PREFACE TO SECOND EDITION

whether the treatment of such knowledge as lies within the province of reason does or does not follow the secure path of a science, is easily to be determined from the outcome. For if after elaborate preparations, frequently renewed, it is brought to a stop immediately it nears its goal; if often it is com­pelled to retrace its steps and strike into some new line of approach; or again, if the various participants are unable to agree in any common plan of procedure, then we may rest assured that it is very far from having entered upon the secure path of a science, and is indeed a merely random groping. In these circumstances, we shall be rendering a service to reason should we succeed in discovering the path upon which it can securely travel, even if, as a result of so doing, much that is comprised in our original aims, adopted without reflection, may have to be abandoned as fruitless.

That logic has already, from the earliest times, proceeded upon this sure path is evidenced by the fact that since Aristotle it has not required to retrace a single step, unless, indeed, we care to count as improvements the removal of certain need­less subtleties or the clearer exposition of its recognised teaching, features which concern the elegance rather than the certainty of the science. It is remarkable also that to the present day this logic has not been able to advance a single step, and is thus to all appearance a closed and completed body of doctrine. If some of the moderns have thought to enlarge it by introducing psychological chapters on the different faculties of knowledge (imagination, wit, etc.), metaphysical chapters on the origin of knowledge or on the different kinds of certainty according to difference in the objects (idealism, scepticism, etc.), or anthropological chapters on prejudices, their causes and remedies, this could only arise from their ignorance of the peculiar nature of logical science. We do not enlarge but disfigure sciences, if we allow them to trespass upon one another’s territory. The sphere of logic is quite precisely delimited; its sole concern is to give an exhaustive exposition and a strict proof of the formal rules of all thought, whether it be a priori or empirical, whatever be its origin or its object, and whatever hindrances, accidental or natural, it may encounter in our minds.

That logic should have been thus successful is an advan­tage which it owes entirely to its limitations, whereby it is justified in abstracting—indeed, it is under obligation to do so—from all objects of knowledge and their differences, leaving the understanding nothing to deal with save itself and its form. But for reason to enter on the sure path of science is, of course, much more difficult, since it has to deal not with itself alone but also with objects. Logic, therefore, as a propaedeutic, forms, as it were, only the vestibule of the sciences; and when we are concerned with specific modes of knowledge, while logic is indeed presupposed in any critical estimate of them, yet for the actual acquiring of them we have to look to the sciences properly so called, that is, to the objective sciences.

Now if reason is to be a factor in these sciences, something in them must be known a priori , and this knowledge may be related to its object in one or other of two ways, either as merely determining it and its concept (which must be supplied from elsewhere) or as also making it actual . The former is theoretical , the latter practical knowledge of reason. In both, that part in which reason determines its object completely a priori , namely, the pure part—however much or little this part may contain—must be first and separately dealt with, in case it be confounded with what comes from other sources; For it is bad management if we blindly pay out what comes in, and are not able, when the income falls into arrears, to distinguish which part of it can justify expenditure, and in which ¹³ line we must make reductions.

Mathematics and physics, the two sciences in which reason yields theoretical knowledge, have to determine their objects a priori , the former doing so quite purely, the latter having to reckon, at least partially, with sources of knowledge other than reason.

In the earliest times to which the history of human reason extends, mathematics , among that wonderful people, the Greeks, had already entered upon the sure path of science. But it must not be supposed that it was as easy for mathematics as it was for logic—in which reason has to deal with itself alone—to light upon, or rather to construct for itself, that royal road. On the contrary, I believe that it long remained, especially among the Egyptians, in the groping stage, and that the trans­formation must have been due to a revolution brought about by the happy thought of a single man, the experiment which he devised marking out the path upon which the science must enter, and by following which, secure progress throughout all time and in endless expansion is infallibly secured. The his­tory of this intellectual revolution—far more important than the discovery of the passage round the celebrated Cape of Good Hope—and of its fortunate author, has not been pre­served. But the fact that Diogenes Laertius, in handing down an account of these matters, names the reputed author of even the least important among the geometrical demonstrations, even of those which, for ordinary consciousness, stand in need of no such proof, does at least show that the memory of the revolution, brought about by the first glimpse of this new path, must have seemed to mathematicians of such outstanding im­portance as to cause it to survive the tide of oblivion. A new light flashed upon the mind of the first man (be he Thales or some other) who demonstrated the properties of the isosceles triangle. The true method, so he found, was not to inspect what he discerned either in the figure, or in the bare concept of it, and from this, as it were, to read off its properties; but to bring out what ¹⁴ was necessarily implied in the concepts that he had himself formed a priori , and had put into the figure in the construction by which he presented it to himself. If he is to know anything with a priori certainty he must not ascribe to the figure any­thing save what necessarily follows from what he has himself set into it in accordance with his concept.

Natural science was very much longer in entering upon the highway of science. It is, indeed, only about a century and a half since Bacon, by his ingenious proposals, partly initiated this discovery, partly inspired fresh vigour in those who were already on the way to it. In this case also the discovery can be explained as being the sudden outcome of an intellectual revolution. In my present remarks I am referring to natural science only in so far as it is founded on empirical principles.

When Galileo caused balls, the weights of which he had himself previously determined, to roll down an inclined plane; when Torricelli made the air carry a weight which he had cal­culated beforehand to be equal to that of a definite volume of water; or in more recent times, when Stahl changed metal into lime, and lime back into metal, by withdrawing some­thing and then restoring it, ¹⁵ a light broke upon all students of nature. They learned that reason has insight only into that which it produces after a plan of its own, and that it must not allow itself to be kept, as it were, in nature’s leading-strings, but must itself show the way with principles of judgment based upon fixed laws, constraining nature to give answer to ques­tions of reason’s own determining. Accidental observations, made in obedience to no previously thought-out plan, can never be made to yield a necessary law, which alone reasop is concerned to discover. Reason, holding in one hand its prin­ciples, according to which alone concordant appearances can be admitted as equivalent to laws, and in the other hand the experiment which it has devised in conformity with these prin­ciples, must approach nature in order to be taught by it. It must not, however, do so in the character of a pupil who listens to everything that the teacher chooses to say, but of an appointed judge who compels the witnesses to answer questions which he has himself formulated. Even physics, therefore, owes the beneficent revolution in its point of view entirely to the happy thought, that while reason must seek in nature, not fictitiously ascribe to it, whatever as not being knowable through reason’s own resources has to be learnt, if learnt at all, only from nature, it must adopt as its guide, in so seeking, that which it has itself put into nature. It is thus that the study of nature has entered on the secure path of a science, after having for so many centuries been nothing but a process of merely random groping.

Metaphysics is a completely isolated speculative science of reason, which soars far above the teachings of experience, and in which reason is indeed meant to be its own pupil. Meta­physics rests on concepts alone—not, like mathematics, on their application to intuition. But though it is older than all other sciences, and would survive even if all the rest were swallowed up in the abyss of an all-destroying barbarism, it has not yet had the good fortune to enter upon the secure path of a science. For in it reason is perpetually being brought to a stand, even when the laws into which it is seeking to have, as it professes, an a priori insight are those that are confirmed by our most com­mon experiences. Ever and again we have to retrace our steps, as not leading us in the direction in which we desire to go. So far, too, are the students of metaphysics from exhibiting any kind of unanimity in their contentions, that metaphysics has rather to be regarded as a battle-ground quite peculiarly suited for those who desire to exercise themselves in mock combats, and in which no participant has ever yet succeeded in gaining even so much as an inch of territory, not at least in such manner as to secure him in its permanent possession. This shows, beyond all questioning, that the procedure of meta­physics has hitherto been a merely random groping, and, what is worst of all, a groping among mere concepts.

What, then, is the reason why, in this field, the sure road to science has not hitherto been found? Is it, perhaps, im­possible of discovery? Why, in that case, should nature have visited our reason with the restless endeavour whereby it is ever searching for such a path, as if this were one of its most important concerns. Nay, more, how little cause have we to place trust in our reason, if, in one of the most important domains of which we would fain have knowledge, it does not merely fail us, but lures us on by deceitful promises, and in the end betrays us! Or if it be only that we have thus far failed to find the true path, are there any indications to justify the hope that by renewed efforts we may have better fortune than has fallen to our predecessors?

The examples of mathematics and natural science, which by a single and sudden revolution have become what they now are, seem to me sufficiently remarkable to suggest our considering what may have been the essential features in the changed point of view by which they have so greatly bene­fited. Their success should incline us, at least by way of experi­ment, to imitate their procedure, so far as the analogy which, as species of rational knowledge, they bear to metaphysics may permit. Hitherto it has been assumed that all our knowledge must conform to objects. But all attempts to extend our know­ledge of objects by establishing something in regard to them a priori , by means of concepts, have, on this assumption, ended in failure. We must therefore make trial whether we may not have more success in the tasks of metaphysics, if we suppose that objects must conform to our knowledge. This would agree better with what is desired, namely, that it should be possible to have knowledge of objects a priori , determining something in regard to them prior to their being given. We should then be proceeding precisely on the lines of Copernicus’ primary hypothesis. ¹⁶ Failing of satisfactory progress irl ex­plaining the movements of the heavenly bodies on the supposi­tion that they all revolved round the spectator, he tried whether he might not have better success if he made the spectator to revolve and the stars to remain at rest. A similar experi­ment can be tried in metaphysics, as regards the intuition of objects. If intuition must conform to the constitution of the objects, I do not see how we could know anything of the latter a priori ; but if the object (as object of the senses) must conform to the constitution of our faculty of intuition, I have no difficulty in conceiving such a possibility. Since I cannot rest in these intuitions if they are to become known, but must relate them as representations to something as their object, and determine this latter through them, either I must assume that the concepts , by means of which I obtain this determination, conform to the object, or else I assume that the objects, or what is the same thing, that the experience in which alone, as given objects, they can be known, conform to the concepts. In the former case, I am again in the same per­plexity as to how I can know anything a priori in regard to the objects. In the latter case the outlook is more hopeful. For experience is itself a species of knowledge which involves understanding; and understanding has rules which I must presuppose as being in me prior to objects being given to me, and therefore as being a priori . They find expression in a priori concepts to which all objects of experience necessarily conform, and with which they must agree. As regards objects which are thought solely through reason, and indeed as necessary, but which can never—at least not in the manner in which reason thinks them—be given in experience, the attempts at thinking them (for they must admit of being thought) will furnish an excellent test of what we are adopting as our new method of thought, namely, that we can know a priori of things only what we ourselves put into them. ¹⁷

This experiment succeeds as well as could be desired, and promises to metaphysics, in its first part—the part that is occupied with those concepts a priori to which the correspond­ing objects, commensurate with them, can be given in ex­perience—the secure path of a science. For the new point of view enables us to explain how there can be knowledge a priori; and, in addition, to furnish satisfactory proofs of the laws which form the a priori basis of nature, regarded as the sum of the objects of experience—neither achievement being possible on the procedure hitherto followed. But this deduction of our power of knowing a priori , in the first part of metaphysics, has a consequence which is startling, and which has the appearance of being highly prejudicial to the whole purpose of meta­physics, as dealt with in the second part. For we are brought to the conclusion that we can never transcend, the limits of possible experience, though that is precisely what this science is concerned, above all else, to achieve. This situation yields, however, just the very experiment by which, indirectly, we are enabled to prove the truth of this first estimate of our a priori knowledge of reason, namely, that such knowledge has to do only with appearances, and must leave the thing in itself ¹⁸ as indeed real per se , but as not known by us. For what necessarily forces us to transcend the limits of experience and of all appearances is the unconditioned , which reason, by necessity and by right, demands in things in themselves, as required to complete the series of con­ditions. If, then, on the supposition that our empirical know­ledge conforms to objects as things in themselves, we find that the unconditioned cannot be thought without contradiction , and that when, on the other hand, we suppose that our repre­sentation of things, as they are given to us, does not conform to these things as they are in themselves, but that these objects, as appearances, conform to our mode of representation, the contradiction vanishes ; and if, therefore, we thus find that the unconditioned is not to be met with in things, so far as we know them, that is, so far as they are given to us, but only so far as we do not know them, that is, so far as they are things in themselves, we are justified in concluding that what we at first assumed for the purposes of experiment is now definitely confirmed. ¹⁹ But when all progress in the field of the supersensible has thus been denied to speculative reason, it is still open to us to enquire whether, in the practical knowledge of reason, data may not be found sufficient to de­termine reason’s transcendent concept of the unconditioned, and so to errable us, in accordance with the wish of meta­physics, and by means of knowledge that is possible a priori , though only from a practical point of view, to pass beyond the limits of all possible experience. Speculative reason has thus at least made room for such an extension; and if it must at the same time leave it empty, yet none the less we are at liberty, indeed we are summoned, to take occupation of it, if we can, by practical data of reason. ²⁰

This attempt to alter the procedure which has hitherto prevailed in metaphysics, by completely revolutionising it in accordance with the example set by the geometers and physicists, forms indeed the main purpose of this critique of pure speculative reason. It is a treatise on the method, not a system of the science itself. But at the same time it marks out the whole plan of the science, both as regards its limits and as regards its entire internal structure. For pure speculative reason has this peculiarity, that it can measure its powers according to the different ways in which it chooses the objects of its thinking, and can also give an exhaustive enumeration of the various ways in which it propounds its problems, and so is able, nay bound, to trace the complete outline of a system of metaphysics. As regards the first point, nothing in a priori knowledge can be ascribed to objects save what the thinking subject derives from itself; as regards the second point, pure reason, so far as the principles of its knowledge are concerned, is a quite separate self-subsistent unity, in which, as in an organised body, every member exists for every other, and all for the sake of each, so that no principle can safely be taken in any one relation, unless it has been investigated in the entirety of its relations to the whole employment of pure reason. Consequently, metaphysics has also this singular advantage, such as falls to the lot of no other science which deals with objects (for logic is concerned only with the form of thought in general), that should it, through this critique, be set upon the secure path of a science, it is capable of acquiring exhaustive knowledge of its entire field. Metaphysics has to deal only with principles, and with the limits of their employment as determined by these principles themselves, and it can therefore finish its work and bequeath it to posterity as a capital to which no addition can be made. Since it is a fundamental science, it is under obligation to achieve this completeness. We must be able to say of it: nil actum reputans , si quid superesset agendum .

But, it will be asked, what sort of a treasure is this that we propose to bequeath to posterity? What is the value of the metaphysics that is alleged to be thus purified by criti­cism and established once for all? On a cursory view of the present work it may seem that its results are merely negative , warning us that we must never venture with speculative reason beyond the limits of experience. Such is in fact its primary use. But such teaching at once acquires a positive value when we recognise that the principles with which speculative reason ventures out beyond its proper limits do not in effect extend the employment of reason, but, as we find on closer scrutiny, inevitably narrow it. These principles properly belong [not to reason but] to sensibility, and when thus employed they threaten to make the bounds of sensibility coextensive with the real, and so to supplant reason in its pure (practical) em­ployment. So far, therefore, as our Critique limits speculative reason, it is indeed negative ; but since it thereby removes an obstacle which stands in the way of the employment of practi­cal reason, nay threatens to destroy it, it has in reality a posi­tive and very important use. At least this is so, immediately we are convinced that there is an absolutely necessary practical employment of pure reason — the moral— in which it inevitably goes beyond the limits of sensibility. Though [practical] reason, in thus proceeding, requires no assistance from speculative reason, it must yet be assured against its opposition, that reason may not be brought into conflict with itself. To deny that the service which the Critique renders is positive in character, would thus be like saying that the police are of no positive benefit, inasmuch as their main busi­ness is merely to prevent the violence of which citizens stand in mutual fear, in order that each may pursue his vocation in peace and security. That space and time are only forms of sens­ible intuition, and so only conditions of the existence of things as appearances; that, moreover, we have no concepts of under­standing, and consequently no elements for the knowledge of things, save in so far as intuition can be given corresponding to these concepts; and that we can therefore have no knowledge of any object as thing in itself, but only in so far as it ²¹ is an object of sensible intuition, that is, an appearance—all this is proved in the analytical part of the Critique. Thus it does in­deed follow that all possible speculative knowledge of reason is limited to mere objects of experience . But our further con­tention must also be duly borne in mind, namely, that though we cannot know these objects as things in themselves, we must yet be in position at least to think them as things in them­selves; ²² otherwise we should be landed in the absurd conclusion that there can be appearance without anything that appears. Now let us suppose that the distinction, which our Critique has shown to be necessary, between things as objects of experience and those same things as things in themselves, had not been made. In that case all things in general, as far as they are efficient causes, would be determined by the principle of caus­ality, and consequently by the mechanism of nature. I could not, therefore, without palpable contradiction, say of one and the same being, for instance the human soul, that its will is free and yet is subject to natural necessity, that is, is not free. For I have taken the soul in both propositions in one and the same sense , namely as a thing in general, that is, as a thing ²³ in itself; and save by means of a preceding critique, could not have done otherwise. But if our Critique is not in error in teaching that the object is to be taken in a twofold sense , namely as appear­ance and as thing in itself; if the deduction of the concepts of understanding is valid, and the principle of causality there­fore applies only to things taken in the former sense, namely, in so far as they are objects of experience—these same objects, taken in the other sense, not being subject to the principle—then there is no contradiction in supposing that one and the same will is, in the appearance, that is, in its visible acts, necessarily subject to the law of nature, and so far not free , while yet, as belonging to a thing in itself, it is not subject to that law, and is therefore free . My soul, viewed from the latter standpoint, cannot indeed be known by means of specu­lative reason (and still less through empirical observation); and freedom as a property of a being to which I attribute effects in the sensible world, is therefore also not knowable in any such fashion. For I should then have to know such a being as determined in its existence, and yet as not determined in time—which is impossible, since I cannot support my concept by any intuition. But though I cannot know , I can yet think freedom; that is to say, the representation of it is at least not self-con­tradictory, provided due account be taken of our critical dis­tinction between the two modes of representation, the sensible and the intellectual, and of the resulting limitation of the pure concepts of understanding and of the principles which flow from them.

If we grant that morality necessarily presupposes freedom (in the strictest sense) as a property of our will; if, that is to say, we grant that it yields practical principles—original prin­ciples, proper to our reason—as a priori data of reason, and that this would be absolutely impossible save on the assumption of freedom; and if at the same time we grant that speculative reason has proved that such freedom does not allow of being thought, then the former supposition—that made on behalf of morality—would have to give way to this other contention, the opposite of which involves a palpable contradiction. For since it is only on the assumption of free­dom that the negation of morality contains any contradiction, freedom, and with it morality, would have to yield to the mechanism of nature.

Morality does not, indeed, require that freedom should be understood, but only that it should not contradict itself, and so should at least allow of being thought, and that as thus thought it should place no obstacle in the way of a free act (viewed in another relation) likewise conforming to the mechan­ism of nature. The doctrine of morality and the doctrine of nature may each, therefore, make good its position. This, however, is only possible in so far as criticism has previously established our unavoidable ignorance of things in themselves, and has limited all that we can theoretically know to mere appearances.

This discussion as to the positive advantage of critical principles of pure reason can be similarly developed in regard to the concept of God and of the simple nature of our soul ; but for the sake of brevity such further discussion may be omitted. [From what has already been said, it is evident that] even the assumption —as made on behalf of the necessary practical employment of my reason—of God , freedom , and immortality is not permissible unless at the same time speculative reason be deprived of its pretensions to transcendent insight. For in order to arrive at such insight it must make use of principles which, in fact, extend only to objects of possible experience, and which, if also applied to what cannot be an object of experience, always really change this into an appearance, thus rendering all practical extension of pure reason impossible. I have therefore found it necessary to deny knowledge , in order to make room for faith . ²⁴ The dogmatism of metaphysics, that is, the precon­ception that it is possible to make headway in metaphysics with­out a previous criticism of pure reason, is the source of all that unbelief, ²⁵ always very dogmatic, which wars against morality.

Though it may not, then, be very difficult to leave to pos­terity the bequest of a systematic metaphysic, constructed in conformity with a critique of pure reason, yet such a gift is not to be valued lightly. For not only will reason be enabled to follow the secure path of a science, instead of, as hitherto, groping at random, without circumspection or self-criticism; our enquiring youth will also be in a position to spend their time more profitably than in the ordinary dogmatism by which they are so early and so greatly encouraged to indulge in easy speculation about things of which they understand nothing, and into which neither they nor any­one else will ever have any insight—encouraged, indeed, to invent new ideas and opinions, while neglecting the study of the better-established sciences. But, above all, there is the inestimable benefit, that all objections to morality and religion will be for ever silenced, and this in Socratic fashion, namely, by the clearest proof of the ignorance of the objectors. There has always existed in the world, and there will always continue to exist, some kind of metaphysics, and with it the dialectic that is natural to pure reason. It is therefore the first and most important task of philosophy to deprive meta­physics, once and for all, of its injurious influence, by attack­ing its errors at their very source.

Notwithstanding this important change in the field of the sciences, and the loss of its fancied possessions which speculative reason must suffer, general human interests remain in the same privileged position as hitherto, and the advantages which the world has hitherto derived from the teachings of pure reason are in no way diminished. The loss affects only the monopoly of the schools , in no respect the interests of humanity . I appeal to the most rigid dogmatist, whether the proof of the continued existence of our soul after death, derived from the simplicity of substance, or of the freedom of the will as opposed to a universal mechanism, arrived at through the subtle but ineffectual distinctions between subjective and objective prac­tical necessity, or of the existence of God as deduced from the concept of an ens realissimum (of the contingency of the changeable and of the necessity of a prime mover), have ever, upon passing out from the schools, succeeded in reaching the public mind or in exercising the slightest influence on its con­victions? That has never been found to occur, and in view of the unfitness of the common human understanding for such subtle speculation, ought never to have been expected. Such widely held convictions, so far as they rest on rational grounds, are due to quite other considerations. The hope of a future life has its source in that notable characteristic of our nature, never to be capable of being satisfied by what is temporal (as insufficient for the capacities of its whole destination); the consciousness of freedom rests exclusively on the clear exhibition of duties, in opposition to all claims of the inclina­tions; the belief in a wise and great Author of the world is generated solely by the glorious order, beauty, and providen­tial care everywhere displayed in nature. When the schools have been brought to recognise that they can lay no claim to higher and fuller insight in a matter of universal human concern than that which is equally within the reach of the great mass of men (ever to be held by us in the highest esteem), and that, as Schools of philosophy, they should limit themselves to the study of those universally comprehensible, and, for moral purposes, sufficient grounds of proof, then not only do these latter possessions remain undisturbed, but through this very fact they acquire yet greater authority. The change affects only the arrogant pretensions of the Schools, which would fain be counted the sole authors and possessors of such truths (as, indeed, they can justly claim to be ia many other branches of knowledge), reserving the key to themselves, and communicating to the public their use only— quod mecum nescit , solus vult scire videri . At the same time due regard is paid to the more moderate claims of the speculative philosopher. He still remains the sole authority in regard to a science which benefits the public without their knowing it, namely, the critique of reason. That critique can never become popular, and indeed there is no need that it should. For just as fine-spun arguments in favour of useful truths make no appeal to the general mind, so neither do the subtle objections that can be raised against them. On the other hand, both inevitably present themselves to everyone who rises to the height of speculation; and it is therefore the duty of the Schools, by means of a thorough investigation of the rights of speculative reason, once for all to prevent the scandal which, sooner or later, is sure to break out even among the masses, as the result of the disputes in which metaphysicians (and, as such, finally also the clergy) inevitably become involved to the consequent perversion of their teaching. Criticism alone can sever the root of materialism , fatalism , atheism , free-thinking , fanati­cism , and superstition , which can be injurious universally; as well as of idealism and scepticism , which are dangerous chiefly to the Schools, and hardly allow of being handed on to the public. If governments think proper to interfere with the affairs of the learned, it would be more consistent with a wise regard for science as well as for mankind, to favour the free­dom of such criticism, by which alone the labours of reason can be established on a firm basis, than to support the ridiculous despotism of the Schools, which raise a loud cry of public danger over the destruction of cobwebs to which the public has never paid any attention, and the loss of which it can therefore never feel.

This critique is not opposed to the dogmatic procedure of reason in its pure knowledge, as science, for that must always be dogmatic, that is, yield strict proof from sure principles a priori . It is opposed only to dogmatism , that is, to the pre­sumption that it is possible to make progress with pure know­ledge, according to principles, from concepts alone (those that are philosophical), as reason has long been in the habit of doing; and that it is possible to do this without having first in­vestigated in what way and by what right reason has come into possession of these concepts. Dogmatism is thus the dogmatic procedure of pure reason, without previous criticism of its own powers . In withstanding dogmatism we must not allow ourselves to give free rein to that loquacious shallowness, which assumes for itself the name of popularity, nor yet to scepticism, which makes short work with all metaphysics. On the contrary, such criticism is the necessary preparation for a thoroughly grounded metaphysics, which, as science, must necessarily be developed dogmatically, according to the strictest demands of system, in such manner as to satisfy not the general public but the re­quirements of the Schools. For that is a demand to which it stands pledged, and which it may not neglect, namely, that it carry out its work entirely a priori , to the complete satisfaction of speculative reason. In the execution of the plan prescribed by the critique, that is, in the future system of metaphysics, we have therefore to follow the strict method of the celebrated Wolff, the greatest of all the dogmatic philosophers. He was the first to show by example (and by his example he awakened that spirit of thoroughness which is not extinct in Germany) how the secure progress of a science is to be attained only through orderly establishment of principles, clear determina­tion of concepts, insistence upon strictness of proof, and avoid­ance of venturesome, non-consecutive steps in our inferences. He was thus peculiarly well fitted to raise metaphysics to the dignity of a science, if only it had occurred to him to prepare the ground beforehand by a critique of the organ, that is, of pure reason itself. The blame for his having failed to do so lies not so much with himself as with the dogmatic way of thinking prevalent in his day, and with which the philo­sophers of his time, and of all previous times, have no right to reproach one another. Those who reject both the method of Wolff and the procedure of a critique of pure reason can have no other aim than to shake off the fetters of science altogether, and thus to change work into play, certainty into opinion, philosophy into philodoxy.

Now, as regards this second edition , I have, as is fitting, endeavoured to profit by the opportunity, in order to remove, wherever possible, difficulties and obscurity which, not per­haps without my fault, may have given rise to the many misunderstandings into which even acute thinkers have fallen in passing judgment upon my book. In the propositions them­selves and their proofs, and also in the form and completeness of the [architectonic] plan, I have found nothing to alter. This is due partly to the long examination to which I have sub­jected them, before offering them ²⁶ to the public, partly to the nature of the subject-matter with which we are dealing. For pure speculative reason has a structure wherein everything is an organ , the whole being for the sake of every part, and every part for the sake of all the others, so that even the smallest imperfection, be it a fault (error) or a deficiency, must inevitably betray itself in use. This system will, as I hope, maintain, throughout the future, this unchangeableness. It is not self-conceit which justifies me in this confidence, but the evidence experimentally obtained through the parity of the result, whether we proceed from the smallest elements to the whole of pure reason or reverse-wise from the whole (for this also is presented to reason through its final end in the sphere of the practical) to each part. Any attempt to change even the smallest part at once gives rise to contradic­tions, not merely in the system, but in human reason in general. As to the mode of exposition , on the other hand, much still remains to be done; and in this edition I have sought to make improvements which should help in removing, first, the misunderstanding in regard to the Aesthetic, especi­ally concerning the concept of time; secondly, the obscurity of the deduction of the concepts of understanding; thirdly, a supposed want of sufficient evidence in the proofs of the prin­ciples of pure understanding; and finally, the false interpreta­tion placed upon the paralogisms charged against rational psychology. Beyond this point, that is, beyond the end of the first chapter of the Transcendental Dialectic, I have made no changes in the mode of exposition. ²⁷ Time was too short to allow of further changes; and besides, I have not found among competent and impartial critics any misapprehension in regard to the remaining sections. Though I shall not venture to name these critics with the praise that is their due, the attention which I have paid to their comments will easily be recognised in the [new] passages [above mentioned]. These improvements involve, however, a small loss, not to be prevented save by making the book too voluminous, namely, that I have had to omit or abridge certain passages, which, though not indeed essential to the completeness of the whole, may yet be missed by many readers as otherwise helpful. Only so could I obtain space for what, as I hope, is now a more intelligible exposition, which, though altering absolutely nothing in the fundamentals of the propositions put for­ward or even in their proofs, yet here and there departs so far from the previous method of treatment, that mere in­terpolations could not be made to suffice. This loss, which is small and can be remedied by consulting the first edition, will, I hope, be compensated by the greater clearness of the new text. I have observed, with pleasure and thankfulness, in various published works—alike in critical reviews and in in­dependent treatises—that the spirit of thoroughness is not extinct in Germany, but has only been temporarily overshadowed by the prevalence of a pretentiously free manner of thinking; and that the thorny paths of the Critique have not discouraged courageous and clear heads from setting them­selves to master my book—a work which leads to a method­ical, and as such alone enduring, and therefore most necessary, science of pure reason. To these worthy men, who so happily combine thoroughness of insight with a talent for lucid ex­position—which I cannot regard myself as possessing—I leave the task of perfecting what, here and there, in its exposition, is still somewhat defective; for in this regard the danger is not that of being refuted, but of not being understood. From now on, though I cannot allow myself to enter into controversy, I shall take careful note of all sugges­tions, be they from friends or from opponents, for use, in accordance with this propaedeutic, in the further elaboration of the system. In the course of these labours I have advanced somewhat far in years (this month I reach my sixty-fourth year), and I must be careful with my time if I am to succeed in my proposed scheme of providing a metaphysic of nature and of morals which will confirm the truth of my Critique in the two fields, of speculative and of practical reason. The clearing up of the obscurities in the present work—they are hardly to be avoided in a new enterprise—and the defence of it as a whole, I must therefore leave to those worthy men who have made my teaching their own. A philosophical work cannot be armed at all points, like a mathematical treatise, and may therefore be open to objection in this or that respect, while yet the structure of the system, taken in its unity, is not in the least endangered. Few have the versatility of mind to familiarise themselves with a new system; and owing to the general distaste for all innovation, still fewer have the inclina­tion to do so. If we take single passages, torn from their contexts, and compare them with one another, apparent con­tradictions are not likely to be lacking, especially in a work that is written with any freedom of expression. In the eyes of those who rely on the judgment of others, such contradic­tions have the effect of placing the work in an unfavourable light; but they are easily resolved by those who have mastered the idea of the whole. If a theory has in itself stability, the stresses and strains which may at first have seemed very threatening to it serve only, in the course of time, to smooth away its inequalities; and if men of impartiality, insight, and true popularity devote themselves to its exposition, it may also, in a short time, secure for itself the necessary elegance of statement.

Königsberg, April 1787. QjzpBLN+9ArgoZi7CaLy9VpT+TY6kY9jUCVAp6cxoyN9thDGtvqyPRTz8MzkwrA+