Preface
This work is called the Critique of Practical Reason, not of the pure practical reason, although its parallelism with the speculative critique would seem to require the latter term. The reason of this appears sufficiently from the treatise itself. Its business is to show that there is pure practical reason, and for this purpose it criticizes the entire practical faculty of reason. If it succeeds in this, it has no need to criticize the pure faculty itself in order to see whether reason in making such a claim does not presumptuously overstep itself (as is the case with the speculative reason). For if, as pure reason, it is actually practical, it proves its own reality and that of its concepts by fact, and all disputation against the possibility of its being real is futile.
This work is called the Critique of Practical Reason, not the Critique of Pure Practical Reason. This is so, although its parallel with the critique of speculative reason would seem to require the latter title. The treatise itself makes the reason for this sufficiently clear. Its task is to show that there is pure practical reason. For this purpose, it examines the entire practical faculty of reason. If the critique succeeds, it need not examine the pure faculty itself. It need not ask whether reason oversteps its bounds in claiming to be practical, as speculative reason does. For if pure reason is actually practical, it proves its own reality and the reality of its concepts through this fact. All arguments against the possibility of its being real are then futile.
With this faculty, transcendental freedom is also established; freedom, namely, in that absolute sense in which speculative reason required it in its use of the concept of causality in order to escape the antinomy into which it inevitably falls, when in the chain of cause and effect it tries to think the unconditioned. Speculative reason could only exhibit this concept (of freedom) problematically as not impossible to thought, without assuring it any objective reality, and merely lest the supposed impossibility of what it must at least allow to be thinkable should endanger its very being and plunge it into an abyss of scepticism.
This faculty also establishes transcendental freedom, meaning freedom in the absolute sense. Speculative reason needed this freedom in its use of the concept of causality to escape an antinomy. It inevitably falls into this contradiction when it tries to think of the unconditioned in a chain of cause and effect. Speculative reason could only present the concept of freedom as problematic, as something not impossible to think. It could not establish that freedom had any objective reality. It did this only because it had to allow that freedom was at least thinkable. Otherwise, the supposed impossibility of freedom would endanger reason’s very existence and plunge it into an abyss of scepticism.
Inasmuch as the reality of the concept of freedom is proved by an apodeictic law of practical reason, it is the keystone of the whole system of pure reason, even the speculative, and all other concepts (those of God and immortality) which, as being mere ideas, remain in it unsupported, now attach themselves to this concept, and by it obtain consistence and objective reality; that is to say, their possibility is proved by the fact that freedom actually exists, for this idea is revealed by the moral law.
A certain law of practical reason proves that freedom is real. Freedom is therefore the keystone of the whole system of pure reason, including speculative reason. All other concepts, including those of God and immortality, remain unsupported in this system as mere ideas. They now attach themselves to the concept of freedom, which gives them consistency and objective reality. In other words, their possibility is proved by the fact that freedom actually exists. The moral law reveals this idea of freedom.
Freedom, however, is the only one of all the ideas of the speculative reason of which we know the possibility a priori (without, however, understanding it), because it is the condition of the moral law which we know. * The ideas of God and immortality, however, are not conditions of the moral law, but only conditions of the necessary object of a will determined by this law; that is to say, conditions of the practical use of our pure reason. Hence, with respect to these ideas, we cannot affirm that we know and understand, I will not say the actuality, but even the possibility of them. However they are the conditions of the application of the morally determined will to its object, which is given to it a priori, viz., the summum bonum. Consequently in this practical point of view their possibility must be assumed, although we cannot theoretically know and understand it. To justify this assumption it is sufficient, in a practical point of view, that they contain no intrinsic impossibility (contradiction). Here we have what, as far as speculative reason is concerned, is a merely subjective principle of assent, which, however, is objectively valid for a reason equally pure but practical, and this principle, by means of the concept of freedom, assures objective reality and authority to the ideas of God and immortality. Nay, there is a subjective necessity (a need of pure reason) to assume them. Nevertheless the theoretical knowledge of reason is not hereby enlarged, but only the possibility is given, which heretofore was merely a problem and now becomes assertion, and thus the practical use of reason is connected with the elements of theoretical reason. And this need is not a merely hypothetical one for the arbitrary purposes of speculation, that we must assume something if we wish in speculation to carry reason to its utmost limits, but it is a need which has the force of law to assume something without which that cannot be which we must inevitably set before us as the aim of our action.
Freedom, however, is the only idea of speculative reason whose possibility we know a priori, although we do not understand it. We know this because freedom is the condition of the moral law, which we know. * The ideas of God and immortality, however, are not conditions of the moral law. They are only conditions of the necessary object of a will determined by this law. In other words, they are conditions of the practical use of our pure reason. So we cannot claim to know or understand even the possibility of God and immortality, much less their actuality. God and immortality are, however, conditions for the morally determined will to pursue its object, which is given to it a priori. This object is the summum bonum, or highest good. From this practical point of view, we must therefore assume that God and immortality are possible, although we cannot know and understand their possibility theoretically. From a practical point of view, the assumption is justified as long as neither idea contains an intrinsic impossibility or contradiction. For speculative reason, this is merely a subjective principle for accepting these ideas. But the principle is objectively valid for reason that is equally pure but practical. Through the concept of freedom, the principle gives objective reality and authority to the ideas of God and immortality. Indeed, there is a subjective necessity, a need of pure reason, to assume them. Nevertheless, this does not expand our theoretical knowledge. It only establishes their possibility, which was previously merely an open question and now becomes an assertion. In this way, the practical use of reason is connected with the elements of theoretical reason. This need is not merely hypothetical, serving the arbitrary purposes of speculation. It is not simply a need to assume something if we wish to push reason to its utmost limits in speculation. Rather, it is a need with the force of law to assume something without which the aim we must inevitably set before us in acting cannot exist.
* Lest any one should imagine that he finds an inconsistency
here when I call freedom the condition of the moral law, and
hereafter maintain in the treatise itself that the moral law
is the condition under which we can first become conscious
of freedom, I will merely remark that freedom is the ratio
essendi of the moral law, while the moral law is the ratio
cognoscendi of freedom. For had not the moral law been
previously distinctly thought in our reason, we should never
consider ourselves justified in assuming such a thing as
freedom, although it be not contradictory. But were there no
freedom it would be impossible to trace the moral law in
ourselves at all.
It would certainly be more satisfactory to our speculative reason if it could solve these problems for itself without this circuit and preserve the solution for practical use as a thing to be referred to, but in fact our faculty of speculation is not so well provided. Those who boast of such high knowledge ought not to keep it back, but to exhibit it publicly that it may be tested and appreciated. They want to prove: very good, let them prove; and the critical philosophy lays its arms at their feet as the victors. Quid statis? Nolint. Atqui licet esse beatis. As they then do not in fact choose to do so, probably because they cannot, we must take up these arms again in order to seek in the mortal use of reason, and to base on this, the notions of God, freedom, and immortality, the possibility of which speculation cannot adequately prove.
Our speculative reason would surely be more satisfied if it could solve these problems on its own, without this detour. It could then keep the solution for practical use. But our capacity for speculation is not really equal to the task. Those who boast of such lofty knowledge should not keep it to themselves. They should present it publicly so that it can be tested and appreciated. They want to prove their claims? Very well, let them prove them. Critical philosophy will lay down its arms at their feet as victors. Why do they stand idle? They refuse. Yet they could be happy. Since they do not in fact choose to prove their claims, probably because they cannot, we must take up these arms again. We must seek the notions of God, freedom, and immortality in the mortal use of reason and base them on it. Speculation cannot adequately prove that these notions are possible.
Here first is explained the enigma of the critical philosophy, viz.: how we deny objective reality to the supersensible use of the categories in speculation and yet admit this reality with respect to the objects of pure practical reason. This must at first seem inconsistent as long as this practical use is only nominally known. But when, by a thorough analysis of it, one becomes aware that the reality spoken of does not imply any theoretical determination of the categories and extension of our knowledge to the supersensible; but that what is meant is that in this respect an object belongs to them, because either they are contained in the necessary determination of the will a priori, or are inseparably connected with its object; then this inconsistency disappears, because the use we make of these concepts is different from what speculative reason requires. On the other hand, there now appears an unexpected and very satisfactory proof of the consistency of the speculative critical philosophy. For whereas it insisted that the objects of experience as such, including our own subject, have only the value of phenomena, while at the same time things in themselves must be supposed as their basis, so that not everything supersensible was to be regarded as a fiction and its concept as empty; so now practical reason itself, without any concert with the speculative, assures reality to a supersensible object of the category of causality, viz., freedom, although (as becomes a practical concept) only for practical use; and this establishes on the evidence of a fact that which in the former case could only be conceived. By this the strange but certain doctrine of the speculative critical philosophy, that the thinking subject is to itself in internal intuition only a phenomenon, obtains in the critical examination of the practical reason its full confirmation, and that so thoroughly that we should be compelled to adopt this doctrine, even if the former had never proved it at all. *
Here, for the first time, the puzzle of critical philosophy is explained. How can we deny objective reality to the speculative use of the categories beyond the sensible world, yet grant it to the objects of pure practical reason? This must seem inconsistent at first, as long as we know this practical use in name only. But a thorough analysis reveals what this reality means. It does not mean that the categories are theoretically determined or that our knowledge extends beyond the sensible world. Rather, it means that the categories have an object in this respect. This is because they are either contained in the necessary determination of the will a priori or inseparably connected with its object. The inconsistency then disappears, because we use these concepts differently from the way speculative reason requires. On the other hand, an unexpected and very satisfactory proof now appears for the consistency of speculative critical philosophy. That philosophy insisted that objects of experience as such, including our own subject, have the status of phenomena only. At the same time, it insisted that we must suppose things in themselves to underlie these phenomena. Thus, not everything beyond the sensible world was to be regarded as a fiction, or its concept as empty. Now practical reason itself, without any coordination with speculative reason, assures the reality of a supersensible object of the category of causality, namely freedom. It does so, however, only for practical use, as befits a practical concept. In this way, practical reason establishes on the evidence of a fact what speculative reason could only conceive. Speculative critical philosophy teaches a strange but certain doctrine: in inner intuition, the thinking subject is to itself only a phenomenon. The critical examination of practical reason fully confirms this doctrine. It confirms the doctrine so thoroughly that we would be compelled to adopt it even if speculative critical philosophy had never proved it at all. *
* The union of causality as freedom with causality as
rational mechanism, the former established by the moral law,
the latter by the law of nature in the same subject, namely,
man, is impossible, unless we conceive him with reference to
the former as a being in himself, and with reference to the
latter as a phenomenon- the former in pure consciousness,
the latter in empirical consciousness. Otherwise reason
inevitably contradicts itself.
By this also I can understand why the most considerable objections which I have as yet met with against the Critique turn about these two points, namely, on the one side, the objective reality of the categories as applied to noumena, which is in the theoretical department of knowledge denied, in the practical affirmed; and on the other side, the paradoxical demand to regard oneself qua subject of freedom as a noumenon, and at the same time from the point of view of physical nature as a phenomenon in one's own empirical consciousness; for as long as one has formed no definite notions of morality and freedom, one could not conjecture on the one side what was intended to be the noumenon, the basis of the alleged phenomenon, and on the other side it seemed doubtful whether it was at all possible to form any notion of it, seeing that we had previously assigned all the notions of the pure understanding in its theoretical use exclusively to phenomena. Nothing but a detailed criticism of the practical reason can remove all this misapprehension and set in a clear light the consistency which constitutes its greatest merit.
This also helps me understand why the most significant objections I have met so far against the Critique concern two points. First, the objective reality of the categories as applied to noumena is denied in theoretical knowledge but affirmed in practical knowledge. Second, there is the paradoxical demand that we regard ourselves as noumena insofar as we are subjects of freedom. At the same time, we must regard ourselves as phenomena in our own empirical consciousness, from the standpoint of physical nature. These objections arise because, as long as people have no definite concepts of morality and freedom, they cannot tell what is meant by the noumenon underlying the supposed phenomenon. It also seems doubtful whether any concept of this noumenon can be formed at all. After all, we had previously restricted all concepts of the pure understanding in its theoretical use to phenomena. Only a detailed critique of practical reason can remove all this misunderstanding. It can also bring to light the consistency that is its greatest merit.
So much by way of justification of the proceeding by which, in this work, the notions and principles of pure speculative reason which have already undergone their special critical examination are, now and then, again subjected to examination. This would not in other cases be in accordance with the systematic process by which a science is established, since matters which have been decided ought only to be cited and not again discussed. In this case, however, it was not only allowable but necessary, because reason is here considered in transition to a different use of these concepts from what it had made of them before. Such a transition necessitates a comparison of the old and the new usage, in order to distinguish well the new path from the old one and, at the same time, to allow their connection to be observed. Accordingly considerations of this kind, including those which are once more directed to the concept of freedom in the practical use of the pure reason, must not be regarded as an interpolation serving only to fill up the gaps in the critical system of speculative reason (for this is for its own purpose complete), or like the props and buttresses which in a hastily constructed building are often added afterwards; but as true members which make the connexion of the system plain, and show us concepts, here presented as real, which there could only be presented problematically. This remark applies especially to the concept of freedom, respecting which one cannot but observe with surprise that so many boast of being able to understand it quite well and to explain its possibility, while they regard it only psychologically, whereas if they had studied it in a transcendental point of view, they must have recognized that it is not only indispensable as a problematical concept, in the complete use of speculative reason, but also quite incomprehensible; and if they afterwards came to consider its practical use, they must needs have come to the very mode of determining the principles of this, to which they are now so loth to assent. The concept of freedom is the stone of stumbling for all empiricists, but at the same time the key to the loftiest practical principles for critical moralists, who perceive by its means that they must necessarily proceed by a rational method. For this reason I beg the reader not to pass lightly over what is said of this concept at the end of the Analytic.
This explains why, in this work, I sometimes reexamine the concepts and principles of pure speculative reason. These have already undergone their own critical examination. In other cases, this would not fit the systematic process of establishing a science. Matters already settled should only be cited, not discussed again. Here, however, reexamination was not only permissible but necessary. For reason is now being considered as it moves from its earlier use of these concepts to a different one. This transition requires us to compare the old and new uses. We must clearly distinguish the new path from the old one and, at the same time, show their connection. These considerations include those that return to the concept of freedom in the practical use of pure reason. They must not be regarded as additions meant only to fill gaps in the critical system of speculative reason. For that system is complete for its own purpose. Nor are they like the supports often added later to a hastily constructed building. Rather, they are genuine parts of the system. They make its connections clear and show us concepts as real that could only be presented there as problematic. This remark applies especially to the concept of freedom. It is surprising that so many people claim they can understand freedom quite well and explain how it is possible. Yet they consider freedom only from a psychological point of view. Had they studied it from a transcendental point of view, they would have recognized two things. Freedom is indispensable as a problematic concept in the complete use of speculative reason. But it is also quite incomprehensible. And if they had then considered its practical use, they would necessarily have arrived at the very way of determining the principles of that use. This is the way they are now so reluctant to accept. The concept of freedom is a stumbling block for all empiricists. At the same time, it is the key to the highest practical principles for critical moralists. Through it, they see that they must proceed by a rational method. For this reason, I ask the reader not to pass lightly over what is said about freedom at the end of the Analytic.
I must leave it to those who are acquainted with works of this kind to judge whether such a system as that of the practical reason, which is here developed from the critical examination of it, has cost much or little trouble, especially in seeking not to miss the true point of view from which the whole can be rightly sketched. It presupposes, indeed, the Fundamental Principles of the Metaphysic of Morals, but only in so far as this gives a preliminary acquaintance with the principle of duty, and assigns and justifies a definite formula thereof; in other respects it is independent. * It results from the nature of this practical faculty itself that the complete classification of all practical sciences cannot be added, as in the critique of the speculative reason. For it is not possible to define duties specially, as human duties, with a view to their classification, until the subject of this definition (viz., man) is known according to his actual nature, at least so far as is necessary with respect to duty; this, however, does not belong to a critical examination of the practical reason, the business of which is only to assign in a complete manner the principles of its possibility, extent, and limits, without special reference to human nature. The classification then belongs to the system of science, not to the system of criticism.
I must leave it to those familiar with works of this kind to judge how much trouble this system has cost. It is a system of practical reason, developed here through a critical examination of practical reason. In particular, readers must judge the trouble involved in finding the right point of view from which to outline the whole system. The system does presuppose the Fundamental Principles of the Metaphysic of Morals. But it does so only because that work gives a preliminary understanding of the principle of duty and states and justifies a definite formula for it. In other respects, the present system is independent. * The nature of the practical faculty itself means that a complete classification of all practical sciences cannot be added here, as it can be in the critique of speculative reason. For we cannot define duties specifically as human duties in order to classify them until we know the actual nature of human beings, at least as far as duty requires. But that knowledge does not belong to a critical examination of practical reason. The task of such an examination is only to state fully the principles governing the possibility, scope, and limits of practical reason, without special reference to human nature. Classification, then, belongs to the system of science, not to the system of criticism.
* A reviewer who wanted to find some fault with this work
has hit the truth better, perhaps, than he thought, when he
says that no new principle of morality is set forth in it,
but only a new formula. But who would think of introducing a
new principle of all morality and making himself as it were
the first discoverer of it, just as if all the world before
him were ignorant what duty was or had been in thorough-
going error? But whoever knows of what importance to a
mathematician a formula is, which defines accurately what is
to be done to work a problem, will not think that a formula
is insignificant and useless which does the same for all
duty in general.
In the second part of the Analytic I have given, as I trust, a sufficient answer to the objection of a truth-loving and acute critic * of the Fundamental Principles of the Metaphysic of Morals- a critic always worthy of respect- the objection, namely, that the notion of good was not established before the moral principle, as he thinks it ought to have been. ** I have also had regard to many of the objections which have reached me from men who show that they have at heart the discovery of the truth, and I shall continue to do so (for those who have only their old system before their eyes, and who have already settled what is to be approved or disapproved, do not desire any explanation which might stand in the way of their own private opinion.)
In the second part of the Analytic, I believe I have adequately answered an objection from an insightful, truth-loving critic * of the Fundamental Principles of the Metaphysic of Morals. This critic always deserves respect. He objects that I did not establish the concept of good before the moral principle, as he thinks I should have done. ** I have also considered many objections from people who show a genuine concern for finding the truth. I will continue to do so (because those who see only their old system, and have already decided what to approve or disapprove, do not want explanations that might challenge their own private opinions).
* [See Kant's "Das mag in der Theoric ricktig seyn," etc.
Werke, vol. vii, p. 182.]
** It might also have been objected to me that I have not
first defined the notion of the faculty of desire, or of the
feeling of Pleasure, although this reproach would be unfair,
because this definition might reasonably be presupposed as
given in psychology. However, the definition there given
might be such as to found the determination of the faculty
of desire on the feeling of pleasure (as is commonly done),
and thus the supreme principle of practical philosophy would
be necessarily made empirical, which, however, remains to be
proved and in this critique is altogether refuted. It will,
therefore, give this definition here in such a manner as it
ought to be given, in order to leave this contested point
open at the beginning, as it should be. LIFE is the faculty
a being has of acting according to laws of the faculty of
desire. The faculty of DESIRE is the being's faculty of
becoming by means of its ideas the cause of the actual
existence of the objects of these ideas. PLEASURE is the
idea of the agreement of the object, or the action with the
subjective conditions of life, i.e., with the faculty of
causality of an idea in respect of the actuality of its
object (or with the determination of the forces of the
subject to action which produces it). I have no further need
for the purposes of this critique of notions borrowed from
psychology; the critique itself supplies the rest. It is
easily seen that the question whether the faculty of desire
is always based on pleasure, or whether under certain
conditions pleasure only follows the determination of
desire, is by this definition left undecided, for it is
composed only of terms belonging to the pure understanding,
i.e., of categories which contain nothing empirical. Such
precaution is very desirable in all philosophy and yet is
often neglected; namely, not to prejudge questions by
adventuring definitions before the notion has been
completely analysed, which is often very late. It may be
observed through the whole course of the critical philosophy
(of the theoretical as well as the practical reason) that
frequent opportunity offers of supplying defects in the old
dogmatic method of philosophy, and of correcting errors
which are not observed until we make such rational use of
these notions viewing them as a whole.
When we have to study a particular faculty of the human mind in its sources, its content, and its limits; then from the nature of human knowledge we must begin with its parts, with an accurate and complete exposition of them; complete, namely, so far as is possible in the present state of our knowledge of its elements. But there is another thing to be attended to which is of a more philosophical and architectonic character, namely, to grasp correctly the idea of the whole, and from thence to get a view of all those parts as mutually related by the aid of pure reason, and by means of their derivation from the concept of the whole. This is only possible through the most intimate acquaintance with the system; and those who find the first inquiry too troublesome, and do not think it worth their while to attain such an acquaintance, cannot reach the second stage, namely, the general view, which is a synthetical return to that which had previously been given analytically. It is no wonder then if they find inconsistencies everywhere, although the gaps which these indicate are not in the system itself, but in their own incoherent train of thought.
When we study a particular faculty of the human mind, we must examine its sources, content, and limits. Given the nature of human knowledge, we must begin with its parts and describe them accurately and completely. The description must be complete, at least as far as our present knowledge of those elements allows. But there is another task to consider, one that is more philosophical and concerned with the structure of the whole. We must correctly grasp the idea of the whole. From there, we must use pure reason to see how all the parts relate to one another by deriving them from the concept of the whole. This is possible only through a very close acquaintance with the system. Some people find the first inquiry too troublesome and do not think such familiarity is worth the effort. They cannot reach the second stage, the general view. This view brings together what the earlier analysis had separated into parts. It is no wonder, then, that they find inconsistencies everywhere. Yet the gaps these inconsistencies point to are not in the system itself, but in their own incoherent reasoning.
I have no fear, as regards this treatise, of the reproach that I wish to introduce a new language, since the sort of knowledge here in question has itself somewhat of an everyday character. Nor even in the case of the former critique could this reproach occur to anyone who had thought it through and not merely turned over the leaves. To invent new words where the language has no lack of expressions for given notions is a childish effort to distinguish oneself from the crowd, if not by new and true thoughts, yet by new patches on the old garment. If, therefore, the readers of that work know any more familiar expressions which are as suitable to the thought as those seem to me to be, or if they think they can show the futility of these thoughts themselves and hence that of the expression, they would, in the first case, very much oblige me, for I only desire to be understood: and, in the second case, they would deserve well of philosophy. But, as long as these thoughts stand, I very much doubt that suitable and yet more common expressions for them can be found. *
I do not fear being accused of trying to introduce a new language in this treatise. The kind of knowledge it concerns is itself somewhat familiar from everyday life. Nor could anyone have made this charge against the earlier critique if they had thought it through rather than merely leafed through it. When a language already has words for certain ideas, inventing new ones is a childish way to stand out from the crowd. It is an attempt to stand out, if not by offering new and true thoughts, then by patching old clothes with new fabric. If readers of the earlier critique know more familiar expressions that fit the ideas as well as mine seem to me to do, they would do me a great favor by suggesting them. I want only to be understood. Or, if they think they can show that the ideas themselves are worthless, and therefore that the expressions are worthless too, they would do philosophy a service. But as long as these ideas stand, I very much doubt that more familiar expressions can be found that fit them as well. *
* I am more afraid in the present treatise of occasional
misconception in respect of some expressions which I have
chosen with the greatest care in order that the notion to
which they point may not be missed. Thus, in the table of
categories of the Practical reason under the title of
Modality, the Permitted, and forbidden (in a practical
objective point of view, possible and impossible) have
almost the same meaning in common language as the next
category, duty and contrary to duty. Here, however, the
former means what coincides with, or contradicts, a merely
possible practical precept (for example, the solution of all
problems of geometry and mechanics); the latter, what is
similarly related to a law actually present in the reason;
and this distinction is not quite foreign even to common
language, although somewhat unusual. For example, it is
forbidden to an orator, as such, to forge new words or
constructions; in a certain degree this is permitted to a
poet; in neither case is there any question of duty. For if
anyone chooses to forfeit his reputation as an orator, no
one can prevent him. We have here only to do with the
distinction of imperatives into problematical, assertorial,
and apodeictic. Similarly in the note in which I have pared
the moral ideas of practical perfection in different
philosophical schools, I have distinguished the idea of
wisdom from that of holiness, although I have stated that
essentially and objectively they are the same. But in that
place I understand by the former only that wisdom to which
man (the Stoic) lays claim; therefore I take it subjectively
as an attribute alleged to belong to man. (Perhaps the
expression virtue, with which also the Stoic made great
show, would better mark the characteristic of his school.)
The expression of a postulate of pure practical reason might
give most occasion to misapprehension in case the reader
confounded it with the signification of the postulates in
pure mathematics, which carry apodeictic certainty with
them. These, however, postulate the possibility of an
action, the object of which has been previously recognized a
priori in theory as possible, and that with perfect
certainty. But the former postulates the possibility of an
object itself (God and the immortality of the soul) from
apodeictic practical laws, and therefore only for the
purposes of a practical reason. This certainty of the
postulated possibility then is not at all theoretic, and
consequently not apodeictic; that is to say, it is not a
known necessity as regards the object, but a necessary
supposition as regards the subject, necessary for the
obedience to its objective but practical laws. It is,
therefore, merely a necessary hypothesis. I could find no
better expression for this rational necessity, which is
subjective, but yet true and unconditional.
In this manner, then, the a priori principles of two faculties of the mind, the faculty of cognition and that of desire, would be found and determined as to the conditions, extent, and limits of their use, and thus a sure foundation be paid for a scientific system of philosophy, both theoretic and practical.
In this way, we would identify the a priori principles of two mental faculties: cognition and desire. We would determine the conditions, scope, and limits of their use. This would lay a secure foundation for a scientific system of philosophy, both theoretical and practical.
Nothing worse could happen to these labours than that anyone should make the unexpected discovery that there neither is, nor can be, any a priori knowledge at all. But there is no danger of this. This would be the same thing as if one sought to prove by reason that there is no reason. For we only say that we know something by reason, when we are conscious that we could have known it, even if it had not been given to us in experience; hence rational knowledge and knowledge a priori are one and the same. It is a clear contradiction to try to extract necessity from a principle of experience (ex pumice aquam), and to try by this to give a judgement true universality (without which there is no rational inference, not even inference from analogy, which is at least a presumed universality and objective necessity). To substitute subjective necessity, that is, custom, for objective, which exists only in a priori judgements, is to deny to reason the power of judging about the object, i.e., of knowing it, and what belongs to it. It implies, for example, that we must not say of something which often or always follows a certain antecedent state that we can conclude from this to that (for this would imply objective necessity and the notion of an a priori connexion), but only that we may expect similar cases (just as animals do), that is that we reject the notion of cause altogether as false and a mere delusion. As to attempting to remedy this want of objective and consequently universal validity by saying that we can see no ground for attributing any other sort of knowledge to other rational beings, if this reasoning were valid, our ignorance would do more for the enlargement of our knowledge than all our meditation. For, then, on this very ground that we have no knowledge of any other rational beings besides man, we should have a right to suppose them to be of the same nature as we know ourselves to be: that is, we should really know them. I omit to mention that universal assent does not prove the objective validity of a judgement (i.e., its validity as a cognition), and although this universal assent should accidentally happen, it could furnish no proof of agreement with the object; on the contrary, it is the objective validity which alone constitutes the basis of a necessary universal consent.
Nothing worse could happen to these efforts than the unexpected discovery that there is no a priori knowledge and cannot be any. But there is no danger of that. It would be like trying to prove by reason that there is no reason. We say that we know something by reason only when we are aware that we could have known it without experience. So rational knowledge and a priori knowledge are one and the same. It is a clear contradiction to try to draw necessity from a principle of experience (ex pumice aquam). It is equally contradictory to try to give a judgment true universality in this way. Without true universality, there can be no rational inference, not even an inference from analogy. An inference from analogy presumes at least universality and objective necessity. To replace objective necessity with subjective necessity, or habit, is to deny reason the power to judge an object. In other words, it denies reason the power to know an object and what belongs to it. Objective necessity exists only in a priori judgments. Suppose, for example, that something often or always follows a certain prior state. We must then not say that we can infer the later event from the earlier state. Such an inference would imply objective necessity and the idea of an a priori connection. We could say only that we may expect similar cases, just as animals do. In other words, we would reject the very idea of cause as false and a mere delusion. Someone might try to remedy this lack of objective, and therefore universal, validity. They might say that we see no reason to attribute any other kind of knowledge to other rational beings. If this reasoning were valid, our ignorance would do more to increase our knowledge than all our reflection. For then, simply because we know of no rational beings besides humans, we would be entitled to suppose that they have the same nature we know ourselves to have. In other words, we would actually know them. I will not dwell on the fact that universal agreement does not prove the objective validity of a judgment, its validity as knowledge. Even if everyone happened to agree, that agreement could not prove that the judgment matches its object. On the contrary, only objective validity can provide the basis for a necessary universal agreement.
Hume would be quite satisfied with this system of universal empiricism, for, as is well known, he desired nothing more than that, instead of ascribing any objective meaning to the necessity in the concept of cause, a merely subjective one should be assumed, viz., custom, in order to deny that reason could judge about God, freedom, and immortality; and if once his principles were granted, he was certainly well able to deduce his conclusions therefrom, with all logical coherence. But even Hume did not make his empiricism so universal as to include mathematics. He holds the principles of mathematics to be analytical; and if his were correct, they would certainly be apodeictic also: but we could not infer from this that reason has the faculty of forming apodeictic judgements in philosophy also- that is to say, those which are synthetical judgements, like the judgement of causality. But if we adopt a universal empiricism, then mathematics will be included.
Hume would be quite satisfied with this system of universal empiricism. As is well known, he wanted the necessity in the concept of cause to have a merely subjective meaning, namely custom. He wanted to give it no objective meaning, so that he could deny that reason could judge about God, freedom, and immortality. Once his principles were granted, he was certainly able to derive his conclusions from them with complete logical consistency. But even Hume did not extend his empiricism to include mathematics. He held that the principles of mathematics are analytic. If he were correct, those principles would certainly also be apodeictic, or necessarily true. But we could not infer from this that reason can also make apodeictic judgments in philosophy. Philosophical judgments, like the judgment of causality, are synthetic. But if we adopt universal empiricism, it will include mathematics.
Now if this science is in contradiction with a reason that admits only empirical principles, as it inevitably is in the antinomy in which mathematics prove the infinite divisibility of space, which empiricism cannot admit; then the greatest possible evidence of demonstration is in manifest contradiction with the alleged conclusions from experience, and we are driven to ask, like Cheselden's blind patient, "Which deceives me, sight or touch?" (for empiricism is based on a necessity felt, rationalism on a necessity seen). And thus universal empiricism reveals itself as absolute scepticism. It is erroneous to attribute this in such an unqualified sense to Hume, * since he left at least one certain touchstone (which can only be found in a priori principles), although experience consists not only of feelings, but also of judgements.
Now suppose this science contradicts a reason that accepts only empirical principles. It inevitably does so in the antinomy where mathematics proves that space is infinitely divisible, which empiricism cannot accept. Then the strongest possible evidence of demonstration plainly contradicts the supposed conclusions drawn from experience. We are forced to ask, like Cheselden's blind patient, "Which deceives me, sight or touch?" (Empiricism rests on a necessity that is felt, while rationalism rests on a necessity that is seen.) Thus universal empiricism reveals itself as absolute scepticism. It is wrong to attribute absolute scepticism so unconditionally to Hume, * since he left at least one certain test (which can be found only in a priori principles), although experience consists not only of feelings but also of judgments.
* Names that designate the followers of a sect have always
been accompanied with much injustice; just as if one said,
"N is an Idealist." For although he not only admits, but
even insists, that our ideas of external things have actual
objects of external things corresponding to them, yet he
holds that the form of the intuition does not depend on them
but on the human mind.
However, as in this philosophical and critical age such empiricism can scarcely be serious, and it is probably put forward only as an intellectual exercise and for the purpose of putting in a clearer light, by contrast, the necessity of rational a priori principles, we can only be grateful to those who employ themselves in this otherwise uninstructive labour.
However, in this philosophical and critical age, such empiricism can hardly be meant seriously. It is probably offered only as an intellectual exercise, to show more clearly, by contrast, the necessity of rational a priori principles. So we can only be grateful to those who undertake this otherwise uninformative work.