Books: The Critique of Practical Reason

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This sort of credential of the moral law, viz., that it is set forth
as a principle of the deduction of freedom, which is a causality of
pure reason, is a sufficient substitute for all a priori
justification, since theoretic reason was compelled to assume at least
the possibility of freedom, in order to satisfy a want of its own. For
the moral law proves its reality, so as even to satisfy the critique
of the speculative reason, by the fact that it adds a positive
definition to a causality previously conceived only negatively, the
possibility of which was incomprehensible to speculative reason, which
yet was compelled to suppose it. For it adds the notion of a reason
that directly determines the will (by imposing on its maxims the
condition of a universal legislative form); and thus it is able for
the first time to give objective, though only practical, reality to
reason, which always became transcendent when it sought to proceed
speculatively with its ideas. It thus changes the transcendent use
of reason into an immanent use (so that reason is itself, by means
of ideas, an efficient cause in the field of experience).

The determination of the causality of beings in the world of
sense, as such, can never be unconditioned; and yet for every series
of conditions there must be something unconditioned, and therefore
there must be a causality which is determined wholly by itself. Hence,
the idea of freedom as a faculty of absolute spontaneity was not found
to be a want but, as far as its possibility is concerned, an
analytic principle of pure speculative reason. But as it is absolutely
impossible to find in experience any example in accordance with this
idea, because amongst the causes of things as phenomena it would be
impossible to meet with any absolutely unconditioned determination
of causality, we were only able to defend our supposition that a
freely acting cause might be a being in the world of sense, in so
far as it is considered in the other point of view as a noumenon,
showing that there is no contradiction in regarding all its actions as
subject to physical conditions so far as they are phenomena, and yet
regarding its causality as physically unconditioned, in so far as
the acting being belongs to the world of understanding, and in thus
making the concept of freedom the regulative principle of reason. By
this principle I do not indeed learn what the object is to which
that sort of causality is attributed; but I remove the difficulty,
for, on the one side, in the explanation of events in the world, and
consequently also of the actions of rational beings, I leave to the
mechanism of physical necessity the right of ascending from
conditioned to condition ad infinitum, while on the other side I
keep open for speculative reason the place which for it is vacant,
namely, the intelligible, in order to transfer the unconditioned
thither. But I was not able to verify this supposition; that is, to
change it into the knowledge of a being so acting, not even into the
knowledge of the possibility of such a being. This vacant place is now
filled by pure practical reason with a definite law of causality in an
intelligible world (causality with freedom), namely, the moral law.
Speculative reason does not hereby gain anything as regards its
insight, but only as regards the certainty of its problematical notion
of freedom, which here obtains objective reality, which, though only
practical, is nevertheless undoubted. Even the notion of causality-
the application, and consequently the signification, of which holds
properly only in relation to phenomena, so as to connect them into
experiences (as is shown by the Critique of Pure Reason)- is not so
enlarged as to extend its use beyond these limits. For if reason
sought to do this, it would have to show how the logical relation of
principle and consequence can be used synthetically in a different
sort of intuition from the sensible; that is how a causa noumenon is
possible. This it can never do; and, as practical reason, it does
not even concern itself with it, since it only places the
determining principle of causality of man as a sensible creature
(which is given) in pure reason (which is therefore called practical);
and therefore it employs the notion of cause, not in order to know
objects, but to determine causality in relation to objects in general.
It can abstract altogether from the application of this notion to
objects with a view to theoretical knowledge (since this concept is
always found a priori in the understanding even independently of any
intuition). Reason, then, employs it only for a practical purpose, and
hence we can transfer the determining principle of the will into the
intelligible order of things, admitting, at the same time, that we
cannot understand how the notion of cause can determine the
knowledge of these things. But reason must cognise causality with
respect to the actions of the will in the sensible world in a definite
manner; otherwise, practical reason could not really produce any
action. But as to the notion which it forms of its own causality as
noumenon, it need not determine it theoretically with a view to the
cognition of its supersensible existence, so as to give it
significance in this way. For it acquires significance apart from
this, though only for practical use, namely, through the moral law.
Theoretically viewed, it remains always a pure a priori concept of the
understanding, which can be applied to objects whether they have
been given sensibly or not, although in the latter case it has no
definite theoretical significance or application, but is only a
formal, though essential, conception of the understanding relating
to an object in general. The significance which reason gives it
through the moral law is merely practical, inasmuch as the idea of the
idea of the law of causality (of the will) has self causality, or is
its determining principle.

II. Of the Right that Pure Reason in its Practical use has to an
Extension which is not possible to it in its Speculative Use.

{BOOK_1|CHAPTER_1 ^paragraph 145}

We have in the moral principle set forth a law of causality, the
determining principle of which is set above all the conditions of
the sensible world; we have it conceived how the will, as belonging to
the intelligible world, is determinable, and therefore we therefore we
have its subject (man) not merely conceived as belonging to a world of
pure understanding, and in this respect unknown (which the critique of
speculative reason enabled us to do), but also defined as regards
his causality by means of a law which cannot be reduced to any
physical law of the sensible world; and therefore our knowledge is
extended beyond the limits of that world, a pretension which the
Critique of Pure Reason declared to be futile in all speculation. Now,
how is the practical use of pure reason here to be reconciled with the
theoretical, as to the determination of the limits of its faculty?

David Hume, of whom we may say that he commenced the assault on
the claims of pure reason, which made a thorough investigation of it
necessary, argued thus: The notion of cause is a notion that
involves the necessity of the connexion of the existence of
different things (and that, in so far as they are different), so that,
given A, I know that something quite distinct there from, namely B,
must necessarily also exist. Now necessity can be attributed to a
connection, only in so far as it is known a priori, for experience
would only enable us to know of such a connection that it exists,
not that it necessarily exists. Now, it is impossible, says he, to
know a priori and as necessary the connection between one thing and
another (or between one attribute and another quite distinct) when
they have not been given in experience. Therefore the notion of a
cause is fictitious and delusive and, to speak in the mildest way,
is an illusion, only excusable inasmuch as the custom (a subjective
necessity) of perceiving certain things, or their attributes as
often associated in existence along with or in succession to one
another, is insensibly taken for an objective necessity of supposing
such a connection in the objects themselves; and thus the notion of
a cause has been acquired surreptitiously and not legitimately; nay,
it can never be so acquired or authenticated, since it demands a
connection in itself vain, chimerical, and untenable in presence of
reason, and to which no object can ever correspond. In this way was
empiricism first introduced as the sole source of principles, as far
as all knowledge of the existence of things is concerned
(mathematics therefore remaining excepted); and with empiricism the
most thorough scepticism, even with regard to the whole science of
nature( as philosophy). For on such principles we can never conclude
from given attributes of things as existing to a consequence (for this
would require the notion of cause, which involves the necessity of
such a connection); we can only, guided by imagination, expect similar
cases- an expectation which is never certain, however of ten it has
been fulfilled. Of no event could we say: a certain thing must have
preceded it, on which it necessarily followed; that is, it must have a
cause; and therefore, however frequent the cases we have known in
which there was such an antecedent, so that a rule could be derived
from them, yet we never could suppose it as always and necessarily
so happening; we should, therefore, be obliged to leave its share to
blind chance, with which all use of reason comes to an end; and this
firmly establishes scepticism in reference to arguments ascending from
effects to causes and makes it impregnable.

Mathematics escaped well, so far, because Hume thought that its
propositions were analytical; that is, proceeded from one property
to another, by virtue of identity and, consequently, according to
the principle of contradiction. This, however, is not the case, since,
on the contrary, they are synthetical; and although geometry, for
example, has not to do with the existence of things, but only with
their a priori properties in a possible intuition, yet it proceeds
just as in the case of the causal notion, from one property (A) to
another wholly distinct (B), as necessarily connected with the former.
Nevertheless, mathematical science, so highly vaunted for its
apodeictic certainty, must at last fall under this empiricism for
the same reason for which Hume put custom in the place of objective
necessity in the notion of cause and, in spite of all its pride,
must consent to lower its bold pretension of claiming assent a
priori and depend for assent to the universality of its propositions
on the kindness of observers, who, when called as witnesses, would
surely not hesitate to admit that what the geometer propounds as a
theorem they have always perceived to be the fact, and,
consequently, although it be not necessarily true, yet they would
permit us to expect it to be true in the future. In this manner Hume's
empiricism leads inevitably to scepticism, even with regard to
mathematics, and consequently in every scientific theoretical use of
reason (for this belongs either to philosophy or mathematics). Whether
with such a terrible overthrow of the chief branches of knowledge,
common reason will escape better, and will not rather become
irrecoverably involved in this destruction of all knowledge, so that
from the same principles a universal scepticism should follow
(affecting, indeed, only the learned), this I will leave everyone to
judge for himself.

As regards my own labours in the critical examination of pure
reason, which were occasioned by Hume's sceptical teaching, but went
much further and embraced the whole field of pure theoretical reason
in its synthetic use and, consequently, the field of what is called
metaphysics in general; I proceeded in the following manner with
respect to the doubts raised by the Scottish philosopher touching
the notion of causality. If Hume took the objects of experience for
things in themselves (as is almost always done), he was quite right in
declaring the notion of cause to be a deception and false illusion;
for as to things in themselves, and their attributes as such, it is
impossible to see why because A is given, B, which is different,
must necessarily be also given, and therefore he could by no means
admit such an a priori knowledge of things in themselves. Still less
could this acute writer allow an empirical origin of this concept,
since this is directly contradictory to the necessity of connection
which constitutes the essence of the notion of causality, hence the
notion was proscribed, and in its place was put custom in the
observation of the course of perceptions.

{BOOK_1|CHAPTER_1 ^paragraph 150}

It resulted, however, from my inquiries, that the objects with which
we have to do in experience are by no means things in themselves,
but merely phenomena; and that although in the case of things in
themselves it is impossible to see how, if A is supposed, it should be
contradictory that B, which is quite different from A, should not also
be supposed (i.e., to see the necessity of the connection between A as
cause and B as effect); yet it can very well be conceived that, as
phenomena, they may be necessarily connected in one experience in a
certain way (e.g., with regard to time-relations); so that they
could not be separated without contradicting that connection, by means
of which this experience is possible in which they are objects and
in which alone they are cognisable by us. And so it was found to be in
fact; so that I was able not only to prove the objective reality of
the concept of cause in regard to objects of experience, but also to
deduce it as an a priori concept by reason of the necessity of the
connection it implied; that is, to show the possibility of its
origin from pure understanding without any empirical sources; and
thus, after removing the source of empiricism, I was able also to
overthrow the inevitable consequence of this, namely, scepticism,
first with regard to physical science, and then with regard to
mathematics (in which empiricism has just the same grounds), both
being sciences which have reference to objects of possible experience;
herewith overthrowing the thorough doubt of whatever theoretic
reason professes to discern.

But how is it with the application of this category of causality
(and all the others; for without them there can be no knowledge of
anything existing) to things which are not objects of possible
experience, but lie beyond its bounds? For I was able to deduce the
objective reality of these concepts only with regard to objects of
possible experience. But even this very fact, that I have saved
them, only in case I have proved that objects may by means of them
be thought, though not determined a priori; this it is that gives them
a place in the pure understanding, by which they are referred to
objects in general (sensible or not sensible). If anything is still
wanting, it is that which is the condition of the application of these
categories, and especially that of causality, to objects, namely,
intuition; for where this is not given, the application with a view to
theoretic knowledge of the object, as a noumenon, is impossible and,
therefore, if anyone ventures on it, is (as in the Critique of Pure
Reason) absolutely forbidden. Still, the objective reality of the
concept (of causality) remains, and it can be used even of noumena,
but without our being able in the least to define the concept
theoretically so as to produce knowledge. For that this concept,
even in reference to an object, contains nothing impossible, was shown
by this, that, even while applied to objects of sense, its seat was
certainly fixed in the pure understanding; and although, when referred
to things in themselves (which cannot be objects of experience), it is
not capable of being determined so as to represent a definite object
for the purpose of theoretic knowledge; yet for any other purpose (for
instance, a practical) it might be capable of being determined so as
to have such application. This could not be the case if, as Hume
maintained, this concept of causality contained something absolutely
impossible to be thought.

In order now to discover this condition of the application of the
said concept to noumena, we need only recall why we are not content
with its application to objects of experience, but desire also to
apply it to things in themselves. It will appear, then, that it is not
a theoretic but a practical purpose that makes this a necessity. In
speculation, even if we were successful in it, we should not really
gain anything in the knowledge of nature, or generally with regard
to such objects as are given, but we should make a wide step from
the sensibly conditioned (in which we have already enough to do to
maintain ourselves, and to follow carefully the chain of causes) to
the supersensible, in order to complete our knowledge of principles
and to fix its limits; whereas there always remains an infinite
chasm unfilled between those limits and what we know; and we should
have hearkened to a vain curiosity rather than a solid-desire of
knowledge.

But, besides the relation in which the understanding stands to
objects (in theoretical knowledge), it has also a relation to the
faculty of desire, which is therefore called the will, and the pure
will, inasmuch as pure understanding (in this case called reason) is
practical through the mere conception of a law. The objective
reality of a pure will, or, what is the same thing, of a pure
practical reason, is given in the moral law a priori, as it were, by a
fact, for so we may name a determination of the will which is
inevitable, although it does not rest on empirical principles. Now, in
the notion of a will the notion of causality is already contained, and
hence the notion of a pure will contains that of a causality
accompanied with freedom, that is, one which is not determinable by
physical laws, and consequently is not capable of any empirical
intuition in proof of its reality, but, nevertheless, completely
justifies its objective reality a priori in the pure practical law;
not, indeed (as is easily seen) for the purposes of the theoretical,
but of the practical use of reason. Now the notion of a being that has
free will is the notion of a causa noumenon, and that this notion
involves no contradiction, we are already assured by the fact- that
inasmuch as the concept of cause has arisen wholly from pure
understanding, and has its objective reality assured by the deduction,
as it is moreover in its origin independent of any sensible
conditions, it is, therefore, not restricted to phenomena (unless we
wanted to make a definite theoretic use of it), but can be applied
equally to things that are objects of the pure understanding. But,
since this application cannot rest on any intuition (for intuition can
only be sensible), therefore, causa noumenon, as regards the theoretic
use of reason, although a possible and thinkable, is yet an empty
notion. Now, I do not desire by means of this to understand
theoretically the nature of a being, in so far as it has a pure
will; it is enough for me to have thereby designated it as such, and
hence to combine the notion of causality with that of freedom (and
what is inseparable from it, the moral law, as its determining
principle). Now, this right I certainly have by virtue of the pure,
not-empirical origin of the notion of cause, since I do not consider
myself entitled to make any use of it except in reference to the moral
law which determines its reality, that is, only a practical use.

If, with Hume, I had denied to the notion of causality all objective
reality in its [theoretic] use, not merely with regard to things in
themselves (the supersensible), but also with regard to the objects of
the senses, it would have lost all significance, and being a
theoretically impossible notion would have been declared to be quite
useless; and since what is nothing cannot be made any use of, the
practical use of a concept theoretically null would have been
absurd. But, as it is, the concept of a causality free from
empirical conditions, although empty, i.e., without any appropriate
intuition), is yet theoretically possible, and refers to an
indeterminate object; but in compensation significance is given to
it in the moral law and consequently in a practical sense. I have,
indeed, no intuition which should determine its objective theoretic
reality, but not the less it has a real application, which is
exhibited in concreto in intentions or maxims; that is, it has a
practical reality which can be specified, and this is sufficient to
justify it even with a view to noumena.

{BOOK_1|CHAPTER_1 ^paragraph 155}

Now, this objective reality of a pure concept of the understanding
in the sphere of the supersensible, once brought in, gives an
objective reality also to all the other categories, although only so
far as they stand in necessary connexion with the determining
principle of the will (the moral law); a reality only of practical
application, which has not the least effect in enlarging our
theoretical knowledge of these objects, or the discernment of their
nature by pure reason. So we shall find also in the sequel that
these categories refer only to beings as intelligences, and in them
only to the relation of reason to the will; consequently, always
only to the practical, and beyond this cannot pretend to any knowledge
of these beings; and whatever other properties belonging to the
theoretical representation of supersensible things may be brought into
connexion with these categories, this is not to be reckoned as
knowledge, but only as a right (in a practical point of view, however,
it is a necessity) to admit and assume such beings, even in the case
where we [conceive] supersensible beings (e.g., God) according to
analogy, that is, a purely rational relation, of which we make a
practical use with reference to what is sensible; and thus the
application to the supersensible solely in a practical point of view
does not give pure theoretic reason the least encouragement to run
riot into the transcendent.

BOOK_1|CHAPTER_2

CHAPTER II. Of the Concept of an Object of Pure Practical Reason.

By a concept of the practical reason I understand the idea of an
object as an effect possible to be produced through freedom. To be
an object of practical knowledge, as such, signifies, therefore,
only the relation of the will to the action by which the object or its
opposite would be realized; and to decide whether something is an
object of pure practical reason or not is only to discern the
possibility or impossibility of willing the action by which, if we had
the required power (about which experience must decide), a certain
object would be realized. If the object be taken as the determining
principle of our desire, it must first be known whether it is
physically possible by the free use of our powers, before we decide
whether it is an object of practical reason or not. On the other hand,
if the law can be considered a priori as the determining principle
of the action, and the latter therefore as determined by pure
practical reason, the judgement whether a thing is an object of pure
practical reason or not does not depend at all on the comparison
with our physical power; and the question is only whether we should
will an action that is directed to the existence of an object, if
the object were in our power; hence the previous question is only as
the moral possibility of the action, for in this case it is not the
object, but the law of the will, that is the determining principle
of the action. The only objects of practical reason are therefore
those of good and evil. For by the former is meant an object
necessarily desired according to a principle of reason; by the
latter one necessarily shunned, also according to a principle of
reason.

If the notion of good is not to be derived from an antecedent
practical law, but, on the contrary, is to serve as its foundation, it
can only be the notion of something whose existence promises pleasure,
and thus determines the causality of the subject to produce it, that
is to say, determines the faculty of desire. Now, since it is
impossible to discern a priori what idea will be accompanied with
pleasure and what with pain, it will depend on experience alone to
find out what is primarily good or evil. The property of the
subject, with reference to which alone this experiment can be made, is
the feeling of pleasure and pain, a receptivity belonging to the
internal sense; thus that only would be primarily good with which
the sensation of pleasure is immediately connected, and that simply
evil which immediately excites pain. Since, however, this is opposed
even to the usage of language, which distinguishes the pleasant from
the good, the unpleasant from the evil, and requires that good and
evil shall always be judged by reason, and, therefore, by concepts
which can be communicated to everyone, and not by mere sensation,
which is limited to individual [subjects] and their susceptibility;
and, since nevertheless, pleasure or pain cannot be connected with any
idea of an object a priori, the philosopher who thought himself
obliged to make a feeling of pleasure the foundation of his
practical judgements would call that good which is a means to the
pleasant, and evil, what is a cause of unpleasantness and pain; for
the judgement on the relation of means to ends certainly belongs to
reason. But, although reason is alone capable of discerning the
connexion of means with their ends (so that the will might even be
defined as the faculty of ends, since these are always determining
principles of the desires), yet the practical maxims which would
follow from the aforesaid principle of the good being merely a
means, would never contain as the object of the will anything good
in itself, but only something good for something; the good would
always be merely the useful, and that for which it is useful must
always lie outside the will, in sensation. Now if this as a pleasant
sensation were to be distinguished from the notion of good, then there
would be nothing primarily good at all, but the good would have to
be sought only in the means to something else, namely, some
pleasantness.

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