Space, time, and gravitation

GENERAL RELATIVITY is Einstein's theory of gravitation. It is not only a theory of gravity: it is a theory of the structure of space and time, and hence a theory of the dynamics of the universe in its entirety. The theory is a vast edifice of pure geometry, indisputably elegant, and of great mathematical interest.

When general relativity emerged in its definitive form in November 1915, and became more widely known the following year with the publication of Einstein's famous exposé Die Grundlage der allgemeinen Relativitätstheorie in Annalen der Physik, the notions it propounded constituted a unique, revolutionary contribution to the progress of science. The story of its rapid, dramatic confirmation by the bending-of-light measurements associated with the eclipse of 1919 is thrilling part of the scientific history. The theory was quickly accepted as physically correct—but at the same time acquired a reputation for formidable mathematical complexity. So much so that it is said that when an American newspaper reporter asked Sir Arthur Eddington (the celebrated astronomer who had led the successful solar eclipse expedition) whether it was true that only three people in the world really understood general relativity, Eddington swiftly replied, “Ah, yes—but who's the third?”

The Cambridge University Press and the editors of the new series of Cambridge Texts in the History of Political Thought have kindly invited me to produce a second edition of Kant's Political Writings, of which the first edition first appeared in an earlier series almost twenty years ago. They also agreed that the volume might be enlarged by three additional texts. To decide on the most suitable texts presented me with anything but an easy choice. The three suitable pieces chosen, the reviews of Herder's Ideas on the Philosophy of the History of Mankind, Conjectures on the Beginning of Human History and What Is Orientation in Thinking?, are not ‘political’ writings in the narrow sense of the word. They do, however, supply a context for the strictly political writings published in the first edition; for all of them illustrate Kant's critical approach to reasoning and his attitude to the public use of reason without which political justice could not, in his view, be achieved. What Is Orientation in Thinking? does so particularly clearly. It also introduces the reader to the moral basis of Kant's politics, while the other two texts illustrate Kant's conception of history, another pillar of his political thought. I greatly regret that there was no space to include the other pieces relating to politics mentioned in the preface to the first edition. Perhaps one day the constraints on space will be less pressing and all writings by Kant which refer to politics, including the whole of the Theory of Right, can be printed in a later edition.

In order to keep down printing costs and make the volume affordable by students the text of the first edition could not be substantially altered. For this reason, it has unfortunately not been possible to revise and enlarge my introduction itself. I have, however, been able to add a postscript in which I take up issues raised during the discussion of Kant's political thought over the past two decades. I have also provided a more extensive bibliography and a new index.

My thanks are due to Barry Nisbet for translating the additional texts and for giving me invaluable help by commenting on and checking my manuscript.

Kant's essay was occasioned by a dispute between Moses Mendelssohn (1729-86), a Jewish philosopher of Berlin with whom Kant corresponded and whom he esteemed greatly, and Friedrich Heinrich Jacobi (1743-1819), a writer and friend of Goethe's who had attacked Mendelssohn's interpretation of Spinoza. It was a bitter dispute because Jacobi had, in Mendelssohn's view, maligned the reputation of their late common friend, the writer and dramatist Gotthold Ephraim Lessing (1729—81) when he claimed that Lessing had been a follower of Spinoza and hence a pantheist who did not believe in a personal God. Mendelssohn rebutted this charge and maintained that Jacobi had misunderstood Lessing. Their argument is of historical interest only.

Kant's essay, however, provides an introduction to his critical philosophy and shows how his discussion of the theoretical use of reason, as argued in detail in the Critique of Pure Reason and in the Prolegomena to Any Future Metaphysics That Can Claim the Status of a Science ﹛Prolegomena zu einer jeden künftigen Metaphysik die als Wissenschaft wird auftreten können) (1783), necessarily leads on to the practical use of reason as defined in his writings on ethics (for instance, in the Critique of Practical Reason (1788) and the Groundwork of the Metaphysics of Morals (Grundlegung zur Metaphysik der Sitten) (1785)), which in turn provide the foundation of his political writing. Kant did not openly attack either of the two writings in question, but thought it necessary to defend his late friend Mendelssohn while at the same time pointing out some shortcomings in Mendelssohn's argument (Mendelssohn had put forward proofs for the existence of God which Kant held to be illegitimate). He proceeds to show that the belief in reason is a ‘signpost or compass'1 which enables us to orientate our thinking. The use of reason is necessary in order to limit our enquiries to what can, in principle, be discovered and to prevent us from seeking to discover what is beyond the boundaries of knowledge. But the right use of reason also makes it possible for us to act morally. We have to avoid falling victim to zealotry or superstition—that would even be politically dangerous, for it would sooner or later lead to political repression by the authorities who would not be willing to tolerate the spreading of foolish and subversive opinions.