Immanuel Kant's

trans. by Norman Kemp Smith

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THE CANON OF PURE REASON
Section 1
THE ULTIMATE END OF THE PURE EMPLOYMENT OF
OUR REASON
Reason is impelled by a tendency of its nature to go out
beyond the field of its empirical employment, and to venture
in a pure employment, by means of ideas alone, to the utmost
limits of all knowledge, and not to be satisfied save through
the completion of its course in [the apprehension of] a self-
subsistent systematic whole. Is this endeavour the outcome
merely of the speculative interests of reason? Must we not
rather regard it as having its source exclusively in the 
practical interests of reason?
I shall, for the moment, leave aside all question as to the
success which attends pure reason in its speculative exercise,
and enquire only as to the problems the solution of which
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constitutes its ultimate aim, whether reached or not, and in
respect of which all other aims are to be regarded only as
means. These highest aims must, from the nature of reason,
have a certain unity, in order that they may, as thus unified,
further that interest of humanity which is subordinate to no
higher interest.
The ultimate aim to which the speculation of reason in its
transcendental employment is directed concerns three objects:
the freedom of the will, the immortality of the soul, and the
existence of God. In respect of all three the merely speculative
interest of reason is very small; and for its sake alone we should
hardly have undertaken the labour of transcendental investigation
-- a labour so fatiguing in its endless wrestling with 
insuperable difficulties -- since whatever discoveries might be
made in regard to these matters, we should not be able to make
use of them in any helpful manner in concreto, that is, in the
study or nature. If the will be free, this can have a bearing only
on the intelligible cause of our volition. For as regards the 
phenomena of its outward expressions, that is, of our actions, we
must account for them -- in accordance with a maxim which
is inviolable, and which is so fundamental that without it we
should not be able to employ reason in any empirical manner
whatsoever -- in the same manner as all other appearances of
nature, namely, in conformity with unchangeable laws. If,
again, we should be able to obtain insight into the spiritual
nature of the soul, and therewith of its immortality, we could
make no use of such insight in explaining either the appearances
of this present life or the specific nature of a future
state. For our concept of an incorporeal nature is merely 
negative, and does not in the least extend our knowledge, yielding
no sufficient material for inferences, save only such as are
merely fictitious and cannot be sanctioned by philosophy. If,
thirdly, the existence of a supreme intelligence be proved, by
its means we might indeed render what is purposive in the
constitution and ordering of the world comprehensible in a
general sort or way, but we should not be in the least warranted
in deriving from it any particular arrangement or disposition,
or in boldly inferring any such, where it is not perceived.
For it is a necessary rule of the speculative employment
of reason, not to pass over natural causes, and, abandoning
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that in regard to which we can be instructed by experience, to
deduce something which we know from something which entirely
transcends all our [possible] knowledge. In short, these
three propositions are for speculative reason always 
transcendent, and allow of no immanent employment -- that is,
employment in reference to objects of experience, and so in
some manner really of service to us -- but are in themselves,
notwithstanding the very heavy labours which they impose
upon our reason, entirely useless.
If, then, these three cardinal propositions are not in any
way necessary for knowledge, and are yet strongly recommended
by our reason, their importance, properly regarded,
must concern only the practical.
By 'the practical' I mean everything that is possible
through freedom. When, however, the conditions of the exercise
of our free will are empirical, reason can have no other
than a regulative employment in regard to it, and can serve
only to effect unity in its empirical laws. Thus, for instance,
in the precepts of prudence, the whole business of reason
consists in uniting all the ends which are prescribed to us by
our desires in the one single end, happiness, and in coordinating
the means for attaining it. In this field, therefore,
reason can supply none but pragmatic laws of free action, for
the attainment of those ends which are commended to us by
the senses; it cannot yield us laws that are pure and determined
completely a priori. Laws of this latter type, pure practical
laws, whose end is given through reason completely a -
priori, and which are prescribed to us not in an empirically
conditioned but in an absolute manner, would be products of
pure reason. Such are the moral laws; and these alone, therefore,
belong to the practical employment of reason, and allow
of a canon.
The whole equipment of reason, in the discipline which
may be entitled pure philosophy, is in fact determined with
a view to the three above-mentioned problems. These, however,
themselves in turn refer us yet further, namely, to the
problem what we ought to do, if the will is free, if there is
a God and a future world. As this concerns our attitude to
the supreme end, it is evident that the ultimate intention
of nature in her wise provision for us has indeed, in the
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constitution of our reason, been directed to moral interests
alone.
But we must be careful, in turning our attention to an
object which is foreign to transcendental philosophy, that we
do not indulge in digressions to the detriment of the unity of
the system, nor on the other hand, by saying too little on this
new topic, fail in producing conviction through lack of 
clearness. I hope to avoid both dangers, by keeping as close as
possible to the transcendental, and by leaving entirely aside
any psychological, that is, empirical, factors that may 
perchance accompany it.
I must first remark that for the present I shall employ the
concept of freedom in this practical sense only, leaving aside
that other transcendental meaning which cannot be empirically
made use of in explanation of appearances, but is itself
a problem for reason, as has been already shown. A will is
purely animal (arbitrium brutum), which cannot be determined
save through sensuous impulses, that is, pathologically.
A will which can be determined independently of sensuous
impulses, and therefore through motives which are represented
only by reason, is entitled free will (arbitrium liberum),
and everything which is bound up with this will, whether as
ground or as consequence, is entitled practical. [The fact of]
practical freedom can be proved through experience. For the
human will is not determined by that alone which stimulates,
that is, immediately affects the senses; we have the power to
overcome the impressions on our faculty of sensuous desire, by
calling up representations of what, in a more indirect manner,
is useful or injurious. But these considerations, as to what is
desirable in respect of our whole state, that is, as to what is
good and useful, are based on reason.
++ All practical concepts relate to objects of satisfaction or 
dissatisfaction, that is, of pleasure and pain, and therefore, at least
indirectly, to the objects of our feelings. But as feeling is not a faculty
whereby we represent things, but lies outside our whole faculty of
knowledge, the elements of our judgments so far as they relate to
pleasure or pain, that is, the elements of practical judgments, do not
belong to transcendental philosophy, which is exclusively concerned
with pure a priori modes of knowledge.
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Reason therefore provides
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laws which are imperatives, that is, objective laws of freedom,
which tell us what ought to happen -- although perhaps it never
does happen -- therein differing from laws of nature, which
relate only to that which happens. These laws are therefore to
be entitled practical laws.
 Whether reason is not, in the actions through which it
prescribes laws, itself again determined by other influences,
and whether that which, in relation to sensuous impulses, is
entitled freedom, may not, in relation to higher and more
remote operating causes, be nature again, is a question which
in the practical field does not concern us, since we are 
demanding of reason nothing but the rule of conduct; it is a
merely speculative question, which we can leave aside so long
as we are considering what ought or ought not to be done.
While we thus through experience know practical freedom to
be one of the causes in nature, namely, to be a causality of
reason in the determination of the will, transcendental freedom
demands the independence of this reason -- in respect of
its causality, in beginning a series of appearances -- from all
determining causes of the sensible world. Transcendental
freedom is thus, as it would seem, contrary to the law of
nature, and therefore to all possible experience; and so 
remains a problem. But this problem does not come within the
province of reason in its practical employment; and we have
therefore in a canon of pure reason to deal with only two
questions, which relate to the practical interest of pure reason,
and in regard to which a canon of its employment must be
possible -- Is there a God? and, Is there a future life? The
question of transcendental freedom is a matter for speculative
knowledge only, and when we are dealing with the practical
we can leave it aside as being an issue with which we have
no concern. Moreover, a quite sufficient discussion of it is to
be found in the antinomy of pure reason.
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THE CANON OF PURE REASON
Section 2
THE IDEAL OF THE HIGHEST GOOD, AS A DETERMINING
GROUND OF THE ULTIMATE END OF PURE REASON
Reason, in its speculative employment, conducted us
through the field of experience, and since it could not find
complete satisfaction there, from thence to speculative
ideas, which, however, in the end brought us back to experience.
In so doing the ideas fulfilled their purpose, but in a
manner which, though useful, is not in accordance with our
expectation. One other line of enquiry still remains open to
us: namely, whether pure reason may not also be met with
in the practical sphere, and whether it may not there conduct
us to ideas which reach to those highest ends of pure reason
that we have just stated, and whether, therefore, reason may
not be able to supply to us from the standpoint of its practical
interest what it altogether refuses to supply in respect of its
speculative interest.
All the interests of my reason, speculative as well as
practical, combine in the three following questions:
1. What can I know?
2. What ought I to do?
3. What may I hope?
The first question is merely speculative. We have, as I
flatter myself, exhausted all the possible answers to it, and at
last have found the answer with which reason must perforce
content itself, and with which, so long as it takes no account of
the practical, it has also good cause to be satisfied. But from
the two great ends to which the whole endeavour of pure
reason was really directed, we have remained just as far 
removed as if through love of ease we had declined this labour
of enquiry at the very outset. So far, then, as knowledge is
concerned, this much, at least, is certain and definitively
established, that in respect of these two latter problems, 
knowledge is unattainable by us.
The second question is purely practical. As such it can
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indeed come within the scope of pure reason, but even so is not
transcendental but moral, and cannot, therefore, in and by
itself, form a proper subject for treatment in this Critique.
The third question -- If I do what I ought to do, what may
I then hope? -- is at once practical and theoretical, in such
fashion that the practical serves only as a clue that leads us to
the answer to the theoretical question, and when this is followed
out, to the speculative question. For all hoping is directed to
happiness, and stands in the same relation to the practical and
the law of morality as knowing and the law of nature to the
theoretical knowledge of things. The former arrives finally
at the conclusion that something is (which determines the
ultimate possible end) because something ought to happen;
the latter, that something is (which operates as the supreme
cause) because something happens.
Happiness is the satisfaction of all our desires, extensively,
in respect of their manifoldness, intensively, in respect of
their degree, and protensively, in respect of their duration.
The practical law, derived from the motive of happiness, I
term pragmatic (rule of prudence), and that law, if there is
such a law, which has no other motive than worthiness of
being happy, I term moral (law of morality). The former
advises us what we have to do if we wish to achieve happiness;
the latter dictates to us how we must behave in order to 
deserve happiness. The former is based on empirical principles;
for only by means of experience can I know what desires there
are which call for satisfaction; or what those natural causes
are which are capable of satisfying them. The latter takes no
account of desires, and the natural means of satisfying them,
and considers only the freedom of a rational being in general,
and the necessary conditions under which alone this freedom
can harmonise with a distribution of happiness that is made
in accordance with principles. This latter law can therefore be
based on mere ideas of pure reason, and known a priori.
 I assume that there really are pure moral laws which 
determine completely a priori (without regard to empirical
motives, that is, to happiness) what is and is not to be done,
that is, which determine the employment of the freedom of a
rational being in general; and that these laws command in an
absolute manner (not merely hypothetically, on the supposition
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of other empirical ends), and are therefore in every respect
necessary. I am justified in making this assumption, in that I
can appeal not only to the proofs employed by the most 
enlightened moralists, but to the moral judgment of every man,
in so far as he makes the effort to think such a law clearly.
Pure reason, then, contains, not indeed in its speculative
employment, but in that practical employment which is also
moral, principles of the possibility of experience, namely, of
such actions as, in accordance with moral precepts, might be
met with in the history of mankind. For since reason commands
that such actions should take place, it must be possible
for them to take place. Consequently, a special kind of 
systematic unity, namely the moral, must likewise be possible.
We have indeed found that the systematic unity of nature
cannot be proved in accordance with speculative principles
of reason. For although reason does indeed have causality in
respect of freedom in general, it does not have causality in
respect of nature as a whole; and although moral principles
of reason can indeed give rise to free actions, they cannot give
rise to laws of nature. Accordingly it is in their practical,
meaning thereby their moral, employment, that the principles
of pure reason have objective reality.
I entitle the world a moral world, in so far as it may be in
accordance with all moral laws; and this is what by means of
the freedom of the rational being it can be, and what according
to the necessary laws of morality it ought to be. Owing to our
here leaving out of account all conditions (ends) and even all
the special difficulties to which morality is exposed (weakness
or depravity of human nature), this world is so far thought as
an intelligible world only. To this extent, therefore, it is a
mere idea, though at the same time a practical idea, which
really can have, as it also ought to have, an influence upon the
sensible world, to bring that world, so far as may be possible,
into conformity with the idea. The idea of a moral world has,
therefore, objective reality, not as referring to an object of an
intelligible intuition (we are quite unable to think any such
object), but as referring to the sensible world, viewed, however,
as being an object of pure reason in its practical employment,
that is, as a corpus mysticum of the rational beings in it,
so far as the free will of each being is, under moral laws, in
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complete systematic unity with itself and with the freedom
of every other.
This is the answer to the first of the two questions of pure
reason that concern its practical interest: -- Do that through
which thou becomest worthy to be happy. The second question
is: -- If I so behave as not to be unworthy of happiness, may I
hope thereby to obtain happiness? In answering this question
we have to consider whether the principles of pure reason,
which prescribe the law a priori, likewise connect this hope
necessarily with it.
I maintain that just as the moral principles are necessary
according to reason in its practical employment, it is in the
view of reason, in the field of its theoretical employment, no
less necessary to assume that everyone has ground to hope
for happiness in the measure in which he has rendered himself
by his conduct worthy of it, and that the system of morality
is therefore inseparably -- though only in the idea of pure
reason -- bound up with that of happiness.
Now in an intelligible world, that is, in the moral world, in
the concept of which we leave out of account all the hindrances
to morality (the desires), such a system, in which happiness is
bound up with and proportioned to morality, can be conceived
as necessary, inasmuch as freedom, partly inspired and
partly restricted by moral laws, would itself be the cause of
general happiness, since rational beings, under the guidance
of such principles, would themselves be the authors both of
their own enduring well-being and of that of others. But such
a system of self-rewarding morality is only an idea, the 
carrying out of which rests on the condition that everyone does
what he ought, that is, that all the actions of rational beings
take place just as if they had proceeded from a supreme will
that comprehends in itself, or under itself, all private wills.
But since the moral law remains binding for every one in the
use of his freedom, even although others do not act in 
conformity with the law, neither the nature of the things of the
world nor the causality of the actions themselves and their
relation to morality determine how the consequences of these
actions will be related to happiness. The alleged necessary
connection of the hope of happiness with the necessary 
endeavour to render the self worthy of happiness cannot therefore
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be known through reason. It can be counted upon only if
a Supreme Reason, that governs according to moral rules, be
likewise posited as underlying nature as its cause.
The idea of such an intelligence in which the most perfect
moral will, united with supreme blessedness, is the cause of all
happiness in the world -- so far as happiness stands in exact 
relation with morality, that is, with worthiness to be happy -- I
entitle the ideal of the supreme good. It is, therefore, only in the
ideal of the supreme original good that pure reason can find
the ground of this connection, which is necessary from the 
practical point of view, between the two elements of the supreme
derivative good -- the ground, namely, of an intelligible, that is,
moral world. Now since we are necessarily constrained by reason
to represent ourselves as belonging to such a world, while the
senses present to us nothing but a world of appearances, we
must assume that moral world to be a consequence of our 
conduct in the world of sense (in which no such connection 
between worthiness and happiness is exhibited), and therefore to
be for us a future world. Thus God and a future life are two
postulates which, according to the principles of pure reason,
are inseparable from the obligation which that same reason
imposes upon us.
Morality, by itself, constitutes a system. Happiness, however,
does not do so, save in so far as it is distributed in exact
proportion to morality. But this is possible only in the 
intelligible world, under a wise Author and Ruler. Such a Ruler,
together with life in such a world, which we must regard as a
future world, reason finds itself constrained to assume; otherwise
it would have to regard the moral laws as empty figments
of the brain, since without this postulate the necessary 
consequence which it itself connects with these laws could not
follow. Hence also everyone regards the moral laws as 
commands; and this the moral laws could not be if they did not
connect a priori suitable consequences with their rules, and
thus carry with them promises and threats. But this again they
could not do, if they did not reside in a necessary being, as the
supreme good, which alone can make such a purposive unit
possible.
Leibniz entitled the world, in so far as we take account
only of the rational beings in it, and of their connection 
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according to moral laws under the government of the supreme
good, the kingdom of grace, distinguishing it from the kingdom
of nature, in which these rational beings do indeed stand
under moral laws, but expect no other consequences from
their actions than such as follow in accordance with the course
of nature in our world of sense. To view ourselves, therefore, as
in the world of grace, where all happiness awaits us, except in so
far as we ourselves limit our share in it through being unworthy
of happiness, is, from the practical standpoint, a necessary idea
of reason.
Practical laws, in so far as they are subjective grounds of
actions, that is, subjective principles, are entitled maxims. The
estimation of morality, in regard to its purity and consequences,
is effected in accordance with ideas, the observance of its laws
in accordance with maxims.
It is necessary that the whole course of our life be subject
to moral maxims; but it is impossible that this should
happen unless reason connects with the moral law, which is a
mere idea, an operative cause which determines for such conduct
as is in accordance with the moral law an outcome, either
in this or in another life, that is in exact conformity with our
supreme ends. Thus without a God and without a world invisible
to us now but hoped for, the glorious ideas of morality
are indeed objects of approval and admiration, but not springs
of purpose and action. For they do not fulfil in its completeness
that end which is natural to every rational being and
which is determined a priori, and rendered necessary, by that
same pure reason.
Happiness, taken by itself, is, for our reason, far from
being the complete good. Reason does not approve happiness
(however inclination may desire it) except in so far as it is united
with worthiness to be happy, that is, with moral conduct.
Morality, taken by itself, and with it, the mere worthiness to
be happy, is also far from being the complete good. To make
the good complete, he who behaves in such a manner as not to
be unworthy of happiness must be able to hope that he will
participate in happiness. Even the reason that is free from all
private purposes, should it put itself in the place of a being that
had to distribute all happiness to others, cannot judge otherwise;
for in the practical idea both elements are essentially
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connected, though in such a manner that it is the moral 
disposition which conditions and makes possible the participation
in happiness, and not conversely the prospect of happiness
that makes possible the moral disposition. For in the latter
case the disposition would not be moral, and therefore would
not be worthy of complete happiness -- happiness which in
the view of reason allows of no limitation save that which
arises from our own immoral conduct.
Happiness, therefore, in exact proportion with the morality
of the rational beings who are thereby rendered worthy of it,
alone constitutes the supreme good of that world wherein, in
accordance with the commands of a pure but practical reason,
we are under obligation to place ourselves. This world is indeed
an intelligible world only, since the sensible world holds
out no promise that any such systematic unity of ends can
arise from the nature of things. Nor is the reality of this unity
based on anything else than the postulate of a supreme original
good. In a supreme good, thus conceived, self-subsistent
reason, equipped with all the sufficiency of a supreme cause,
establishes, maintains, and completes the universal order of
things, according to the most perfect design -- an order which
in the world of sense is in large part concealed from us.
This moral theology has the peculiar advantage over
speculative theology that it inevitably leads to the concept of
a sole, all-perfect, and rational primordial being, to which
speculative theology does not, on objective grounds, even so
much as point the way, and as to the existence of which it is
still less capable of yielding any conviction. For neither in
transcendental nor in natural theology, however far reason
may carry us, do we find any considerable ground for assuming
only some one single being which we should be justified
in placing prior to all natural causes, and upon which
we might make them in all respects dependent. On the
other hand, if we consider from the point of view of moral
unity, as a necessary law of the world, what the cause must
be that can alone give to this law its appropriate effect, and
so for us obligatory force, we conclude that there must be
one sole supreme will, which comprehends all these laws in
itself. For how, under different wills, should we find complete
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unity of ends. This Divine Being must be omnipotent, in
order that the whole of nature and its relation to morality
in the world may be subject to his will; omniscient, that
He may know our innermost sentiments and their moral
worth; omnipresent, that He may be immediately at hand for
the satisfying of every need which the highest good demands;
eternal, that this harmony of nature and freedom may never
fail, etc.
But this systematic unity of ends in this world of intelligences
-- a world which is indeed, as mere nature, a sensible
world only, but which, as a system of freedom, can be entitled
an intelligible, that is, a moral world (regnum gratiae) -- leads 
inevitably also to the purposive unity of all things, which constitute
this great whole, in accordance with universal laws of nature (just
as the former unity is in accordance with universal and necessary
laws of morality), and thus unites the practical with the
speculative reason. The world must be represented as having
originated from an idea if it is to be in harmony with that 
employment of reason without which we should indeed hold 
ourselves to be unworthy of reason, namely, with the moral 
employment -- which is founded entirely on the idea of the supreme
good. In this way all investigation of nature tends to take the
form of a system of ends, and in its widest extension becomes a
physico-theology. But this, as it has its source in the moral order,
as a unity grounded in freedom's own essential nature, and not
accidentally instituted through external commands, connects
the purposiveness of nature with grounds which must be
inseparably connected a priori with the inner possibility of
things, and so leads to a transcendental theology -- a theology
which takes the ideal of supreme ontological perfection as a
principle of systematic unity. And since all things have their
origin in the absolute necessity of the one primordial being,
that principle connects them in accordance with universal and
necessary laws of nature.
What use can we make of our understanding, even in respect
of experience, if we do not propose ends to ourselves?
But the highest ends are those of morality, and these we can
know only as they are given us by pure reason. But though
provided with these, and employing them as a clue, we cannot
make use of the knowledge of nature in any serviceable manner
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in the building up of knowledge, unless nature has itself
shown unity of design. For without this unity we should 
ourselves have no reason, inasmuch as there would be no school
for reason, and no fertilisation through objects such as might
afford materials for the necessary concepts. But the former
purposive unity is necessary, and founded on the will's own
essential nature, and this latter unity [of design in nature]
which contains the condition of its application in concreto,
must be so likewise. And thus the transcendental enlargement
of our knowledge, as secured through reason, is not to be
regarded as the cause, but merely as the effect of the practical
purposiveness which pure reason imposes upon us.
Accordingly we find, in the history of human reason, that
until the moral concepts were sufficiently purified and determined,
and until the systematic unity of their ends was understood
in accordance with these concepts and from necessary
principles, the knowledge of nature, and even a quite 
considerable development of reason in many other sciences, could
give rise only to crude and incoherent concepts of the Deity,
or as sometimes happened resulted in an astonishing indifference
in regard to all such matters. A greater preoccupation
with moral ideas, which was rendered necessary by the
extraordinarily pure moral law of our religion, made reason
more acutely aware of its object, through the interest which it
was compelled to take in it. And this came about, independently
of any influence exercised by more extended views of
nature or by correct and reliable transcendental insight (for
that has always been lacking). It was the moral ideas that gave
rise to that concept of the Divine Being which we now hold
to be correct -- and we so regard it not because speculative
reason convinces us of its correctness, but because it completely
harmonises with the moral principles of reason. Thus it
is always only to pure reason, though only in its practical
employment, that we must finally ascribe the merit of having
connected with our highest interest a knowledge which reason
can think only, and cannot establish, and of having thereby
shown it to be, not indeed a demonstrated dogma, but a
postulate which is absolutely necessary in view of what are
reason's own most essential ends.
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But when practical reason has reached this goal, namely,
the concept of a sole primordial being as the supreme good,
it must not presume to think that it has raised itself above all
empirical conditions of its application, and has attained to an
immediate knowledge of new objects, and can therefore start
from this concept, and can deduce from it the moral laws
themselves. For it is these very laws that have led us, in virtue
of their inner practical necessity, to the postulate of a self-
sufficient cause, or of a wise Ruler of the world, in order that
through such agency effect may be given to them. We may
not, therefore, in reversal of such procedure, regard them as
accidental and as derived from the mere will of the Ruler,
especially as we have no conception of such a will, except as
formed in accordance with these laws. So far, then, as practical
reason has the right to serve as our guide, we shall not
look upon actions as obligatory because they are the commands
of God, but shall regard them as divine commands because
we have an inward obligation to them. We shall study freedom
according to the purposive unity that is determined in accordance
with the principles of reason, and shall believe ourselves
to be acting in conformity with the divine will in so far only
as we hold sacred the moral law which reason teaches us from
the nature of the actions themselves; and we shall believe that
we can serve that will only by furthering what is best in the
world, alike in ourselves and in others. Moral theology is thus
of immanent use only. It enables us to fulfil our vocation in
this present world by showing us how to adapt ourselves to the
system of all ends, and by warning us against the fanaticism,
and indeed the impiety, of abandoning the guidance of a
morally legislative reason in the right conduct of our lives, in
order to derive guidance directly from the idea of the Supreme
Being. For we should then be making a transcendent employment
of moral theology; and that, like a transcendent use
of pure speculation, must pervert and frustrate the ultimate
ends of reason.
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THE CANON OF PURE REASON
Section 3
OPINING, KNOWING, AND BELIEVING
The holding of a thing to be true is an occurrence in our
understanding which, though it may rest on objective grounds,
also requires subjective causes in the mind of the individual
who makes the judgment. If the judgment is valid for everyone,
provided only he is in possession of reason, its ground is 
objectively sufficient, and the holding of it to be true is entitled
conviction. If it has its ground only in the special character of
the subject, it is entitled persuasion.
Persuasion is a mere illusion, because the ground of the
judgment, which lies solely in the subject, is regarded as 
objective. Such a judgment has only private validity, and the 
holding of it to be true does not allow of being communicated.
But truth depends upon agreement with the object, and in 
respect of it the judgments of each and every understanding
must therefore be in agreement with each other (consentientia
uni tertio, consentiunt inter se). The touchstone whereby we
decide whether our holding a thing to be true is conviction
or mere persuasion is therefore external, namely, the possibility
of communicating it and of finding it to be valid for all
human reason. For there is then at least a presumption that
the ground of the agreement of all judgments with each other,
notwithstanding the differing characters of individuals, rests
upon the common ground, namely, upon the object, and that
it is for this reason that they are all in agreement with the
object -- the truth of the judgment being thereby proved.
So long, therefore, as the subject views the judgment merely
as an appearance of his mind, persuasion cannot be subjectively
distinguished from conviction. The experiment, however,
whereby we test upon the understanding of others
whether those grounds of the judgment which are valid for us
have the same effect on the reason of others as on our own, is
a means, although only a subjective means, not indeed of producing
conviction, but of detecting any merely private validity
P 646
in the judgment, that is, anything in it which is mere 
persuasion. 
If, in addition, we can specify the subjective causes of the
judgment, which we have taken as being its objective grounds,
and can thus explain the deceptive judgment as an event in
our mind, and can do so without having to take account of the
character of the object, we expose the illusion and are no longer
deceived by it, although always still in some degree liable to
come under its influence, in so far as the subjective cause of
the illusion is inherent in our nature.
I cannot assert anything, that is, declare it to be a judgment
necessarily valid for everyone, save as it gives rise to
conviction. Persuasion I can hold to on my own account, if it
so pleases me, but I cannot, and ought not, to profess to
impose it as binding on anyone but myself.
The holding of a thing to be true, or the subjective validity
of the judgment, in its relation to conviction (which is at the
same time objectively valid), has the following three degrees:
opining, believing, and knowing. Opining is such holding of a
judgment as is consciously insufficient, not only objectively,
but also subjectively. If our holding of the judgment be only
subjectively sufficient, and is at the same time taken as being
objectively insufficient, we have what is termed believing.
Lastly, when the holding of a thing to be true is sufficient
both subjectively and objectively, it is knowledge. The 
subjective sufficiency is termed conviction (for myself), the
objective sufficiency is termed certainty (for everyone).
There is no call for me to spend further time on the 
explanation of such easily understood terms.
I must never presume to opine, without knowing at least
something by means of which the judgment, in itself merely
problematic, secures connection with truth, a connection
which, although not complete, is yet more than arbitrary
fiction. Moreover, the law of such a connection must be certain.
For if, in respect of this law also, I have nothing but
opinion, it is all merely a play of the imagination, without the
least relation to truth. Again, opining is not in any way 
permissible in judging by means of pure reason. For since such
judging is not based on grounds of experience, but being in
P 647
every case necessary has all to be arrived at a priori, the 
principle of the connection requires universality and necessity, and
therefore complete certainty; otherwise we should have no
guidance as to truth. Hence it is absurd to have an opinion
in pure mathematics; either we must know, or we must
abstain from all acts of judgment. It is so likewise in the case
of the principles of morality, since we must not venture upon
an action on the mere opinion that it is allowed, but must
know it to be so.
In the transcendental employment of reason, on the other
hand, while opining is doubtless too weak a term to be 
applicable, the term knowing is too strong. In the merely 
speculative sphere we cannot therefore make any judgments 
whatsoever. For the subjective grounds upon which we may hold
something to be true, such as those which are able to produce
belief, are not permissible in speculative questions, inasmuch
as they do not hold independently of all empirical support,
and do not allow of being communicated in equal measure to
others.
But it is only from a practical point of view that the 
theoretically insufficient holding of a thing to be true can be
termed believing. This practical point of view is either in
reference to skill or in reference to morality, the former being
concerned with optional and contingent ends, the latter with
ends that are absolutely necessary.
Once an end is accepted, the conditions of its attainment
are hypothetically necessary. This necessity is subjectively,
but still only comparatively, sufficient, if I know of no other
conditions under which the end can be attained. On the other
hand, it is sufficient, absolutely and for everyone, if I know
with certainty that no one can have knowledge of any other
conditions which lead to the proposed end. In the former case
my assumption and the holding of certain conditions to be
true is a merely contingent belief; in the latter case it is a
necessary belief. The physician must do something for a
patient in danger, but does not know the nature of his illness.
He observes the symptoms, and if he can find no more likely
alternative, judges it to be a case of phthisis. Now even in his
own estimation his belief is contingent only; another observer
P 648
might perhaps come to a sounder conclusion. Such contingent
belief, which yet forms the ground for the actual employment
of means to certain actions, I entitle pragmatic belief.
The usual touchstone, whether that which someone asserts
is merely his persuasion -- or at least his subjective conviction,
that is, his firm belief -- is betting. It often happens that 
someone propounds his views with such positive and uncompromising
assurance that he seems to have entirely set aside all
thought of possible error. A bet disconcerts him. Sometimes
it turns out that he has a conviction which can be estimated at
a value of one ducat, but not of ten. For he is very willing to
venture one ducat, but when it is a question of ten he becomes
aware, as he had not previously been, that it may very well be
that he is in error. If, in a given case, we represent ourselves
as staking the happiness of our whole life, the triumphant
tone of our judgment is greatly abated; we become extremely
diffident, and discover for the first time that our belief does not
reach so far. Thus pragmatic belief always exists in some
specific degree, which, according to differences in the interests
at stake, may be large or may be small.
But in many cases, when we are dealing with an object
about which nothing can be done by us, and in regard to which
our judgment is therefore purely theoretical, we can conceive
and picture to ourselves an attitude for which we regard
ourselves as having sufficient grounds, while yet there is no
existing means of arriving at certainty in the matter. Thus
even in purely theoretical judgments there is an analogon
of practical judgments, to the mental entertaining of which
the term 'belief' is appropriate, and which we may entitle
doctrinal belief. I should be ready to stake my all on the 
contention -- were it possible by means of any experience to settle
the question -- that at least one of the planets which we see is
inhabited. Hence I say that it is not merely opinion, but a
strong belief, on the correctness of which I should be prepared
to run great risks, that other worlds are inhabited.
 Now we must admit that the doctrine of the existence of
God belongs to doctrinal belief. For as regards theoretical
knowledge of the world, I can cite nothing which necessarily
presupposes this thought as the condition of my explanations
P 649
of the appearances exhibited by the world, but rather am
bound so to employ my reason as if everything were mere
nature. Purposive unity is, however, so important a condition
of the application of reason to nature that I cannot ignore it,
especially as experience supplies me so richly with examples of
it. But I know no other condition under which this unity can 
supply me with guidance in the investigation of nature, save only
the postulate that a supreme intelligence has ordered all things
in accordance with the wisest ends. Consequently, as a condition
of what is indeed a contingent, but still not unimportant
purpose, namely, to have guidance in the investigation of
nature, we must postulate a wise Author of the world. Moreover,
the outcome of my attempts [in explanation of nature]
so frequently confirms the usefulness of this postulate, while
nothing decisive can be cited against it, that I am saying much
too little if I proceed to declare that I hold it merely as an
opinion. Even in this theoretical relation it can be said that I
firmly believe in God. This belief is not, therefore, strictly
speaking, practical; it must be entitled a doctrinal belief to
which the theology of nature (physico-theology) must always
necessarily give rise. In view of the magnificent equipment of
our human nature, and the shortness of life so ill-suited to the
full exercise of our powers, we can find in this same divine
wisdom a no less sufficient ground for a doctrinal belief in
the future life of the human soul.
In such cases the expression of belief is, from the objective
point of view, an expression of modesty, and yet at the same
time, from the subjective point of view, an expression of the
firmness of our confidence. Were I even to go the length of
describing the merely theoretical holding of the belief as an
hypothesis which I am justified in assuming, I should thereby
be pledging myself to have a more adequate concept of the
character of a cause of the world and of the character of
another world than I am really in a position to supply. For
if I assume anything, even merely as an hypothesis, I must
at least know so much of its properties that I require to
assume, not its concept, but only its existence. The term
'belief' refers only to the guidance which an idea gives me,
and to its subjective influence in that furthering of the 
activities of my reason which confirms me in the idea, and which
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yet does so without my being in a position to give a 
speculative account of it.
But the merely doctrinal belief is somewhat lacking in
stability; we often lose hold of it, owing to the speculative
difficulties which we encounter, although in the end we
always inevitably return to it.
It is quite otherwise with moral belief. For here it is 
absolutely necessary that something must happen, namely, that I
must in all points conform to the moral law. The end is here
irrefragably established, and according to such insight as I
can have, there is only one possible condition under which this
end can connect with all other ends, and thereby have practical
validity, namely, that there be a God and a future world.
I also know with complete certainty that no one can be 
acquainted with any other conditions which lead to the same
unity of ends under the moral law. Since, therefore, the moral
precept is at the same time my maxim (reason prescribing that
it should be so), I inevitably believe in the existence of God
and in a future life, and I am certain that nothing can shake
this belief, since my moral principles would thereby be 
themselves overthrown, and I cannot disclaim them without 
becoming abhorrent in my own eyes.
Thus even after reason has failed in all its ambitious 
attempts to pass beyond the limits of all experience, there is
still enough left to satisfy us, so far as our practical 
standpoint is concerned. No one, indeed, will be able to boast
that he knows that there is a God, and a future life; if he
knows this, he is the very man for whom I have long [and
vainly] sought. All knowledge, if it concerns an object of
mere reason, can be communicated; and I might therefore
hope that under his instruction my own knowledge would be
extended in this wonderful fashion. No, my conviction is not
logical, but moral certainty; and since it rests on subjective
grounds (of the moral sentiment), I must not even say, 'It is
morally certain that there is a God, etc. ', but 'I am morally
certain, etc. ' In other words, belief in a God and in another
world is so interwoven with my moral sentiment that as there
is little danger of my losing the latter, there is equally little
cause for fear that the former can ever be taken from me.
P 651
The only point that may seem questionable is the basing
of this rational belief on the assumption of moral sentiments.
If we leave these aside, and take a man who is completely
indifferent with regard to moral laws, the question propounded
by reason then becomes merely a problem for speculation,
and can, indeed, be supported by strong grounds of analogy,
but not by such as must compel the most stubborn scepticism
to give way. But in these questions no man is free from all
interest. For although, through lack of good sentiments, he
may be cut off from moral interest, still even in this case
enough remains to make him fear the existence of a God
and a future life. Nothing more is required for this than that
he at least cannot pretend that there is any certainty that
there is no such being and no such life. Since that would have
to be proved by mere reason, and therefore apodeictically, he
would have to prove the impossibility of both, which assuredly
no one can reasonably undertake to do. This may therefore
serve as negative belief, which may not, indeed, give rise to
morality and good sentiments, but may still give rise to an
analogon of these, namely, a powerful check upon the 
outbreak of evil sentiments.
 But, it will be said, is this all that pure reason acheives
in opening up prospects beyond the limits of experience?
Nothing more than two articles of belief? Surely the common
understanding could have achieved as much, without 
appealing to philosophers for counsel in the matter.
I shall not here dwell upon the service which philosophy
has done to human reason through the laborious efforts of its
criticism, granting even that in the end it should turn out to
be merely negative; something more will be said on this point
in the next section.
++ The human mind (as, I likewise believe, must necessarily be the
case with every rational being) takes a natural interest in morality,
although this interest is not undivided and practically preponderant.
If we confirm and increase this interest, we shall find reason very
teachable and in itself more enlightened as regards the uniting of the
speculative with the practical interest. But if we do not take care that
we first make men good, at least in some measure good, we shall never
make honest believers of them.
P 651
But I may at once reply: Do you really
require that a mode of knowledge which concerns all men
P 652
should transcend the common understanding, and should only
be revealed to you by philosophers? Precisely what you find
fault with is the best confirmation of the correctness of the
above assertions. For we have thereby revealed to us, what
could not at the start have been foreseen, namely, that in
matters which concern all men without distinction nature is
not guilty of any partial distribution of her gifts, and that in
regard to the essential ends of human nature the highest
philosophy cannot advance further than is possible under the
guidance which nature has bestowed even upon the most
ordinary understanding.
P 653
THE TRANSCENDENTAL DOCTRINE OF METHOD
CHAPTER III
THE ARCHITECTONIC OF PURE REASON
BY an architectonic I understand the art of constructing 
systems. As systematic unity is what first raises ordinary 
knowledge to the rank of science, that is, makes a system out of a
mere aggregate of knowledge, architectonic is the doctrine of
the scientific in our knowledge, and therefore necessarily
forms part of the doctrine of method.
In accordance with reason's legislative prescriptions, our
diverse modes of knowledge must not be permitted to be a
mere rhapsody, but must form a system. Only so can they
further the essential ends of reason. By a system I understand
the unity of the manifold modes of knowledge under one idea.
This idea is the concept provided by reason -- of the form of a
whole -- in so far as the concept determines a priori not only
the scope of its manifold content, but also the positions which
the parts occupy relatively to one another. The scientific concept
of reason contains, therefore, the end and the form of that
whole which is congruent with this requirement. The unity of
the end to which all the parts relate and in the idea of which
they all stand in relation to one another, makes it possible for
us to determine from our knowledge of the other parts whether
any part be missing, and to prevent any arbitrary addition, or
in respect of its completeness any indeterminateness that does
not conform to the limits which are thus determined a priori.
The whole is thus an organised unity (articulatio), and not an
aggregate (coacervatio). It may grow from within (per 
intussusceptionem), but not by external addition (per appositionem).
It is thus like an animal body, the growth of which is not by
P 654
the addition of a new member, but by the rendering of each
member, without change of proportion, stronger and more
effective for its purposes.
The idea requires for its realisation a schema, that is, a
constituent manifold and an order of its parts, both of which
must be determined a priori from the principle defined by its
end. The schema, which is not devised in accordance with an
idea, that is, in terms of the ultimate aim of reason, but 
empirically in accordance with purposes that are contingently
occasioned (the number of which cannot be foreseen) yields
technical unity; whereas the schema which originates from an
idea (in which reason propounds the ends a priori, and does
not wait for them to be empirically given) serves as the basis
of architectonic unity. Now that which we call science, the
schema of which must contain the outline (monogramma) and
the division of the whole into parts, in conformity with the
idea, that is, a priori, and in so doing must distinguish it with
certainty and according to principles from all other wholes, is
not formed in technical fashion, in view of the similarity of
its manifold constituents or of the contingent use of our knowledge
in concreto for all sorts of optional external ends, but in
architectonic fashion, in view of the affinity of its parts and of
their derivation from a single supreme and inner end, through
which the whole is first made possible.
No one attempts to establish a science unless he has an
idea upon which to base it. But in the working out of the
science the schema, nay even the definition which, at the start,
he first gave of the science, is very seldom adequate to his idea.
For this idea lies hidden in reason, like a germ in which the
parts are still undeveloped and barely recognisable even under
microscopic observation. Consequently, since sciences are 
devised from the point of view of a certain universal interest,
we must not explain and determine them according to the
description which their founder gives of them, but in 
conformity with the idea which, out of the natural unity of the
parts that we have assembled, we find to be grounded in
reason itself. For we shall then find that its founder, and often
even his latest successors, are groping for an idea which they
have never succeeded in making clear to themselves, and that
P 655
consequently they have not been in a position to determine the
proper content, the articulation (systematic unity), and limits
of the science.
It is unfortunate that only after we have spent much time
in the collection of materials in somewhat random fashion at
the suggestion of an idea lying hidden in our minds, and after
we have, indeed, over a long period assembled the materials in
a merely technical manner, does it first become possible for
us to discern the idea in a clearer light, and to devise a whole
architectonically in accordance with the ends of reason.
Systems seem to be formed in the manner of lowly organisms
through a generatio aequivoca from the mere confluence of
assembled concepts, at first imperfect, and only gradually
attaining to completeness, although they one and all have had
their schema, as the original germ, in the sheer self-development
of reason. Hence, not only is each system articulated in
accordance with an idea, but they are one and all organically
united in a system of human knowledge, as members of one
whole, and so as admitting of an architectonic of all human
knowledge, which, at the present time, in view of the great
amount of material that has been collected, or which can be
obtained from the ruins of ancient systems, is not only possible,
but would not indeed be difficult. We shall content ourselves
here with the completion of our task, namely, merely to
outline the architectonic of all knowledge arising from pure
reason; and in doing so we shall begin from the point at which
the common root of our faculty of knowledge divides and
throws out two stems, one of which is reason. By reason I here
understand the whole higher faculty of knowledge, and am
therefore contrasting the rational with the empirical.
If I abstract from all the content of knowledge, objectively
regarded, then all knowledge, subjectively regarded, is either
historical or rational. Historical knowledge is cognitio ex datis;
rational knowledge is cognitio ex principiis. However a mode
of knowledge may originally be given, it is still, in relation to
the individual who possesses it, simply historical, if he knows
only so much of it as has been given to him from outside (and
this in the form in which it has been given to him), whether
through immediate experience or narration, or (as in the case
P 656
of general knowledge) through instruction. Anyone, therefore,
who has learnt (in the strict sense of that term) a system of
philosophy, such as that of Wolff, although he may have all
its principles, explanations, and proofs, together with the
formal divisions of the whole body of doctrine, in his head,
and, so to speak, at his fingers' ends, has no more than a
complete historical knowledge of the Wolffian philosophy.
He knows and judges only what has been given him. If we
dispute a definition, he does not know whence to obtain
another. He has formed his mind on another's, and the imitative
faculty is not itself productive. In other words, his
knowledge has not in him arisen out of reason, and although,
objectively considered, it is indeed knowledge due to reason,
it is yet, in its subjective character, merely historical. He has
grasped and kept; that is, he has learnt well, and is merely
a plaster-cast of a living man. Modes of rational knowledge
which are rational objectively (that is, which can have their
first origin solely in human reason) can be so entitled 
subjectively also, only when they have been derived from universal
sources of reason, that is, from principles -- the sources
from which there can also arise criticism, nay, even the 
rejection of what has been learnt.
All knowledge arising out of reason is derived either from
concepts or from the construction of concepts. The former is
called philosophical, the latter mathematical. I have already
treated of the fundamental difference between these two modes
of knowledge in the first chapter [of this Transcendental 
Doctrine of Method]. Knowledge [as we have just noted] can be
objectively philosophical, and yet subjectively historical, as is
the case with most novices, and with all those who have never
looked beyond their School, and who remain novices all their
lives. But it is noteworthy that mathematical knowledge, in its
subjective character, and precisely as it has been learned, can
also be regarded as knowledge arising out of reason, and that
there is therefore in regard to mathematical knowledge no such
distinction as we have drawn in the case of philosophical 
knowledge. This is due to the fact that the sources of knowledge,
from which alone the teacher can derive his knowledge, lie nowhere
but in the essential and genuine principles of reason, and
consequently cannot be acquired by the novice from any other
P 657
source, and cannot be disputed; and this, in turn, is owing to
the fact that the employment of reason is here in concreto only,
although likewise a priori, namely, in intuition which is pure,
and which precisely on that account is infallible, excluding
all illusion and error. Mathematics, therefore, alone of all the
sciences (a priori) arising from reason, can be learned; 
philosophy can never be learned, save only in historical fashion;
as regards what concerns reason, we can at most learn to
philosophise.
Philosophy is the system of all philosophical knowledge.
If we are to understand by it the archetype for the estimation
of all attempts at philosophising, and if this archetype is to
serve for the estimation of each subjective philosophy, the structure
of which is often so diverse and liable to alteration, it must
be taken objectively. Thus regarded, philosophy is a mere idea
of a possible science which nowhere exists in concreto, but to
which, by many different paths, we endeavour to approximate,
until the one true path, overgrown by the products of 
sensibility, has at last been discovered, and the image, hitherto
so abortive, has achieved likeness to the archetype, so far as
this is granted to [mortal] man. Till then we cannot learn
philosophy; for where is it, who is in possession of it, and how
shall we recognise it? We can only learn to philosophise, that
is, to exercise the talent of reason, in accordance with its
universal principles, on certain actually existing attempts at
philosophy, always, however, reserving the right of reason to
investigate, to confirm, or to reject these principles in their
very sources.
Hitherto the concept of philosophy has been a merely scholastic
concept -- a concept of a system of knowledge which is
sought solely in its character as a science, and which has 
therefore in view only the systematic unity appropriate to science,
and consequently no more than the logical perfection of 
knowledge. But there is likewise another concept of philosophy, a
conceptus cosmicus, which has always formed the real basis of
the term 'philosophy', especially when it has been as it were
personified and its archetype represented in the ideal philosopher.
On this view, philosophy is the science of the relation
of all knowledge to the essential ends of human reason
P 658
(teleologia rationis humanae), and the philosopher is not an
artificer in the field of reason, but himself the lawgiver of
human reason. In this sense of the term it would be very
vainglorious to entitle oneself a philosopher, and to pretend
to have equalled the pattern which exists in the idea alone.
The mathematician, the natural philosopher, and the
logician, however successful the two former may have been in
their advances in the field of rational knowledge, and the two
latter more especially in philosophical knowledge, are yet only
artificers in the field of reason. There is a teacher, [conceived]
in the ideal, who sets them their tasks, and employs them as
instruments, to further the essential ends of human reason.
Him alone we must call philosopher; but as he nowhere exists,
while the idea of his legislation is to be found in that reason
with which every human being is endowed, we shall keep
entirely to the latter, determining more precisely what 
philosophy prescribes as regards systematic unity, in accordance
with this cosmical concept, from the standpoint of its essential
ends.
Essential ends are not as such the highest ends; in view
of the demand of reason for complete systematic unity, only
one of them can be so described. Essential ends are therefore
either the ultimate end or subordinate ends which are 
necessarily connected with the former as means. The former is no
other than the whole vocation of man, and the philosophy
which deals with it is entitled moral philosophy. On account
of this superiority which moral philosophy has over all other
occupations of reason, the ancients in their use of the term
'philosopher' always meant, more especially, the moralist; and
even at the present day we are led by a certain analogy to
entitle anyone a philosopher who appears to exhibit self-control
under the guidance of reason, however limited his knowledge
may be.
++ By 'cosmical concept' [Weltbegriff] is here meant the concept
which relates to that in which everyone necessarily has an interest;
and accordingly if a science is to be regarded merely as one of the
disciplines designed in view of certain optionally chosen ends, I must
determine it in conformity with scholastic concepts.
P 658
The legislation of human reason (philosophy) has two
objects, nature and freedom, and therefore contains not only
P 659
the law of nature, but also the moral law, presenting them
at first in two distinct systems, but ultimately in one single
philosophical system. The philosophy of nature deals with all
that is, the philosophy of morals with that which ought to be.
All philosophy is either knowledge arising out of pure
reason, or knowledge obtained by reason from empirical
principles. The former is termed pure, the latter empirical
philosophy.
The philosophy of pure reason is either a propaedeutic
(preparation), which investigates the faculty of reason in
respect of all its pure a priori knowledge, and is entitled
the science which exhibits in systematic connection the whole
body (true as well as illusory) of philosophical knowledge
arising out of pure reason, and which is entitled metaphysics.
The title 'metaphysics' may also, however, be given to the
whole of pure philosophy, inclusive of criticism, and so as 
comprehending the investigation of all that can ever be known
a priori as well as the exposition of that which constitutes a
system of the pure philosophical modes of knowledge of this
type -- in distinction, therefore, from all empirical and from
all mathematical employment of reason.
Metaphysics is divided into that of the speculative and that
of the practical employment of pure reason, and is therefore
either metaphysics of nature or metaphysics of morals.
The former contains all the principles of pure reason that
are derived from mere concepts (therefore excluding 
mathematics), and employed in the theoretical knowledge of all
things; the latter, the principles which in a priori fashion
determine and make necessary all our actions. Now morality
is the only code of laws applying to our actions which can
be derived completely a priori from principles. Accordingly,
the metaphysics of morals is really pure moral philosophy,
with no underlying basis of anthropology or of other empirical
conditions. The term 'metaphysics', in its strict sense, is 
commonly reserved for the metaphysics of speculative reason.
But as pure moral philosophy really forms part of this special
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branch of human and philosophical knowledge derived from
pure reason, we shall retain for it the title 'metaphysics'. We
are not, however, at present concerned with it, and may 
therefore leave it aside.
It is of the utmost importance to isolate the various modes
of knowledge according as they differ in kind and in origin,
and to secure that they be not confounded owing to the fact
that usually, in our employment of them, they are combined.
What the chemist does in the analysis of substances, and
the mathematician in his special disciplines, is in still greater
degree incumbent upon the philosopher, that he may be able
to determine with certainty the part which belongs to each
special kind of knowledge in the diversified employment of the
understanding and its special value and influence. Human
reason, since it first began to think, or rather to reflect, has never
been able to dispense with a metaphysics; but also has never
been able to obtain it in a form sufficiently free from all foreign
elements. The idea of such a science is as old as speculative
human reason; and what rational being does not speculate,
either in scholastic or in popular fashion? It must be admitted,
however, that the two elements of our knowledge -- that
which is in our power completely a priori, and that which is
obtainable only a posteriori from experience -- have never been
very clearly distinguished, not even by professional thinkers,
and that they have therefore failed to bring about the delimitation
of a special kind of knowledge, and thereby the true idea
of the science which has preoccupied human reason so long and
so greatly. When metaphysics was declared to be the science
of the first principles of human knowledge, the intention was
not to mark out a quite special kind of knowledge, but only
a certain precedence in respect of generality, which was not
sufficient to distinguish such knowledge from the empirical.
For among empirical principles we can distinguish some that
are more general, and so higher in rank than others; but
where in such a series of subordinated members -- a series in
which we do not distinguish what is completely a priori from
what is known only a posteriori -- are we to draw the line
which distinguishes the highest or first members from the
lower subordinate members? What should we say, if in the
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reckoning of time we could distinguish the epochs of the
world only by dividing them into the first centuries and those
that follow? We should ask: Does the fifth, the tenth century,
etc. , belong with the first centuries? So in like manner I ask:
Does the concept of the extended belong to metaphysics?
You answer, Yes. Then, that of body too? Yes. And that of
fluid body? You now become perplexed; for at this rate everything
will belong to metaphysics. It is evident, therefore, that
the mere degree of subordination (of the particular under
the general) cannot determine the limits of a science; in the
case under consideration, only complete difference of kind and
of origin will suffice. But the fundamental idea of metaphysics
was obscured on yet another side, owing to its exhibiting, as
a priori knowledge, a certain similarity to mathematics.
Certainly they are related, in so far as they both have an
a priori origin; but when we bear in mind the difference
between philosophical and mathematical knowledge, namely,
that the one is derived from concepts, whereas in the other
we arrive at a priori judgments only through the construction
which has indeed always been in a manner felt but could
never be defined by means of any clear criteria. Thus it
has come about that since philosophers failed in the task of
developing even the idea of their science, they could have
no determinate end or secure guidance in the elaboration
of it, and, accordingly, in this arbitrarily conceived enterprise,
ignorant as they were of the path to be taken, they have
always been at odds with one another as regards the discoveries
which each claimed to have made on his own separate
path, with the result that their science has been brought into
contempt, first among outsiders, and finally even among
themselves.
All pure a priori knowledge, owing to the special faculty
of knowledge in which alone it can originate, has in itself a
peculiar unity; and metaphysics is the philosophy which has
as its task the statement of that knowledge in this systematic
unity. Its speculative part, which has especially appropriated
this name, namely, what we entitle metaphysics of nature, and
which considers everything in so far as it is (not that which
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ought to be) by means of a priori concepts, is divided in the
following manner.
Metaphysics, in the narrower meaning of the term, consists
of transcendental philosophy and physiology of pure
reason. The former treats only of the understanding and of
reason, in a system of concepts and principles which relate to
objects in general but take no account of objects that may be
given (Ontologia); the latter treats of nature, that is, of the
sum of given objects (whether given to the senses, or, if we will,
to some other kind of intuition) and is therefore physiology --
although only rationalis. The employment of reason in this
rational study of nature is either physical or hyperphysical,
or, in more adequate terms, is either immanent or transcendent.
The former is concerned with such knowledge of nature
as can be applied in experience (in concreto), the latter with
that connection of objects of experience which transcends
all experience. This transcendent physiology has as its object
either an inner connection or an outer connection, both, 
however, transcending possible experience. As dealing with an
inner connection it is the physiology of nature as a whole,
that is, the transcendental knowledge of the world; as dealing
with an outer connection, it is the physiology of the relation
of nature as a whole to a being above nature, that is to say,
it is the transcendental knowledge of God.
Immanent physiology, on the other hand, views nature as
the sum of all objects of the senses, and therefore just as it is
given us, but solely in accordance with a priori conditions,
under which alone it can ever be given us. There are only two
kinds of such objects. Those of the outer senses, and so
their sum, corporeal nature. The object of inner sense,
the soul, and in accordance with our fundamental concepts of
it, thinking nature. The metaphysics of corporeal nature is
entitled physics; and as it must contain only the principles of
an a priori knowledge of it, rational physics. The metaphysics
of thinking nature is entitled psychology, and on the same
ground is to be understood as being only the rational 
knowledge of it.
The whole system of metaphysics thus consists of four
main parts: (1) ontology; (2) rational physiology; (3) rational
cosmology; (4) rational theology. The second part, namely,
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the doctrine of nature as developed by pure reason, contains
two divisions physica rationalis and psychologia rationalis.
The originative idea of a philosophy of pure reason itself
prescribes this division, which is therefore architectonic, in
accordance with the essential ends of reason, and not merely
technical, in accordance with accidentally observed similarities,
and so instituted as it were at haphazard. Accordingly
the division is also unchangeable and of legislative authority.
There are, however, some points which may well seem doubtful,
and may weaken our conviction as to the legitimacy of
its claims.
First of all, how can I expect to have knowledge a priori
(and therefore a metaphysics) of objects in so far as they are
given to our senses, that is, given in an a posteriori manner?
And how is it possible to know the nature of things and
to arrive at a rational physiology according to principles
a priori?  The answer is this: we take nothing more from experience
than is required to give us an object of outer or of inner
sense. The object of outer sense we obtain through the mere
concept of matter (impenetrable, lifeless extension), the object
of inner sense through the concept of a thinking being (in the
empirical inner representation, 'I think'). As to the rest, in the
whole metaphysical treatment of these objects, we must entirely
dispense with all empirical principles which profess to
add to these concepts any other more special experience, with
a view to our passing further judgments upon the objects.
++ I must not be taken as meaning thereby what is commonly
called physica generalis; the latter is rather mathematics than 
philosophy of nature. The metaphysics of nature is quite distinct from
mathematics. It is very far from enlarging our knowledge in the
fruitful manner of mathematics, but still is very important as 
yielding a criticism of the pure knowledge of understanding in its
application to nature. For lack of it, even mathematicians, holding
to certain common concepts, which though common are yet in
fact metaphysical, have unconsciously encumbered their doctrine
of nature with hypotheses which vanish upon criticism of the 
principles involved, without, however, doing the least injury to the
employment of mathematics -- employment which is quite 
indispensable in this field.
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Secondly, how are we to regard empirical psychology,
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which has always claimed its place in metaphysics, and from
which in our times such great things have been expected for
the advancement of metaphysics, the hope of succeeding by
a priori methods having been abandoned. I answer that it belongs
where the proper (empirical) doctrine of nature belongs,
namely, by the side of applied philosophy, the a priori principles
of which are contained in pure philosophy; it is therefore
so far connected with applied philosophy, though not to be
confounded with it. Empirical psychology is thus completely
banished from the domain of metaphysics; it is indeed already
completely excluded by the very idea of the latter science. In
conformity, however, with scholastic usage we must allow it
some sort of a place (although as an episode only) in metaphysics
and this from economical motives, because it is not yet
so rich as to be able to form a subject of study by itself, and yet
is too important to be entirely excluded and forced to settle
elsewhere, in a neighbourhood that might well prove much
less congenial than that of metaphysics. Though it is but a
stranger it has long been accepted as a member of the household,
and we allow it to stay for some time longer, until it is in
a position to set up an establishment of its own in a complete
anthropology, the pendant to the empirical doctrine of nature.
Such, then, in general, is the idea of metaphysics. At first
more was expected from metaphysics than could reasonably be
demanded, and for some time it diverted itself with pleasant
anticipations. But these hopes having proved deceptive, it
has now fallen into general disrepute. The argument of our
Critique, taken as a whole, must have sufficiently convinced
the reader that although metaphysics cannot be the foundation
of religion, it must always continue to be a bulwark of it, and
that human reason, being by its very nature dialectical, can
never dispense with such a science, which curbs it, and by a
scientific and completely convincing self-knowledge, prevents
the devastations of which a lawless speculative reason would
otherwise quite inevitably be guilty in the field of morals as
well as in that of religion. We can therefore be sure that 
however cold or contemptuously critical may be the attitude of
those who judge a science not by its nature but by its accidental
effects, we shall always return to metaphysics as to a 
beloved one with whom we have had a quarrel. For here we are
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concerned with essential ends -- ends with which metaphysics
must ceaselessly occupy itself, either in striving for genuine
insight into them, or in refuting those who profess already to
have attained it.
Metaphysics, alike of nature and of morals, and especially
that criticism of our adventurous and self-reliant reason which
serves as an introduction or propaedeutic to metaphysics,
alone properly constitutes what may be entitled philosophy,
in the strict sense of the term. Its sole preoccupation is wisdom;
and it seeks it by the path of science, which, once it has been
trodden, can never be overgrown, and permits of no wandering.
Mathematics, natural science, even our empirical knowledge,
have a high value as means, for the most part, to contingent
ends, but also, in the ultimate outcome, to ends that
are necessary and essential to humanity. This latter service,
however, they can discharge only as they are aided by a 
knowledge through reason from pure concepts, which, however we
may choose to entitle it, is really nothing but metaphysics.
For the same reason metaphysics is also the full and 
complete development of human reason. Quite apart from its
influence, as science, in connection with certain specific ends
it is an indispensable discipline. For in dealing with reason it
treats of those elements and highest maxims which must form
the basis of the very possibility of some sciences, and of the
use of all. That, as mere speculation, it serves rather to prevent
errors than to extend knowledge, does not detract from its
value. On the contrary this gives it dignity and authority,
through that censorship which secures general order and 
harmony, and indeed the well-being of the scientific 
commonwealth, preventing those who labour courageously and 
fruitfully on its behalf from losing sight of the supreme end, the
happiness of all mankind.
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THE TRANSCENDENTAL DOCTRINE OF METHOD
CHAPTER IV
THE HISTORY OF PURE REASON
THIS title stands here only in order to indicate one remaining
division of the system, which future workers must complete.
I content myself with casting a cursory glance, from a purely
transcendental point of view, namely, that of the nature of
pure reason, on the works of those who have laboured in this
field -- a glance which reveals [many stately] structures, but in
ruins only.
It is a very notable fact, although it could not have been
otherwise, that in the infancy of philosophy men began where
we should incline to end, namely, with the knowledge of God,
occupying themselves with the hope, or rather indeed with
the specific nature, of another world. However gross the
religious concepts generated by the ancient practices which
still persisted in each community from an earlier more
barbarous state, this did not prevent the more enlightened
members from devoting themselves to free investigation of
these matters; and they easily discerned that there could be
no better ground or more dependable way of pleasing the 
invisible power that governs the world, and so of being happy
in another world at least, than by living the good life. 
Accordingly theology and morals were the two motives, or rather
the two points of reference, in all those abstract enquiries of
reason to which men came to devote themselves. It was chiefly,
however, the former that step by step committed the purely
speculative reason to those labours which afterwards became
so renowned under the name of metaphysics.
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I shall not here attempt to distinguish the periods of history
in which this or that change in metaphysics came about,
but shall only give a cursory sketch of the various ideas which
gave rise to the chief revolutions [in metaphysical theory].
And here I find that there are three issues in regard to
which the most noteworthy changes have taken place in the
course of the resulting controversies.
1. In respect of the object of all our 'knowledge through
reason', some have been mere sensualists, others mere 
intellectualists. Epicurus may be regarded as the outstanding
philosopher among the former, and Plato among the latter.
The distinction between the two schools, subtle as it is,
dates from the earliest times; and the two positions have
ever since been maintained in unbroken continuity. Those
of the former school maintained that reality is to be found
solely in the objects of the senses, and that all else is fiction;
those of the latter school, on the other hand, declared that
in the senses there is nothing but illusion, and that only
the understanding knows what is true. The former did not
indeed deny reality to the concepts of the understanding; but
this reality was for them merely logical, whereas for the others
it was mystical. The former conceded intellectual concepts, but
admitted sensible objects only. The latter required that true
objects should be purely intelligible, and maintained that by
means of the pure understanding we have an intuition that
is unaccompanied by the senses -- the senses, in their view,
serving only to confuse the understanding.
2. In respect of the origin of the modes of 'knowledge
through pure reason', the question is as to whether they are
derived from experience, or whether in independence of 
experience they have their origin in reason. Aristotle may be
regarded as the chief of the empiricists, and Plato as the
chief of the noologists. Locke, who in modern times followed
Aristotle, and Leibniz, who followed Plato (although in 
considerable disagreement with his mystical system), have not
been able to bring this conflict to any definitive conclusion.
However we may regard Epicurus, he was at least much more
consistent in this sensual system than Aristotle and Locke,
inasmuch as he never sought to pass by inference beyond the
limits of experience. This is especially true as regards Locke,
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who, after having derived all concepts and principles from
experience, goes so far in the use of them as to assert that we
can prove the existence of God and the immortality of the
soul with the same conclusiveness as any mathematical 
proposition -- though both lie entirely outside the limits of
possible experience.
3. In respect of method. -- If anything is to receive the
title of method, it must be a procedure in accordance with
principles. We may divide the methods now prevailing in this
field of enquiry into the naturalistic and the scientific. The
naturalist of pure reason adopts as his principle that through
common reason, without science, that is, through what he
calls sound reason, he is able, in regard to those most sublime
questions which form the problem of metaphysics, to achieve
more than is possible through speculation. Thus he is virtually
asserting that we can determine the size and distance of
the moon with greater certainty by the naked eye than by
mathematical devices. This is mere misology, reduced to
principles; and what is most absurd of all, the neglect of all
artificial means is eulogised as a special method of extending
our knowledge. For as regards those who are naturalists from
lack of more insight, they cannot rightly be blamed. They
follow common reason, without boasting of their ignorance
as a method which contains the secret how we are to fetch
truth from the deep well of Democritus. Quod sapio, satis
est mihi, non ego curo, esse quod Arcesilas aerumnosique
Solones is the motto with which they may lead a cheerful
and praiseworthy life, not troubling themselves about science,
nor by their interference bringing it into confusion.
As regards those who adopt a scientific method, they have
the choice of proceeding either dogmatically or sceptically;
but in any case they are under obligation to proceed 
systematically. I may cite the celebrated Wolff as a representative
of the former mode of procedure, and David Hume as a 
representative of the latter, and may then, conformably with my
present purpose, leave all others unnamed. The critical path
alone is still open. If the reader has had the courtesy and
patience to accompany me along this path, he may now judge
for himself whether, if he cares to lend his aid in making this
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path into a high-road, it may not be possible to achieve 
before the end of the present century what many centuries have
not been able to accomplish; namely, to secure for human
reason complete satisfaction in regard to that with which it
has all along so eagerly occupied itself, though hitherto
in vain.
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++ Persius.

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