presented and the aid furnished by experience。
So much for the pleteness and thoroughness necessary in the
execution of the present task。 The aims set before us are not
arbitrarily proposed； but are imposed upon us by the nature of
cognition itself。
The above remarks relate to the matter of our critical inquiry。 As
regards the form； there are two indispensable conditions； which any
one who undertakes so difficult a task as that of a critique of pure
reason； is bound to fulfil。 These conditions are certitude and
clearness。
As regards certitude； I have fully convinced myself that； in this
sphere of thought； opinion is perfectly inadmissible； and that
everything which bears the least semblance of an hypothesis must be
excluded； as of no value in such discussions。 For it is a necessary
condition of every cognition that is to be established upon a priori
grounds that it shall be held to be absolutely necessary； much more is
this the case with an attempt to determine all pure a priori
cognition； and to furnish the standard… and consequently an example…
of all apodeictic （philosophical） certitude。 Whether I have
succeeded in what I professed to do； it is for the reader to
determine； it is the author's business merely to adduce grounds and
reasons； without determining what influence these ought to have on the
mind of his judges。 But； lest anything he may have said may bee the
innocent cause of doubt in their minds； or tend to weaken the effect
which his arguments might otherwise produce… he may be allowed to
point out those passages which may occasion mistrust or difficulty；
although these do not concern the main purpose of the present work。 He
does this solely with the view of removing from the mind of the reader
any doubts which might affect his judgement of the work as a whole；
and in regard to its ultimate aim。
I know no investigations more necessary for a full insight into
the nature of the faculty which we call understanding； and at the same
time for the determination of the rules and limits of its use； than
those undertaken in the second chapter of the 〃Transcendental
Analytic；〃 under the title of 〃Deduction of the Pure Conceptions of
the Understanding〃； and they have also cost me by far the greatest
labour… labour which； I hope； will not remain unpensated。 The
view there taken； which goes somewhat deeply into the subject； has two
sides； The one relates to the objects of the pure understanding； and
is intended to demonstrate and to render prehensible the
objective validity of its a priori conceptions； and it forms for
this reason an essential part of the Critique。 The other considers the
pure understanding itself； its possibility and its powers of
cognition… that is； from a subjective point of view； and； although
this exposition is of great importance； it does not belong essentially
to the main purpose of the work； because the grand question is what
and how much can reason and understanding； apart from experience；
cognize； and not； how is the faculty of thought itself possible？ As
the latter is an； inquiry into the cause of a given effect； and has
thus in it some semblance of an hypothesis （although； as I shall
show on another occasion； this is really not the fact）； it would
seem that； in the present instance； I had allowed myself to enounce
a mere opinion； and that the reader must therefore be at liberty to
hold a different opinion。 But I beg to remind him that； if my
subjective deduction does not produce in his mind the conviction of
its certitude at which I aimed； the objective deduction； with which
alone the present work is properly concerned； is in every respect
satisfactory。
As regards clearness； the reader has a right to demand； in the first
place； discursive or logical clearness； that is； on the basis of
conceptions； and； secondly； intuitive or aesthetic clearness； by means
of intuitions； that is； by examples or other modes of illustration
in concreto。 I have done what I could for the first kind of
intelligibility。 This was essential to my purpose； and it thus
became the accidental cause of my inability to do plete justice
to the second requirement。 I have been almost always at a loss； during
the progress of this work； how to settle this question。 Examples and
illustrations always appeared to me necessary； and； in the first
sketch of the Critique； naturally fell into their proper places。 But I
very soon became aware of the magnitude of my task； and the numerous
problems with which I should be engaged； and； as I perceived that this
critical investigation would； even if delivered in the driest
scholastic manner； be far from being brief； I found it unadvisable
to enlarge it still more with examples and explanations； which are
necessary only from a popular point of view。 I was induced to take
this course from the consideration also that the present work is not
intended for popular use； that those devoted to science do not require
such helps； although they are always acceptable； and that they would
have materially interfered with my present purpose。 Abbe Terrasson
remarks with great justice that； if we estimate the size of a work；
not from the number of its pages； but from the time which we require
to make ourselves master of it； it may be said of many a book that
it would be much shorter； if it were not so short。 On the other
hand； as regards the prehensibility of a system of speculative
cognition； connected under a single principle； we may say with equal
justice： many a book would have been much clearer； if it had not
been intended to be so very clear。 For explanations and examples；
and other helps to intelligibility； aid us in the prehension of
parts； but they distract the attention； dissipate the mental power
of the reader； and stand in the way of his forming a clear
conception of the whole； as he cannot attain soon enough to a survey
of the system； and the colouring and embellishments bestowed upon it
prevent his observing its articulation or organization… which is the
most important consideration with him； when he es to judge of its
unity and stability。
The reader must naturally have a strong inducement to co…operate
with the present author； if he has formed the intention of erecting
a plete and solid edifice of metaphysical science； according to the
plan now laid before him。 Metaphysics； as here represented； is the
only science which admits of pletion… and with little labour； if it
is united； in a short time； so that nothing will be left to future
generations except the task of illustrating and applying it
didactically。 For this science is nothing more than the inventory of
all that is given us by pure reason； systematically arranged。
Nothing can escape our notice； for what reason produces from itself
cannot lie concealed； but must be brought to the light by reason
itself； so soon as we have discovered the mon principle of the
ideas we seek。 The perfect unity of this kind of cognitions； which are
based upon pure conceptions； and uninfluenced by any empirical
element； or any peculiar intuition leading to determinate
experience； renders this pleteness not only practicable； but also
necessary。
Tecum habita； et noris quam sit tibi curta supellex。*
*Persius。 ＇Satirae iv。 52。 〃Dwell with yourself； and you will know
how short your household stuff is。〃
Such a system of pure speculative reason I hope to be able to
publish under the title of Metaphysic of Nature。 The content of this
work （which will not be half so long） will be very much richer than
that of the present Critique； which has to discover the sources of
this cognition and expose the conditions of its possibility； and at
the same time to clear and level a fit foundation for the scientific
edifice。 In the present work； I look for the patient hearing and the
impartiality of a judge； in the other； for the good…will and
assistance of a co…labourer。 For； however plete the list of
principles for this system may be in the Critique； the correctness
of the system requires that no deduced conceptions should be absent。
These cannot be presented a priori； but must be gradually
discovered； and； while the synthesis of conceptions has been fully
exhausted in the Critique； it is necessary that； in the proposed work；
the same should be the case with their analysis。 But this will be
rather an amusement than a labour。
PREFACE TO THE SECOND EDITION； 1787
Whether the treatment of that portion of our knowledge which lies
within the province of pure reason advances with that undeviating
certainty which characterizes the progress of science； we shall be
at no loss to determine。 If we find those who are engaged in
metaphysical pursuits； unable to e to an understanding as to the
method which they ought to follow； if we find them； after the most
elaborate preparations； invariably brought to a stand before the
goal is reached； and pelled to retrace their steps and strike
into fresh paths； we may then feel quite sure that they are far from
having attained to the certainty of scientific progress and may rather
be said to be merely groping about in the dark。 In these circumstances
we shall render an important service to reaso