advance knowledge a single step. The empiricists described
it as a process of comparison and discrimination, as the mere perception
and recognition of the relations and connections already existing between
ideas; while in reality judgment does not discover the relations and
connections of representations, but itself establishes them. In the former
case the synthetic moment is ignored, in the latter the active moment. The
imperfect view of judgment was one of the reasons for the appearance of
extreme theories concerning the origin of ideas in reason or in perception.
Rationalism regards even those concepts which have a content as innate,
whereas it is only formal concepts which are so.
Empiricism regards all,
even the highest formal concepts (the categories), as abstracted from
experience, whereas experience furnishes only the content of knowledge,
and not the synthesis which is necessary to it. On the one hand too much,
and on the other too little, is regarded as the original possession of the
understanding. The question "What concepts are innate?"
can be decided only
by answering the further question, What are the concepts through which the
faculty of judgment connects the representations obtained from experience?
These connective concepts, these formal instruments of synthesis are
_a priori_. The agreement of the two schools is still greater in regard to
the relation of sense and understanding, notwithstanding the apparently
sharp contrast between them. The empiricist considers thought transformed,
sublimated perception, while the rationalist sees in perception only
confused and less distinct thought. For the former concepts are faded
images of sensations, for the latter sensations are concepts which have not
yet become clear; the difference is scarcely greater than if the one should
call ice frozen water, and the other should prefer to call water melted
ice. Both arrange intuition and thought in a single series, and derive the
one from the other by enhancement or attenuation. Both make the mistake of
recognizing only a difference in degree where a difference in kind exists.
In such a case only an energetic dualism can afford help. Sense and
understanding are not one and the same cognitive power at different stages,
but two heterogeneous faculties. Sensation and thought are not different in
degree, but in kind. As Descartes began with the metaphysical dualism of
extension and thought, so Kant begins with the noëtical dualism of
intuition and thought.
Much more serious, however, than any of the mistakes yet mentioned was
a sin of omission of which the two schools were alike guilty, and the
recognition and avoidance of which constituted in Kant's own eyes the
distinctive character of his philosophy and its principiant-advance beyond
preceding systems. The pre-Kantian thinker had proceeded to the discussion
of knowledge without raising _the question of the possibility of
knowledge_. He had approached things in the full confidence that the human
mind was capable of cognizing them, and with a naïve trust in the power of
reason to possess itself of the truth. His trust was naïve and ingenuous,
because the idea that it could deceive him had never entered his mind. Now
no matter whether this belief in man's capacity for knowledge and in the
possibility of knowing things is justifiable or not, and no matter how
far it may be justifiable, it was in any case untested; so that when the
skeptic approached with his objections the dogmatist was defenseless.
All previous philosophy, so far as it had not been skeptical, had been,
according to Kant's expression, dogmatic; that is, it had held as an
article of faith, and without precedent inquiry, that we possess the power
of cognizing objects. It had not asked _how_ this is possible; it had not
even asked what knowledge is, what may and must be demanded of it, and by
what means our reason is in a position to satisfy such demands. It had left
human intelligence and its extent uninvestigated. The skeptic, on the other
hand, had been no more thorough. He had doubted and denied man's capacity
for knowledge just as uncritically as the dogmatist had believed and
presupposed it. He had directed his ingenuity against the theories of
dogmatic philosophy, instead of toward the fundamental question of the
possibility of knowledge. Human intelligence, which the dogmatist had
approached with unreasoned trust and the skeptic with just as unreasoned
distrust, is subjected, according to the plan of the critical philosopher,
to a searching examination. For this reason Kant termed his standpoint
"criticism," and his undertaking a "Critique of Reason."
Instead of
asserting and denying, he investigates how knowledge arises, of what
factors it is composed, and how far it extends. He inquires into the origin
and extent of knowledge, into its sources and its limits, into the grounds
of its existence and of its legitimacy. The Critique of Reason finds itself
confronted by two problems, the second of which cannot be solved until
after the solution of the first. The investigation of the sources of
knowledge must precede the inquiry into the extent of knowledge. Only after
the conditions of knowledge have been established can it be ascertained
what objects are attainable by it. Its sphere cannot be determined except
from its origin.
Whether the critical philosopher stands nearer to the skeptic or to the
dogmatist is rather an idle question. He is specifically distinct from
both, in that he summons and guides the reason to self-contemplation, to
a methodical examination of its capacity for knowledge.
Where the one had
blindly trusted and the other suspected and denied, he investigates; they
overlook, he raises the question of the possibility of knowledge. The
critical problem does not mean, Does a faculty of knowledge exist? but, Of
what powers is it composed? are all objects knowable which have been so
regarded? Kant does not ask whether, but how and by what means, knowledge
is possible. Everyone who gives himself to scientific reflection must
postulate that knowledge is possible, and the demand of the noëtical
theorists of the day for a philosophy absolutely without assumptions is
quite incapable of fulfillment. Nay, in order to be able to begin his
inquiry at all, it was necessary for Kant to assume still more special
postulates; for that a cognition of cognition is possible, that there is a
critical, self-investigating reason could, at first, be only a matter of
belief. This would not have excluded a supplementary detailed statement
concerning the _how_ of this self-knowledge, concerning the organ of the
critical philosophy. But Kant never gave one, and the omission subsequently
led to a sharp debate concerning the character and method of the Critique
of Reason. On this point, if we may so express it, Kant remained a
dogmatist.
Kant felt himself to be the finisher of skepticism; but this was chiefly
because he had received the strongest impulse to the development of his
critique of knowledge from Hume's inquiries concerning causation. Brought
up in the dogmatic rationalism of the Wolffian school, to which he
remained true for a considerable period as a teacher and writer (till about
1760), although at the same time he was inquiring with an independent
spirit, Kant was gradually won over through the influence of the English
philosophy to the side of empirical skepticism. Then--as the result, no
doubt, of reading the _Nouveaux Essais_ of Leibnitz, published in
1765--he returned to rationalistic principles, until finally, after a
renewal of empirical influences,[1] he took the position crystallized in
the _Critique of Pure Reason_, 1781, which, however, experienced still
other, though less considerable, changes in the sequel, just as in itself
it shows the traces of previous transformations.
[Footnote 1: Cf. H. Vaihinger's _Kommentar zu Kants Kritik der reinen
Vernunft_, vol. i., 1881, pp. 48-49. This is a work marked by acuteness,
great industry, and an objective point of view which merits respect. The
second volume, which treats of the Transcendental Aesthetic, appeared in
1892.]
It would be a most interesting task to trace in the writings which belong
to Kant's pre-critical period the growth and development of the fundamental
critical positions. Here, however, we can only mention in passing the
subjects of his reflection and some of the most striking anticipations and
beginnings of his epoch-making position. Even his maiden work, _Thoughts on
the True Estimation of Vis Viva_, 1747, betokens the mediating nature of
its author. In this it is argued that when men of profound and penetrating
minds maintain exactly opposite opinions, attention must be chiefly
directed to some intermediate principle to a certain degree compatible with
the correctness of both parties. The question under discussion was whether
the measure of _vis viva_ is equal, as the Cartesians thought, to the
product of the mass into the velocity, or, according to the Leibnitzians,
to the product of the mass into the square of the velocity. Kant's
unsatisfactory solution of the problem--the law of Descartes holds for
dead, and that of Leibnitz for living forces--drew upon him the derision
of Lessing, who said that he had endeavored to estimate living forces
without having tested his own. A similar tendency toward compromise--this
time it is a synthesis of Leibnitz and Newton--is seen in his
_Habilitationsschrift, Principiorum Primorum Cognitionis Metaphysicae Nova
Dilucidatio_, 1755, and in the dissertation _Monadologia Physica_, 1756.
The former distinguishes between _ratio essendi_ and _ratio cognoscendi_,
rejects the ontological argument, and defends determinism against Crusius
on Leibnitzian grounds. In the _Physical Monadology_
Kant gives his
adherence to dynamism (matter the product of attraction and repulsion), and
makes the monads or elements of body fill space without prejudice to
their simplicity. A series of treatises is devoted to subjects in natural
science: The Effect of the Tides in retarding the Earth's Rotation; The
Obsolescence of the Earth; Fire (Inaugural Dissertation), Earthquakes, and
the Theory of the Winds. The most important of these, the _General Natural
History and Theory of the Heavens_, 1755, which for a long time remained
unnoticed, and which was dedicated to Frederick II., developed the
hypothesis (carried out forty years later by Laplace in ignorance of Kant's
work) of the mechanical origin of the universe and of the motion of the
planets. It presupposes merely the two forces of matter, attraction and
repulsion, and its primitive chaotic condition, a world-mist with elements
of different density. It is noticeable that Kant acknowledges the failure
of the mechanical theory at two points: it is brought to a halt at the
origin of the organic world and at the origin of matter.
The mechanical
cosmogony is far from denying creation; on the contrary, the proof that
this well-ordered and purposive world necessarily arose from the regular
action of material forces under law and without divine intervention, can
only serve to support our assumption of a Supreme Intelligence as the
author of matter and its laws; the belief is necessary, just because
nature, even in its chaotic condition, can act only in an orderly and
regular way.
The empirical phase of Kant's development is represented by the writings
of the 60's. _The False Subtlety of the Four Syllogistic Figures_, 1762,
asserts that the first figure is the only natural one, and that the others
are superfluous and need reduction to the first. In the _Only Possible
Foundation for a Demonstration of the Existence of God_, 1763, which, in
the seventh Reflection of the Second Division, recapitulates the cosmogony
advanced in the _Natural History of the Heavens_, the discussions
concerning being ("existence" is absolute position, not a predicate which
increases the sum of the qualities but is posited in a merely relative
way), and the conclusion, prophetical of his later point of view, "It is
altogether necessary that we should be _convinced_ of the existence of God,
but not so necessary that his existence should be _demonstrated_" are more
noteworthy than the argument itself. This runs: All possibility presupposes
something actual wherein and whereby all that is conceivable is given as
a determination or a consequence. That actuality the destruction of which
would destroy all possibility is absolutely necessary.
Therefore there
exists an absolutely necessary Being as the ultimate real ground of all
possibility; this Being is one, simple, unchangeable, eternal, the _ens
realissimum_ and a spirit. The _Attempt to introduce the Notion of
Negative Quantities into Philosophy_, 1763, distinguishes--contrary to
Crusius--between logical opposition, contradiction or mere negation (_a_
and _not-a_, pleasure and the absence of pleasure, power and lack of
power), and real opposition, which cannot be explained by logic (+_a_ and
-_a_, pleasure and pain, capital and debts, attraction and repulsion;
in real opposition both determinations are positive, but in opposite
directions). Parallel with this it distinguishes, also, between logical
ground and real ground. The prize essay, _Inquiry concerning the Clearness_
(Evidence) _of the Principles of Natural Theology and Ethics_, 1764, draws
a sharp distinction between mathematical and metaphysical knowledge, and
warns philosophy against the hurtful imitation of the geometrical method,
in place of which it should rather take as an example the method which
Newton introduced into natural science. Quantity constitutes the object of
mathematics, qualities, the object of philosophy; the former is easy and
simple, the latter difficult and complicated--how much more comprehensible
the conception of a trillion is than the philosophical idea of freedom,
which the philosophers thus far have been unable to make intelligible.
In mathematics the general is considered under symbols _in concrete_, in
philosophy, by means of symbols _in abstracto_; the former constructs its
object in sensuous intuition, while the object of the latter is given
to it, and that as a confused concept to be decomposed.
Mathematics,
therefore, may well begin with definitions, since the conception which is
to be explained is first brought into being through the definition, while
philosophy must begin by seeking her conceptions. In the former the
definition is first in order, and in the latter almost always last; in the
one case the method is synthetic, in the other it is analytic. It is the
function of mathematics to connect and compare clear and certain concepts
of quantity in order to draw conclusions from them; the function of
philosophy is to analyze concepts given in a confused state, and to make
them detailed and definite. Philosophy has also this disadvantage, that
it possesses very many undecomposable concepts and undemonstrable
propositions, while mathematics has only a few such.
"Philosophical truths
are like meteors, whose brightness gives no assurance of their permanence.
They vanish, but mathematics remains. Metaphysics is without doubt the most
difficult of all human sciences _(Einsichten)_, but a metaphysic has
never yet been written"; for one cannot be so kind as to
"apply the term
philosophy to all that is contained in the books which bear this title." In
the closing paragraphs, on the ultimate bases of ethics, the stern features
of the categorical imperative are already seen, veiled by the English
theory of moral sense, while the attractive _Observations on the Feeling
of the Beautiful and the Sublime_, which appeared in the same year, still
naïvely follow the empirical road.
The empirical phase reaches its skeptical termination in the satire _Dreams
of a Ghost-seer explained by the Dreams of Metaphysics_, 1766, which pours
out its ingenious sarcasm impartially on spiritualism and on the assumed
knowledge of the suprasensible. Here Kant is already clearly conscious of
his new problem, a theory of the limits of human reason, conscious also
that the attack on this problem is to be begun by a discussion of the
question of space. This second question had been for many years a frequent
subject of his reflections;[1] and it was this part of the general critical
problem that first received definitive solution. In the Latin dissertation
_On the Form and Principles of the Sensible and Intelligible World_, 1770,
which concludes the pre-critical period, and which was written on the
occasion of his assumption of his chair as ordinary professor, the
critique of sensibility, the new theory of space and time, is set forth in
approximately the same form as in the _Critique of Pure Reason_, while the
critique of the understanding and of reason, the theory of the categories
and the Ideas and of the sphere of their validity, required for its
completion the intellectual labor of several more years.
For this essay,
_De Mundi Sensibilis atque Intelligibilis Forma et Principiis_, leaves
unchallenged the possibility of a knowledge of things in themselves and of
God, thus showing that its author has abandoned the skepticism maintained
in the _Dreams of a Ghost-seer_, and has turned anew to dogmatic
rationalism, whose final overthrow required another swing in the direction
of skeptical empiricism. In regard to the progress of this latter phase
of opinion, the letters to M. Herz are almost the only, though not very
valuable, source of information.
[Footnote 1: _New Theory of Motion and Rest_, 1758; _On the First Ground of
the Distinction of Positions in Space_, 1768; besides several of the works
mentioned above.]
The _Critique of Pure Reason_ appeared in 1781, much later than Kant had
hoped when he began a work on "The Limits of Sensibility and Reason," and a
second, altered edition in 1787.[1] After the _Prolegomena to every Future
Metaphysic which may present itself as Science_, 1783, had given a popular
form to the critical doctrine of knowledge, it was followed by the critical
philosophy of ethics in the _Foundation of the Metaphysics of Ethics_,
1785, and the _Critique of Practical Reason_, 1788; by the critical
aesthetics and teleology in the _Critique of Judgment_, 1790; and by the
critical philosophy of religion in _Religion within the Limits of Reason
Only_, 1793[2] (consisting of four essays, of which the first, "Of Radical
Evil," had already appeared in the _Berliner Monatsschrift_ in 1792). The
_Metaphysical Elements of Natural Science_, 1786, and the _Metaphysics
of Ethics_, 1797 (in two parts, "Metaphysical Elements of the Theory of
Right," and "Metaphysical Elements of the Theory of Virtue "), are devoted
to the development of the system. The year 1798 brought two more larger
works, the _Conflict of the Faculties_ and the _Anthropology_. Of the
reviews, that on Herder's _Ideen_ maybe mentioned, and among the minor
essays, the following: _Idea for a Universal History in a Cosmopolitan
Sense, Answer to the Question: What is Illumination f_
both in 1784;
_What does it mean to Orient oneself in Thought_? 1786; _On the Use of
Teleological Principles in Philosophy_, 1788; _On a Discovery according to
which all Recent Criticism of Pure Reason is to be superseded by a Previous
One_, 1790; _On the Progress of Metaphysics since the Time of Wolff; On
Philosophy in General, The End of all Things_, 1794; _On Everlasting
Peace_, 1795. Kant's _Logic_ was published by Jäsche in 1800; his _Physical
Geography_ and his _Observations on Pedagogics_ by F.T.
Rink in 1803; his
lectures on the _Philosophical Theory of Religion_
(1817; 2d. ed., 1830)
and on _Metaphysics_ (1821; cf. Benno Erdmann in the _Philosophische
Monatshefte_, vol. xix. 1883, p. 129 _seq_., and vol.
xx. 1884, p. 65
_seq_.) by Pölitz. If we may judge by the specimens given by Reicke in the
_Altpreussische Monatsschrift_, 1882-84, and by Krause himself,[3]
the promised publication of a manuscript of Kant's last years, now in
possession of the Hamburg pastor, Albrecht Krause, and which discusses the
transition from the metaphysical elements of natural science to physics,
will hardly meet the expectations which some have cherished concerning it.
Benno Erdmann has issued _Nachträge zu Kants Kritik der reinen Vernunft aus
Kants Nachlass_, 1881, and _Reflexionen Kants zur kritischen Philosophie
aus handschriftlichen Aufzeichnungen_--the first volume first _Heft
(Reflexionen zur Anthropologie_) appearing in 1882, the second volume
_(Reflexionen zur Kritik der reinen Vernunft, aus Kants Handexemplar
von Baumgartens Metaphysica)_ in 1884. Max Müller has made an English
translation of the _Critique of Pure Reason_, 2 vols., 1881.[4]