Solution: How is metaphysics possible as a science?
Original German
Auflösung der allgemeinen Frage der Prolegomenen.
Wie ist Metaphysik als Wissenschaft möglich?
Metaphysik als Naturanlage der Vernunft ist wirklich, aber sie ist auch für sich allein (wie die analytische Auflösung der dritten Hauptfrage bewies) dialektisch und trüglich. Aus dieser also die Grundsätze hernehmen wollen und in dem Gebrauche derselben dem zwar natürlichen, nichts destoweniger aber falschen Scheine folgen, kann niemals Wissenschaft, sondern nur eitele dialektische Kunst hervorbringen, darin es eine Schule der andern zuvorthun, keine aber jemals einen rechtmäßigen und dauernden Beifall erwerben kann.
Damit sie nun als Wissenschaft nicht blos auf trügliche Überredung, sondern auf Einsicht und Überzeugung Anspruch machen könne, so muß eine Kritik der Vernunft selbst den ganzen Vorrath der Begriffe a priori, die Eintheilung derselben nach den verschiedenen Quellen, der Sinnlichkeit, dem Verstande und der Vernunft, ferner eine vollständige Tafel derselben und die Zergliederung aller dieser Begriffe mit allem, was daraus gefolgert werden kann, darauf aber vornehmlich die Möglichkeit des synthetischen Erkenntnisses a priori vermittelst der Deduction dieser Begriffe, die Grundsätze ihres Gebrauchs, endlich auch die Grenzen desselben, alles aber in einem vollständigen System darlegen. Also enthält Kritik und auch sie ganz allein den ganzen wohlgeprüften und bewährten Plan, ja sogar alle Mittel der Vollziehung in sich, wornach Metaphysik als Wissenschaft zu Stande gebracht werden kann; durch andere Wege und Mittel ist sie unmöglich. Es frägt sich also hier nicht sowohl, wie dieses Geschäfte möglich, sondern nur wie es in Gang zu bringen und gute Köpfe von der bisherigen verkehrten und fruchtlosen zu einer untrüglichen Bearbeitung zu bewegen seien, und wie eine solche Vereinigung auf den gemeinschaftlichen Zweck am füglichsten gelenkt werden könne.
So viel ist gewiß: wer einmal Kritik gekostet hat, den ekelt auf immer alles dogmatische Gewäsche, womit er vorher aus Noth vorlieb nahm, weil seine Vernunft etwas bedurfte und nichts Besseres zu ihrer Unterhaltung finden konnte. Die Kritik verhält sich zur gewöhnlichen Schulmetaphysik gerade wie Chemie zur Alchymie, oder wie Astronomie zur wahrsagenden Astrologie. Ich bin dafür gut, daß Niemand, der die Grundsätze der Kritik auch nur in diesen Prolegomenen durchgedacht und gefaßt hat, jemals wieder zu jener alten und sophistischen Scheinwissenschaft zurückkehren werde; vielmehr wird er mit einem gewissen Ergötzen auf eine Metaphysik hinaussehen, die nunmehr allerdings in seiner Gewalt ist, auch keiner vorbereitenden Entdeckungen mehr bedarf, und die zuerst der Vernunft daurende Befriedigung verschaffen kann. Denn das ist ein Vorzug, auf welchen unter allen möglichen Wissenschaften Metaphysik allein mit Zuversicht rechnen kann, nämlich daß sie zur Vollendung und in den beharrlichen Zustand gebracht werden kann, da sie sich weiter nicht verändern darf, auch keiner Vermehrung durch neue Entdeckungen fähig ist: weil die Vernunft hier die Quellen ihrer Erkenntniß nicht in den Gegenständen und ihrer Anschauung (durch die sie nicht ferner eines Mehreren belehrt werden kann), sondern in sich selbst hat, und, wenn sie die Grundgesetze ihres Vermögens vollständig und gegen alle Mißdeutung bestimmt dargestellt hat, nichts übrig bleibt, was reine Vernunft a priori erkennen, ja auch nur, was sie mit Grunde fragen könnte. Die sichere Aussicht auf ein so bestimmtes und geschlossenes Wissen hat einen besondern Reiz bei sich, wenn man gleich allen Nutzen (von welchem ich hernach noch reden werde) bei Seite setzt.
Alle falsche Kunst, alle eitele Weisheit dauert ihre Zeit; denn endlich zerstört sie sich selbst, und die höchste Cultur derselben ist zugleich der Zeitpunkt ihres Unterganges. Daß in Ansehung der Metaphysik diese Zeit jetzt da sei, beweiset der Zustand, in welchen sie bei allem Eifer, womit sonst Wissenschaften aller Art bearbeitet werden, unter allen gelehrten Völkern verfallen ist. Die alte Einrichtung der Universitätsstudien erhält noch ihren Schatten, eine einzige Akademie der Wissenschaften bewegt noch dann und wann durch ausgesetzte Preise, einen und anderen Versuch darin zu machen; aber unter gründliche Wissenschaften wird sie nicht mehr gezählt, und man mag selbst urtheilen, wie etwa ein geistreicher Mann, den man einen großen Metaphysiker nennen wollte, diesen wohlgemeinten, aber kaum von jemanden beneideten Lobspruch aufnehmen würde.
Ob aber gleich die Zeit des Verfalls aller dogmatischen Metaphysik ungezweifelt da ist, so fehlt doch noch manches dran, um sagen zu können, daß die Zeit ihrer Wiedergeburt vermittelst einer gründlichen und vollendeten Kritik der Vernunft dagegen schon erschienen sei. Alle Übergänge von einer Neigung zu der ihr entgegengesetzten gehen durch den Zustand der Gleichgültigkeit, und dieser Zeitpunkt ist der gefährlichste für einen Verfasser, aber, wie mich dünkt, doch der günstigste für die Wissenschaft. Denn wenn durch gänzliche Trennung vormaliger Verbindungen der Parteigeist erloschen ist, so sind die Gemüther in der besten Verfassung, um allmählig Vorschläge zur Verbindung nach einem anderen Plane anzuhören.
Wenn ich sage, daß ich von diesen Prolegomenen hoffe, sie werden die Nachforschung im Felde der Kritik vielleicht rege machen und dem allgemeinen Geiste der Philosophie, dem es im speculativen Theile an Nahrung zu fehlen scheint, einen neuen und viel versprechenden Gegenstand der Unterhaltung darreichen, so kann ich mir schon zum voraus vorstellen: daß jedermann, den die dornichten Wege, die ich ihn in der Kritik geführt habe, unwillig und überdrüssig gemacht haben, mich fragen werde, worauf ich wohl diese Hoffnung gründe. Ich antworte: auf das unwiderstehliche Gesetz der Nothwendigkeit.
Daß der Geist des Menschen metaphysische Untersuchungen einmal gänzlich aufgeben werde, ist eben so wenig zu erwarten, als daß wir, um nicht immer unreine Luft zu schöpfen, das Athemholen einmal lieber ganz und gar einstellen würden. Es wird also in der Welt jederzeit, und was noch mehr, bei jedem, vornehmlich dem nachdenkenden Menschen Metaphysik sein, die in Ermangelung eines öffentlichen Richtmaßes jeder sich nach seiner Art zuschneiden wird. Nun kann das, was bis daher Metaphysik geheißen hat, keinem prüfenden Kopfe ein Gnüge thun, ihr aber gänzlich zu entsagen, ist doch auch unmöglich: also muß endlich eine Kritik der reinen Vernunft selbst versucht, oder, wenn eine da ist, untersucht und in allgemeine Prüfung gezogen werden, weil es sonst kein Mittel giebt, diesem dringenden Bedürfniß, welches noch etwas mehr als bloße Wißbegierde ist, abzuhelfen.
Seitdem ich Kritik kenne, habe ich am Ende des Durchlesens einer Schrift metaphysischen Inhalts, die mich durch Bestimmung ihrer Begriffe, durch Mannigfaltigkeit und Ordnung und einen leichten Vortrag sowohl unterhielt, als auch cultivirte, mich nicht entbrechen können, zu fragen: hat dieser Autor wohl die Metaphysik um einen Schritt weiter gebracht? Ich bitte die gelehrte Männer um Vergebung, deren Schriften mir in anderer Absicht genutzt und immer zur Cultur der Gemüthskräfte beigetragen haben, weil ich gestehe, daß ich weder in ihren noch in meinen geringeren Versuchen (denen doch Eigenliebe zum Vortheil spricht) habe finden können, daß dadurch die Wissenschaft im mindesten weiter gebracht worden, und dieses zwar aus dem ganz natürlichen Grunde, weil die Wissenschaft noch nicht existirte und auch nicht stückweise zusammengebracht werden kann, sondern ihr Keim in der Kritik vorher völlig präformirt sein muß. Man muß aber, um alle Mißdeutung zu verhüten, sich aus dem vorigen wohl erinnern, daß durch analytische Behandlung unserer Begriffe zwar dem Verstande allerdings recht viel genutzt, die Wissenschaft (der Metaphysik) aber dadurch nicht im mindesten weiter gebracht werde: weil jene Zergliederungen der Begriffe nur Materialien sind, daraus allererst Wissenschaft gezimmert werden soll. So mag man den Begriff von Substanz und Accidens noch so schön zergliedern und bestimmen; das ist recht gut als Vorbereitung zu irgend einem künftigen Gebrauche. Kann ich aber gar nicht beweisen, daß in allem, was da ist, die Substanz beharre, und nur die Accidenzen wechseln, so war durch alle jene Zergliederung die Wissenschaft nicht im mindesten weiter gebracht. Nun hat Metaphysik weder diesen Satz, noch den Satz des zureichenden Grundes, viel weniger irgend einen zusammengesetztern, als z. B. einen zur Seelenlehre oder Kosmologie gehörigen, und überall gar keinen synthetischen Satz bisher a priori gültig beweisen können: also ist durch alle jene Analysis nichts ausgerichtet, nichts geschafft und gefördert worden, und die Wissenschaft ist nach so viel Gewühl und Geräusch noch immer da, wo sie zu Aristoteles’ Zeiten war, obzwar die Veranstaltungen dazu, wenn man nur erst den Leitfaden zu synthetischen Erkenntnissen gefunden hätte, unstreitig viel besser wie sonst getroffen worden.
Glaubt jemand sich hiedurch beleidigt, so kann er diese Beschuldigung leicht zu nichte machen, wenn er nur einen einzigen synthetischen, zur Metaphysik gehörigen Satz anführen will, den er auf dogmatische Art a priori zu beweisen sich erbietet; denn nur dann, wenn er dieses leistet, werde ich ihm einräumen, daß er wirklich die Wissenschaft weiter gebracht habe: sollte dieser Satz auch sonst durch die gemeine Erfahrung genug bestätigt sein. Keine Forderung kann gemäßigter und billiger sein und im (unausbleiblich gewissen) Fall der Nichtleistung kein Ausspruch gerechter, als der: daß Metaphysik als Wissenschaft bisher noch gar nicht existirt habe.
Nur zwei Dinge muß ich im Fall, daß die Ausforderung angenommen wird, verbitten: erstlich das Spielwerk von Wahrscheinlichkeit und Muthmaßung, welches der Metaphysik eben so schlecht ansteht als der Geometrie; zweitens die Entscheidung vermittelst der Wünschelruthe des so genannten gesunden Menschenverstandes, die nicht jedermann schlägt, sondern sich nach persönlichen Eigenschaften richtet.
Denn was das erstere anlangt, so kann wohl nichts Ungereimteres gefunden werden, als in einer Metaphysik, einer Philosophie aus reiner Vernunft, seine Urtheile auf Wahrscheinlichkeit und Muthmaßung gründen zu wollen. Alles, was a priori erkannt werden soll, wird eben dadurch für apodiktisch gewiß ausgegeben und muß also auch so bewiesen werden. Man könnte eben so gut eine Geometrie oder Arithmetik auf Muthmaßungen gründen wollen; denn was den calculus probabilium der letzteren betrifft, so enthält er nicht wahrscheinliche, sondern ganz gewisse Urtheile über den Grad der Möglichkeit gewisser Fälle unter gegebenen gleichartigen Bedingungen, die in der Summe aller möglichen Fälle ganz unfehlbar der Regel gemäß zutreffen müssen, ob diese gleich in Ansehung jedes einzelnen Zufalles nicht gnug bestimmt ist. Nur in der empirischen Naturwissenschaft können Muthmaßungen (vermittelst der Induction und Analogie) gelitten werden, doch so, daß wenigstens die Möglichkeit dessen, was ich annehme, völlig gewiß sein muß.
Mit der Berufung auf den gesunden Menschenverstand, wenn von Begriffen und Grundsätzen, nicht so fern sie in Ansehung der Erfahrung gültig sein sollen, sondern so fern sie auch außer den Bedingungen der Erfahrung für geltend ausgegeben werden wollen, die Rede ist, ist es wo möglich noch schlechter bewandt. Denn was ist der gesunde Verstand? Es ist der gemeine Verstand, so fern er richtig urtheilt. Und was ist nun der gemeine Verstand? Er ist das Vermögen der Erkenntniß und des Gebrauchs der Regeln in concreto zum Unterschiede des speculativen Verstandes, welcher ein Vermögen der Erkenntniß der Regeln in abstracto ist. So wird der gemeine Verstand die Regel, daß alles, was geschieht, vermittelst seiner Ursache bestimmt sei, kaum verstehen, niemals aber so im allgemeinen einsehen können. Er fordert daher ein Beispiel aus Erfahrung, und wenn er hört, daß dieses nichts anders bedeute, als was er jederzeit gedacht hat, wenn ihm eine Fensterscheibe zerbrochen oder ein Hausrath verschwunden war, so versteht er den Grundsatz und räumt ihn auch ein. Gemeiner Verstand hat also weiter keinen Gebrauch, als so fern er seine Regeln (obgleich dieselben ihm wirklich a priori beiwohnen) in der Erfahrung bestätigt sehen kann; mithin sie a priori und unabhängig von der Erfahrung einzusehen, gehört vor den speculativen Verstand und liegt ganz außer dem Gesichtskreise des gemeinen Verstandes. Metaphysik hat es ja aber lediglich mit der letzteren Art Erkenntniß zu thun; und es ist gewiß ein schlechtes Zeichen eines gesunden Verstandes, sich auf jenen Gewährsmann zu berufen, der hier gar kein Urtheil hat, und den man sonst wohl nur über die Achsel ansieht, außer wenn man sich im Gedränge sieht und sich in seiner Speculation weder zu rathen, noch zu helfen weiß.
Es ist eine gewöhnliche Ausflucht, deren sich diese falsche Freunde des gemeinen Menschenverstandes (die ihn gelegentlich hoch preisen, gemeiniglich aber verachten) zu bedienen pflegen, daß sie sagen: Es müssen doch endlich einige Sätze sein, die unmittelbar gewiß sind, und von denen man nicht allein keinen Beweis, sondern auch überall keine Rechenschaft zu geben brauche, weil man sonst mit den Gründen seiner Urtheile niemals zu Ende kommen würde; aber zum Beweise dieser Befugniß können sie (außer dem Satze des Widerspruchs, der aber die Wahrheit synthetischer Urtheile darzuthun nicht hinreichend ist) niemals etwas anderes Ungezweifeltes, was sie dem gemeinen Menschenverstande unmittelbar beimessen dürfen, anführen, als mathematische Sätze: z. B. daß zweimal zwei vier ausmachen, daß zwischen zwei Punkten nur eine gerade Linie sei, u. a. m. Das sind aber Urtheile, die von denen der Metaphysik himmelweit unterschieden sind. Denn in der Mathematik kann ich alles das durch mein Denken selbst machen (construiren), was ich mir durch einen Begriff als möglich vorstelle: ich thue zu einer Zwei die andere Zwei nach und nach hinzu und mache selbst die Zahl vier, oder ziehe in Gedanken von einem Punkte zum andern allerlei Linien und kann nur eine einzige ziehen, die sich in allen ihren Theilen (gleichen sowohl als ungleichen) ähnlich ist. Aber ich kann aus dem Begriffe eines Dinges durch meine ganze Denkkraft nicht den Begriff von etwas anderem, dessen Dasein nothwendig mit dem ersteren verknüpft ist, herausbringen, sondern muß die Erfahrung zu rathe ziehen; und obgleich mir mein Verstand a priori (doch immer nur in Beziehung auf mögliche Erfahrung) den Begriff von einer solchen Verknüpfung (der Causalität) an die Hand giebt, so kann ich ihn doch nicht, wie die Begriffe der Mathematik a priori in der Anschauung darstellen und also seine Möglichkeit a priori darlegen; sondern dieser Begriff sammt den Grundsätzen seiner Anwendung bedarf immer, wenn er a priori gültig sein soll — wie es doch in der Metaphysik verlangt wird —, eine Rechtfertigung und Deduction seiner Möglichkeit, weil man sonst nicht weiß, wie weit er gültig sei, und ob er nur in der Erfahrung oder auch außer ihr gebraucht werden könne. Also kann man sich in der Metaphysik, als einer speculativen Wissenschaft der reinen Vernunft, niemals auf den gemeinen Menschenverstand berufen, aber wohl, wenn man genöthigt ist, sie zu verlassen und auf alles reine speculative Erkenntniß, welches jederzeit ein Wissen sein muß, mithin auch auf Metaphysik selbst und deren Belehrung (bei gewissen Angelegenheiten) Verzicht zu thun, und ein vernünftiger Glaube uns allein möglich, zu unserm Bedürfniß auch hinreichend (vielleicht gar heilsamer als das Wissen selbst) befunden wird. Denn alsdann ist die Gestalt der Sache ganz verändert. Metaphysik muß Wissenschaft sein, nicht allein im Ganzen, sondern auch allen ihren Theilen, sonst ist sie gar nichts, weil sie als Speculation der reinen Vernunft sonst nirgends Haltung hat als an allgemeinen Einsichten. Außer ihr aber können Wahrscheinlichkeit und gesunder Menschenverstand gar wohl ihren nützlichen und rechtmäßigen Gebrauch haben, aber nach ganz eigenen Grundsätzen, deren Gewicht immer von der Beziehung aufs Praktische abhängt.
Das ist es, was ich zur Möglichkeit einer Metaphysik als Wissenschaft zu fordern mich berechtigt halte.
Musean translation
Mouseia’s complete machine-assisted Musean translation, made directly from the complete German of the Prolegomena (AA IV 253–383, all §§1–60 and the Appendix), for fidelity, the steps of Kant’s argument, clarity and structure.
Solution of the general question of the Prolegomena.
How is metaphysics possible as a science?
Metaphysics exists as a natural predisposition of reason, but on its own it is also dialectical and deceptive, as the analytic solution of the third principal question showed. To draw principles from this predisposition, then, and in using them to follow an illusion that is natural but nonetheless false, can never produce science. It can produce only a vain dialectical art, in which one school may outdo another, but none can ever win rightful and lasting assent.
If metaphysics as a science is to claim not merely deceptive persuasion but insight and conviction, a critique of reason itself must set out the entire stock of a priori concepts; their division according to their various sources (sensibility, understanding, and reason); a complete table of them; and the analysis of all these concepts, together with everything that can be inferred from them. Above all, it must then establish, through the deduction of these concepts, the possibility of synthetic a priori cognition, the principles of their use, and finally the limits of that use—all within a complete system. Critique, and critique alone, thus contains the entire thoroughly tested and substantiated plan, indeed all the means of carrying it out, by which metaphysics can be brought into being as a science. By any other paths or means it is impossible. The question here, then, is not so much how this undertaking is possible, but how to set it in motion, how to turn capable minds from their previous misguided and fruitless work toward an unerring approach, and how best to direct their united efforts toward the common goal.
This much is certain: anyone who has once tasted critique will forever be disgusted by all the dogmatic babble he previously made do with out of necessity, because his reason needed something and could find nothing better to occupy it. Critique stands to ordinary school metaphysics exactly as chemistry stands to alchemy, or astronomy to fortune-telling astrology. I will vouch for this: no one who has thought through and grasped the principles of critique, even as presented in these Prolegomena alone, will ever return to that old and sophistical sham science. Rather, he will look forward with a certain delight to a metaphysics now entirely within his power, requiring no further preliminary discoveries, and capable for the first time of giving reason lasting satisfaction. For among all possible sciences, metaphysics alone can confidently count on this advantage: it can be brought to completion and to a stable condition, in which it need undergo no further change and can receive no additions through new discoveries. Here reason has the sources of its cognition not in objects and their intuition, from which it cannot learn anything further, but within itself. Once it has set out the fundamental laws of its capacity completely and with a precision that excludes every misinterpretation, nothing remains that pure reason could cognize a priori, or even ask about with justification. The assured prospect of knowledge so definite and self-contained has a particular attraction, even if we set aside all its usefulness, of which I will speak later.
Every spurious art, every hollow wisdom, has its day; eventually it destroys itself, and its highest cultivation is also the moment of its downfall. That this time has now come for metaphysics is shown by the condition into which it has fallen among all learned nations, despite the zeal otherwise devoted to sciences of every kind. The old organization of university studies still preserves its shadow; a single academy of sciences still occasionally encourages one attempt or another by offering prizes. Yet it is no longer counted among the solid sciences, and anyone may judge for himself how an intelligent man would receive the well-meant but scarcely envied compliment of being called a great metaphysician.
But although the time of decline for all dogmatic metaphysics is undoubtedly here, much is still lacking before we can say that the time of its rebirth through a thorough and complete critique of reason has arrived in turn. Every transition from one inclination to its opposite passes through a state of indifference, and this moment is the most dangerous for an author, but, it seems to me, the most favorable for the science. For when partisan feeling has died out through the complete dissolution of former ties, minds are in the best condition to listen gradually to proposals for an alliance on a different plan.
When I say that I hope these Prolegomena may stimulate inquiry in the field of critique and offer the general spirit of philosophy, which seems to lack nourishment in its speculative part, a new and promising subject to engage it, I can already imagine the question everyone will ask who grew impatient and weary on the thorny paths along which I led him in the Critique: On what do I base this hope? I answer: on the irresistible law of necessity.
We can no more expect the human mind ever to abandon metaphysical inquiries altogether than expect ourselves to stop breathing altogether rather than keep drawing impure air. There will therefore always be metaphysics in the world, and, what is more, in every person, especially every reflective person. In the absence of a public standard, each will fashion it to suit himself. Now, what has so far been called metaphysics can satisfy no examining mind, yet renouncing it altogether is also impossible. In the end, then, a critique of pure reason itself must be attempted, or, if one already exists, examined and submitted to general scrutiny. There is otherwise no means of meeting this pressing need, which is something more than mere curiosity.
Since becoming acquainted with critique, whenever I have finished reading a work of metaphysical content that entertained and cultivated me through the precision of its concepts, its variety and order, and its easy presentation, I have been unable to refrain from asking: Has this author advanced metaphysics even a single step? I ask the forgiveness of those learned men whose writings have benefited me in other respects and have always helped cultivate my mental powers. For I confess that neither in their attempts nor in my own more modest ones, for which self-love nonetheless pleads, have I been able to find the slightest advance in the science. The reason is quite natural: the science did not yet exist, and it cannot be assembled piecemeal; its germ must first be fully preformed in critique. To prevent any misunderstanding, however, we must recall from what has gone before that although the analytic treatment of our concepts certainly does much to benefit the understanding, it does not advance the science of metaphysics in the least. These analyses of concepts are only the materials from which the science must first be built. Thus one may analyze and define the concept of substance and accident as beautifully as one likes; that is all very well as preparation for some future use. But if I cannot prove that in everything that exists substance persists and only accidents change, all that analysis has not advanced the science in the least. So far metaphysics has been unable to give a valid a priori proof of this proposition, or of the principle of sufficient reason, much less of any more complex proposition, such as one belonging to the doctrine of the soul or cosmology, or indeed of any synthetic proposition whatever. All that analysis has therefore accomplished, created, and advanced nothing; after so much bustle and noise, the science still stands where it stood in Aristotle’s day, although the preparations for it have unquestionably been made much better than before, if only the guiding thread to synthetic cognitions had first been found.
If anyone feels offended by this, he can easily refute the charge. Let him cite just one synthetic proposition belonging to metaphysics that he offers to prove a priori in a dogmatic manner. Only when he achieves this will I grant that he has really advanced the science, even if ordinary experience already confirms the proposition sufficiently. No demand could be more moderate or fair; and in the inevitably certain event of failure, no verdict could be more just than this: metaphysics as a science has never yet existed at all.
Should the challenge be accepted, I must ask that only two things be excluded: first, the plaything of probability and conjecture, which suits metaphysics as poorly as it does geometry; second, decisions reached by the divining rod of so-called common sense, which does not respond for everyone but follows personal characteristics.
As for the first, nothing could be more absurd than to seek to ground one’s judgments on probability and conjecture in metaphysics, a philosophy of pure reason. Whatever is to be cognized a priori is thereby declared apodictically certain, and must therefore be proved as such. One might just as well try to found geometry or arithmetic on conjectures. For the latter’s calculus probabilium contains not probable judgments but entirely certain judgments about the degree of possibility of certain cases under given conditions of the same kind. In the sum of all possible cases these must accord with the rule without fail, although the rule is not sufficiently determinate for each individual occurrence. Only in empirical natural science may conjectures be admitted, through induction and analogy, and even there the possibility of what I assume must at least be entirely certain.
The appeal to common sense is, if possible, in an even worse position when the issue is concepts and principles, not insofar as they are to hold for experience, but insofar as they are claimed to hold even outside the conditions of experience. For what is sound understanding? It is ordinary understanding insofar as it judges correctly. And what, then, is ordinary understanding? It is the capacity to cognize and use rules in concreto, as distinguished from speculative understanding, which is the capacity to cognize rules in abstracto. Ordinary understanding will thus scarcely understand the rule that everything that happens is determined through its cause, and will never be able to discern it in this general form. It therefore asks for an example from experience. When it hears that this means nothing other than what it has always thought whenever a windowpane was broken or a household object went missing, it understands the principle and accepts it as well. Ordinary understanding thus has no further use than where it can see its rules confirmed in experience, although they really do belong to it a priori. To discern them a priori and independently of experience, then, is a matter for speculative understanding and lies entirely outside the horizon of ordinary understanding. Yet metaphysics is concerned solely with the latter kind of cognition. It is surely a poor sign of sound understanding to appeal to that authority, which has no judgment at all in this matter and which one otherwise tends to look down on, except when one is hard pressed and at a loss for guidance or help in one’s speculation.
There is a familiar evasion regularly employed by these false friends of ordinary common sense, who praise it highly on occasion but generally despise it. They say: There must, after all, be some propositions that are immediately certain, for which not only is no proof required, but no account at all; otherwise we could never reach an end to the grounds of our judgments. But to justify this license they can never cite anything indubitable that they may immediately attribute to ordinary common sense—apart from the principle of contradiction, which is insufficient to establish the truth of synthetic judgments—except mathematical propositions: for example, that twice two makes four, that between two points there is only one straight line, and so on. But these judgments are worlds apart from those of metaphysics. For in mathematics I can myself make, or construct, through my thinking everything that I represent to myself through a concept as possible. I successively add one two to another two and myself make the number four; or in thought I draw all sorts of lines from one point to another, and can draw only a single one that is similar to itself in all its parts, equal as well as unequal. But from the concept of one thing, all my powers of thought cannot extract the concept of something else whose existence is necessarily connected with the first. I must consult experience. And although my understanding supplies me a priori—yet always only in relation to possible experience—with the concept of such a connection, that of causality, I still cannot present it a priori in intuition, as I can the concepts of mathematics, and thus demonstrate its possibility a priori. Rather, if this concept is to be valid a priori—as metaphysics requires—then, together with the principles of its application, it always needs a justification and a deduction of its possibility. Otherwise we do not know how far it is valid, or whether it can be used only within experience or also beyond it. In metaphysics, then, as a speculative science of pure reason, we can never appeal to ordinary common sense. We can, however, appeal to it when we are compelled to leave metaphysics behind and renounce all pure speculative cognition, which must always be knowledge, and therefore also renounce metaphysics itself and its instruction in certain matters; when a rational faith is found to be the only thing possible for us and sufficient for our needs, perhaps even more beneficial than knowledge itself. For then the situation is entirely changed. Metaphysics must be science, not only as a whole but in all its parts, or else it is nothing at all; as speculation of pure reason, it has nowhere to find support except in universal insights. Outside it, however, probability and common sense may well have their useful and rightful employment, but according to quite distinct principles, whose weight always depends on their relation to the practical.
This is what I consider myself entitled to require for the possibility of metaphysics as a science.
Plain English translation
Mouseia’s complete Plain English edition, made independently and directly from the same complete German text.
Answer to the general question of the Prolegomena.
How is metaphysics possible as a science?
Metaphysics exists as a natural tendency of reason. But on its own it also leads to dialectical conflict and deception, as the analytical answer to the third main question showed. So if we take our principles from this tendency and follow its natural but still false illusion when using them, we can never produce science. We can produce only an empty art of dialectic. One school may outdo another in this art, but none can ever win justified and lasting acceptance.
For metaphysics to claim insight and conviction as a science, rather than deceptive persuasion alone, a critique of reason itself must set out everything in a complete system. This includes the whole stock of a priori concepts; their division according to their different sources in sensibility, understanding, and reason; a complete table of them; and an analysis of all these concepts, together with everything that can be inferred from them. Above all, it must establish the possibility of synthetic a priori cognition by a deduction of these concepts. It must also set out the principles for using them and, finally, the limits of that use. Critique, and critique alone, therefore contains the whole carefully tested and verified plan for establishing metaphysics as a science. It even contains all the means for carrying out that plan. No other ways or means can achieve this. So the question here is not so much how the task is possible. It is how to get it started, how to lead able minds away from their previous misguided and fruitless work toward a reliable approach, and how best to direct their combined efforts toward the shared goal.
One thing is certain. Anyone who has once tried critique will always be disgusted by the dogmatic chatter he used to put up with out of necessity. His reason needed something, and he could find nothing better to occupy it. Critique stands in exactly the same relation to ordinary school metaphysics as chemistry to alchemy, or astronomy to fortune-telling astrology. I guarantee that no one who has thought through and grasped the principles of critique, even just in these Prolegomena, will ever return to that old, sophistical sham science. Instead, he will look forward with real pleasure to a metaphysics now fully within his reach. It needs no further preliminary discoveries, and it can for the first time give reason lasting satisfaction. Among all possible sciences, metaphysics alone can confidently count on this advantage: it can be completed and brought to a stable condition. It will then need no further changes and cannot be enlarged by new discoveries. Here reason finds the sources of its cognition not in objects and its intuition of them, through which it can learn nothing further, but within itself. Once it has completely set out the fundamental laws of its capacity, in a form secure against every misinterpretation, nothing remains that pure reason could know a priori, or could even reasonably ask. The sure prospect of knowledge so definite and complete has a special appeal, even if we set aside all its usefulness, which I will discuss later.
Every false art and every empty claim to wisdom lasts for a time. Eventually it destroys itself, and its highest development is also the moment of its downfall. For metaphysics, that time has now come. Its decline among all learned nations proves this, despite the energy devoted to every other kind of science. The old organization of university studies still preserves its shadow. One academy of sciences still occasionally offers prizes to encourage one attempt or another in it. But metaphysics is no longer counted among the solid sciences. Readers can judge for themselves how an intelligent man might receive the well-meant but hardly enviable compliment of being called a great metaphysician.
The time for the decline of all dogmatic metaphysics has undoubtedly arrived. But much is still missing before we can say that the time for its rebirth through a thorough and complete critique of reason has also arrived. Every transition from one inclination to its opposite passes through a state of indifference. This moment is the most dangerous for an author, but in my view it is the most favorable for science. Once former alliances have broken up completely and partisan feeling has died out, minds are in the best condition to listen gradually to proposals for joining forces on a different plan.
I hope these Prolegomena may stimulate research in the field of critique. I hope they may give the general spirit of philosophy a new and promising subject to occupy it, since its speculative side seems to lack nourishment. When I say this, I can already imagine the question from everyone whom the thorny paths I led them along in the Critique have irritated and exhausted: What grounds do I have for this hope? My answer is: the irresistible law of necessity.
We can no more expect the human mind to give up metaphysical investigations entirely than expect ourselves to stop breathing altogether to avoid always breathing impure air. So there will always be metaphysics in the world. More than that, everyone, especially every reflective person, will have one. Without a public standard, each will shape it in his own way. Now, what has so far been called metaphysics cannot satisfy a questioning mind. Yet giving it up altogether is also impossible. So in the end a critique of pure reason itself must be attempted. Or, if one already exists, it must be examined and submitted to general scrutiny. There is no other way to meet this urgent need, which is more than mere curiosity.
Since becoming familiar with critique, whenever I have finished reading a work on metaphysics that both entertained and educated me through its precise concepts, its variety and order, and its easy presentation, I have been unable to avoid asking: Has this author advanced metaphysics by even one step? I ask the learned men whose writings have helped me in other ways, and have always helped develop my mental powers, to forgive this admission. Neither in their attempts nor in my own lesser ones, for which self-love still speaks favorably, have I found that the science has advanced in the slightest. The reason is quite natural. The science did not yet exist, and it cannot be assembled piece by piece. Its seed must first be fully formed in critique. To prevent any misunderstanding, we must remember what was said earlier. An analytical treatment of our concepts can certainly do a great deal for the understanding. But it does not advance the science of metaphysics in the slightest. These analyses of concepts are only materials from which the science must first be built. We may analyze and define the concept of substance and accident as well as we like. This is very good as preparation for some future use. But unless I can prove that substance persists in everything that exists and only accidents change, all that analysis has not advanced the science in the slightest. So far metaphysics has been unable to give a valid a priori proof of this proposition or of the principle of sufficient reason. Still less has it proved any more complex proposition, such as one belonging to the theory of the soul or to cosmology. In fact it has proved no synthetic proposition at all in this way. So all that analysis has accomplished, created, and advanced nothing. After so much activity and noise, the science is still where it was in Aristotle's time. Admittedly, the preparations for it are much better than before, if only a guiding thread for synthetic cognition had first been found.
Anyone who feels offended by this can easily refute the accusation. He need only present a single synthetic proposition belonging to metaphysics that he offers to prove a priori by the dogmatic method. Only when he supplies that proof will I concede that he has really advanced the science, even if ordinary experience already confirms the proposition well enough. No demand could be more moderate or fair. And if he fails, as he inevitably and certainly will, no judgment could be more just than this: metaphysics as a science has so far never existed.
If the challenge is accepted, I must exclude just two things. First, no playing with probability and guesswork. They are as inappropriate in metaphysics as in geometry. Second, no settling the matter with the divining rod of so-called common sense. This rod does not respond for everyone; its responses depend on personal characteristics.
As for the first, nothing could be more absurd than trying to base judgments on probability and guesswork in metaphysics, a philosophy drawn from pure reason. To claim that something is known a priori is to claim that it is absolutely and necessarily certain. So it must also be proved in that way. We might just as well try to base geometry or arithmetic on guesses. Arithmetic's calculus probabilium does not contain probable judgments. It contains entirely certain judgments about the degree of possibility of particular cases under given conditions of the same kind. Across the total of all possible cases, these must unfailingly agree with the rule, even though the rule is not definite enough for each individual occurrence. Only in empirical natural science can conjectures be allowed, through induction and analogy. Even there, at least the possibility of what I assume must be completely certain.
The appeal to common sense is, if possible, in an even worse position. Here we are talking about concepts and principles not insofar as they are supposed to hold for experience, but insofar as they are claimed to hold even outside the conditions of experience. What is sound understanding? It is ordinary understanding insofar as it judges correctly. And what is ordinary understanding? It is the ability to know and use rules in concrete cases, as distinct from speculative understanding, which is the ability to know rules in the abstract. Ordinary understanding will scarcely understand the rule that everything that happens is determined through its cause. It can never grasp it in this general form. So it asks for an example from experience. When it hears that the rule means nothing different from what it has always thought when a windowpane broke or a household item went missing, it understands and accepts the principle. Ordinary understanding therefore has no use beyond cases where it can see its rules confirmed in experience, even though it really does possess them a priori. Understanding them a priori and independently of experience belongs instead to speculative understanding. It lies entirely outside the range of ordinary understanding. But metaphysics deals solely with this latter kind of cognition. It is surely a poor sign of sound understanding to appeal to a witness who has no judgment at all in this matter. Usually this witness is looked down on, except when people find themselves cornered and cannot find any guidance or help in their speculations.
These false friends of ordinary common sense praise it highly on occasion but usually despise it. They have a familiar escape. They say that there must ultimately be some propositions that are immediately certain. Not only do these need no proof; no account of them at all need be given. Otherwise we would never reach an end to the grounds of our judgments. But to justify this claim, they can never cite anything beyond mathematical propositions as unquestionably and immediately available to ordinary common sense. Examples are that twice two is four and that only one straight line lies between two points, and so on. They can also cite the principle of contradiction, but that is not enough to establish the truth of synthetic judgments. Mathematical judgments, however, are worlds apart from those of metaphysics. In mathematics I can make, or construct, through my own thinking everything that a concept represents to me as possible. I add another two to two step by step, and make the number four myself. Or I mentally draw all kinds of lines from one point to another. I can draw only one that is alike in all its parts, whether those parts are equal or unequal. But no amount of thinking can extract from the concept of one thing the concept of something else whose existence is necessarily connected with the first. I have to consult experience. My understanding does provide me a priori with the concept of such a connection, causality, though always only in relation to possible experience. Yet I cannot present this concept a priori in intuition, as I can with mathematical concepts, and so establish its possibility a priori. Instead, if this concept and the principles for applying it are to be valid a priori, as metaphysics requires, their possibility always needs a justification and a deduction. Otherwise we do not know how far the concept is valid, or whether it can be used only within experience or outside it as well. So in metaphysics, as a speculative science of pure reason, we can never appeal to ordinary common sense. We can do so, however, when we are forced to leave metaphysics behind and give up all pure speculative cognition, which must always be knowledge. That means also giving up metaphysics itself and its teachings on certain matters. In that case, reasonable belief may turn out to be all that is possible for us and enough for our needs—perhaps even healthier than knowledge itself. The situation is then completely different. Metaphysics must be science, not just as a whole but in every part. Otherwise it is nothing at all. As speculation by pure reason, it has no support anywhere except in universal insights. Outside metaphysics, however, probability and common sense can certainly have their useful and legitimate applications. But these follow principles of their own, whose weight always depends on their relation to practical matters.
These are the requirements I consider myself entitled to set for the possibility of metaphysics as a science.
About this section
Solution: How is metaphysics possible as a science? is part of Prolegomena to Any Future Metaphysics by Immanuel Kant. This page sets the German original beside 2 direct-source translations, so any line can be checked against the source. It is section 71 of 72 in the work, which is kept in the European tradition.
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