<p1> [Bvii] Preface to the Second Edition
This book is concerned with the sorts of knowledge which are the business of reason. You can easily tell whether or not such knowledge has developed along the sure path of a science, by considering how well it has succeeded. Suppose the outcome is as follows:
If so, you can be certain that an academic discipline like this is still far from having entered upon the sure path of a science — it is merely groping around. It will already be a service to reason if we can possibly discover this path, even if we have to abandon many of its traditional objectives as futile, since they were adopted without reflection.
<p2> [Bviii] Logic has followed this sure path right from antiquity till now. This is obvious because it has never had to take a step backwards since Aristotle. You might say that it has been improved by the removal of some unnecessary subtleties, and by the clearer definition of its doctrines — but these are more questions of style, than of its certainty as a science. It is also remarkable that, to the present day, logic has not been able to take any step forward, and therefore to all appearance it seems to be closed and complete.
<p3> Some modern logicians have thought to extend it, by adding:
But this is due to their ignorance of the essential nature of this science. It is not an extension but a deformation of the sciences if you allow them to cross each other’s boundaries. The boundaries of logic are defined with absolute precision. It is a science [Bix] whose sole function is to provide a complete enumeration and a strict proof of the formal rules of all thought:
<p4> The advantage which has made logic so successful consists simply in its limitedness, which allows it — indeed, requires it — to leave out of account all objects of knowledge, and the differences between them. So in logic, the understanding is concerned with nothing other than itself and its form. Obviously it must be far more difficult for reason to enter upon the sure path of a science, since it has to deal with objects as well as just itself. Hence logic is only a preparatory discipline — the forecourt to the sciences, so to speak. As for actual knowledge, a logic is certainly required for establishing whether it is true or false; but the knowledge itself can be acquired only through the particular sciences, in the strict and objective sense.
<p5> In so far as reason has a role to play in the sciences, something must be known in them apriori. This knowledge can relate to its object in two ways:
The first is the theoretical knowledge of reason; the second is the practical. The pure part is that in which reason determines its object completely apriori. In both cases, the pure part, however much or however little it may contain, must be dealt with first and separately. It must not be mixed up with whatever comes from other sources. It is bad financial management if you blindly spend whatever income you receive. If you later get into financial difficulties, you need to be able to distinguish which part of your expenditure is covered by your income, and which must be cut back.
<p6> Mathematics and physics are the two sciences through which reason achieves theoretical knowledge, because they must determine their objects a priori. Mathematics does this absolutely purely; physics does this at least partly purely, but also using criteria drawn from sources of knowledge other than reason itself.
<p7> Mathematics has proceeded along the sure path of a science, ever since the earliest time the history of human reason reaches back to, among that amazing race, the Greeks. However, you should not think that this was as easy for mathematics as it was for logic. In the case of logic, reason only had to deal with itself in order to hit upon that royal road [Bxi] — or rather to construct that road from its own resources. Far from being easy, I believe that for a long time mathematics was stuck at the stage of groping around, especially among the Egyptians. The change is to be ascribed to a revolution, brought about by the brain-wave of a single man. The project he thought up meant that the necessary way forward could no longer be missed, and the sure path of a science was entered upon and signposted for all time and to an infinite distance.
<p8> This revolution in our way of thinking was much more important than the discovery of the passage round the Cape of Good Hope. Yet its history, and that of the inspired person who brought it about, has not been preserved. Diogenes Laertius names the reputed discoverers of the most insignificant items of geometrical demonstration — even ones which are generally accepted as not needing any proof at all. However, the legendary account he has handed down to us shows that the memory of the revolution which was brought about by the first hint of the discovery of this new path must have seemed so important to mathematicians as to be unforgettable.
<p9> A light dawned on the first person to demonstrate the properties of an isosceles triangle, whether it was Thales, or someone with a different name. He discovered that [Bxii] what he had to do was not to investigate what he saw in the figure, nor even to investigate the pure concept of the figure, and learn what its properties were from its concept. Instead, he had to bring out what he himself had thought into the figure apriori in accordance with concepts, and had represented to himself by constructing it. He also discovered that, in order to be certain that he knew something apriori, he must not attribute to the object of his knowledge anything which did not follow necessarily from what he himself had injected into it in accordance with its concept.
<p10> Natural science took much longer to find the highway of science. It is only about a century and half since the programme of that highly original thinker, Francis Bacon, initiated the discovery of the highway, or at least provided new encouragement to those who were already on the track of it. This can equally be described as a sudden revolution in the way we think. In what follows, I shall consider natural science only in so far as it depends on empirical principles.
<p11> Galileo rolled balls of a weight chosen by himself down an inclined plane. Torricelli made air bear a weight which he had previously calculated to be equal to that of a column of water already known to him. More recently, Stahl turned metal into calx and calx back into metal, [Bxiii] by taking something out and then putting it back again.*
[*Here I am not following the exact course of the history of the experimental method, since its first beginnings are not fully known.]
When they did these things, a light dawned on all students of nature. They grasped that reason has insight only into what it produces itself on the basis of its own plan. Reason must lead the way, with principles of judgment based on unchanging laws, and it must compel nature to answer its questions. It must not let itself be strung along by nature alone, as if in a baby-walker. Random observations made without a previously thought-out plan can never hang together so as to result in a necessary law — yet this is what reason looks for and needs.
<p12> In order to be taught by nature, reason must approach it with:
However, reason should not learn from nature like a schoolchild, who merely regurgitates whatever the teacher wants, but like an authoritative judge, who compels the witnesses to answer the questions he asks them.
<p13> So even physical science owes this revolution in its way of thinking, which has proved so fruitful, to a single inspired idea. [Bxiv] This is that, when there are things which reason cannot know through its own resources, but only by learning from nature, it must not simply ascribe these things to nature, but instead it must search them out on the basis of what reason itself has put into nature. This is how natural science was first brought onto the sure path of a science, after so many centuries of mere groping around.
<p14> Metaphysics is a wholly distinct branch of the theoretical knowledge of reason, in that it rises completely above learning from experience. It depends on concepts alone, and, unlike mathematics, it does not depend on applying concepts to intuition. So in metaphysics, reason itself must be its own pupil. However, it has not yet had the good fortune to enter the sure path of a science, even though it is older than all the other disciplines, and would remain even if the rest of them together were to be completely gobbled up in the maw of an all-destroying collapse of civilisation.
<p15> In metaphysics, reason is continually brought to an impasse, even when the laws it wants to have apriori insight into (and apriori insight is what it claims) are confirmed by the most everyday experience. Time and time again we have to turn back, because we find that the path does not lead where we want. Again, there is no agreement among metaphysicians in what they assert. [Bxv] Indeed, there is so much disagreement, that metaphysics seems more like a battleground which has been specially designed for people to practise their skills in war games. In this battleground, none of the combatants have ever managed to gain the least bit of ground, or at least to hold it permanently if they have had a victory. So there can be no doubt that the method of metaphysics has up to now been no more than a groping around, and, what is worst of all, a groping around among mere concepts.
<p16> But why has metaphysics not been able to find the sure path of a science? Perhaps it is impossible. If so, then why has nature plagued our reason with an unrelenting urge to discover this path, as one of reason’s most important concerns? Even worse, what little justification we have to trust our reason, if, in one of the most important areas of our search after knowledge, it does not merely abandon us, but jollies us along with illusory hopes, and finally betrays us! Or is it that we have merely failed to find the path so far? If so, what evidence is there to justify any optimism that, if we renew the search, we will be any more successful than our predecessors?
<p17> The key feature in the success of mathematics and natural science is that they arrived at their present state through a one-off revolution. [Bxvi] I think we should take them as an example, and reflect on what was essential about the change in the way of thinking which made them so successful. At least as an experiment, we should try imitating them, in so far as they are analogous to metaphysics as systems of knowledge based on reason.
<p18> Until now, it has been assumed that all our knowledge must accommodate itself to its objects. However, on this assumption, all attempts to find out anything about the objects of our knowledge apriori through concepts have been unsuccessful — at least anything which would extend our knowledge. So let us see whether we might not make better progress towards fulfilling the objectives of metaphysics by assuming instead that objects must accommodate themselves to our knowledge. This already fits better with what we want, namely the possibility of an apriori knowledge of objects, which establishes something about them before they are given to us.
<p19> Here it is the same as with the first thoughts of Copernicus. He made little progress in explaining the motions of the heavenly bodies on the assumption that they all revolved round the observer. So he wondered if he might not make better progress if he let the observer revolve, and left the stars at rest. In metaphysics, [Bxvii] you can make a similar thought experiment about the intuition of objects. If intuition must accommodate itself to the nature of the object, I do not see how you can know anything about it apriori. But if the object (as object of the senses) accommodates itself to the nature of our faculty of intuition, then I can easily conceive that such knowledge is possible.
<p20> If these intuitions are to become knowledge, I cannot leave them as they are, but I must turn them into representations by referring them to something as their object, and determining the object through these representations. I can therefore make one of two assumptions:
If I make the first assumption, then I am back in the same difficulty as to how I can know anything about objects apriori. If I make the second assumption, I immediately see an easier way out. Experience is itself a kind of knowledge, which requires understanding; and I must therefore presuppose that the rules of understanding are in me before any objects are given to me, and hence apriori. These rules are encapsulated in apriori concepts, to which all objects of experience must [Bxviii] necessarily accommodate themselves, and with which they must be in harmony.
<p21> Then there are objects which can be thought only through reason (and indeed necessarily so), and which cannot be given in experience at all — at least not in the way that reason thinks them. It must be possible to think such objects, and the attempts at thinking them will later provide an excellent test for the validity of the new method of thinking I have adopted, namely that we can know of things apriori only what we ourselves put into them.*
[<p22> *This method, which is modelled on that of scientific research, consists in looking for the elements of pure reason in what can be confirmed or rejected through an experiment. Now propositions of pure reason, especially when they venture beyond the limits of any possible experience, are not testable by any experiment on their objects (unlike the situation in natural science). Here we are dealing with concepts and axioms, which we assume apriori. All we can do is to set them up so that the very same objects can be considered from two different points of view:
Now, this experiment will show decisively that the above distinction is correct, if it turns out that:
<p23> This new approach succeeds as hoped, and it promises metaphysics the sure path of a science in its first part — namely the part which deals with apriori concepts for which experience can provide appropriately corresponding objects. [Bxix] For this changed way of thinking can give a complete explanation of how apriori knowledge is possible. What is more, it can provide sufficient proofs of the laws which lie apriori at the very basis of nature (that is, nature considered as the totality of objects of experience). Both of these were impossible using the method which has prevailed up till now.
<p24> However, this deduction of our capacity for apriori knowledge in the first part of metaphysics results in a surprising outcome, which seems very damaging to the whole purpose of the second part of metaphysics. The outcome is that we can never use our capacity for apriori knowledge to go beyond the limits of possible experience — despite the fact that this is precisely the essential objective of the science of metaphysics.
<p25> [Bxx] But this constitutes precisely the experiment of cross-checking the truth of the outcome of that first assessment of our rational apriori knowledge, namely that it only applies to appearances, whereas the thing in itself, while actual for itself, remains unknown to us. For what necessarily drives us to go beyond the limits of experience and all appearances is the unconditioned, which reason necessarily and rightly demands in the thing in itself for everything which is conditioned, thus bringing to an end the series of conditions. Now if we suppose that our experiential knowledge accommodates itself to objects as things in themselves, then it emerges that the unconditioned cannot be thought at all without contradiction. On the other hand, the contradiction disappears if we suppose that our representation of things as they are given to us does not accommodate itself to them as things in themselves, but instead these objects, as appearances, accommodate themselves to our way of representing them. Consequently, the unconditioned cannot be found in things as we know them (as they are given to us), but rather in things as we do not know them (as things in themselves). So what we originally undertook merely as an experiment turns out to have been [Bxxi] established.*
[<p26> *This experiment of pure reason is very similar to what chemists sometimes call the test of ‘reduction’, or more generally the ‘synthetic method’. The analysis of the metaphysician divides pure apriori knowledge into two very dissimilar doctrines: that of things as appearances, and that of things in themselves. The dialectic connects them together again into a coherent whole through the necessary rational idea of the unconditioned. It turns out that this coherence could only emerge through that distinction, which is therefore the true one.]
<p27> So speculative reason has been denied any progress in this realm which lies beyond the senses. It now remains to explore whether the knowledge of practical reason might not include data for determining the transcendent rational concept of the unconditioned. This way it might fulfil the desire of metaphysics to get beyond the bounds of all possible experience, by means of apriori knowledge which is possible for us — though only in the practical function of reason. Through the above method, speculative reason has at least made a space for such an extension of our knowledge, even though it has had to leave it completely empty. So we are still at liberty — indeed, we are urged by reason itself — to fill this space if we can, by means of the [Bxxii] practical data of reason.*
[<p28> *Similarly, the fundamental laws of the motion of the heavenly bodies gave definitive certainty to what Copernicus originally assumed merely as a hypothesis. At the same time, they proved the existence of the invisible force (Newtonian attraction) which binds the universe together. This force would never have been discovered if Copernicus had not dared to look for the motions as observed, not in the objects in the sky, but in the person observing them — contrary to what our senses tell us, yet true. Like the Copernican hypothesis, in this Preface I propose a reversal in our way of thinking merely as a hypothesis, which will be carried forward in the body of the Critique. In the Critique itself, this reversal will not be treated hypothetically, but it will be proved with absolute certainty from the nature of our representations of space and time, and from the foundational concepts of the understanding. I merely want to point out that the first attempts at such a reversal in thinking are always hypothetical.]
<p29> The job of this critique of pure speculative reason is the experiment of turning the traditional procedure of metaphysics upside down. In this way, I shall undertake a complete revolution in metaphysics, following the example of the geometrician and the natural scientist. The Critique is a treatise on method, not a systematic exposition of the science of metaphysics itself. However, it establishes a complete outline of this science, both as to its limits, and as to [Bxxiii] its whole internal structure.
<p30> It is peculiar to pure speculative reason that it can and should establish a complete preliminary outline for a system of metaphysics. It has two means of doing this:
The first is possible because, in apriori knowledge, nothing can be attributed to the object which the thinking subject does not derive from itself. The second is possible because, as far as the principles of knowledge are concerned, pure speculative reason is a completely separate and self-subsistent unity. As in an organism, every part exists for the sake of all the others, and all for the sake of each individual. No principle can be accepted as certain in just one connection, unless its holistic connectedness with the whole sphere of pure reason has also been investigated.
<p31> Consequently, metaphysics also has another rare advantage, not enjoyed by any other rational science which has to do with objects. (It is shared by logic — but logic is concerned only with the form of thought in general.) The advantage is that, if this Critique brings metaphysics onto the sure path of a science, then it can have complete coverage of all the knowledge that falls within its territory. [Bxxiv] Metaphysics is concerned merely with principles, and with the limitations to their application which are determined by the principles themselves. So it can bring its work to completion, and bequeath it to posterity as a fixed asset which will never be increased. In fact, as a foundational science, it has a duty to be complete, and it must be possible to say of it: ‘Consider nothing done, as long as anything remains to be done.’
<p32> But, you will ask, what sort of treasure is this that I am thinking of bequeathing to posterity? What is the worth of a metaphysics which has been purified by such criticism, and thereby established for all time? On a quick glance at this work, you might think that it had merely a negative use, telling us never to risk taking speculative reason beyond the bounds of experience. And this is in fact its first use. But this use becomes positive as soon as you realise that the axioms with which speculative reason ventures beyond its limits do not in fact extend the use of reason, but, if you consider things more closely, inevitably have the effect of restricting it. This is because the axioms essentially belong to sensibility, and they actually threaten to expand the limits of sensibility [Bxxv] to include everything, and thus completely supplant the practical use of pure reason.
<p33> Hence a critique which limits the speculative use of reason is to that extent indeed negative. But in that it thereby removes an obstacle which limits, or even threatens to obliterate the practical use of reason, it is in fact of positive and very important use. This is provided you are convinced that there is an absolutely necessary use of pure reason (namely the moral), in which it inevitably extends itself beyond the limits of sensibility. It needs no assistance from speculative reason to do this; yet it must be secure from its opposition, so that reason does not fall into contraction with itself. To deny that this function of the Critique is a positive use would be like saying that the police are of no positive use, because their main job is only to prevent the violence which citizens fear from each other, so that each can carry on their business in peace and safety.
<p34> In the analytic part of the Critique, I shall show:
<p35> From this it obviously follows that all speculative knowledge of reason (even if it is only possible knowledge) is limited to mere objects of experience. However, it must always be borne in mind — and this is something important to note — that even though we cannot know these objects as things in themselves, yet we must at least be able to think them as things in themselves.*
[<p36> *In order to know an object, I must be able to prove its possibility — whether from its actuality as attested by experience, or apriori through reason. But I can think whatever I want, provided only that I do not contradict myself. It is enough for my concept to be a possible thought, even if I cannot answer for whether or not there is also an object corresponding to this particular possibility among the total of all possibilities. The possibility of the concept is merely logical, and something more is required to attribute objective validity, or real possibility, to such a concept. But this something more does not necessarily have to be looked for in theoretical sources of knowledge, since it can also be found in practical ones.]
<p37> For otherwise there would follow the absurd proposition that there was [Bxxvii] an appearance without that which appeared.
<p38> My Critique has shown that it is necessary to distinguish between things as objects of experience, and the very same things as things in themselves. Now let us see what follows if we suppose that this distinction had not been made. On this supposition, absolutely everything would be an efficient cause governed by the axiom of causality, and subject to the determinism of mechanistic nature. Thus I would not, without falling into a manifest contradiction, be able to say of one and the same being, for example the human soul, that its will is free, and yet at the same time subject to the determinism of nature — i.e. not free. This is because I have used the word ‘soul’ in exactly the same sense in both propositions, namely as a thing in general, i.e. as a thing in itself. Without a prior critique, I could not have used it in any other way.
<p39> In the Critique, I have argued that ‘object’ must be taken in two senses, namely as an appearance, and as a thing in itself. And in the Deduction of the Concepts of the Understanding, I have argued that the axiom of causality applies to things only in the first sense, namely in so far as they are objects of experience; but the same things taken in the second sense are not subject to the axiom. If I am right, then there is no contradiction in thinking of one and the same will [Bxxviii] as necessarily subject to the law of nature, and to that extent not free, in the realm of appearance (in its observable actions); and on the other hand, in thinking of it as not subject to that law, and hence as free, in so far as it belongs to a thing in itself.
<p40> Now I cannot know my soul considered as a thing in itself through any speculative reason, still less through empirical observation. Consequently, I cannot know freedom as the property of a being to which I ascribe effects in the world of the senses. This is because I would have to know such a being as determined in respect of its existence, but not as determined in time (and it is impossible for it to be determined in time, since I cannot ground my concept of it in any intuition). All the same, I can think freedom, in that the representation of it at least contains no internal contradiction — provided we have in place my critical distinction between the two modes of representation (the sensory and the intellectual), and the consequential limitation of the concepts of the understanding, as also of the axioms which flow from them.
<p41> Let us assume that morality presupposes freedom (in the strongest sense) as a property of our will, since morality depends on basic practical axioms embedded in our reason as its apriori premises. These axioms would be utterly impossible if freedom were not presupposed. [Bxxix] But if it were the case that speculative reason had proved that freedom could not be thought, then our first assumption (namely that the precondition for morality is fulfilled) must necessarily give way to the dictates of speculative reason, since the opposite of what is proved by speculative reason contains a manifest contradiction. Consequently, freedom would have to be replaced by the mechanism of nature, and morality would have to go with it, since the opposite of morality contains no contradiction unless freedom is presupposed.
<p42> All I need for morality is that: the concept of freedom should not:
Consequently, ethics and natural science each have their own distinct spheres. This would not have been the case if criticism had not previously taught us that we are inevitably ignorant of things in themselves, and that anything of which we can have theoretical knowledge is limited to mere appearances.
<p43> Precisely the same account of the positive usefulness of the critical axioms of pure reason can be given in the case of God, and of the simple nature of our soul. But I shall omit these for the sake of brevity.
<p44> [Bxxx] God, freedom and immortality are things I cannot assume for the sake of the necessary practical use of my reason, unless at the same time I deprive speculative reason of its claim to transcendent insights. In order to achieve its insights, speculative reason would have to use axioms which in fact apply only to objects of possible experience. If these axioms are applied to that which cannot be an object of experience, then in effect the object of experience is always turned into an appearance, and any extension of pure reason in its practical function will be declared impossible.
<p45> I have therefore had to deny knowledge, in order to make room for faith. The dogmatism of metaphysics is the prejudice that progress can be made in metaphysics without a critique of pure reason. This is the true source of all the unbelief which fights against morality, and which is always very dogmatic.
<p46> So, even though it cannot be difficult to hand down to posterity the legacy of a systematic metaphysics constructed in accordance with the Critique of Pure Reason, it is a gift which should not be despised. You need merely compare the cultivation of reason along the sure path of a science in general, with its groundless fumbling and unreflective [Bxxxi] wandering around in the absence of a critique.
<p47> Another benefit is that students with a thirst for knowledge will occupy their time more profitably. In the usual dogmatic philosophy, they are given too much encouragement, and at too early a stage, to quibble confidently about things they don’t understand, and into which neither they nor anyone else in the whole wide world will ever have any insight. They are even encouraged to try and invent new thoughts and opinions, and thus to neglect their study of well-grounded sciences.
<p48> But the greatest advantage of all which you should take into account, is that all objections against morality and religion will be silenced for ever. And the critical philosophy achieves this in the Socratic way, namely by the clearest proof of the ignorance of the opponent. For there always has been, and always will be some sort of metaphysics or other in the world; and it brings with it a dialectic of pure reason, because dialectic is natural to reason. Therefore it is the primary and most important task of philosophy to purge metaphysics of all the pernicious influence of dialectic for once and for all, by putting a stop to errors at source.
<p49> This important change in the relations between the sciences means that speculative reason must lose territory which it once imagined it possessed. However, everything remains in the same advantageous state as it always was in respect of universal [Bxxxii] human concerns, and the usefulness which the world has hitherto gained from the teachings of pure reason. The loss affects only the monopoly of university philosophy, and it has no effect at all on the interests of humanity. I ask the most inflexible dogmatist whether any of the following proofs emanating from the universities could ever have penetrated to the general public, or had the slightest influence on its convictions:
<p50> This has not happened, and can never be expected to happen, because the understanding of ordinary people is unsuited to such subtle speculation. The above convictions are widespread among the general public; but in so far as they rest on rational grounds at all, these grounds must be completely independent of the speculative proofs, as follows:
<p51> These grounds for conviction remain undisturbed. Indeed, they are reinforced by the fact that schools of philosophy are now told that they have no higher or more extensive insight into any point concerning the universal human condition, than is available to ordinary mortals, who deserve our highest respect. Schools of philosophy should therefore limit themselves to the cultivation of these grounds of proof alone, since they can be understood by everyone, and are sufficient from the moral point of view. The change affects only the arrogant claims of philosophy schools, which would prefer to be accepted as the sole possessors and guardians of such truths — as they are rightly held to be in many other areas. As sole guardians, they would share with the general public only the use of these truths, but they would keep the key to them for themselves. ‘Even though he is as ignorant as I am, he wants to be thought to be the only person who knows’.
<p52> Nevertheless, [Bxxxiv] a more modest claim is still reserved for speculative philosophers. They will always remain the sole trustees of a science which benefits the general public without their knowing it, namely the critique of reason. It can never become popular; but there is no need for it to be so. Ordinary people are no more willing to fill their heads with fine-spun arguments for useful truths, than the equally subtle objections against them are likely ever to enter their minds. By contrast, academics inevitably find themselves involved in both, just like everyone who aspires to speculation. It is therefore the duty of schools of philosophy to conduct a fundamental investigation into the rights of speculative reason, so as to prevent, for once and for all, the scandal which would break out sooner or later, when even ordinary people became aware of the disputes which metaphysicians (and hence eventually the clergy as well) inevitably get involved in, through lack of a critical philosophy. The outcome of these disputes is that metaphysicians themselves thereby demonstrate the falsehood of their own teachings. Only the critical philosophy can cut out the root of materialism, fatalism, atheism, free-thinking unbelief, fanaticism, and superstition. These can be harmful to everyone; but it also eliminates idealism and scepticism, which are a danger mainly to philosophy schools, and hardly likely to infect the general public.
<p53> If governments [Bxxxv] think fit to concern themselves with what happens in universities, they would show a wise concern for the sciences as well for humankind by favouring the freedom of such a critique, since it alone can put the cultivation of reason on a firm footing. Instead, they support the ridiculous despotism of schools of philosophy, which raise a loud cry about the danger to society whenever their cobwebs are torn apart — even though the general public has never paid any attention to them, and so could never feel their loss.
<p54> The critical philosophy is not opposed to the dogmatic procedure of reason in the pure knowledge it has as a science, since science must always be dogmatic, in the sense of strictly proving things apriori on the basis of firm principles. Rather, it is opposed to dogmatism, by which I mean the presumption that it is possible to make progress with nothing but pure knowledge derived from philosophical concepts in accordance with principles. Reason has long been accustomed to doing this, but without asking by what means or by what right it has acquired these concepts and principles. So dogmatism is the dogmatic procedure of pure reason, but without a previous critique of its own powers.
<p55> Opposition to dogmatism should not be taken as condoning superficial waffle, supposedly in the interest of ordinary people; [Bxxxvi] nor should it be taken as condoning scepticism, which gives short shrift to the whole of metaphysics. Rather, criticism is a preliminary activity necessary for the advancement of a metaphysics which is well-founded as a science. Such a metaphysics must necessarily be pursued dogmatically, and in the most strictly systematic way — hence it is suitable for teaching at university, and not for popular consumption. For it cannot abandon the requirement which it has promised to fulfil, namely that it must conduct its business completely apriori, and hence to the complete satisfaction of pure reason.
<p56> In the future, when I carry out the plan prescribed in the Critique (that is, when I write a System of Metaphysics), I shall have to follow the strict method of the famous Wolff, the greatest of all dogmatic philosophers. Wolff showed by his example how the path of a science is to be taken — an example through which he founded the German spirit of thoroughness, which is not yet extinct. His method consisted in the orderly establishment of principles, the clear definition of concepts, the attempt at strictness of proof, and the avoidance of rash inferential leaps. This is why he was supremely qualified to turn metaphysics round from its present state onto the sure path of a science, if only it had occurred to him to prepare the ground first through a critique of the relevant mental faculty, namely pure reason [Bxxxvii] itself. The blame for this omission lies not so much with Wolff himself, as with the dogmatic style of thinking characteristic of his age — so the philosophers of that period, as well as of earlier periods, have no reason to reproach each other for it. Those who reject both Wolff’s method and the procedure of the critique of pure reason can have nothing else in mind than to shake off the fetters of science altogether, and to turn work into play, certainty into opinion, and love of wisdom (philosophy) into love of self-glorification (philodoxy).
<p57> As for this second edition, I have naturally taken the opportunity to remove as many difficulties and obscurities as possible. These could have given rise to various misinterpretations which even clever thinkers have fallen into in passing judgment on the book — and perhaps I was partly to blame. I have found nothing to change in the propositions themselves or in the grounds of their proofs, nor in the form or completeness of the plan. One reason for this is the long time I spent testing them before publishing the book. The other reason is the essential characteristic of the subject-matter itself. A pure speculative reason is by nature an organism, in which the whole exists for the sake of every part, and [Bxxxviii] every individual part exists for the sake of the whole. Consequently, even the slightest weakness, whether it is a positive mistake (an error) or an omission, must inevitably show up when speculative reason is put to use.
<p58> I hope that this system will continue to maintain its unalterability in future. It is not pride that justifies my confidence in this, but simply the obviousness of the outcome of my experiment. It makes no difference if you start out from the least significant element to the whole of pure reason, or if you go in the reverse direction from the whole to every part. For even the whole is given in itself through the ultimate goal of pure reason in its practical aspect. Consequently, any attempt to alter even the smallest part at once introduces contradictions, not simply to the system, but to human reason in general.
<p59> It is only in the manner of expression that much remains to be done, and here I have tried to make improvements in this edition. These should remove:
My alterations to the manner of expression extend only this far (namely only to the end of the first chapter of the Transcendental [Bxxxix] Dialectic), and no further.*
[<p60> *The only thing I could really call an addition, and then only in the manner of proof, is at p.275, where I have provided a new refutation of psychological idealism, and a strict proof of the objective reality of outer intuition (which I believe is also the only possible proof of it). However innocuous idealism may be held to be in relation to the essential aims of metaphysics (though in fact it is not innocuous), it always remains a scandal for philosophy and for human reason in general, that the existence of things outside us must be taken merely on faith. For it is from these external things that we get all the material for our knowledge (even for our inner sense), and it is scandalous that, if it occurs to anyone to doubt it, we cannot counter their doubts with any satisfactory proof.
<p61> Since there is some obscurity of expression in the proof from line 3 to line 6, could you please change this sentence to the following: ‘However, that which is permanent cannot be an intuition in me. For the only grounds for determining my existence which can be met with in me are representations. But as such, they too need something permanent distinct from themselves, by reference to which their changes can be determined, and hence my existence at the time in which they change.’
<p62> The following will probably be said against this proof: ‘I am immediately conscious only of what is in me, namely my representation of outer things. Therefore it still remains undecided whether or not there is something outside me which corresponds to it.’ My answer is that, [Bxl] through inner experience, I am conscious of my existence in time, and consequently of the determinability of my existence in time. This is more than merely being conscious of my representation. In fact it is identical with the empirical consciousness of my existence, which is determinable only through its relation to something which, while bound up with my existence, is outside me. This consciousness of my existence in time is thus analytically connected with the consciousness of a relationship to something outside me. So it is experience and not fantasy, sensation and not imagination, that inseparably connects what is outer with my inner sense. For outer sense is already in itself a relating of intuition to something actual outside me. The reality of outer sense, as distinct from imagination, depends entirely on the fact that it is inseparably connected with inner experience itself, as the precondition of the possibility of outer sense. And this is what happens here.
<p63> The intellectual consciousness of my existence in the representation ‘I think’ accompanies all my judgments and other acts of understanding. If I could at the same time connect this consciousness to a determination of my existence through an intellectual intuition, then it would not be necessary for it to include consciousness of a relationship to something outside me, in order for me to be conscious of my existence. But, although intellectual consciousness does indeed occur, the only inner intuition through which my existence can be determined is sensory, and tied to temporal preconditions. However, this determination, and hence inner experience itself, depends on something permanent. Since this something permanent is not in me, it can only be in something outside [Bxli] me, and I must consider myself as standing in a relation to it. Thus for experience in general to be possible, the reality of the outer sense is necessarily connected with the reality of the inner sense. That is, I am just as surely conscious that there are things outside me which are related to my senses, as I am conscious that I myself exist determined in time.
<p64> But now there arises the question of which given intuitions actually have objects outside me corresponding to them, and thus belong to outer sense, and are to be ascribed to outer sense rather than to the imagination. This must be decided in each individual case, in accordance with the rules by which experience in general (even inner experience) is distinguished from imagination. And this procedure always presupposes the proposition that there really is outer experience.
<p65> One further observation can be added: The representation of something persisting in existence is not the same as a persisting representation. For the representation of something persisting can be very variable and changing (like all our representations, even representations of matter), while still being related to something persistent. This is why it must be an outer thing, distinct from all my representations. Its existence is necessarily included in the determination of my own existence, and together they constitute just one single experience, which could never be had inwardly, if it were not also (partly) outer. As for how this is possible, it is no more capable of further explanation than how it is generally possible for us to think the permanent in time, the co-existence of which with the changing gives rise to the concept of alteration.]
<p66> [Bxl] Time was too short, and I had not come across any misunderstandings on the part of competent and impartial [Bxli] critics in relation to the rest of the work. Although I would not presume to name these critics with the praise they deserve, [Bxlii] the attention I have paid to their comments will be evident to them in the relevant passages.
<p67> However, the improvements I have made bring with them a small loss for the reader, which I could not avoid without making the book too long. This is that I have had to leave out or shorten various passages, which, while not in any way essential for the completeness of the whole, may yet be missed by many readers, since they could otherwise have been useful for some alternative purpose. I did so in order to make space for what I hope is now a more comprehensible exposition, which has changed absolutely nothing fundamental as to the propositions put forward, or even their proofs; but here and there it departs so much from the previous edition in the method of exposition, that the task could not be carried out merely by adding a few bits. I hope that this small loss, which can in any case be remedied by comparing it with the first edition if anyone wishes, will be more than compensated for by its greater comprehensibility.
<p68> In various publications (partly in occasional reviews of a number of books, and partly in my own writings), I have observed with grateful satisfaction that the spirit of thoroughness has not died out in Germany, but has only been drowned out for a short while by the fashionable noise of a freedom of thought which thinks it is being clever. [Bxliii] Courageous and clear-headed people have not been deterred from mastering the thorny paths of the Critique, which lead to a science of pure reason; and because this science is intellectually rigorous, it alone will survive, and hence it is of the utmost necessity. I leave it to these worthy people to complete the revision of my work. They are lucky to combine thoroughness of insight with the gift of clear exposition, which I am conscious of lacking myself — and I know that my revision is still defective in a number of places. In the case of the present book, the danger is not that it will be refuted, but that it will not be understood.
<p69> For my own part, I can no longer let myself become involved in controversies. However, I shall take careful note of any suggestions, whether from supporters or from opponents, so that I can use them in the future development of the system which will be based on the present introductory work. During the course of my labour I have become rather advanced in age (I am 64 this month). So I must be careful with my time if I am to fulfil my ambition of producing both a Metaphysics of Nature and a Metaphysics of Morals, confirming the correctness of the critique, both of speculative and of practical reason. I must leave it to those worthy people who have made my teaching their own, to defend it as a whole, and to clarify the obscurities in the present work, which are hardly to be avoided in a new venture.
<p70> [Bxliv] Every philosophical treatise will have a number of vulnerable points, since it cannot come before the public as fully armoured as a mathematical one. Nevertheless, the overall structure of the system, considered as a unity, is not in the least danger. When a system is new, only a few people have the mental agility to grasp it as a whole, and even fewer have the inclination to do so, because any novelty is a nuisance to them. Furthermore, if individual passages are torn out of their context and compared with each other, it is possible to winkle out apparent contradictions, especially in a work which has been written in free continuous prose. In the eyes of those who rely on the judgment of others, these apparent contradictions cast an adverse light on the work; but they can very easily be resolved by those who have mastered the grand conception of the work as a whole. In any case, if a theory is essentially robust, the forces of action and reaction which threaten great danger to it in its initial stages will, in time, only serve to smooth over its rough spots. If people who are impartial, insightful, and sincere communicators devote themselves to the task, then it will not be long before it also acquires the required elegance of expression.
Königsberg, April 1787.