The title page and frontispiece engraving of an 18th-century book written in German. The title of the book is written in red in a Gothic font

The frontispiece engraving from Vernünfftige Gedancken von Gott, der Welt und der Seele des Menschen (first published in 1720) by Christian Wolff. The sun bursts out from clouds beneath the banner Lucem post nubila reddit (After a cloudy time He brings back the light). Courtesy the Franke Foundations, Halle, Germany


The great, forgotten Wolff

Written for laymen, read by women and kings, Christian Wolff’s mathematical method made him a key Enlightenment philosopher

by Michael Walschots + BIO

The frontispiece engraving from Vernünfftige Gedancken von Gott, der Welt und der Seele des Menschen (first published in 1720) by Christian Wolff. The sun bursts out from clouds beneath the banner Lucem post nubila reddit (After a cloudy time He brings back the light). Courtesy the Franke Foundations, Halle, Germany

Writing primarily during the first half of the 18th century, Christian Wolff (1679-1754) and his philosophical system, ‘Wolffianism’, dominated the intellectual landscape to such an extent that during his own lifetime he became one of the most influential philosophers in all of Europe. He made substantial contributions to virtually every sub-field of philosophy (as well as to mathematics and natural science), shaped the way philosophy was practised in the German-speaking lands of Europe and beyond for decades if not centuries to come, and even had an influence on the German language itself.

And yet, in the present day, Wolff is not a stable figure of the Western philosophical tradition. This is a tragedy, because Wolffianism had such an impact that a large and important piece of German philosophy’s history remains obscure unless we can come to better appreciate Wolff’s philosophy and the ideas to which it gave rise.

Just how influential was Wolff’s philosophy? And how could it come to be that his philosophical system eventually became pushed into the background?

Wolff was born in Breslau, at the time the capital of the historical region of Silesia, now Wrocław in Poland. Raised in a devout Lutheran household, Wolff’s early educational environment shaped his later development in a big way: at Gymnasium, Wolff was introduced to Cartesian philosophy and mathematics and, having been exposed to disputes between Lutherans and Catholics during his youth, Wolff saw in mathematics the promise of ending these disagreements once and for all. As he writes in his autobiography: ‘I was eager to learn the mathematical method in order to endeavour to make theology incontrovertibly certain.’

The mathematical method became a cornerstone of Wolff’s philosophy, which he characterised as following three general principles: 1) beginning with clearly defined terms, and consistently using the same term for the same idea throughout one’s writings; 2) arguing strictly according to conceptual analysis and deductive inference; and 3) never using a principle as a major premise in an argument that had not been previously proven. This method embodies a faith in reason that became characteristic of the Enlightenment: by presenting his arguments in steps that ideally anyone could follow, Wolff’s hope was that all people who applied their mind to the same topic would come to agree, leading to less intellectual – and political – conflict and thus more human happiness.

Wolff’s first publication of note, a thesis from 1703 that granted him permission to teach at the university level, sought to prove the fruitfulness of the mathematical method as applied to practical philosophy in particular. Entitled Universal Practical Philosophy, Written According to the Mathematical Method, this text founded the discipline of ‘universal practical philosophy’, a general, abstract branch of knowledge that treated foundational concepts in practical philosophy, such as obligation, the nature of ‘law’ and the highest good, which were presupposed and utilised in the more particular practical disciplines of ethics, politics and economics. It was Wolff’s first success: the examiner in Leipzig, Otto Mencke, was so impressed that he sent a copy to the German polymath Gottfried Wilhelm Leibniz, which led to a correspondence and productive friendship between the two figures that lasted until Leibniz’s death in 1716. Mencke also hired Wolff to work for the Acta eruditorum, the first scientific journal for German-speaking intellectuals, for which Wolff went on to write approximately 40 papers and 485 book reviews; Wolff even learned foreign languages such as English to review works like John Locke’s Of the Conduct of the Understanding (1706).

Wolff’s textbook on logic was given an initial print run of 8,000 copies, a number unheard of at the time

With Leibniz’s help, Wolff attained his first position as a professor of mathematics in 1707 at the newly founded Friedrichs University of Halle. In line with this role, Wolff initially lectured on mathematics and his first subsequent publications were mathematical textbooks that grew out of his lecturing activity. He soon taught philosophy and physics as well, and it was the publications resulting from these lectures that brought him almost immediate fame both at home and abroad. He wrote a series of textbooks outlining his philosophical system in virtually every sub-discipline of philosophy, organised systematically in line with the mathematical method. After a foundational volume on logic, Wolff added volumes on metaphysics, ethics, politics, physics, teleology, and physiology.

The success of these works was astonishing. Wolff’s textbook on logic, for instance, was given an initial print run of 8,000 copies, a number unheard of at the time (Kant’s Critique of Practical Reason, for example, received an initial run of only 1,000 copies), and went through 14 editions in his lifetime. Similarly, Wolff’s textbook on metaphysics, Rational Thoughts on God, the World, and the Soul of Human Beings, as Well as All Things in General, went through 12 editions. On the basis of these texts, Wolff was offered chairs at several other German universities and Czar Peter the Great offered him a position at the St Petersburg Academy (all of which he turned down); he was also granted memberships in virtually every important academic society at the time, including the Royal Society of London, the Berlin Academy, the St Petersburg Academy of Sciences, and the Academy of Sciences in Paris.

A main reason for the success of this first series of Wolff’s writings had to do with the fact that he chose to publish them in the German vernacular rather than in Latin. In this respect, Wolff was following in the footsteps of his new colleague in Halle, Christian Thomasius, who had been the first to publicly announce that he was going to deliver his lectures in German. To be sure, philosophical treatises had been published in German before Wolff, including by Thomasius, but philosophical German was in a poor state at the end of the 17th century. Leibniz, for instance, complained in two treatises that the German language was unfit for scholarly works, in part because it incorporated so many foreign expressions.

Wolff forever changed philosophical German by being the first to employ a stable and consistent philosophical vocabulary. His efforts here were in part a result of his commitment to the mathematical method: because definition was central to his attempt to achieve certainty, he went to great lengths to define every technical term he used, as well as to use them consistently to refer to a single idea throughout his works. Wolff even attached indexes to the end of his works to make it clear to his readers which Latin terms corresponded to the German terms he was in some cases inventing. To cite just one important example, whereas the word Begriff had a variety of meanings in Middle High German, it was Wolff who fixed it as the accepted philosophical term for ‘idea’, ‘concept’, or ‘notion’.

His efforts with respect to lending the German language stability were connected to his broader Enlightenment aspirations: by improving the precision of language, Wolff believed he could improve how common people thought. Indeed, Wolff was not only attempting to save his students time from taking notes by writing his textbooks in German, so that they might focus more on the ideas he was presenting, he also wanted his writings to be accessible to the uneducated layperson. This was Thomasius’s motivation for writing in German, too, namely for philosophy to be useful to all, regardless of both sex and social standing. Wolff followed suit and, to make his philosophy less offensive to the uneducated, he refrained from ‘dressing’ his arguments in ‘mathematical clothing’, that is, from explicitly outlining his system in terms of definitions and axioms, and instead opted to preserve this method beneath the surface.

Wolff’s philosophy was soon taught at every major German university, including Jena, Göttingen, Tübingen, Leipzig and Königsberg. And his attempt to appeal to laypersons in particular was such a success that Wolffianism became a topic in broader culture: there soon emerged a number of satirical works, such as a treatise about a shoemaker who used the mathematical method and the principle of sufficient reason to advance his trade, a text about the use of pre-established harmony in marriage, and a parody of Wolff seducing a young woman using scientific arguments.

An important aspect of Wolff’s impact on broader culture was the reception of his thought by female readers. In fact, his philosophy was so popular among women at the time that one of his contemporaries remarked that an ‘actual lycanthropie’ had broken out among the female sex. Numerous efforts were therefore made to popularise Wolff’s thought for a specifically female readership. Samuel Formey, for instance, published a six-volume philosophical novel in French entitled La Belle Wolffienne (1741), meant to provide an overview of Wolff’s thought. Wolff himself even began to write a version of his philosophy specifically intended for women, in the form of a series of letters between himself and a young noblewoman. Somewhat curiously, he never completed this project, even though the Queen of Prussia herself expressed interest in it. One of the most interesting texts written in this connection was by Johanna Charlotte Unzer, who has been called the first female German philosopher. Unzer’s Outline of a Philosophy for Women (1751) is the first metaphysical treatise intended exclusively for a female audience, and it consists in a popularisation of Wolffian logic and metaphysics. That a specialised book of this nature received a second edition is a testament to its success.

Wolff’s early popularity and success brought him turmoil as well: at the university of Halle, tension quickly grew between him and members of the theology faculty, especially Joachim Lange, a Pietist Lutheran who was not only jealous of Wolff’s success as an instructor, but was also offended by his claim that philosophy, rather than theology, is the foundation of all the other sciences. The conflict peaked in 1721 when Wolff delivered a speech entitled ‘Oration on the Practical Philosophy of the Chinese’ when handing over the office of pro-rector to Lange. In this speech, Wolff argued that the ancient Chinese developed a perfectly plausible theory of morality based on reason alone, and thus without the help of divine revelation. One of his more fascinating claims is that Confucius accepted the principle of sufficient reason, according to which everything has a cause or reason for why it exists in the way that it does. Wolff therefore saw in Confucius a version of his own theory, according to which grasping the reasons underlying reality could alter our behaviour and make us more rational. Wolff added that Confucius served as proof that one does not need to be a Christian to lead a moral life.

Thomas Jefferson underlined numerous passages related to the right of civil war and neutrality

The theology faculty in Halle was so enraged by the speech that its members argued to officials in Berlin that Wolff’s writings were blasphemous, hoping to get his teaching restricted to mathematics. The officials did more than this, however, and told the ‘Soldier King’ Friedrich Wilhelm I that Wolff’s compatibilist conception of freedom implied that soldiers could not be held responsible for deserting the battlefield; indeed, that Wolff’s philosophy might even encourage desertion. The king was convinced and issued a decree, written in his own hand, stripping Wolff of his professorship and ordering him to leave Prussia within 48 hours on penalty of death. Wolff complied.

His expulsion from Prussia had the opposite effect from what his critics intended: Wolff became known throughout Europe as a martyr of reason and the Enlightenment, thereby only increasing his fame. The Crown Prince of Prussia, Friedrich II (later Frederick the Great), commissioned a French translation of Wolff’s so-called ‘German Metaphysics’ in 1736, and rumour has it that he read it so often that his pet monkey Mimi threw it into the fire out of jealousy. This translation was significant, for it found its way into the hands of Émilie du Châtelet, who went on to summarise the foundations of Wolff’s philosophy in the first chapter of her work The Foundations of Physics (1740). Wolff’s expulsion caught the attention of Voltaire too, who came up with the motto ‘Wolfio docente, Rege Philosopho regnante, Germania applaudente Athenas invisi’ (‘I visited Athens with Wolff teaching, Philosopher King reigning, Germany applauding’). Wolff’s works were also both a source and an example for the creation of Denis Diderot and Jean d’Alembert’s Encyclopédie: not only are a number of the entries near-literal translations from his works, but the systematic nature of his philosophy served as an example of the systematic arrangement of all knowledge that the Encyclopédie attempted to embody.

The influence of Wolff’s own philosophy reached its high point in Europe in the 1730s. In 1740, one of Frederick the Great’s first official orders as the new king was to invite Wolff back to Halle, to which Wolff complied. Ironically, and somewhat tragically, Wolffianism was on the decline when he was in the middle of the massive undertaking to rewrite his entire philosophical system in Latin in order to reach a wider audience. Wolff devoted the rest of his life to this task and, although he left it unfinished, he wrote an astonishing amount. The Wolff scholar Clemens Schwaiger has claimed that Wolff could be considered the most productive philosophical writer of all time. By the time he died in 1754, at the age of 75, he had published more than 50,000 pages.

Wolffianism nonetheless continued to be present in the intellectual landscape until the end of the century by means of the modified versions of Wolff’s system invented by his many students and followers. To mention just one very important example, Alexander Gottlieb Baumgarten, the founder of the discipline of aesthetics, wrote a series of Latin textbooks that explicitly acknowledge their debt to Wolff. In his Elements of First Practical Philosophy (1760), for instance, one of the texts that Kant read from in his lectures on moral philosophy, Baumgarten states that his aim is ‘abridging’ and ‘explaining’ Wolff’s universal practical philosophy. And even once Kant published the first works of his ‘critical philosophy’, one of the major waves of critical reactions was waged by defenders of Wolff’s philosophy, such as Moses Mendelssohn who speaks of Kant as the ‘all-destroying’ critic of metaphysics.

By the end of the century, Wolff’s philosophy had been taught across Europe and Wolffianism was even represented in such faraway places as the Athonite Academy on Mount Athos in Greece, as well as in Turkey and South America. Both Wolff’s own writings and others written by his disciples made their way to North America too: George Washington checked out a copy of Emmerich de Vattel’s The Law of Nations (1758) from the library of the New York Society – an important text in the history of international law and a popularisation of Wolff’s thought on the subject. Thomas Jefferson owned a 1772 dual (French and Latin) edition of Wolff’s Institutes of the Laws of Nature and Nations (1750), in which he underlined numerous passages related to the right of civil war and neutrality. It has even been claimed that Wolff is the source of the idea, present in the US Declaration of Independence, that freedom is an inalienable right – an idea not to be found in other possible sources, such as Locke.

So while the influence of Wolffianism did not end with Wolff’s death, its legacy changed dramatically by the beginning of the 19th century, and Wolff was instantly pushed into the background. Consider the way in which his thought is treated in a German-language history of philosophy published at the beginning of the 19th century, Wilhelm Gottlieb Tennemann’s 11-volume History of Philosophy. In the work’s final volume on modern philosophy, covering the period from Locke to David Hume, Wolff’s name is mentioned fewer than 10 times, and only in passing. Tennemann’s history of philosophy is extremely important because it went on to influence other English and French histories of philosophy of the period, so Wolff’s meagre portrayal there likely shaped how he was perceived abroad. But the important question is: how could this happen? How could a philosopher who dominated the philosophical landscape just a few decades earlier come to be a mere footnote?

Wolff came to be seen as a mere follower and imitator of Leibniz

There are a few reasons for why this happened. The first concerns the development of late 18th- and early 19th-century German philosophy. Although the uptake of Kant’s critical philosophy was somewhat slow at first, it eventually came to dominate philosophical discussion by the final decade of the 18th century. And with the subsequent rise of German Idealism and Romanticism, intellectual fashion had shifted such that the philosophical outlooks of the previous century, which seemed outdated and scholastic by comparison, necessarily fell into the background. The damage done by this to Wolff’s fate in particular was exacerbated by what the philosophical giants on the horizon had to say about him. For instance, although Kant describes Wolff as ‘the greatest among all dogmatic philosophers’ in the Critique of Pure Reason (1781), he goes on to level a damning critique of dogmatism, which he understands as at least in part involving a commitment to Wolff’s method, subsequently concluding that only the ‘critical path’ remains open. Hegel too praises Wolff in his lectures on the history of philosophy ‘for raising Germany to a culture of the understanding’, which Wolff undoubtedly did by means of his improvement of the German language, but he accuses Wolff elsewhere of carrying out his method ‘to the height of pedantry’. The impact of these figures’ own philosophies, paired with their negative opinion of Wolff, was therefore doubly disadvantageous and could not but demotivate interest in Wolff’s philosophy.

The most important reason for Wolff’s decline, however, has to do with the fact that he was considered by many to have merely presented a version of Leibniz’s philosophy from very early on. One of Wolff’s early followers, Georg Bernhard Bilfinger, commended Wolff for founding the ‘Leibnizian-Wolffian’ school of philosophy. Intended as praise, Wolff’s critics quickly misappropriated the term and Wolff came to be seen as a mere follower and imitator of Leibniz. Voltaire accused Wolff of lacking originality and merely presenting what Leibniz had already discovered. Hegel claimed that Wolff is a mere systematiser of Leibniz’s philosophy, and Schelling accused Wolff of having ‘appropriated’ Leibnizian ideas. This opinion has persisted to the present day, with many general histories of philosophy and even more specialised histories of ethics referring to Wolff as a mere follower of Leibniz, if his name is mentioned at all.

The label ‘Leibnizian-Wolffian’ philosophy is misleading however, and the identification of their philosophies is problematic, not least because Wolff himself explicitly denied that his aim was ever to expand or explain Leibniz’s philosophy. It is also doubtful that Wolff could have known enough about Leibniz’s philosophy to have been able to appropriate it: although it is true that the two were acquaintances and engaged in a correspondence, their conversations on topics in philosophy were somewhat limited to issues in ethics and philosophical theology. Furthermore, Leibniz published very little during his lifetime, and some of his most famous texts, such as The Principles of Nature and Grace, The Monadology and the New Essays Concerning Human Understanding, were not only published posthumously, but only after Wolff had written his major German works on metaphysics and ethics. Even more significantly, Leibniz himself says that Wolff likely knew little of his philosophy, or at least no more than what anyone else with access to his published writings could have known:

Mr. Wolff has adopted some of my opinions, but since he is very busy with teaching, especially in mathematics, and we have not had much correspondence together on philosophy, he can know very little about my opinions beyond those which I have published.

To be sure, some aspects, though certainly not all, of Wolff’s philosophy show the influence of Leibniz, and a limited number of them can be regarded as advancing a particular interpretation of Leibniz’s thought. And in retrospect, Wolff published his works at an opportune time: due to the general interest in Leibniz’s philosophy but also the fact that there was no extensive presentation of it, the learned public were eager to digest the ‘Leibnizian’ system they considered Wolff and his disciples to be presenting. The label ‘Leibnizian-Wolffian’ philosophy therefore both helped attract attention to Wolff’s philosophy and sealed Wolff’s fate as a mere ‘systematiser’. Once a first collection of Leibniz’s writings appeared in the mid-18th century, and more expansive editions of his German and philosophical writings followed in the mid-19th century, interest in Leibniz’s philosophy was repeatedly renewed. And once the opinion that Wolff was a mere appropriator of Leibniz was solidified in public consciousness, many felt no need to read Wolff himself.

Neglect of Wolff is to be regretted, however. It leaves a large and important piece of the history of German philosophy obscure. Aside from the fact that understanding him as a mere Leibnizian discourages noticing what is original about his thought, without an accurate understanding of Wolffianism we cannot grasp a number of crucial texts written by and for women intellectuals of the period, nor can we properly appreciate a rare instance of a Western figure promoting Eastern thinking. Rediscovering his philosophy is therefore a gateway into an important period of the history of German philosophy that we ignore to our detriment. Not only this, but his philosophy itself serves as an example of an ambitious attempt to help readers from all walks of life to not only think more clearly, but to put their knowledge into practice and live happier lives as a result.