Leibniz mainly wrote in three languages: scholastic Latin, French and German. During his lifetime, he published many pamphlets and scholarly articles, but only two "philosophical" books, the Combinatorial Art and the Théodicée. (He published numerous pamphlets, often anonymous, on behalf of the House of Brunswick-Lüneburg, most notably the "De jure suprematum" a major consideration of the nature of sovereignty). One substantial book appeared posthumously, his Nouveaux essais sur l'entendement humain, which Leibniz had withheld from publication after the death of John Locke. Only in 1895, when Bodemann completed his catalogue of Leibniz's manuscripts and correspondence, did the enormous extent of Leibniz's Nachlass become clear: about 15,000 letters to more than 1000 recipients plus more than 40,000 other items. Moreover, quite a few of these letters are of essay length. Much of his vast correspondence, especially the letters dated after 1700, remains unpublished, and much of what is published has been so only in recent decades. The amount, variety, and disorder of Leibniz's writings are a predictable result of a situation he described in a letter as follows:
I cannot tell you how extraordinarily distracted and spread out I am. I am trying to find various things in the archives; I look at old papers and hunt up unpublished documents. From these I hope to shed some light on the history of the [House of] Brunswick. I receive and answer a huge number of letters. At the same time, I have so many mathematical results, philosophical thoughts, and other literary innovations that should not be allowed to vanish that I often do not know where to begin.
The extant parts of the critical edition of Leibniz's writings are organized as follows:
- Series 1. Political, Historical, and General Correspondence. 25 vols., 1666–1706.
- Series 2. Philosophical Correspondence. 3 vols., 1663–1700.
- Series 3. Mathematical, Scientific, and Technical Correspondence. 8 vols., 1672–1698.
- Series 4. Political Writings. 7 vols., 1667–99.
- Series 5. Historical and Linguistic Writings. Inactive.
- Series 6. Philosophical Writings. 7 vols., 1663–90, and Nouveaux essais sur l'entendement humain.
- Series 7. Mathematical Writings. 6 vols., 1672–76.
- Series 8. Scientific, Medical, and Technical Writings. 1 vol., 1668-76.
The systematic cataloguing of all of Leibniz's Nachlass began in 1901. It was hampered by two world wars and decades of German division in two states with the cold war's "iron curtain" in between, separating scholars, and also scattering portions of his literary estates. The ambitious project has had to deal with seven languages contained in some 200,000 pages of written and printed paper. In 1985 it was reorganized and included in a joint program of German federal and state (Länder) academies. Since then the branches in Potsdam, Münster, Hanover and Berlin have jointly published 57 volumes of the critical edition, with an average of 870 pages, and prepared index and concordance works.
The year given is usually that in which the work was completed, not of its eventual publication.
- 1666. De Arte Combinatoria (On the Art of Combination); partially translated in Loemker §1 and Parkinson (1966).
- 1671. Hypothesis Physica Nova (New Physical Hypothesis); Loemker §8.I (partial).
- 1673 Confessio philosophi (A Philosopher's Creed); an English translation is available.
- 1684. Nova methodus pro maximis et minimis (New method for maximums and minimums); translated in Struik, D. J., 1969. A Source Book in Mathematics, 1200–1800. Harvard University Press: 271–81.
- 1686. Discours de métaphysique; Martin and Brown (1988), Ariew and Garber 35, Loemker §35, Wiener III.3, Woolhouse and Francks 1. An online translation by Jonathan Bennett is available.
- 1686. Generales inquisitiones de analysi notionum et veritatum (General Inquiries About the Analysis of Concepts and of Truths)
- 1695. Système nouveau de la nature et de la communication des substances (New System of Nature)
- 1703. Explication de l'Arithmétique Binaire (Explanation of Binary Arithmetic); Gerhardt, Mathematical Writings VII.223. An online translation by Lloyd Strickland is available.
- 1710. Théodicée; Farrer, A.M., and Huggard, E.M., trans., 1985 (1952). Wiener III.11 (part). An online translation is available at Project Gutenberg.
- 1714. Monadologie; translated by Nicholas Rescher, 1991. The Monadology: An Edition for Students. University of Pittsburgh Press. Ariew and Garber 213, Loemker §67, Wiener III.13, Woolhouse and Francks 19. Online translations: Jonathan Bennett's translation; Latta's translation; French, Latin and Spanish edition, with facsimile of Leibniz's manuscript.
- 1717. Collectanea Etymologica, edited by the secretary of Leibniz Johann Georg von Eckhart
- 1765. Nouveaux essais sur l'entendement humain; completed in 1704. Remnant, Peter, and Bennett, Jonathan, trans., 1996. New Essays on Human Understanding Langley translation 1896. Cambridge University Press. Wiener III.6 (part). An online translation of the Preface and Book I by Jonathan Bennett is available.
Six important collections of English translations are Wiener (1951), Parkinson (1966), Loemker (1969), Ariew and Garber (1989), Woolhouse and Francks (1998), and Strickland (2006). The ongoing critical edition of all of Leibniz's writings is Sämtliche Schriften und Briefe.