In this country Leibniz has received less attention than any other of the great philosophers. Mr. Merz has given, in a small volume, a general outline of Leibniz’s thought and work, Professor Sorley has written for the Encyclopaedia Britannica a remarkably clear, but brief, account of his philosophy, and there are American translations of the Nouveaux Essais and of some of his philosophical papers. That is very nearly the whole of English writing about him. Yet few philosophical systems stand so much in need of exposition as that of Leibniz. His theories have to be extracted from seven large volumes of correspondence, criticism, magazine articles, and other discursive writings, and it is only in recent years that this material has been made fully available by the publication of Gerhardt’s edition. No complete and detailed account of Leibniz’s philosophy has hitherto been published in English, and accordingly I have written a very full introduction to this book, with illustrative foot-notes, consisting mainly of translations from Leibniz himself.
The endeavour of the book is to make the Monadology clear to students. I cannot agree with Dillmann in treating it as of little importance. Leibniz himself expressly intended it to be a compact and ordered statement of the views he had expounded in many scattered papers and in his somewhat desultory Théodicée, the only book he published. There is evidence of this in his correspondence and in the fact that he annotated the Monadology with references to passages in the Théodicée. My original intention was to publish a translation of these passages along with the Monadology, but on re-consideration it seemed better to translate several short papers illustrating different parts of Leibniz’s system and explaining its growth. Thus the Monadology, as being the centre of the book, is printed first of the translations (although in date it is last), while the other writings follow in choronological order. The only disadvantage of this arrangement is that it places the Principles of Nature and of Grace, which is most akin to the Monadology, farthest away from it.
If I might venture to suggest to the student the way in which the book should be read, I would recommend him first to read Part I of the Introduction, then the Monadology (without the notes), afterwards Parts II and III of the Introduction, the Monadology again (with the notes), the other translations, and finally Part IV of the Introduction, in which I have endeavoured to ‘place’ the philosophy of Leibniz in relation to the systems which came before and after his.
My indebtedness to authors is so great and varied that I cannot acknowledge it in detail; but I may mention as specially helpful to me the works of Boutroux, Dillmann, Nourisson, Nolen, and Stein. My thanks are due to Professor Jones, of Glasgow, who read the Introduction in manuscript, for much valuable suggestion and criticism, and I am more than grateful to Professor Ritchie, of St. Andrews, who read the whole hook, both in manuscript and in proof, and to whom it owes numerous improvements as well in form as in matter.
I have adopted the spelling ‘Leibniz’ in place of the traditional ‘Leibnitz,’ because the former was invariably used by Leibniz in signing his own name.
It ought perhaps also to be mentioned that Parts II and III of the Introduction were accepted by the University of Edinburgh as a thesis for the degree of Doctor of Philosophy.
University of St. Andrews
On June 21, 1646, two years before the close of the Thirty Years’ War, Gottfried Wilhelm Leibniz was born at Leipzig. His family was of Bohemian origin; but his ancestors for several generations had lived in Saxony and Prussia, and his father was a Professor of Philosophy in the University of Leipzig. Leibniz was only six years of age when his father died; and, though in his early years he had the training of a pious mother, she also passed away before he had completed his University studies. The boys of Leipzig in Leibniz’s time appear to have been brought up on ‘the picture-book of Comenius and the little Catechism’ (Luther’s); but the soul of Leibniz already sought stronger meat, and having found in the house an illustrated copy of Livy, of which he could not thoroughly understand a single line, he managed to get a tolerable idea of its contents, supplementing his scanty Latin by a study of the pictures and some judicious guessing. As an indirect result of this precocity, his father’s library was thrown open to him, and he wandered at will from volume to volume, finding (as was ever characteristic of him) some good in all. Providence or Fortune seemed to say to him, Tolle, lege; and it is significant for the philosophy to come that he turned first to the Ancients, to Cicero, Quintilian, Seneca, Pliny, Herodotus. Xenophon, Plato, the historians of the Roman Empire, and the Fathers of the Church. Of these he tells us that ‘he understood at first nothing, then gradually something, and finally enough’; but unconsciously his mind was coloured by their style and thought, ‘as men walking in the sun have their faces browned without knowing it,’ and under their inspiration he made it the rule of his life ever to seek clearness in speaking and a useful purpose in acting (in verbis claritas, in rebus usus). Thus at fourteen years of age he was counted by his fellows a prodigy of learning and ability, and already his reading of Logic and intense determination towards clearness of thought and speech had led him to ideas which were afterwards developed into the suggestion of a logical Calculus and an ‘Alphabet of Concepts’ as means to the discovery of truth.
At fifteen years of age Leibniz became a student at the University of Leipzig, and about the same time he became acquainted with the works of some of the modern philosophers, beginning with Bacon’s De Augmentis Scientiarum. At this time also, as he himself tells us, he read with interest the works of Cardan and Campanella and the suggestions of a better philosophy in Kepler, Galileo, and Descartes. But he was no ‘reading-machine, all wound up and going.’ He thought for himself: he read in order to ‘weigh and consider.’ And thus in after-years he recalls how, when he was fifteen years of age, he walked alone in a wood near Leipzig, called the Rosenthal, to consider whether or not he should retain in his philosophy the ‘Substantial Forms’ of the Scholastics. Although his favourite teacher at Leipzig was Jacob Thomasius, a Professor of Philosophy, deeply versed in ancient and scholastic learning, the private reading of Leibniz at first prevailed in his thought and he turned from the older philosophies to ‘mechanism’ and mathematics. The ‘Substantial Forms’ were for the time set aside, to reappear, transmuted, in later years. His scholastic studies, however, bore fruit in the earliest of his published writings, a graduation thesis with the significant title De principio individui, in which he defended the Nominalist position. Intending to devote himself to the profession of law, he went for a year (in 1663) to Jena, where the mathematician, Erhard Weigel, was lecturing on ‘the Law of Nature,’ or what we should now call Jurisprudence in general. Doubtless the influence of Weigel tended to confirm Leibniz’s mathematical bent, and he still continued his study of history. In 1666 the University of Leipzig, ostensibly on the ground of his youth, refused to give him the Doctorate in Law; but his thesis, De casibus perplexis in jure, was immediately accepted by the University of Altdorf (near Nürnberg), where he declined the offer of a professorship. Thus ended his connexion with Leipzig.
In Nürnberg, at that time the capital of a small republic, which had suffered less than many other German States from the Thirty Years’ War, Leibniz spent a year, in the course of which his extensive curiosity led him to become a member of a secret society of the Rosicrucians, who were trying to find the philosopher’s stone. Fontenelle tells us that Leibniz’s method of gaining admission to the society was to collect from books on alchemy all the most obscure phrases he could find and to make of them an unintelligible letter, which he produced as evidence of his fitness for membership. The society was so impressed that it immediately appointed him to be its secretary. The chief gain to Leibniz appears to have been that through this society he became acquainted with Baron von Boineburg, ‘one of the most celebrated diplomatists of his age,’ who had formerly been minister to the Elector and Archbishop of Mainz, the most powerful man in the Empire. With Boineburg Leibniz went to Frankfort, where he wrote and published a paper on legal education, which was the means of introducing him to the archbishop, in whose service he remained for some time. This was the beginning of his career as a diplomatist. The long war had left Germany in ruins, and, ere there was time to rebuild, the whole empire was threatened by the immense power of Louis XIV, who was dreaming of world-wide sway. The Elector of Mainz, says Leibniz, ‘had seen the miseries of Germany, whose ruins were still smoking: he was one of those who had laboured most to bring back rest to the land, from which life seemed almost to have gone. The country was (as one might hardly say) “peopled” with little children, and if war were to break out again (as might be expected when Sweden was irritated and France threatening) there was every reason to fear that this seed of a new population would be destroyed and a great part of poor Germany left almost without inhabitant .’ The treaty of Westphalia had secured peace and some measure of political unity, but it pointed also to an ecclesiastical reunion, yet to be realized, which to men like the Elector of Mainz and Boineburg seemed the best means of restoring power and happiness to the country. Negotiations for the reunion of Roman Catholics and Protestants had already been begun, and thus early in his diplomatic career Leibniz took part in the work of conciliation which in various ways he continued throughout his life. At the suggestion of Boineburg he made a special study of the doctrine of transubstantiation, with the result (expressed in a letter to Arnauld in 1671) that he found it impossible to reconcile the Cartesian view of material substance as pure extension either with the Roman Catholic or with the Lutheran doctrine. He accordingly formed the purpose of discovering a theory of substance which should satisfy both, and should thus become a philosophical basis for the reconciliation of the Churches.
Presently events occurred which led him away from Mainz and gave him new opportunities of study and of intercourse with learned men. Leibniz and his friends felt strongly the necessity of drawing into safe channels the military ambitions of Louis XIV, and accordingly Leibniz prepared a most elaborate work in which he suggested to the King of France the advantages that would arise from a conquest of Egypt, and tried to convince him that it was more worthy of a Christian king to fight the unchristian Turks than to harass a poor little people like the Dutch. This book was never actually presented to King Louis, but Leibniz in 1672 went by invitation to Paris to explain his project. His advice was not taken; but he remained in Paris for four years, during which he devoted himself to the study of the higher mathematics and to the discussion of the Cartesian philosophy. He had already corresponded with Arnauld, and he now met also Huygens and Male-branche. At this time, says Leibniz himself, ‘law and history were my forte .’ But intercourse with Huygens and the study of the mathematical works of Pascal introduced him to the problems of modern mathematics. Huygens, he tells us, ‘had no taste for metaphysics,’ but Leibniz learned from him mathematical methods and principles which influenced the growth of his philosophy, and which set him on the way to the discovery of the Differential Calculus. At this time also Leibniz invented a calculating machine, superior to that of Pascal, which could only add and subtract, while his own machine could also multiply, divide, and extract roots. And in other ways the residence of Leibniz in Paris greatly affected his life-work. For instance, it probably led to his writing so much in French. He had already, in his essay on the philosophical style of Nizolius (1670), advocated the use of the German language for philosophical and other works. But in the time of Louis XIV Paris was the intellectual centre of Europe, and to write for the world was to write in French. While, therefore, Leibniz has rightly been called ‘the father of German philosophy,’ he is only to a very small extent a German author.
The four years’ residence of Leibniz in Paris was broken by a brief visit to England in the early months of 1673. Leibniz had already sought the favour of English learning by dedicating one of his publications to the Royal Society, and he had also been greatly interested in the philosophy of Hobbes, with which to a great extent he found himself in agreement, especially as regards questions of physics, although he was strongly opposed to his political theories. In 1670 he wrote a letter to Hobbes, to which he received no answer, and afterwards he began another letter, but left it unfinished. It has recently been maintained that, up to the year 1670, Leibniz was ‘more deeply affected by Hobbes than by any other of the leading spirits of the new time .’ When Leibniz visited London, Hobbes was still living there, but he was eighty-five years of age, and some years earlier Leibniz had heard from his countryman Oldenburg, who was secretary of the Royal Society, that Hobbes was in his dotage. Accordingly it is not surprising that they did not meet. Apart from Oldenburg, the man with whom Leibniz seems to have had most intercourse during this visit to London was Robert Boyle, the famous physicist; but there is no reason to suppose that Leibniz gained much from his stay in England, except an additional stimulus to the study of the higher mathematics, which he carried on more systematically after his return to Paris. As a fitting conclusion of his Parisian period came the discovery of the Differential Calculus, which was practically accomplished by Leibniz in 1676. There can be no doubt that Newton was in possession of a similar method as early as 1665. He at first made known only some of the results of the method, and not the method itself. Hence an attempt has been made to show that Leibniz got hints of the method during his first visit to England, and that he was thus more or less a plagiarist of Newton. But there is nothing to confirm this, and a full consideration makes it much more likely that each discovered the method independently. Leibniz published his account of the method in 1684: Newton’s was first published in 1693. To Newton belongs the glory of priority, whatever that may be worth; while the form which Leibniz gave to the Calculus, the names and the signs which he used, have come to be universally employed in preference to those of Newton.
Shortly before Leibniz went to London, Boineburg died; and the visit to London was unexpectedly brought to an end in March, 1673, by the death of the Archbishop of Mainz. Leibniz was now without an official position, and during the next few years he made various unsuccesful attempts to obtain a diplomatic appointment. At last, in 1676, he somewhat reluctantly accepted the post of librarian to the Duke of Brunswick at Hanover, which to be his home during the remainder of his life. During the earlier years of his residence in Paris, Leibniz had given much attention to the philosophy of Descartes and the Cartesians, with the result that he became more and more convinced of its insufficiency. In his endeavor after a more satisfactory metaphysic he afterwards made a considerable study of Plato, and in 1676 he translated the Phacdo and the Theactetus. Towards the end of 1675 Leibniz became acquainted with the young Bohemian nobleman, Tschirnhausen, Spinoza’s acute critic and correspondent, who was at that time in Paris, and who had earlier in the same year written some of the remarkable letters on account of which his name will always be associated with that of Spinoza. Leibniz had already (in 1671) written to Spinoza from Frankfort about a question of optics; but now Tschirnhausen seems to have aroused in him the hope that a solution of the difficulties of Cartesianism might be found in the unpublished system of Spinoza. In November, 1675, a medical friend of Spinoza in Amsterdam (G. H. Schuller) wrote to him: ‘Von Tschirnhausen further mentions that he has found at Paris a man called Leibniz, remarkably learned and most skilled in various sciences, as also free from the vulgar prejudices of theology. With him he has formed an intimate acquaintance, founded on the fact that Leibniz labours with him to pursue the perfection of the intellect, and, in fact, reckons nothing better or more useful. Von Tschirnhausen says that he is most practised in ethics, and speaks without any impulse derived from the passions, but by the sole dictate of reason. He adds that he is most skilled in physics, and also in metaphysical studies concerning God and the soul. Finally, he concludes that he is most worthy of having communicated to him the master’s writings, if you will first give your permission, for he believes that the author will thence gain a great advantage, as he promises to show at length, if the master be so pleased. But if not, do not doubt in the least that he will honourably keep them concealed as he has promised, as in fact he has not made the slightest mention of them. Leibniz also highly values the Theologico-Political Treatise, on the subject of which he once wrote the master a letter, if he is not mistaken .’ Spinoza, in reply, recollects having some correspondence with Leibniz, but Leibniz was at that time a counsellor at Frankfort, and Spinoza would like to know, before entrusting his writings to him, what he is doing in France, and he would also like to have Tschirnhausen’s opinion of Leibniz, after a longer and more intimate acquaintance. Spinoza’s shyness had probably no other effect than to whet the curiosity of Leibniz, and accordingly, when he left Paris in October, 1676, he went for a week to London (where he met for the first time Newton’s friend Collins) and then crossed to Amsterdam, where he stayed four weeks with Schuller, eagerly reading and criticizing every writing of Spinoza’s which Schuller could give him. At last, in November, Leibniz obtained an interview with Spinoza at the Hague, where he seems to have spent some time. They had many conversations together regarding philosophical matters, of which Leibniz has left hardly any record except the remark that ‘Spinoza did not quite clearly see the defects of Descartes’ laws of motion: he was surprised when I began to show him that they were inconsistent with the equality of cause and effect .’ The persistence of Leibniz ultimately induced Spinoza to show him the MS. of the Ethics (or at least a portion of it), and he seems even to have had permission to make a copy of the leading definitions, axioms, and propositions. What at this time most dissatisfied Leibniz was Spinoza’s treatment of Final Causes. His recent study of Plato had impressed Leibniz with the value of teleological considerations, and he was already seeking in that direction an escape from the imperfections of the mechanical view of things. But his general hostility to Spinoza’s system did not show itself until ten years later, when he had settled the essential points of his own doctrine of substance. At this time Leibniz was still seeking light in every quarter.
Leibniz arrived at Hanover in the last days of 1676. Efforts had already been made to convert him to the Roman Catholic faith, and he had begun a correspondence with Pellisson (a distinguished convert from Protestantism) in the hope of finding some means of Church reunion. This correspondence led to others, of which the most important was one with Bossuet. But, though Leibniz was more or less occupied with these discussions throughout the rest of his life, nothing practical came of them. Bossuet’s attitude in the discussion was only too well expressed in his exclamation regarding Leibniz: Utinam ex nostris esset! ‘Would that he were one of us!’ And Leibniz was too much of a scientific inquirer to unite two opposed religious communions. He might draw up a statement of dogma to which both sides could assent, but inevitably it would express the real belief of neither. The endeavour to convert Leibniz was not given up for a very long time, and a brief visit of his to Rome in 1689 seems to have caused a flutter of excitement. He was offered the librarianship of the Vatican and other posts with a vista of preferment; but conversion was so far from his mind that we hear of him bringing from the Catacombs a piece of glass, reddened with the blood of martyrs, in order to submit it to chemical analysis!
It was during the early years of his residence in Hanover that Leibniz worked out the leading ideas of his system. Disappointed in his hope of finding in Spinoza a saviour from the errors of Descartes, and being the rather confirmed, by Spinoza’s conclusions, in his conviction of the insufficiency of any merely mechanical interpretation of things, he turned with renewed interest to Plato, with the result that towards 1680 he had reached the conception of substance as essentially active force. It is possible also that, in spite of his general dissatisfaction with Spinoza’s position, some of Spinoza’s ideas (such as that of the conatus or self-preserving tendency of things) may have contributed to the development of his new view of substance. One further step was needed to complete the theory, namely, the recognition that the force constituting a substance is not a universal world-principle, but something individual — that there are substances which are forces. To this position he seems to have attained about 1684 or a little later, through a return to the consideration of Aristotle and the Peripatetic Schools, whose views he had set aside in his boyhood, nearly twenty-five years before. The main ideas of his philosophy (such as his conception of ‘simple substance’ and his pre-established harmony) were first stated in the correspondence with Arnauld, which took place between 1686 and 1690. This correspondence, however, was not published as a whole until 1846; and the learned world was first made aware that Leibniz had worked out a philosophical system of his own by two papers which he published in 1695 — one (the Specimen Dynamicum) in the Leipzig Acta Eruditorum, and the other (the Système Nouveau) in the French Journal des Savants. Leibniz uses the term ‘monad’ for the first time in 1697.
Having thus definitely fixed his philosophical system, and having published its leading principles, Leibniz gradually expounded it in detail, for the most part by means of correspondence and criticism. Hitherto he had given most attention to ontological or purely metaphysical problems. But now he began to consider more carefully the theory of knowledge and the psychological questions that are connected with it. Locke’s Essay was published in 1690, and a few years afterwards Leibniz read it, writing (as was his custom) notes and comments as he read. Some of these criticisms were in 1697 sent to Locke, who treated them with contempt, and made no reply. In 1703 Leibniz wrote the Nouveaux Essais sur l’Entendement humain, a long dialogue, in which the views of Locke and of himself are set in contrast throughout a discussion dealing with the subjects of Locke’s Essay chapter by chapter. This book was evidently intended to call forth a rejoinder from Locke. But before it was ready for publication Locke died (in 1704); and Leibniz, saying that he ‘greatly disliked publishing refutations of dead authors,’ and that he now ‘preferred to publish his thoughts independently of another person’s,’ allowed the Nouveaux Essais to remain in manuscript, so that the book was first published by Raspe in 1765, nearly fifty years after Leibniz’s death.
After writing some other papers on psychological and epistemological subjects, Leibniz, in 1710, published his Théodicée, the one great work of his which was printed in his lifetime. It was written, not continuously, but at intervals, in a very diffuse and discursive style, and its purpose was to develop the principles of its author’s philosophy in maintaining, against the arguments of Pierre Bayle, the harmony of faith and reason, and to ‘vindicate the ways of God to man.’ The writing of the Theodicee was suggested to Leibniz as the result of conversations with Queen Sophia Charlotte of Prussia, who also induced him to write various other philosophical papers, and who encouraged him in his plans for the founding of an Academy at Berlin. Besides the exposition of his system which he gives in such elaborate works as the Nouveaux Essais and the Theodicee, Leibniz met the objections of critics and suggested new applications of his principles in the course of a varied correspondence. On questions of mathematics and physics in their connexion with metaphysics, he corresponded with John Bernouilli for more than twenty years (from 1694 to 1716), and for ten years (1706-1716) he discussed with Des Bosses the possibility of combining his philosophy of substance with the presuppositions of the doctrine of transubstantiation. Further, among many other epistolary discussions, mention may be made of Leibniz’s correspondence, during the last two years of his life, with Bourguet on the chief doctrines of his philosophy, with special reference to biological questions, and with Clarke on space and time and the Divine attributes.
The amazing intellectual activity of Leibniz found expression in many other writings. During the greater part of his residence at Hanover he worked at a history of the house of Brunswick, in connexion with which he travelled much and ransacked the libraries of Germany and Italy. He suggested the development of mining in the Harz Mountains, and in connexion with this he studied and wrote on geological subjects and on the currency. But, above all, the interest of Leibniz in these later years lay in the endeavour to extend science and civilization throughout Europe. With this end in view, he, who (according to Frederick the Great) was an Academy in himself, succeeded after much effort in obtaining the foundation of an Academy at Berlin, of which he himself was appointed the first president (1700). Afterwards he made long-continued but unsuccessful attempts to induce the King of Poland, the Czar, and the Emperor to found similar Academies at Dresden, St. Petersburg, and Vienna. He had interviews with Peter the Great, whom he expected to become ‘the Solon of Russia,’ and he lived for some time in Vienna, where he tried to bring about an alliance between the Czar and the Emperor. Charles VI favoured his projects for the founding of learned societies, and he was also strongly supported by Prince Eugene of Savoy, for whom in 1714 he wrote the Monadologie (or, as Gerhardt maintains, the Principes de la Nature et de la Grâce). But Europe was full of wars and rumours of wars, and the peaceful plans of Leibniz were set aside. The Berlin Academy had a struggling existence, and no other was founded until long after Leibniz’s death.
The happiest years of the life of Leibniz were now over. The Duke of Brunswick died in 1698, and Leibniz seems gradually to have lost favour with his son and successor, our George I. After the death of his friends, ‘the two Electresses,’ Sophia and Sophia Charlotte (the mother and the sister of George I), Leibniz’s position became intolerable. George I succeeded to the English crown in 1714, and his prejudices against Leibniz, shown in his displeasure on account of the latter’s residence in Vienna, were encouraged by some of Newton’s friends, whom he met in England. Leibniz thought of leaving Hanover; but in later years his health had been somewhat broken, and on November 14, 1716, he died during an attack of gout. His secretary, Eckhart, invited all the people of the Court to his funeral, but not one of them came, and Eckhart alone followed his master’s body to the grave. An acquaintance of Leibniz, John Ker of Kersland, who had come to Hanover on the very day of Leibniz’s death, says that he was buried ‘more like a robber than, what he really was, the ornament of his country.’ No minister of religion was present; for Leibniz was parcus deorum cultor et infrequens, and his absence from church was counted to him for irreligion, so that from priests and people he got the nickname Lövenix (the Low German for Glaubet nichts, believer in nothing). The Berlin Academy and the Royal Society of London took no notice of his death; but a year afterwards Fontenelle commemorated it in a fine oration, delivered before the Parisian Academy.
As to the personal characteristics of Leibniz, Eckhart tells us that he was of middle height, with a somewhat large head, dark-brown hair, and small but very sharp eyes. He was near-sighted, but had no difficulty in reading, and himself wrote a very small hand. His lungs were not strong, and he had a thin but clear voice, with a difficulty in pronouncing gutturals. He was broad-shouldered and always walked with his head bent forward, so that he looked like a man with a humped back. In figure he was slim rather than stout, and his legs were crooked. His household arrangements (if they can be called ‘arrangements’) were very irregular. He had no fixed hours for meals, but, when a convenient opportunity came in the course of his studies, he sent out for something to eat. He once made a proposal of marriage (when he was fifty years of age), but the lady took time to consider, and (Fontenelle says) ‘this gave Leibniz also time to consider, and he never married.’ He slept little, but well: he often spent the night in his chair, and sometimes he would remain in it for several days at a time. This enabled him to do a great deal of work; but it led to illness, for which, disliking physicians, he employed remedies more ‘heroic’ than wise. He enjoyed intercourse with all sorts and conditions of men, believing that he could always learn something even from the most ignorant. ‘Cum Socrate semper ad discendum paratus sum.’ ‘He spoke well of everybody,’ says Eckhart, ‘and made the best of everything’ (er kehrte alles zum Besten). He often congratulates himself on being self-taught (αύτοδίδακτος), and thus able to avoid acquiescence in superficial, ready-made knowledge and to strike out paths of his own. For he is ever (he tells us) ‘eager to penetrate into all things more deeply than is usually done and to find something new.’
‘When,’ says Diderot, ‘one considers oneself and compares one’s talents with those of a Leibniz, one is tempted to throw books away and seek some hidden corner of the world where one may die in peace. This man’s mind was a foe of disorder: the most entangled things fell into order when they entered it. He combined two great qualities which are almost incompatible with one another — the spirit of discovery and that of method; and the most determined and varied study, through which he accumulated knowledge of the most widely differing kinds, weakened neither the one quality nor the other. In the fullest meaning these words can bear, he was a philosopher and a mathematician .’
Many of the most important philosophical works of Leibniz were not published till after his death. Large quantities of manuscript were preserved in the Royal Library at Hanover, and successive editors have continually drawn upon it for publication. The chief editions of the philosophical works are that of Erdmann (1840) and that of Gerhardt (1875-90), the latter being the most complete. In 1866 Janet published an edition in French, containing the principal works as they are given in Erdmann, with the addition of the correspondence between Leibniz and Arnauld, which had not been published when Erdmann’s edition appeared. The mathematical works were published by Gerhardt in seven volumes (1850-63). Of the historical and political works Onno Klopp published ten volumes (1864-77). Foucher de Careil also published in seven volumes (1859-75) some of Leibniz’s political works, along with his correspondence on the reunion of Christendom and his writings in connexion with the founding of academies. In addition to these may be mentioned the old edition of Dutens in six volumes (1768), which contains some things not included in any of the others, and the booklet of Mollat (1885), containing some papers of Leibniz on ethics and jurisprudence.
The following are the principal philosophical works of Leibniz, with the dates at which they were written or published. The letters J. S. indicate those which appeared in the Journal des Savants, and the letters A. E. those which appeared in the Acta Eruditorum. Those marked with an asterisk were published in Leibniz’s lifetime.
In the preface to his Théodicée Leibniz declares that ‘there are two famous labyrinths, in which our reason often goes astray: the one relates to the great question of liberty and necessity, especially in regard to the production and origin of evil; the other consists in the discussion of continuity and of the indivisible points which appear to be its elements, and this question involves the consideration of the infinite. The former of these perplexes almost all the human race, the latter claims the attention of philosophers alone.’ Accordingly, while a right understanding of the principle of continuity is of the utmost speculative importance, the practical value of a true knowledge of necessity is equally great. Thus, Leibniz makes his Théodicée an investigation of the meaning of liberty and necessity, while in others of his writings he offers a solution of the problem which he describes as the special perplexity of philosophers.
It is this latter problem with which we are here mainly concerned. The philosophical work of Leibniz was an endeavour to reconcile the notion of substance as continuous with the contrary notion of substance as consisting of indivisible elements. The opposition of these two notions seemed to him to arise from an inadequate conception of substance, and the task he set himself was that of deepening the current notion of substance, or, as he himself would have put it, finding a better hypothesis than that which had satisfied his Cartesian predecessors.
Stated in another way the problem is: How are we to interpret the relation of whole and parts so that the continuity or complete unity of the whole shall not be in conflict with the definiteness or real diversity of the parts? To say that the whole is continuous or really one seems to mean that, if it is divisible at all, it is infinitely divisible. If it were not infinitely divisible, it would consist of insoluble ultimate elements, and would thus be discontinuous. Accordingly, if the whole be really continuous there seem to be no fixed boundaries or lines of division within it, that is to say, no real, but only arbitrary parts.
On the other hand, if the whole consists of real parts and not merely possible subdivisions, these parts must be definite, bounded, separate from one another, and consequently the whole which they constitute must be, not a real continuous unity, but a mere collection or arbitrary unity. Nevertheless, we cannot hold either that the whole is real and the parts unreal, or that the parts are real and the whole unreal.
Quantitative or extensive Notion of Substance held by Descartes and Spinoza, on the one hand, and by the Atomists on the other.