SOLUTION OF THE GENERAL QUESTION OF THE PROLEGOMENA, "HOW IS
METAPHYSICS POSSIBLE AS A SCIENCE?"
Metaphysics, as a natural disposition of reason, is actual, but if
considered by itself alone (as the analytical solution of the third
principal question showed), dialectical and illusory. If we think of
taking principles from it, and in using them follow the natural, but
on that account not less false, illusion, we can never produce
science, but only a vain dialectical art, in which one school may
outdo another, but none can ever acquire a just and lasting
approbation.
In order that as a science metaphysics may be entitled to claim not
mere fallacious plausibility, but in sight and conviction, a Critique
of Reason must itself exhibit the whole stock of a priori concepts,
their division according to their various sources (Sensibility,
Understanding, and Reason), together with a complete table of them,
the analysis of all these concepts, with all their consequences,
especially by means of the deduction of these concepts, the
possibility of synthetical cognition a priori, the principles of its
application and finally its bounds, all in a complete system.
Critique, therefore, and critique alone, contains in itself the whole
well-proved and well-tested plan, and even all the means required to
accomplish metaphysics, as a science; by other ways and means it is
impossible. The question here therefore is not so much how this
performance is possible, as how to set it going, and induce men of
clear heads to quit their hitherto perverted and fruitless cultivation
for one that will not deceive, and how such a union for the common end
may best be directed.
This much is certain, that whoever has once tasted Critique will be
ever after disgusted with all dogmatical twaddle which he formerly put
up with, because his reason must have something, and could find
nothing better for its support.
Critique stands in the same relation to the common metaphysics of the
schools, as chemistry does to alchemy, or as astronomy to the
astrology of the fortune-teller. I pledge myself that nobody who has
read through and through, and grasped the principles of, the Critique
even in these Prolegomena only, will ever return to that old and
sophistical pseudo-science; but will rather with a certain delight
look forward to metaphysics which is now indeed in his power,
requiring no more preparatory discoveries, and now at last affording
permanent satisfaction to reason. For here is an advantage upon which,
of all possible sciences, metaphysics alone can with certainty reckon:
that it can be brought to such completion and fixity as to be
incapable of further change, or of any augmentation by new
discoveries; because here reason has the sources of its knowledge in
itself, not in objects and their observation (Anschauung), by which
latter its stock of knowledge cannot be further increased. When
therefore it has exhibited the fundamental laws of its faculty
completely and so definitely as to avoid all misunderstanding, there
remains nothing for pure reason to cognise a priori, nay, there is
even no ground to raise further questions. The sure prospect of
knowledge so definite and so compact has a peculiar charm, even though
we should set aside all its advantages, of which I shall hereafter
speak.
All false art, all vain wisdom, lasts its time, but finally destroys
itself, and its highest culture is also the epoch of its decay. That
this time is come for metaphysics appears from the state into which it
has fallen among all learned nations, despite of all the zeal with
which other sciences of every kind are prosecuted. The old arrangement
of our university studies still preserves its shadow; now and then an
Academy of Science tempts men by offering prizes to write essays on
it, but it is no longer numbered among thorough sciences; and let any
one judge for himself how a man of genius, if he were called a great
metaphysician, would receive the compliment, which may be well-meant,
but is scarce envied by anybody.
Yet, though the period of the downfall of all dogmatical metaphysics
has undoubtedly arrived, we are yet far from being able to say that
the period of its regeneration is come by means of a thorough and
complete Critique of Reason. All transitions from a tendency to its
contrary pass through the stage of indifference, and this moment is
the most dangerous for an author, but, in my opinion, the most
favorable for the science. For, when party spirit has died out by a
total dissolution of former connexions, minds are in the best state to
listen to several proposals for an organisation according to a new
plan.
When I say, that I hope these Prolegomena will excite investigation in
the field of critique and afford a new and promising object to sustain
the general spirit of philosophy, which seems on its speculative side
to want sustenance, I can imagine beforehand, that every one, whom the
thorny paths of my Critique have tired and put out of humor, will ask
me, upon what I found this hope. My answer is, upon the irresistible
law of necessity.
That the human mind will ever give up metaphysical researches is as
little to be expected as that we should prefer to give up breathing
altogether, to avoid inhaling impure air. There will therefore always
be metaphysics in the world; nay, every one, especially every man of
reflexion, will have it, and for want of a recognised standard, will
shape it for himself after his own pattern. What has hitherto been
called metaphysics, cannot satisfy any critical mind, but to forego it
entirely is impossible; therefore a Critique of Pure Reason itself
must now be attempted or, if one exists, investigated, and brought to
the full test, because there is no other means of supplying this
pressing want, which is something more than mere thirst for knowledge.
Ever since I have come to know critique, whenever I finish reading a
book of metaphysical contents, which, by the preciseness of its
notions, by variety, order, and an easy style, was not only
entertaining but also helpful, I cannot help asking, "Has this author
indeed advanced metaphysics a single step?" The learned men, whose
works have been useful to me in other respects and always contributed
to the culture of my mental powers, will, I hope, forgive me for
saying, that I have never been able to find either their essays or my
own less important ones (though self-love may recommend them to me) to
have advanced the science of metaphysics in the least, and why?
Here is the very obvious reason: metaphysics did not then exist as a
science, nor can it be gathered piecemeal, but its germ must be fully
preformed in the Critique. But in order to prevent all misconception,
we must remember what has been already said, that by the analytical
treatment of our concepts the understanding gains indeed a great deal,
but the science (of metaphysics) is thereby not in the least advanced,
because these dissections of concepts are nothing but the materials
from which the intention is to carpenter our science. Let the concepts
of substance and of accident be ever so well dissected and determined,
all this is very well as a preparation for some future use. But if we
cannot prove, that in all which exists the substance endures, and only
the accidents vary, our science is not the least advanced by all our
analyses.
Metaphysics has hitherto never been able to prove a priori either this
proposition, or that of sufficient reason, still, less any more
complex theorem, such as belongs to psychology or cosmology, or indeed
any synthetical proposition. By all its analysing therefore nothing is
affected, nothing obtained or forwarded, and the science, after all
this bustle and noise, still remains as it was in the days of
Aristotle, though far better preparations were made for it than of
old, if the clue to synthetical cognitions had only been discovered.
If any one thinks himself offended, he is at liberty to refute my
charge by producing a single synthetical proposition belonging to
metaphysics, which he would prove dogmatically a priori, for until he
has actually performed this feat, I shall not grant that he has truly
advanced the science; even should this proposition be sufficiently
confirmed by common experience. No demand can be more moderate or more
equitable, and in the (inevitably certain) event of its
non-performance, no assertion more just, than that hitherto
metaphysics has never existed as a science.
But there are two things which, in case the challenge be accepted, I
must deprecate: first, trifling about probability and conjecture,
which are suited as little to metaphysics, as to geometry; and
secondly, a decision by means of the magic wand of common sense, which
does not convince every one, but which accommodates itself to personal
peculiarities.
For as to the former, nothing can be more absurd, than in metaphysics,
a philosophy from pure reason to think of grounding our judgments upon
probability and conjecture. Everything that is to be cognised a
priori, is thereby announced as apodeictically certain, and must
therefore be proved in this way. We might as well think of grounding
geometry or arithmetic upon conjectures. As to the doctrine of chances
in the latter, it does not contain probable, but perfectly certain,
judgments concerning the degree of the probability of certain cases,
under given uniform conditions, which, in the sum of all possible
cases, infallibly happen according to the rule, though it is not
sufficiently determined in respect to every single chance. Conjectures
(by means of induction and of analogy) can be suffered in an empirical
science of nature only, yet even there the possibility at least of
what we assume must be quite certain.
The appeal to common sense is even more absurd, when concept and
principles are announced as valid, not in so far as they hold with
regard to experience, but even beyond the conditions of experience.
For what is common sense? It is normal good sense, so far it judges
right. But what is normal good sense? It is the faculty of the
knowledge and use of rules in concreto, as distinguished from the
speculative understanding, which is a faculty of knowing rules in
abstracto. Common sense can hardly understand the rule, "that every
event is determined by means of its cause," and can never comprehend
it thus generally. It therefore demands an example from experience,
and when it hears that this rule means nothing but what it always
thought when a pane was broken or a kitchen-utensil missing, it then
understands the principle and grants it. Common sense therefore is
only of use so far as it can see its rules (though they actually are a
priori) confirmed by experience; consequently to comprehend them a
priori, or independently of experience, belongs to the speculative
understanding, and lies quite beyond the horizon of common sense. But
the province of metaphysics is entirely confined to the latter kind of
knowledge, and it is certainly a bad index of common sense to appeal
to it as a witness, for it cannot here form any opinion whatever, and
men look down upon it with contempt until they are in difficulties,
and can find in their speculation neither in nor out.
It is a common subterfuge of those false friends of common sense (who
occasionally prize it highly, but usually despise it) to say, that
there must surely be at all events some propositions which are
immediately certain, and of which there is no occasion to give any
proof, or even any account at all, because we otherwise could never
stop inquiring into the grounds of our judgments. But if we except the
principle of contradiction, which is not sufficient to show the truth
of synthetical judgments, they can never adduce, in proof of this
privilege, anything else indubitable, which they can immediately
ascribe to common sense, except mathematical propositions, such as
twice two make four, between two points there is but one straight
line, etc. But these judgments are radically different from those of
metaphysics. For in mathematics I myself can by thinking construct
whatever I represent to myself as possible by a concept: I add to the
first two the other two, one by one, and myself make the number four,
or I draw in thought from one point to another all manner of lines,
equal as well as unequal; yet I can draw one only, which is like
itself in all its parts. But I cannot, by all my power of thinking,
extract from the concept of a thing the concept of something else,
whose existence is necessarily connected with the former, but I must
call in experience. And though my understanding furnishes me a priori
(yet only in reference to possible experience) with the concept of
such a connexion (i.e., causation), I cannot exhibit it, like the
concepts of mathematics, by (Anschauung) visualising them, a priori,
and so show its possibility a priori. This concept, together with the
principles of its application, always requires, if it shall hold a
priori—as is requisite in metaphysics—a justification and
deduction of its possibility, because we cannot otherwise know how far
it holds good, and whether it can be used in experience only or beyond
it also.
Therefore in metaphysics, as a speculative science of pure reason, we
can never appeal to common sense, but may do so only when we are
forced to surrender it, and to renounce all purely speculative
cognition, which must always be knowledge, and consequently when we
forego metaphysics itself and its instruction, for the sake of
adopting a rational faith which alone may be possible for us, and
sufficient to our wants, perhaps even more salutary than knowledge
itself. For in this case the attitude of the question is quite
altered. Metaphysics must be science, not only as a whole, but in all
its parts, otherwise it is nothing; because, as a speculation of pure
reason, it finds a hold only on general opinions. Beyond its field,
however, probability and common sense may be used with advantage and
justly, but on quite special principles, of which the importance
always depends on the reference to practical life.
This is what I hold myself justified in requiring for the possibility
of metaphysics as a science.