One hundred and fifty years ago Immanuel Kant died, having spent the eighty years of his life in the Prussian provincial town of Königsberg. For years his retirement had been complete,1 and his friends intended a quiet burial. But this son of an artisan was buried like a king. When the rumour of his death spread through the town the people flocked to his house demanding to see him. On the day of the funeral the life of the town was at a standstill. The coffin was followed by thousands, while the bells of all the churches tolled. Nothing like this had ever before happened in Königsberg, say the chroniclers.2
It is difficult to account for this astonishing upsurge of popular feeling. Was it due solely to Kant’s reputation as a great philosopher and a good man? It seems to me that there was more in it than this; and I suggest that in the year 1804, under the absolute monarchy of Frederick William, those bells tolling for Kant carried an echo of the American and French revolutions—of the ideas of 1776 and 1789. I suggest that to his countrymen Kant had become an embodiment of these ideas.3 They came to show their gratitude to a teacher of the Rights of Man, of equality before the law, of world citizenship, of peace on earth, and, perhaps most important, of emancipation through knowledge.4
Most of these ideas had reached the Continent from England through a book published in 1733, Voltaire’s Letters Concerning the English Nation. In this book Voltaire contrasts English constitutional government with Continental absolute monarchy; English religious toleration with the attitude of the Roman Church; and the explanatory power of Newton’s cosmology and of Locke’s analytic empiricism with the dogmatism of Descartes. Voltaire’s book was burnt; but its publication marks the beginning of a philosophical movement—a movement whose peculiar mood of intellectual aggressiveness was little understood in England, where there was no occasion for it.
Sixty years after Kant’s death these same English ideas were being presented to the English as a ‘shallow and pretentious intellectualism’: and ironically enough the English word ‘Enlightenment’, which was then used to name the movement started by Voltaire, is still beset by this connotation of shallowness and pretentiousness; this, at least, is what the Oxford English Dictionary tells us.5 I need hardly add that no such connotation is intended when I use the word ‘Enlightenment’.
Kant believed in the Enlightenment. He was its last great defender. I realize that this is not the usual view. While I see Kant as the defender of the Enlightenment, he is more often taken as the founder of the school which destroyed it—of the Romantic School of Fichte, Schelling, and Hegel. I contend that these two interpretations are incompatible.
Fichte, and later Hegel, tried to appropriate Kant as the founder of their school. But Kant lived long enough to reject the persistent advances of Fichte, who proclaimed himself Kant’s successor and heir. In A Public Declaration Concerning Fichte,6 which is too little known, Kant wrote: ‘May God protect us from our friends. … For there are fraudulent and perfidious so-called friends who are scheming for our ruin while speaking the language of good-will.’ It was only after Kant’s death, when he could no longer protest, that this world-citizen was successfully pressed into the service of the nationalistic Romantic School, in spite of all his warnings against romanticism, sentimental enthusiasm, and Schwärmerei. But let us see how Kant himself describes the idea of the Enlightenment:7
Enlightenment is the emancipation of man from a state of self-imposed tutelage … of incapacity to use his own intelligence without external guidance. Such a state of tutelage I call ‘self-imposed’ if it is due, not to lack of intelligence, but to lack of courage or determination to use one’s own intelligence without the help of a leader. Sapere aude! Dare to use your own intelligence! This is the battle-cry of the Enlightenment.
Kant is saying something very personal here. It is part of his own history. Brought up in near poverty, in the narrow outlook of Pietism—a severe German version of Puritanism—his own life was a story of emancipation through knowledge. In later years he used to look back with horror to what he called8 ‘the slavery of childhood’, his period of tutelage. One might well say that the dominant theme of his whole life was the struggle for spiritual freedom.
A decisive role in this struggle was played by Newton’s theory, which had been made known on the Continent by Voltaire. The cosmology of Copernicus and Newton became the powerful and exciting inspiration of Kant’s intellectual life. His first important book,9 The Theory of the Heavens, has the interesting sub-title: An Essay on the Constitution and the Mechanical Origin of the Universe, Treated According to Newtonian Principles. It is one of the greatest contributions ever made to cosmology and cosmogony. It contains the first formulation not only of what is now called the ‘Kant-Laplace hypothesis’ of the origin of the solar system, but also, anticipating Jeans, an application of this idea to the ‘Milky Way’ (which Thomas Wright had interpreted as a stellar system five years earlier). But all this is excelled by Kant’s identification of the nebulae as other ‘Milky Ways’—distant stellar systems similar to our own.
It was the cosmological problem, as Kant explains in one of his letters,10 which led him to his theory of knowledge, and to his Critique of Pure Reason. He was concerned with the knotty problem (which has to be faced by every cosmologist) of the finitude or infinity of the universe, with respect to both space and time. As far as space is concerned a fascinating solution has been suggested since, by Einstein, in the form of a world which is both finite and without limits. This solution cuts right through the Kantian knot, but it uses more powerful means than those available to Kant and his contemporaries. As far as time is concerned no equally promising solution of Kant’s difficulties has been offered up to now.
Kant tells us11 that he came upon the central problem of his Critique when considering whether the universe had a beginning in time or not. He found to his dismay that he could produce seemingly valid proofs for both of these possibilities. The two proofs12 are interesting; it needs concentration to follow them, but they are not long, and not hard to understand.
For the first proof we start by analysing the idea of an infinite sequence of years (or days, or any other equal and finite intervals of time). Such an infinite sequence of years must be a sequence which goes on and on and never comes to an end. It can never be completed: a completed or an elapsed infinity of years is a contradiction in terms. Now in his first proof Kant simply argues that the world must have a beginning in time since otherwise, at this present moment, an infinite number of years must have elapsed; which is impossible. This concludes the first proof.
For the second proof we start by analysing the idea of a completely empty time—the time before there was a world. Such an empty time, in which there is nothing whatever, must be a time none of whose time-intervals is differentiated from any other by its temporal relation to things and events, since things and events simply do not exist at all. Now take the last interval of the empty time—the one immediately before the world begins. Clearly, this interval is differentiated from all earlier intervals since it is characterized by its close temporal relation to an event—the beginning of the world; yet the same interval is supposed to be empty, which is a contradiction in terms. Now in his second proof Kant simply argues that the world cannot have a beginning in time since otherwise there would be a time-interval—the moment immediately before the world began—which is empty and yet characterized by its immediate temporal relation to an event in the world; which is impossible.
We have here a clash between two proofs. Such a clash Kant called an ‘antinomy’. I shall not trouble you with the other antinomies in which Kant found himself entangled, such as those concerning the limits of the universe in space.
What lesson did Kant draw from these bewildering antinomies? He concluded13 that our ideas of space and time are inapplicable to the universe as a whole. We can, of course, apply the ideas of space and time to ordinary physical things and physical events. But space and time themselves are neither things nor events: they cannot even be observed: they are more elusive. They are a kind of framework for things and events: something like a system of pigeon-holes, or a filing system, for observations. Space and time are not part of the real empirical world of things and events, but rather part of our mental outfit, our apparatus for grasping this world. Their proper use is as instruments of observation: in observing any event we locate it, as a rule, immediately and intuitively in an order of space and time. Thus space and time may be described as a frame of reference which is not based upon experience but intuitively used in experience, and properly applicable to experience. This is why we get into trouble if we misapply the ideas of space and time by using them in a field which transcends all possible experience—as we did in our two proofs about the universe as a whole.
To the view which I have just outlined Kant chose to give the ugly and doubly misleading name ‘Transcendental Idealism’. He soon regretted this choice,14 for it made people believe that he was an idealist in the sense of denying the reality of physical things: that he declared physical things to be mere ideas. Kant hastened to explain that he had only denied that space and time are empirical and real— empirical and real in the sense in which physical things and events are empirical and real. But in vain did he protest. His difficult style sealed his fate: he was to be revered as the father of German Idealism. I suggest that it is time to put this right. Kant always insisted15 that the physical things in space and time are real. And as to the wild and obscure metaphysical speculations of the German Idealists, the very title of Kant’s Critique was chosen to announce a critical attack upon all such speculative reasoning. For what the Critique criticizes is pure reason; it criticizes and attacks all reasoning about the world that is ‘pure’ in the sense of being untainted by sense experience. Kant attacked pure reason by showing that pure reasoning about the world must always entangle us in antinomies. Stimulated by Hume, Kant wrote his Critique in order to establish16 that the limits of sense experience are the limits of all sound reasoning about the world.
Kant’s faith in his theory of space and time as an intuitive frame of reference was confirmed when he found in it a key to the solution of a second problem. This was the problem of the validity of Newtonian theory in whose absolute and unquestionable truth he believed,17 in common with all contemporary physicists. It was inconceivable, he felt, that this exact mathematical theory should be nothing but the result of accumulated observations. But what else could be its basis? Kant approached this problem by first considering the status of geometry. Euclid’s geometry is not based upon observation, he said, but upon our intuition of spatial relations. Newtonian science is in a similar position. Although confirmed by observations it is the result not of these observations but of our own ways of thinking, of our attempts to order our sense-data, to understand them, and to digest them intellectually. It is not these sense-data but our own intellect, the organization of the digestive system of our mind, which is responsible for our theories. Nature as we know it, with its order and with its laws, is thus largely a product of the assimilating and ordering activities of our mind. In Kant’s own striking formulation of this view,18 ‘Our intellect does not draw its laws from nature, but imposes its laws upon nature’.
This formula sums up an idea which Kant himself proudly calls his ‘Copernican Revolution’. As Kant puts it, Copernicus,19 finding that no progress was being made with the theory of the revolving heavens, broke the deadlock by turning the tables, as it were: he assumed that it is not the heavens which revolve while we the observers stand still, but that we the observers revolve while the heavens stand still. In a similar way, Kant says, the problem of scientific knowledge is to be solved— the problem how an exact science, such as Newtonian theory, is possible, and how it could ever have been found. We must give up the view that we are passive observers, waiting for nature to impress its regularity upon us. Instead we must adopt the view that in digesting our sense-data we actively impress the order and the laws of our intellect upon them. Our cosmos bears the imprint of our minds.
By emphasizing the role played by the observer, the investigator, the theorist, Kant made an indelible impression not only upon philosophy but also upon physics and cosmology. There is a Kantian climate of thought without which Einstein’s theories or Bohr’s are hardly conceivable; and Eddington might be said to be more of a Kantian, in some respects, than Kant himself. Even those who, like myself, cannot follow Kant all the way can accept his view that the experimenter must not wait till it pleases nature to reveal her secrets, but that he must question her.20 He must cross-examine nature in the light of his doubts, his conjectures, his theories, his ideas, and his inspirations. Here, I believe, is a wonderful philosophical find. It makes it possible to look upon science, whether theoretical or experimental, as a human creation, and to look upon its history as part of the history of ideas, on a level with the history of art or of literature.
There is a second and even more interesting meaning inherent in Kant’s version of the Copernican Revolution, a meaning which may perhaps indicate an ambivalence in his attitude towards it. For Kant’s Copernican Revolution solves a human problem to which Copernicus’ own revolution gave rise. Copernicus deprived man of his central position in the physical universe. Kant’s Copernican Revolution takes the sting out of this. He shows us not only that our location in the physical universe is irrelevant, but also that in a sense our universe may well be said to turn about us; for it is we who produce, at least in part, the order we find in it; it is we who create our knowledge of it. We are discoverers: and discovery is a creative art.
From Kant the cosmologist, the philosopher of knowledge and of science, I now turn to Kant the moralist. I do not know whether it has been noticed before that the fundamental idea of Kant’s ethics amounts to another Copernican Revolution, analogous in every respect to the one I have described. For Kant makes man the lawgiver of morality just as he makes him the lawgiver of nature. And in doing so he gives back to man his central place both in his moral and in his physical universe. Kant humanized ethics, as he had humanized science.
Kant’s Copernican Revolution in the field of ethics21 is contained in his doctrine of autonomy—the doctrine that we cannot accept the command of an authority, however exalted, as the ultimate basis of ethics. For whenever we are faced with a command by an authority, it is our responsibility to judge whether this command is moral or immoral. The authority may have power to enforce its commands, and we may be powerless to resist. But unless we are physically prevented from choosing the responsibility remains ours. It is our decision whether to obey a command, whether to accept authority.
Kant boldly carries this revolution into the field of religion. Here is a striking passage:22
Much as my words may startle you, you must not condemn me for saying: every man creates his God. From the moral point of view … you even have to create your God, in order to worship in Him your creator. For in whatever way … the Deity should be made known to you, and even … if He should reveal Himself to you: it is you … who must judge whether you are permitted [by your conscience] to believe in Him, and to worship Him.
Kant’s ethical theory is not confined to the statement that a man’s conscience is his moral authority. He also tries to tell us what our conscience may demand from us. Of this, the moral law, he gives several formulations. One of them is:23 ‘Always regard every man as an end in himself, and never use him merely as a means to your ends.’ The spirit of Kant’s ethics may well be summed up in these words: dare to be free; and respect the freedom of others.
Upon the basis of these ethics Kant erected his most important theory of the state,24 and his theory of international law. He demanded25 a league of nations, or a federal union of states, which ultimately was to proclaim and to maintain eternal peace on earth.
I have tried to sketch in broad outline Kant’s philosophy of man and his world, and its two main inspirations—Newtonian cosmology, and the ethics of freedom; the two inspirations to which Kant referred when he spoke26 of the starry heavens above us and the moral law within us.
Stepping back further to get a still more distant view of Kant’s historical role, we may compare him with Socrates. Both were accused of perverting the state religion, and of corrupting the minds of the young. Both denied the charge; and both stood up for freedom of thought. Freedom meant more to them than absence of constraint; it was for both a way of life.
From Socrates’ apology and from his death there sprang a new idea of a free man: the idea of a man whose spirit cannot be subdued; of a man who is free because he is self-sufficient; who is not in need of constraint because he is able to rule himself, and to accept freely the rule of law.
To this Socratic idea of self-sufficiency, which forms part of our western heritage, Kant has given a new meaning in the fields of both knowledge and morals. And he has added to it further the idea of a community of free men—of all men. For he has shown that every man is free; not because he is born free, but because he is born with the burden of responsibility for free decision.
A broadcast given on the eve of the hundred and fiftieth anniversary of Kant’s death. First published (without the footnotes) under the title ‘Immanuel Kant: Philosopher of the Enlightenment’ in The Listener, 51, 1954.
1 Six years before Kant’s death, Pörschke reports (see his letter to Fichte of 2nd July 1798) that owing to Kant’s retired way of life, he was being forgotten even in Königsberg.
2 C.E.A.Ch. Wasianski, Immanuel Kant in seinen letzten Lebensjahren (from Ueber Immanuel Kant. Dritter Band, Königsberg, bei Nicolovius, 1804). ‘The public newspapers and a special publication have made Kant’s funeral known in all its circumstances.’
3 Kant’s sympathies with the ideas of 1776 and 1789 were well known, for he used to express them in public. (Cf. Motherby’s eye-witness report on Kant’s first meeting with Green in R. B. Jachmann, Immanuel Kant geschildert in Briefen—Ueber Immanuel Kant, Zweiter Band, Königsberg bei Nicolovius, 1804; eighth letter; pp. 54 f. of the edition of 1902).
4 I say ‘most important’ because Kant’s well-deserved rise from near poverty to fame and comparatively easy circumstances helped to create on the Continent the idea of emancipation through self-education, in this form hardly known in England where the ‘self-made man’ was the uncultured upstart. On the Continent, the educated had been for a long time the middle classes, while in England they were the upper classes.
5 The O.E.D. says (some of the italics are mine): ‘Enlightenment … 2. Sometimes used [after the German Aufklärung, Aufklärerei] to designate the spirit and the aims of the French philosophers of the 18th c., of others whom it is intended to associate with them in the implied charge of shallow and pretentious intellectualism, unreasonable contempt of tradition and authority, etc.’ The O.E.D. does not mention that ‘Aufklärung’ is a translation of the French ‘éclaircissement’, and that it does not have these connotations in German, while ‘Aufklärerei’ (or ‘Aufkläricht’) are disparaging neologisms invented and exclusively used by the Romantics, the enemies of the Enlightenment. The O.E.D. quotes J. H. Stirling, The Secret of Hegel, 1865, and Caird, The Philosophy of Kant, 1889, as users of the word in sense 2.
6 The date of this Declaration is 1799. Cf. WWC (i.e. Immanuel Kant’s Werke, ed. Ernst Cassirer, et al.), vol. VIII, pp. 515 f., and my Open Society, note 58 to ch. 12 (4th edn. 1962, vol. II, p. 313).
7 What is Enlightenment (1785); WWC, IV, p. 169.
8 See T. G. von Hippel’s Biography (Gotha, 1801, pp. 78 f.). See also the letter to Kant from D. Ruhnken (one of Kant’s schoolfellows in the Pietist Frederickan College), in Latin, of 10th March 1771, in which he speaks of the ‘stern yet not regrettable discipline of the fanatics’ who had educated them.
9 Published in 1755. The full principal title might be translated: General Natural History [of the Heavens] and Theory of the Heavens. The words ‘General Natural History’ are used to indicate that the work is a contribution to the theory of the evolution of stellar systems.
10 To C. Garve, 21st September 1798. ‘My starting point was not an investigation into the existence of God, but the antinomy of pure reason: “The world has a beginning: it has no beginning”, etc. down to the fourth …’ (Here comes a place where Kant, apparently, mixes up his third and fourth antinomies.) ‘It was these [antinomies] which first stirred me from my dogmatic slumber and drove me to the critique of reason …, in order to resolve the scandal of the apparent contradiction of reason with itself.’
11 See the foregoing note. Cf. also Leibniz’s correspondence with Clarke (Philos. Bibl. edited by Kirchmann, 107, pp. 134 f., 147 f., 188 ff.), and Kant’s Reflexionen zur Kritischen Philosophie, edited by B. Erdmann; esp. No. 4.
12 See Critique of Pure Reason (2nd edn.), 454 ff.
13 Op. cit., 518 ff. ‘The Doctrine of Transcendental Idealism as the Key to the Solution of the Cosmological Dialectic.’
14 Prolegomena (1783), Appendix: ‘Specimen of a Judgment on the Critique Anticipating its Investigation’. See also the Critique, 2nd edn. (1787; the first edition had been published in 1781), pp. 274–9, ‘The Refutation of Idealism’, and the last footnote to the Preface of the Critique of Practical Reason.
15 See the passages mentioned in the foregoing note.
16 See Kant’s letter to M. Herz, of 21st February 1772, in which he gives, as a tentative title of what became the first Critique, ‘The Limits of Sense Experience and of Reason’. See also the Critique of Pure Reason (2nd edn.), pp. 738 f. (italics mine): ‘There is no need for a critique of reason in its empirical use; for its principles are continuously submitted to tests, being tested by the touchstone of experience. Similarly, there is no need for it within the field of mathematics, where its conceptions must be presented at once in pure intuition [of space and time] … But in a field in which reason is constrained neither by sense-experience nor by pure intuition to follow a visible track—namely, in the field of its transcendental use …—there is much need to discipline reason, so that its tendency to overstep the narrow limits of possible experience may be subdued …’
17 See, for example, Kant’s Metaphysical Foundations of Natural Science (1786), containing the a priori demonstration of Newtonian mechanics. See also the end of the penultimate paragraph of the Critique of Practical Reason. I have tried to show elsewhere (chapter 2 of this volume) that some of the greatest difficulties in Kant are due to the tacit assumption that Newtonian Science is demonstrably true (that it is epistēmē), and that, with the realization that this is not so, one of the most fundamental problems of the Critique dissolves. See also ch. 8, below.
18 See Prolegomena, end of section 37. Kant’s footnote referring to Crusius is interesting: it suggests that Kant had an inkling of the analogy between what he called his ‘Copernican Revolution’ and his principle of autonomy in ethics.
19 My text here is a free translation from the Critique of Pure Reason, 2nd edn., pp. xvi f.
20 Op. cit., pp. xii f.; cf. especially the passage: ‘The physicists … realized that they … had to compel Nature to reply to their questions, rather than let themselves be tied to her apron-strings, as it were.’
21 See the Grundlegung zur Met. d. Sitten, 2nd section (WWC, pp. 291 ff., especially 299 ff.): ‘The Autonomy of the Will as the Highest Principle of Morality’, and the 3rd section (WWC, pp. 305 ff.).
22 This is a free translation (although as close as is compatible with lucidity, I believe) from a passage contained in the footnote to the Fourth Chapter, Part II, § 1, of Religion within the Limits of Pure Reason (2nd edn., 1794 = WWC, vi, p. 318; the passage is not in the 1st edn., 1793. See also the Introduction to the present volume, note 9). The passage is foreshadowed by the following: ‘We ourselves judge revelation by the moral law’ (Lectures on Ethics by Immanuel Kant, translated by L. Infield 1930; the translation of the passage is corrected by P. A. Schilpp, Kant’s Pre-Critical Ethics, 1938, p. 166, note 63). Just before Kant says of the moral law that ‘our own reason is capable of revealing it to us’.
23 See the Grundlegung, 2nd section (WWC, iv, p. 287). My translation is, again, free.
24 See, especially, Kant’s various formulations to the effect that the principle of the just state is to establish equality in those limitations of the freedom of its citizens which are unavoidable if the freedom of each should coexist with the freedom of all (e.g. Critique of Pure Reason, 2nd edn., p. 373).
25 On Peace Eternal (1795).
26 At the ‘Conclusion’ of the Critique of Practical Reason; see especially the end of the penultimate paragraph, referred to in note 17 above.