Kant undoubtedly casts a long shadow in the history of eighteenthcentury German philosophy. Not only did he initiate a revolution inphilosophy, but in the course of doing so he thoroughly exposed themetaphysical systems of his predecessors as rationalistic castles inthe air. This latter, negative part of his project was in fact sosuccessful that the pre-Kantian period of German philosophy is widelyviewed, even today, as a period of benighted dogmatism. During thistime, German philosophy, such as it was, is thought to be preoccupiedwith the sort of dry scholasticism and hidebound metaphysics that hadlong since been superseded in Britain and France, a circumstancereflected in the fact that nearly all intellectuals of note wereuniversity professors—male, of course, as women could not attenduniversity—who published lengthy academic tomes (and evenlectured) in Latin rather than the vernacular. Indeed, isolated fromthe rest of Europe by enduring confessional tensions and theconvolutions of internal politics, the German-speaking lands thatconstituted the Holy Roman Empire might seem like a sort ofintellectual island, a bulwark against the advance of modernphilosophical innovations and a place from which few ideas of noteever emanated, not, that is, until the advent of the Kantianphilosophy.

Yet quite to the contrary of the whiggish philosophical historiesKant’s success inspired (and continues to inspire), theGerman-speaking lands of Europe in the period before Kant were host toa rich intellectualmilieu. It was of course the homeland ofLeibniz, whose contributions to the flourishing of intellectualculture include his sparse publications but also his fruitful effortsto found a German learned society and his support of forward-thinkingphilosophers for university positions, thereby acceleratingGermany’s transition into the era of Enlightenment. Germanacademic philosophers were thoroughly influenced by Leibniz’sthought, but their creative appropriations of it resulted ininnovations such as the invention of the disciplines of aesthetics andempirical psychology. Germany was also the site of vigorous andpublicly-enacted intellectual disputes, such as that at the newuniversity in Halle where thelibertas philosophandi itselfcame under threat but was ultimately (if not immediately) vindicated.Outside of the academic context, radical philosophical thinkingcirculated underground in clandestine texts that linked Germany withthe current of ideas flowing through the rest of Europe and Britain.It was, moreover, a period in the history of philosophy in which womenand other under-represented thinkers contributed in integral ways tothe conception, propagation, and refinement of modern ideas and to theexpansion of the Enlightenment. In short, this is a vibrant period inthe history of philosophy that is eminently worthy of study, evenapart from its relation—whether as a foil or as acrucible—to the great philosopher of Königsberg.

• 1. Christian Thomasius
  • 1.1 Life and Works
  • 1.2 Philosophy
• 2. Radical Philosophy
• 3. The Controversy between Wolff and the Pietists
  • 3.1 The “Leibnizian-Wolffian” Philosophy
  • 3.2 The Halle Pietists
  • 3.3 The Controversy and its Aftermath
• 4. Alexander Gottlieb Baumgarten
  • 4.1 Life and Works
  • 4.2 Philosophy
• 5. Christian August Crusius
  • 5.1 Life and Works
  • 5.2 Philosophy
• 6. Women and Other Under-Represented Thinkers
  • 6.1 Women and the Thomasian Philosophy
  • 6.2 Women and the Leibnizian-Wolffian Philosophy
  • 6.3 Anton Wilhelm Amo
• Bibliography
  • Primary Literature
    • By Author
    • Collections (English)
  • Secondary Literature
    • General
    • Section 1: Christian Thomasius
    • Section 2: Radical Philosophy
    • Section 3: The Controversy between Wolff and the Pietists
    • Section 4: Alexander Gottlieb Baumgarten
    • Section 5: Christian August Crusius
    • Section 6: Women and Other Under-Represented Thinkers
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• Other Internet Resources
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1. Christian Thomasius

1.1 Life and Works

Christian Thomasius was born on 1 January 1655 in Leipzig. He was theson of Jakob Thomasius (1622–84), a well-known jurist andphilosopher at the University of Leipzig who counted Leibniz among hisstudents. Christian (hereafter simply ‘Thomasius’)matriculated in the philosophy faculty at Leipzig in 1669, and waspromoted toMagister artium in 1672. As a result of hisfather’s lectures, particularly on Hugo Grotius’Dejure belli ac pacis, and his interest in Samuel Pufendorf’sDe jure naturae et gentium, Thomasius took up the study oflaw in Frankfurt an der Oder in 1675 and was awarded a doctorate in1679. After a brief journey to Holland, Thomasius returned to Leipzigwhere he worked (unhappily) as a lawyer while also holding privatelectures on natural jurisprudence. Thomasius attests to thefundamental reorientation of his thinking effected by his reading ofPufendorf, and theApologia pro se et suo libro (1674) inparticular, which he credits for convincing him of the independence ofnatural law from theology as well as of the need to question authorityand resist religious intolerance (Thomasius 1688a, “Diss.Proem.” §§5–10; Hochstrasser 2000:113–121). This new anti-authoritarian cast of mind is clearlyevident in a dissertation on bigamy of 1685, in which Thomasiusdefends the practice as consistent with natural law, and whichunsurprisingly led to a confrontation with a professor in the theologyfaculty at Leipzig. Thomasius’ pioneering decision to holdlectures in German, announced (in German) in 1687, likewise provokedcontroversy, as did his publication beginning in 1688 of a monthlyjournal (the first periodical published in German), entitled theMonatsgespräche, in which Thomasius commented,frequently satirically, on the local intellectual scene.Thomasius’ lectures and publications increasingly generatedconflict with the theological faculty in Leipzig, which upheld arather strict form of Lutheran orthodoxy, and while his connectionswith the Saxon court stood him in good stead for a time, his defenceof an inter-faith marriage involving a (Lutheran) Saxon count and a(Calvinist) Brandenburg princess cost him his protection, and in March1690 he was prohibited from publishing and holding lectures (privateand academic) in Electoral Saxony.

Thomasius sought refuge in Berlin, in the neighbouring state ofBrandenburg which was led by the Calvinist Elector Friedrich III(later king Friedrich I) and had a tradition of toleration. Partlythrough the support of Pufendorf himself, Thomasius was given anappointment as councillor to the court, and was allowed to lecture atthe Ritterakademie in Halle an der Saale, which in 1694 would becomethe Friedrichs-Universität, with Thomasius among the foundingfaculty (in law). Thomasius was soon joined by the Pietistorientalist, theologian and educational reformer, August HermannFrancke, who had likewise run afoul of the religious authorities inLeipzig. Thomasius himself had been sympathetic with theanti-scholastic and anti-authoritarian bent of the Pietists (see§3.2 below), and had publicly defended Francke at one point in Leipzig;however, a public break occurred when Thomasius published a criticism,in 1699, of the pedagogy Francke had adopted in his famous educationalinstitutions in Halle. Thomasius continued to stir controversy withhis lectures and publications, which frequently over-reached thepurview of the juristic faculty (such as his critical discussion ofwitchcraft trials—Beck 1969: 253–254), and breacheddecorum by personally attacking his theological colleagues, all ofwhich led to a reprimand from the Brandenburg court in 1702 and anorder to adhere to the boundaries between faculties. Thomasius’dissertationDe concubinatu of 1713, in which he contendedthat the use of concubines does not violate the marriage contractgiven that the purpose of marriage is solely procreation, alsogenerated heated discussion. While Thomasius and Francke reconciled in1714, Thomasius did not play a significant role in the latercontroversy between Wolff and the Pietists. He died in Halle on 23September 1728.

Thomasius’ works cover a wide range of topics. In addition tothe topical essays and dissertations already mentioned, Thomasiuspublished major texts on natural law, including theInstitutionesjurisprudentiae divinae (Institutions of DivineJurisprudence) of 1688 and theFundamentum iuris naturae etgentium (Foundations of the Law of Nature and Nations)of 1705 (for discussion of Thomasius’ contributions to naturallaw theory, which will not be taken up here, see especiallyHochstrasser 2000: ch. 4; Kühnel 2001; and Lutterbeck 2002).Thomasius also published on topics in theoretical and practicalphilosophy, especially during his time in Halle. Thomasius wrote anumber of texts on logic, such as theIntroductio ad philosophiamauliam (Introduction to Court Philosophy) of 1688, aswell as theEinleitung zur Vernunfft-Lehre (Introductionto the Doctrine of Reason) and theAusübung derVernunfft-Lehre (Application of the Doctrine of Reason)both of 1691. These were followed by a parallel exhibition of hismoral philosophy in theEinleitung zur Sitten-Lehre(Introduction to the Doctrine of Morals) of 1692 and theAusübung der Sitten-Lehre (Application of theDoctrine of Morals) of 1696, as well as an influential excursioninto metaphysics in theVersuch von Wesen des Geistes(Essay on the Essence of Spirit) in 1699 (second edition1709).

1.2 Philosophy

Thomasius is decidedly not a systematic philosopher; instead, andquite consistent with his mature distaste for dogmatism in all itsforms, he is best characterized as a conscientiously eclectic thinker(M. Albrecht 1994: 398–416; Bottin & Longo 2015:301–315). That said, Thomasius’ thought is unified by anoverarching conviction in the priority of practical life, and thebelief that erudition in whatever sphere of knowledge should bepursued for the sake of the improvement of our will and intellect foruse in our ordinary life. This is made clear, for instance, in thedefinition of learnedness (“Gelahrheit”) thatThomasius provides at the outset of hisIntroduction to theDoctrine of Reason:

Learnedness is knowledge through which the human being is made capableof properly distinguishing the true from the false and the good fromthe bad […] in order that one might promote one’s owntemporal and lasting welfare, and that of others, in ordinary life andaffairs. (Thomasius 1691a: ch. 1, §1 [2019: 18])

Significantly, and unlike subsequent Enlightenment thinkers, Thomasiusis also explicit in holding that because the attainment of learnednessis possible wholly through the use of the natural (rather than thesupernatural) light of the mind (cf. Thomasius 1691a: ch. 1,§16), it is accessible by all, regardless of gender or class (formore on this, see§6.1, below).

In light of this, the aim of logic for Thomasius is to cultivate thepowers of the mind, and the faculty of reason in particular, so thatwe are capable of discerning what the natural light of the mindreveals to be true or false in any field to which it is applied. Thisinvolves not just supplying positive guidance with respect to howtruth might be recognized and attained, but also negativelyidentifying and dispelling prejudices that obscure the natural light.Thomasius’ logic, therefore, is not primarily intended to offera theory of demonstration (as with scholastic logics) nor an organonfor specifically scientific discovery (as with Cartesian logics or,later, with Wolff’s logic). This distinctive aim does not,however, prevent him from weighing in on matters of traditionallogical and epistemological import; for instance, he contends thatthought has to do with images ultimately derived from the externalsenses (thereby rejecting innate ideas—Thomasius 1691a: ch. 3,§22), and he outlines a theory of demonstration that focuses onpreservingconviction in truths through their connection toincontrovertible first principles.

Thomasius’Application of the Doctrine of Reasoncontributes to the project initiated in theIntroduction byoutlining the means of avoiding error. Avoiding error involves theeradication of prejudices, which are among the causes of thecorruption of reason and which are grouped into two main groups,namely, prejudices of authority and of precipitancy or hastiness.That, in turn, is accomplished through what he identifies as dogmaticdoubt, not the Cartesian doubt that deems everything false so as tofind a first indubitable principle, which is a pointless enterprise,according to Thomasius. Dogmatic doubt is the doubt about particularthings, beliefs, and opinions, and this he found healthy and conduciveto preventing error.

In any case, the centrepiece of Thomasius’ logic, and probablyits most influential aspect, is his theory of truth. According toThomasius’ definition, truth consists in

nothing other than an agreement between human thoughts and theconstitution of things outside your thoughts. (Thomasius 1691a:ch. 5, §13 [2019: 28]; italics in original)

While this definitioncontains the classical correspondencetheory of truth (in accordance with which truth consists in thecorrespondence of our thoughts with things), Thomasius contends thatthe correspondence works in the other direction as well, namely, thattruth also requires the correspondence of things with our powers ofthought:

Here, however, you should not ask whether the understanding must agreewith things, or the things with the understanding; rather this harmonyis so constituted that neither provides the guiding principle for theother, but this harmony is simultaneously presupposed by both eventhough external things as it were initiate it. (Thomasius 1691a: ch.5, §14 [2019: 28])

In accordance with this conception of truth, Thomasius conceives ofthe mind as fundamentally active with its ideas (rather than merelypassively reflecting the order of nature) such that things must be inagreement with its nature and capacities in order to be cognized orwilled. Thomasius does not himself explore the principles that mightgovern the mind’s activity nor draw any idealistic consequencesfrom this conception of truth—that, for instance, things insofaras they agree with our intellect might differ considered apart fromit—though his successors such as Adolph Friedrich Hoffmann andChristian August Crusius would (on the latter, see§5.2 below).

This conception of the human mind as fundamentally active is taken upagain in Thomasius’ lone substantial contribution tometaphysics, theEssay on the Essence of Spirit, whereThomasius distinguishes spirit (Geist) from matter in virtueof its activity. While this would appear to result in a metaphysicaldualism, Thomasius complicates things by endorsing a hierarchy ofspirits, not just between the human being and God, but also a class ofspirits responsible for various effects in bodies (such as heating andcooling). Yet, his further postulation of an “air and lightspirit [ein Lufft- und Licht-Geist]” which fills thespaces between parts of matter, not to mention his apparentidentification of space itself as “pure spirit” (Thomasius1709: 60, 167–8) muddles the original, starkly dualisticpicture.

Thomasius’s moral theory is a theory of the will. He held thatin moral matters, the will dominates reason. While human beings havefree choice if not externally constrained, the will is not free;rather, it is dominated by human affects—our passions, impulses,and desires. Like Hobbes, Thomasius believed that even though subjectto such inner (psychological) constraints, the will still chooses(with the aid of reason); it consciously wills. And a conscious choiceis precisely what is required for a (good) action to be consideredmoral: a good instinct or good inclinations may make us good, may evenbe desirable, but by itself this is not enough to make us moral.Morality requires a conscious act of will. The trouble with moralityarises because the will is determined by evil desires, in particular,lust, ambition, and avarice. Although there are noble sentiments aswell, which similarly influence the will, they are in conflict withthe negative dispositions. The conflict can be brought to a positiveconclusion only by appeal to divine grace (God’s salvation), andThomasiusApplication of the Doctrine of Morals is notablefor its positive treatment of mystical experience.

Thomasius’ moral philosophy is accordingly informed bytheological considerations in a way not shared by his works intheoretical philosophy. While, in the theoretical context, he didbelieve in natural reason’s capacity to overcome corruption, inthe practical context he held that an evil will is at the root of ourcorruption, and to ameliorate it we require God’s grace.Moreover, Thomasius’s moral outlook seems to develop from hisinitial presentation of morality in theIntroduction to theDoctrine of Morals in 1692, which is an optimistic affirmation ofthe viability of a moral position he identified as one involving“rational love” (vernünftige Liebe) as theonly means to a “happy, courteous and cheerful life”, to amore pessimistic position in hisApplication in 1696 where hecontends that human self-interest and an evil will constitutesignificant obstacles to moral improvement (a development likely dueto his Pietist conversion during the period; cf. Beck 1969: 251;Ahnert 2006: 27–42).

This ambivalence and return to theology aside, Thomasius’s moralposition is a distinctive one. The theory of rational love is based onthe fundamental equality of human beings as well as on their abilityto think and choose independently (of authority). Ultimately,Thomasius’s ethics is a social ethics. The theory isother-directed, and given the absence of laws and principles,constitutes a contrast to the formalist universalist ethics Kant woulddevelop by the end of the next century. At the same time, the lack ofany way of making this theory applicable in a context governed not bysimilar but instead by conflicting interests, makes something like aformalist ethics an inevitability. By the end of theIntroductionto Moral Theory, even Thomasius recognizes that “rationallove” will function only in relatively harmonious contexts. Inother contexts, however, particularly those characterized by unequalpower positions, justice may well be required, a distinction in dutieswhich Thomasius influentially characterizes in terms of“internal” and “external” obligation (cf.Barnard 1988; Schneewind 1998: 165–166).

2. Radical Philosophy

Through the efforts of Thomasius, and later Christian Wolff, theFriedrichs-Universität in Halle became the intellectual centre ofthe early Enlightenment in Germany. And despite, for instance,Thomasius’ conflict with Orthodox Lutheranism in Leipzig, andWolff’s controversy with his Pietist colleagues (§3.3, below), neither were explicitly hostile towards religious belief, theChurch, or to (appropriately exercised) religious authority; nor forthat matter did either seek to challenge the existing political order.Beyond the German academy, however, a more radical philosophicaltradition flourished, one that drew on the thought of, among others,Hobbes, Gassendi, and Spinoza, and proliferated through thetransmission of clandestine literature within networks that spannedacross Europe. While there was considerable diversity among the viewsheld by the thinkers within this radical philosophical tradition, theytended to be highly critical of organized religion (if not necessarilyprofessed atheists) and of the established political order, rejectedthe authority of the Bible as a source of revealed truth, and defendeda (not always sophisticated) materialistic conception of the soul (cf.Stiehler 1966; Israel 2001: 628–636; Mulsow 2006 [2015]). Itbears noting that while this tradition flourished outside of a narrowacademic context, there was nonetheless considerable exchange andmutual influence between figures in both the mainstream and radicaltraditions.

Among the most important German thinkers within this radicalphilosophical tradition, and quite representative of its intellectualdiversity, are Friedrich Wilhelm Stosch (1648–1704) and TheodorLudwig Lau (1670–1740). Stosch was the son of a Reformedminister and court chaplain in Brandenburg and worked as a courtsecretary until ill-health forced him to resign in 1686. Stoschsubsequently pursued philosophical interests and in 1692 published hissole known text, theConcordia rationis et fidei (Concordof Reason and Faith). In spite of its title, theConcordseeks to subordinate the claims of faith to the canons of reason, inaccordance with a broadly Socinian outlook, and Stosch denies thatthere is any basis in reason for conviction in the natural immortalityof the soul (for which he also provides a materialist account), andrejects the reasonableness of eternal damnation. Stosch’sConcord was published anonymously (with Amsterdam listed asthe place of publication) with only 100 copies printed, but when thesewere discovered for sale, they were seized and burned. Stosch wasforced to identify himself as the author, was arrested, andsubsequently investigated by a committee consisting of, among others,Pufendorf, concluding with Stosch’s public retraction of thebook in 1694.

Lau had studied law in his home town of Königsberg before movingto Halle in 1694 where he attended lectures by Thomasius. In 1695, heembarked on a trip through Europe and England (where he apparently metNewton), taking up a position as councillor with the young Duke ofCourland on his return. The early death of his patron saw Lau turn tointellectual pursuits, and in 1717 he published a number of treatiseson various subjects, including the anonymousMeditationesphilosophicae de Deo, mundo et homine (PhilosophicalMeditations concerning God, the World, and the Human Being). Thetext covers a wide range of philosophical (and medical and political)topics, and is distinctive in its eclectic borrowings from Spinoza,Locke, Plotinus, and Giordano Bruno, among others. Its generalphilosophical outlook might most accurately be characterized aspantheistic, both in the Spinozistic sense inasmuch as Lau defends theworld’s pre-existence in God and denies its creationexnihilo (although the extent of Lau’s Spinozism is disputed;cf. Schröder 1987: 128–132), but also and especially in thesense of the Irish freethinker John Toland’s pantheism inasmuchas Lau attempts to outline the foundations of a universal religion.Due to its strident denunciation of the clergy and a genealogicalcritique of the current political order, theMeditations wasinstantly controversial, and Lau’s publisher was eventuallypressured into revealing Lau’s authorship. This led toLau’s imprisonment, during which he attempted suicide, and hissubsequent expulsion from Frankfurt am Main; Lau’s appeal to hismentor, Thomasius, for a review of the proceedings was also met with apainful denunciation. Lau attempted to return to his study of the law,but his unorthodox opinions and previous brush with infamy made thisimpossible (in spite of a formal recantation of his earlier views). Hedied, in poor mental health, in Altona in 1740.

3. The Controversy between Wolff and the Pietists

Thomasius would continue to exercise an important influence on Germanphilosophy throughout the first half of the eighteenth century.However, it was his colleague in the philosophy faculty at theFriedrichs-Universität, Christian Wolff, who would contribute themost to the modernization of the German intellectual landscape and thespread of the Enlightenment. Wolff achieved this primarily through hisdistinctive philosophical system, the so-called“Leibnizian-Wolffian” philosophy, which incorporated thelatest philosophical ideas and methods, including but not limited tothose of Leibniz himself. The relevance and accessibility ofWolff’s system, expanded and refined by his many students,quickly saw it gain a foothold in academies across Germany. Wolff wasnot without his detractors, of course, and none were more vocal, normore successful (at least initially) in their efforts to limit hisinfluence, than his Pietist colleagues in the faculty of theology. Thefamous controversy between Wolff and the Pietists, which at its climaxsaw Wolff exiled from Prussia on pain of hanging in 1723, put the fullmenu of modern ideas—including materialism, idealism, atheism,and Spinozism—before the literate public and drew the attentionof the rest of Europe to the German intellectual scene.

3.1 The “Leibnizian-Wolffian” Philosophy

Christian Wolff was born in Breslau (today, Wrocław) on 24January 1679. By all accounts a gifted student, he developed aninterest in theology and mathematics during his time in Gymnasium, andstudied theology and mathematics at the University of Jena and then inLeipzig, gaining hisMagister at Leizpig in 1702. HissubsequentHabilitationsschrift on introducing mathematicalmethod to practical philosophy drew Leibniz’s attention to him.They began a correspondence that continued until Leibniz’s deathin 1716, and which covered topics from mathematics to metaphysics.Partially through Leibniz’s support, Wolff was appointed to avacant chair in mathematics at the Friedrichs-Universität inHalle, delivering his inaugural lecture in 1707.

Understandably, given the nature of his position, most ofWolff’s initial publications were devoted to mathematics andnatural science, including an introduction to mathematics in 1710 andan influential mathematical dictionary in 1716. Around 1710, however,he began to lecture on more narrowly philosophical topics, publishinghisVernünfftige Gedancken von den Kräfften desmenschlichen Verstandes und ihrem richtigen Gebrauche inErkäntnis der Wahrheit (Rational Thoughts on the Powersof the Human Understanding and its Propert Use in the Cognition ofTruth) [the “German Logic”, hereafter GL] in1713. Thus began Wolff’s famous series of German-languagetextbooks on philosophical topics, which would grow to include theVernünftige Gedanken von Gott, der Welt und der Seele desMenschen, auch allen Dingen überhaupt (Rational Thoughtson God, the World and the Soul of Man, and on All Things inGeneral) [the “German Metaphysics”,hereafter GM] in 1719 (albeit with a publication date of 1720), andtheVernünfftige Gedancken von der Menschen Thun und Lassen,zu Beförderung ihrer Glückseligkeit (RationalThoughts on Human Actions for the Promotion of their Happiness)[the “German Ethics”, hereafter GE] in 1720,followed by the “German Politics” in 1721, the“German Physics” in 1723, and the“German Teleology” in 1724.

This series of texts constitutes the first presentation of theso-called “Leibnizian-Wolffian” philosophy that would cometo dominate the philosophical landscape in Germany. There is, ofcourse, no question that Wolff’s philosophical system isthoroughly informed by Leibniz’s: Wolff himself admits that thereading of Leibniz’s 1684 essay “Meditations on Cognition,Truth, and Ideas”, and Leibniz’s classification of ideasin particular, had sparked a “great light” that informedhisGerman Logic (cf. GL “Vorrede”); moreover,Wolff himself reports that he incorporated a number of Leibnizianconcepts into his presentation of ontology, cosmology, and rationalpsychology in theGerman Metaphysics (cf. Wuttke 1841:141–142). Even so, Wolff points out that when he started writinghis series of philosophical textbooks there were few ofLeibniz’s texts available through which one might get a sense ofthe wider Leibnizian philosophy (Wuttke 1841: 140–141; cf. alsoWilson 1994); thus he takes issue with the designation of his systemas “Leibnizian-Wolffian”—a coinage he credits to oneof his students, Georg Bernhard Bilfinger (Wuttke 1841: 142). Theextent of Leibniz’s influence on Wolff is widely debated (cf.Corr 1975; École 1979), but it is in any case clear thatLeibniz is not the sole, nor in every case the most important,influence on the development of Wolff’s ideas, as figures suchas Ehrenfried Walther von Tschirnhaus (1651–1708), John Locke,and late Scholastic thinkers also exerted an important influence onhis metaphysics, epistemology, and theory of science (Neveu 2018;Leduc 2018; Dyck 2021a).

Turning to a brief overview of Wolff’s philosophical works, theGerman Logic is intended, quite in contrast toThomasius’, as a handbook for the acquisition, justification,and orderly presentation of scientific cognition. So, in addition tothe now expected treatment of concepts, propositions, and syllogisms,Wolff’s text contains discussion of drawing universalpropositions from individual experiences, of experiments, and ofscience and its distinction from faith and opinion. Moreover, theGerman Logic contains Wolff’s mature presentation ofhis mathematical method, through which we proceed from definitions andaxioms to the formulation of theorems and postulates, and ultimatelyto demonstrations, and it outlines how the method can be employed forthe purpose of scientific discovery (for discussion, see Frketich2019; Gava 2019). Significantly, it is this method that gainswidespread application throughout Wolff’s philosophicalenterprise, including in his metaphysics.

TheGerman Metaphysics was Wolff’s next majorphilosophical text, and in it he formally introduces the division ofmetaphysical topics into ontology, cosmology, empirical and rationalpsychology and natural theology, a division that Kant, among others,would subsequently take up. The initial chapter attempts to makeevident, in a Cartesian vein, both an indubitable truth (“we arecertain that we exist”) and to establish a canon for what willcount as acertain cognition for the remainder of theenterprise. In the second chapter Wolff sets out the two (Leibnizian)principles governing his philosophical thought: the principle ofcontradiction (“something cannot both be and not be at the sametime” GM §10) and the principle of sufficient reason.Significantly, Wolff suggests that while the first is self-evident,the second admits of proof, for which Wolff (in a departure fromLeibniz) offers two arguments. The first proceeds as follows:

Were it the case that something could be, or take place, in a thingwithout a reason why it should occur being met with either in thatthing itself or something else, then it would come to be from nothing.Since, however, it is impossible that something could come to be fromnothing,everything that is must have a sufficient reason why itis. (GM §30 [2019: 101])

In the remainder of the ontology, Wolff provides accounts of conceptsthat will be key for his subsequent treatment of specific metaphysicaltopics, including essence and attribute, space and time, simple andcomposite, substance, power, and cause.

The chapters on empirical and rational psychology outline an accountof the soul in general and of the human soul in particular. In hisempirical treatment, Wolff considers what can be known of the soul bymeans of our ordinary inner experience. He contends that we candistinguish thoughts in terms of obscurity, clarity, and distinctness,but we can also distinguish the soul’s representations in termsof their content. Accordingly, they can be classified into sensations,imaginings, and thoughts proper, which can in turn be traced back tovarious faculties of the soul, including sensibility, imagination, andthe understanding, in virtue of which it is capable of these distinctthoughts. We also discern that the soul is subject to pleasure anddispleasure in its (distinct or indistinct) cognition of good andevil, which give rise to desires and willing (based on indistinct anddistinct cognition respectively), and when that willing is inaccordance with what pleases the soul the most then, for Wolff, itsacts are free (GM §519).

On the basis of these empirical cognitions of the soul, rationalpsychology seeks to draw inferences regarding the soul’s essenceand nature. Wolff argues that the soul must be immaterial given thatit is impossible that a body should think (GM §738), and as aresult that the soul is a simple substance endowed with a power ofwhich its thoughts are effects, which power is identified as a powerof representation (GM §§742–7). This secures thesoul’s natural immortality, or incorruptibility, but Wolffargues for the soul’s personal immortality, or its preservationof its state of conscious representation and memory in the afterlife(GM §§925–6). It is in the context of rationalpsychology that Wolff also offers a defence of the Leibnizian doctrineof pre-established harmony (§765), which he think accounts forthe empirically-observed agreement between the states of the soul andthe body better than the competing systems of physical influence andoccasional causation.

The final pair of topics concern the world (cosmology) and God(natural theology). Regarding the former, Wolff identifies the worldas the “series of changeable things that are next to one anotherand follow one upon the other” (GM §544 [2019: 120]). Assuch, the world is a composite consisting of ultimately simplesubstances, though Wolff declines to identify them as Leibnizianmonads as he hesitates to ascribe representational states to theconstituents (“elements”) of matter (GM§§598–9). Things and events in the world arenonetheless connected to one another in accordance with the principleof sufficient reason, and Wolff concludes that all events are certainas a result (GM §561). Concerning God, Wolff argues that He mustexist inasmuch as our own evident existence requires a necessary beingto serve as its sufficient reason, which necessary being must also beindependent, eternal, and simple (GM §§928–936); itcannot, therefore, be the world (a composite) nor our own soul (abeing dependant on the world), and so can only be God (GM §945).In addition to these attributes, God must have an understanding,through which He distinctly represents all that is possible, and afree will inasmuch as He chooses that world which pleases Him most tomake actual (GM §980).

Rounding out Wolff’s major philosophical works of this period,theGerman Ethics is composed of four parts, a theoreticalpart that treats the foundation of practical philosophy and threepractical parts that present a doctrine of duties that human beingshave towards themselves, God, and others. The central notion inWolff’s ethics is the (metaphysical) notion of perfection whichconcerns the “agreement” of elements in a given manifold(cf. GM §152), and which is cognized through our intellectualpowers. It is the cognition of the (apparent) perfection in an actionthat moves us to act, a fact that accounts for Wolff’s emphasison the duty to cultivate our understanding among our duties toourselves so that we can be moved to act in (what are in fact) themost perfect ways. Promoting the perfection of ourselves and othersserves for Wolff as the universal rule in accordance with which weought to choose between two (or more) possible actions (GE §12).That is to say, when making a free choice we ought to consider whetherthe action “promotes the perfection of our inner and outerstate” (GE §2) and that means considering whether the stateof the soul and the body accords with the prior state or contradictsit. The outcome has greater perfection to the extent that itcontributes to the continued “natural human state and itsharmonious preservation over time”(GE §2). The naturalhuman state Wolff envisions is the state of the soul in its manifoldefforts to find truth, and everything has to be done to maximize thatstate. It so happens, that this is where happiness lies as well, andas Wolff indicates at the end of the ethics, it is incumbent uponhuman beings to ensure not only their own perfection/happiness, but to“contribute as much as possible to the happiness ofothers” (GE §767).

3.2 The Halle Pietists

Next to Thomasius and Wolff, the most important intellectual figure inthe early history of the Friedrichs-Universität in Halle wasAugust Hermann Francke (1663–1723). As we have seen, Francke hadcourted controversy in Leipzig through his involvement in the Pietistmovement. Pietism was a spiritual movement within the Lutherantradition that rejected the scholastic and theological turn thatLutheranism had taken and proposed a further, internal reformation tosupplement the already-effected external one, and aimed at cultivatinga “living faith” rather than mere lip-service to Christianideals. The Pietists sought the personal and interior experience of arelationship to Christ, an individual transformation that was theresult of an act of divine grace modelled on Francke’s ownconversion experience (cf. Wallmann 1990: 63–4). To this end,the Pietists focused on the study of the Bible itself and devotionalliterature in small groups—the so-called conventicles orcollegia pietatis—which were notable, andcontroversial, for welcoming the involvement of women (R. Albrecht2004; Gierl 2015).

After falling out (in spite of Thomasius’ support) with theLutheran authorities in Leipzig, Francke followed Thomasius to Halle.He took up a position as a pastor in the neighbouring town of Glaucha,and held lectures on oriental languages in 1692. Francke was himself adisciple of the movement’s intellectual founder, Philipp JakobSpener (1635–1705), though Francke contributed immeasurably tothe spread of Pietism, primarily through his educational institutionsin Halle, beginning with a school for poor children founded in 1695.Through the institutions that arose from this humble school, Franckesought a reform of educational principles in line with Pietist ideals,and in this was enormously successful. The pedagogical institutionssupplied an influential model for similar institutions in and outsideof Germany (especially due to the fact that it was a largelyself-funded philanthropic institution), became the hub of an expansivemissionary network, and trained the next generation of Germantheologians, as well as some philosophers (like A. G. Baumgarten), notto mention Prussian civil administrators, bureaucrats, and pastors.Indeed, Francke enjoyed a close relationship to the Prussian court,and king Friedrich I’s successor, Friedrich Wilhelm I became anenthusiastic supporter of his projects after a visit to Halle (cf.Hinrichs 1971).

Another significant member of the theology faculty in Halle wasJoachim Lange (1670–1744). Lange had come under Francke’stutelage in Leipzig (where he also met Thomasius), following him toErfurt and (briefly) Halle, before taking up positions at variousGymnasia in and around Berlin. During this time he also lectured onclassical languages and wrote a very successful Latin grammar. In1709, he accepted an appointment at the Friedrichs-Universität,in the theology faculty that was now thoroughly steeped inFrancke’s Pietism. During his time in Berlin, Lange completed anotable philosophical work, theMedicina mentis (Medicineof the Mind), printed in Halle in 1704. Lange’s text sharesa title with Tschirnhaus’Medicina mentis of 1687, butlittle else as Lange instead emphasizes the futility and vanity ofhuman attempts to attain cognition through their own efforts,highlighting the mind’s proneness to error and prejudice in itsfallen state. Rather, according to Lange, it is only by means ofdivine grace and the divine light that we can heal the corruptedintellect and the will (Schönfeld 2010).

A final figure worthy of mention in this context, albeit notstrictly-speaking a Pietist thinker, is Johann Franz Budde(1667–1729). Budde had studied theology in Wittenberg, and afterlecturing at Jena, had been called to an appointment in moralphilosophy at Halle in 1693, where he remained until returning to Jenain 1705 as a professor of theology. Budde adopted a conscientiouslyeclectic philosophical outlook, one influenced by Thomasius, and whichalso informed his theological commitments to Lutheranism (if not toPietism specifically). A prolific writer, he published a number ofphilosophical works during his time in Halle, including theInstitutiones philosophiae eclecticae that appeared in twoparts in 1703. The two parts are the “Elementa philosophiaetheoreticae”, roughly a metaphysics, and the “Elementaphilosophiae instrumentalis”, Budde’s logic. A later work,entitledTheses theologicae de atheismo et superstitione(1717), is also notable in that Budde seeks to refute various threatsto natural and revealed religion, including Spinozism (cf. Rumore2019: 44–8), an issue that would come to the fore in the comingcontroversy with Wolff.

3.3 The Controversy and its Aftermath

The controversy between Wolff and his Pietist colleagues is nottypically held to be of much philosophical significance. Rather, thePietists’ hostility towards Wolff is taken to be a reflection oftheir fundamentally un-enlightened anti-intellectualism, and theoutbreak of the controversy itself a result of personal andprofessional rivalries—competition for students and universitychairs. That this appraisal is generally accepted is to no smallextent due to the efforts of subsequent histories of the disputewritten by devoted Wolffians, such as C. G. Ludovici (1707–78)and Georg Volckmar Hartmann (fl. 1729–1737). And while it cannotbe denied that the voluminous texts exchanged during the course of thecontroversy, on both sides, only infrequently rise above the level ofthe polemical, it would be unfair to dismiss the ground of thePietists’ objections as philosophically insignificant, or indeedirrelevant for the subsequent development of German philosophy (up toand including Kant).

The controversy itself was the result of long-simmering tensionsbetween Wolff and the Pietists. Wolff’s turn to lecturing onphilosophical topics, such as metaphysics (including a treatment ofnatural theology), beginning in 1710, not to mention his discussion intheGerman Logic of Scriptural interpretation, provoked theire of the theology faculty and led to warnings to their studentsabout attending Wolff’s lectures (on account of his“Atheisterey”; cf. Beutel 2007: 165–6). Thepublication of Wolff’sGerman Metaphysics in 1719, withits peculiar proof of God’s existence and apparent endorsementof natural necessitation, provided a broad target for their criticalattention. This largely behind-the-scenes friction broke into the openwith Wolff’s address on 12 July 1721, on the occasion of thetransition of the pro-rectorship from himself to Lange, in which hedefended the consistency of Confucian (i.e., non-Christian) practicalphilosophy with Enlightened reason (and Wolffian moral philosophy inparticular; cf. M. Albrecht 1985).

The address caused an uproar among the Pietists and Francke demandedto see a copy of Wolff’s address to scrutinize for himself,which request Wolff denied citing the independence of the philosophyfaculty. Lange at this point took up the study of Wolff’smetaphysics, penning a damning appraisal for the theology faculty thatwas sent to the authorities in Berlin. Wolff was invited to reply, andhis rejection of the hostile characterization of his views led to theformation of an official commission in late October 1723 toinvestigate the charges against Wolff. The king himself would soonintervene, and decisively: after the dangers of Wolffian philosophywere explained to two of his generals visiting Halle—thedoctrine of the pre-established harmony in particular was said tojustify the desertion of soldiers (Beutel 2001: 189)—and thisthreat conveyed to the king, Friedrich Wilhelm I asked his trustedadvisor Francke to outline the problematic doctrines defended byWolff, which he promptly did. Horrified by Wolff’s evidentgodlessness, the king dismissed Wolff from his position and orderedhim to leave Prussia in 48 hours on pain of hanging, an order that wasreceived in Halle on 12 November 1723. Wolff reacted swiftly, crossingover to nearby Electoral Saxony, refunding his students’ fees,and ultimately took up the offer of a position in Marburg where hereceived an enthusiastic reception.

Wolff’s expulsion only meant that the dispute moved into thepublic domain, and the next decade would see dozens of treatisesexchanged between Wolff (and his defenders) and his opponents, Langeand Budde foremost among them. A range of issues were canvassed in thedebate. So, the issue of thelibertas philosophandi hadalready surfaced in the conflict between the philosophical andtheological faculties, and there were significant differences betweenWolff and the Pietists concerning the ground of moral obligation(Grote 2017); however, the principal topics were metaphysical. Theseinclude the pre-established harmony, which Lange rejected asinconsistent with any proper union between soul and body, defendinginstead a natural connection between them achieved through physicalinflux (Lange 1724: 48–50 [2019: 141–2]).

Even so, the Pietists’ foremost philosophical concern was withpreserving the genuine freedom of the human (and divine) will againstWolff’s Leibniz-inspired assaults (cf. Bianco 1989). Accordingto Lange, Wolff’s endorsement of the principle of sufficientreason has the consequence of reducing the soul to an automaton andrendering the series of events that constitute the world a fatallydetermined concatenation. The result is a necessitarianismdistinguishable from total Spinozism only because Wolff accepts aplurality of substances (Lange 1724: 72–3 [2019: 153]). Againstthis, Lange contends that the freedom (rather than mere spontaneity)of the will is directly evident through experience (particularlythrough our conscience) and constitutes the essence of the humanbeing, that it is required for morality and religion, and that itserves to exempt human beings from the chain of natural necessitation.In spite of his unsympathetic reception in the history of philosophy,Lange succeeds in outlining a coherent antithesis to theLeibnizian-Wolffian conception of the soul and its place in nature,one that would prove influential for later Pietist critics (likeCrusius) and that would also form an important part of the backgroundto Kant’s own later discussion of freedom.

After their initial success with Wolff’s expulsion, Lange andthe Pietists suffered diminished influence at the Prussian court. Bycontrast, the affair only served to burnish Wolff’s Europeanreputation. In Prussia, Wolff’s works on metaphysics andpractical philosophy were added to the list of atheist books, but henow saw himself as speaking to Europeans, not merely Germans, andbegan a series of Latin works, commencing with thePhilosophiarationalis sive logica (Latin Logic) in 1728. FriedrichWilhelm I seemed to think better of his precipitous decision andinvited Wolff to return to Prussia in 1733, an invitation which Wolffdeclined. But the ban on his writings was reversed in 1734, and theverdict of an inter-confessional Prussian commission in 1737vindicated Wolff’s philosophy of the charges levelled by thePietists. The crown prince (later Friedrich II) was an enthusiasticbooster of Wolff at the court (and no friend of the Pietists), andwith his ascension in 1740 he invited Wolff to return to Prussia.After turning down the proffered presidency of the Berlin Academy,Wolff returned to a professor- and vice-chancellorship in Halle togreat acclaim, devoting his remaining time to completing his works onpractical philosophy.

4. Alexander Gottlieb Baumgarten

A. G. Baumgarten is best known for authoring the textbook inmetaphysics that Kant used for his lectures on the topic, though hewas an important and innovative thinker in his own right. Hisphilosophical ambitions are, moreover, deeply informed by thecontroversy in Halle, as he had an abiding intellectual sympathy withWolffianism but theological and personal connections to the Pietists.Among his students was the notable Wolffian philosopher GeorgFriedrich Meier (1717–77), and his own influence extended toKant but also to Moses Mendelssohn and J. G. Herder.

4.1 Life and Works

Alexander Gottlieb Baumgarten was born in Berlin on 17 June 1714.Baumgarten’s mother died when he was three, and his father, agarrison chaplain and pastor, died when he was eight in 1722, leavinghim to the care of his grandmother and older brothers. In accordancewith his father’s wishes, Baumgarten went to Halle to study,enrolling in the Latin school at Francke’sWaisenhauswhere his older brother Siegmund Jakob (1706–57), who wouldhimself become a famous theologian, was an inspector. Baumgartenthrived in his studies, and in 1730 matriculated at the university,where he attended lectures by Francke and Lange in theology. While itwas still forbidden to teach Wolff’s philosophy, Baumgartenundertook (with his brother’s encouragement) a thorough study ofWolff’s thought, lecturing on his logic in the Latin school andvisiting Wolffians at the university in Jena. Baumgarten turned to thestudy of philosophy, attaining hisMagister in 1735, and heldlectures on logic and Wolffian metaphysics, dictating from his ownnotes on the latter (rather than a textbook) from which notes his ownlaterMetaphysica derives. In 1736, a chronic lung ailmentinterrupted his academic work and saw him hospitalized in Berlin,returning to Halle in 1737 where he continued to lecture to greatacclaim. His position at Halle had been as an (unpaid) extraordinaryprofessor, but in 1739 he was called to a position at the universityat Frankfurt an der Oder, and he left Halle in 1740 just beforeWolff’s triumphant return. In Frankfurt, Baumgarten lecturedwidely in philosophy, including on aesthetics for the first time in1742. Health problems, likely tuberculosis, and other difficulties,marked the last decade of Baumgarten’s life, and he died on 26May 1762.

Baumgarten’s philosophical works cover a wide range of topics.The 1000 sections of hisMetaphysica of 1739 offers asynopsis of his views, following the Wolffian division, on ontology,cosmology, empirical and rational psychology, and natural theology. Healso published two influential textbooks on ethics: theEthicaphilosophica (Philosophical Ethics) of 1740 andInitia philosophiae practicae primae (Elements of FirstPractical Philosophy), both of which Kant also regularly used inhis lectures on moral philosophy. Baumgarten’s abiding interestin aesthetics issued in two texts, the first a dissertation entitledMeditationes philosophicae de nonnullis ad poemapertinentibus (Reflections on Poetry) in 1735, and thesecond the ambitiousAesthetica, the first volume of whichappeared in 1750, with a second unfinished volume printed (at therequest of the publisher) in 1758.

4.2 Philosophy

Baumgarten’s metaphysics is frequently characterized asinclining more towards Leibniz than to the“Leibnizian-Wolffian” philosophy; for instance, he makesexplicit reference to monads in his presentation of ontology andcosmology, and concerning the pre-established harmony he accepts thatit obtains between all substances (not just between soul and body) anddoes not qualify his endorsement of the system as Wolff came to do(Baumgarten 1739: §761–9; cf. Watkins 2005: 73–81 fordiscussion). While there is no doubt that Baumgarten adopts afundamentally Leibnizian picture in his ontology, including theendorsement of the principle of sufficient reason, to leave it at thiswould be to ignore the important and fruitful role that his Pietistbackground plays in his philosophical thought (Look 2018). Indeed,Baumgarten’s originality as a thinker consists in his efforts toamend key planks of Leibnizian (and Wolffian) thinking in light of hisunderlying Pietist commitments.

This is particularly evident in Baumgarten’s treatment offreedom and immortality, where Wolff’s position on each wastargeted by his Pietist critics. By way of addressing the Pietistobjections to Wolff’s moral intellectualism and his reduction offreedom to mere spontaneity, Baumgarten offers an enriched empiricalpsychology, one that considers the influence of expectations of thefuture (and a future life) as motives, that allows that immoral actioncan proceed not only from ignorance but also from less livelycognition of the good, and that explicitly distinguishes spontaneityfrom freedom proper (Schwaiger 2011: 82–92). On the topic ofimmortality, the Pietists had likewise objected to Wolff’semphasis on the human soul’s preservation of itscognitive capacities in the afterlife, which state seems forWolff to be disconnected to the human’s cultivation of virtueand piety in this life. Baumgarten seeks to rectify this by arguingthat in addition to preserving its cognitive capacities in theafterlife, the soul will also retain its moral capacities includingfreedom, and that its condition of blessedness or damnation in thelife to come will be a direct function of its moral condition (1739:§§782, 791; Dyck 2018).

Consistent with his orientation in metaphysics, Baumgarten is anoriginal moral philosopher within the Wolffian tradition. He isnotable, for instance, for the centrality of the notion of obligationin his ethics. Wolff had framed a novel concept of obligation, rootedin the nature of things and actions themselves rather than the will ofa sovereign, in accordance with which an obligation arises simplyinsofar as some motive is naturally connected to an action (GE§9). Yet, whereas Wolff only treats obligation briefly beforeconsidering specific duties, in Baumgarten’s hands the problemof obligation becomes the unifying theme for ethics, particularly inhisInitia (Schwaiger 2009). Moreover, while Baumgartenaccepts Wolff’s ethical perfectionism, in contrast with Wolff hedownplays the connection between perfection and happiness, perhaps inresponse to Pietist denunciations of Wolff’s perfectionism as aveiled form of hedonism (Schwaiger 2011: 163ff; Bacin 2015). A lastinnovation is Baumgarten’s consideration of the ways in whichethical systems themselves can be flawed in that, for instance, theymake a virtuous condition too easily attainable (flattering ethics) orset the bar for virtue too high for human nature (chimerical ethics)(Thorndike 2008; Dyck 2012).

Turning finally to Baumgarten’s aesthetics, it is notable thatwhile Wolff himself had comparatively little to say about thephilosophy of art (but see Beiser 2009; and Buchenau 2013), a numberof thinkers in the Wolffian interest took a keen interest in thetopic. The first to develop a theory of the arts, particularly poetry,was Johann Christoph Gottsched (1700–1766), who published hisVersuch einer critischen Dichtkunst vor die Deutschen(Attempt at a Critical Poetry for the Germans) in 1730.Treating poetry scientifically, he set out a set of rules that were toguide the composition. Given his conception of what a poem was (amoral fable) and given as well his idea of what was involved in itscomposition (a set of rules), there was little room here for beautyand even less for sentiment and inspiration.

It was left to Baumgarten to formulate a recognizably modern aestheticdoctrine on Wolffian foundations. This he did through focusing on thesoul’s faculty of sensibility, ultimately identifying aestheticsas the science of sensible cognition. Where Wolff had conceived of thesenses merely as providing the raw material for thinking, Baumgartenthought that the senses had their own rules and their own perfection,rules and perfection that differ from logical rules and the knowledgegenerated by the process of intellectual clarification. So, whilerepresentations might be logically perfect and attain to intensiveclarity insofar as we distinguish a number of marks within it,representations of the senses, even as confused representations, canattain toextensive clarity inasmuch as they represent amultitude of things (Baumgarten 1735: §17). In this way, poeticrepresentation can be richer, and more moving, than representationsattained through the use of the understanding—moving sinceBaumgarten contends that such representations as (aesthetically)perfect can also occasion pleasure in us. One cannot but see theinfluence that Baumgarten likely had on Kant’s Criticalphilosophy — his vindication of the senses reappears in aninherently Kantian way both in the Transcendental Aesthetic of theCritique of Pure Reason and in theCritique of the Powerof Judgment.

5. Christian August Crusius

As Baumgarten sought in a conciliatory spirit to make the Wolffianphilosophy responsive to Pietist concerns, Christian August Crusiusmounted a renewed, Pietist-inspired but philosophically-sophisticatedassault on the foundations of that system. Through his dissertationsand textbooks, Crusius succeeded in raising trenchant objections tothe Leibnizian-Wolffian philosophy, and indeed to the strongest formsof philosophical rationalism, and he formulated an influential andsystematic alternative in which the will and its freedom are centralconcerns.

5.1 Life and Works

Christian August Crusius was born 10 June 1715 in Leuna, near Halle,the son of a pastor (and his mother was a pastor’s daughter). Hematriculated at the University of Leipzig in 1734, where he studied anumber of subjects but was particularly interested in theology andphilosophy. At Leipzig, Crusius came under the influence of thephilosopher (and physician) Adolf Friedrich Hoffmann(1707–1741), a disciple of Andreas Rüdiger(1673–1731) who had been a close associate of Thomasius. Crusiusattained theMagister in philosophy in 1737 and habilitatedin philosophy in 1740. He followed his philosophical studies with abaccalaureat in theology in 1742, though he would proceed to seek aposition in the philosophy faculty. To this end, he defended twodissertations in philosophy, one of which, theDissertatiophilosophica de usu et limitibus principii rationis determinantis,vulgo sufficientis (Philosophical Dissertation on the Use andLimits of the Principle of Determining Reason, commonly calledSufficient) of 1743 was a critical discussion of the principle ofsufficient reason. He became a professor of philosophy(extraordinarius) at Leipzig in 1744.

Crusius’ major philosophical works followed in quick succession.He published his textbook on ethics, theAnweisung vernünftigzu Leben (Guide to Rational Living) in 1744; this wasfollowed by the elaboration of his metaphysics,Entwurf dernothwendigen Vernunft-Wahrheiten (Sketch of the NecessaryTruths of Reason) in 1745; and a text in logic, theWeg zurGewißheit und Zuverläßigkeit der menschlichenErkenntiß (Path to the Certainty and Reliability ofHuman Cognition) was published in 1747 (a final philosophicaltreatise on physics followed in 1749). As an ordinary professorship inphilosophy was not available, Crusius joined the theology faculty atLeipzig in 1750. While he remained a member of the philosophy facultyand continued his lectures (and revised his previous publications forlater editions), from this point on his original publications aredevoted to theological topics. He died in Leipzig on 18 October1775.

5.2 Philosophy

Widely and rightly regarded as the most sophisticated philosopherwithin the Thomasian-Pietist tradition, Crusius sets out to offer analternative to the core claims of the Leibnizian-Wolffian philosophyon topics in metaphysics, epistemology, logic and practicalphilosophy. As Lange had previously, Crusius targets the principle ofsufficient reason, and its employment in Leibnizian-Wolffianmetaphysics, for criticism. Crusius diagnoses a number of ambiguitiesin the Wolffian presentation of the principle. He opts to refer to areason (ratio;Grund) that, when present, determinessomething to come to be such that the opposite would be impossible asadetermining reason, and accordingly refers to the principle(in the sense intended by Leibniz and Wolff) as theprinciple ofdetermining reason (Crusius 1743: §II–III). Crusiusthen critically discusses each of Wolff’s attempts to prove theprinciple—concerning the first such proof (presented in§3.1, above), Crusius claims that the most charitable reconstruction of itis circular. To show this, Crusius reformulates Wolff’s proof asthe following syllogism (using Wolff’s preferredterminology):

Whatever cannot come to be except from some other cause, has asufficient reason.

Everything that is cannot come to be except from another cause.

Therefore, whatever is has a sufficient reason. (Crusius 1743:§XI [2019: 207])

As Crusius notes, however, the minor in this case is just a version ofthe principle of sufficient reason itself, so that as a proof of thatprinciple this argument begs the question.

More positively, Crusius endorses the principle of determining reasonbut denies that it admits of unlimited use, which he claims, echoingLange, would entail fatalism. Rather, Crusius excludes what he terms“free first [orfundamental] actions” from thescope of the principle. These actions are such that they proceeddirectly from the basic powers of the acting substance underappropriate circumstances (Crusius 1745: §82), but are such thatthey can be undertaken or omitted by the acting subject (that is, theyare notdetermined) (Crusius 1743: §XXV). That suchactions are possible, Crusius claims, is clear given that God’saction would be of this sort, but also given the testimony of our owninner experience, which discloses the acts of our own will to be justsuch actions (Crusius 1743: §IX). Crusius thus accepts that theprinciple of determining reason holds for all events that arenot the result of a free first action, whereas free firstactions no doubt have a cause but are not such that could not haveoccurred otherwise (or not at all).

Along with his efforts to secure a place for genuine freedom of thewill in his metaphysics, Crusius also emphasizes the limits of thehuman understanding. Crusius claims that the acts of the understandingare governed by principles, including a formal principle (theprinciple of contradiction), but also and importantly a number of“material” principles that govern what is thinkable forthe human mind (where what is unthinkable is not for that reasoncontradictory). Among these principles are theprinciple ofinseparability, according to which that which cannot be separatedin thought cannot be separated in fact, and thepriniciple ofincombinability, according to which that which cannot be combinedin thought cannot in fact be combined (Crusius 1743: §XXVII;1745: §15). Significantly, and drawing on Thomasius (via Hoffmann1737), Crusius contends that these principles which togetherconstitute the “essence of the understanding” supply uswith a criterion of truth, which consists in the agreement of thoughtswith things, such that only that can be true which conforms to theprinciples of human understanding (Crusius 1745: §15; 1747:§51). These material principles are subsequently used by Crusiusto vindicate a variety of substantive metaphysical claims, includingone he dubs the principle of sufficientcause (Crusius 1745:§31). On this basis, Crusius erects his own distinctivemetaphysics, proceeding through the now-established Wolffian topics,though Crusius assigns natural theology a place more befitting itsimportance and ignores empirical psychology because it takes upspontaneous and free acts of the mind and so does not concernnecessary truths of reason, the only proper subject ofmetaphysics.

Crusius’ attack on Wolffianism continues in his logic and histhoughts on moral philosophy. In a clear rebuke of Wolff, Crusiusbegins his logic by rigidly distinguishing between the methods ofmathematics and philosophy, contending that where the former makes useof demonstrations that rely solely on the principle of contradiction(and relate to mere possibilities or hypothetical realities), thelatter must take into account other principles when, for instance, theinvestigation of causes are at issue (Crusius 1747: §10).Commensurate with this, Crusius’ considerations of thetraditional topics of logic—concepts, propositions, andinferences—is thoroughly informed by his account of the essenceof the understanding: a philosophical inference, as opposed to amathematical syllogism, can have as its basis what permits of beingseparated or combined in thought (Crusius 1747: §262). Crusiusalso considers the relation between philosophy and theology orrevealed religion, contending for the utility of philosophy forstudents of theology but also arguing that religion provides a neededcorrective to the misuse of philosophy which, when left to its owndevices, tends to lay claim to the unrestricted use of its principles(such as PSR) whereas the appropriate restrictions are typicallyevident to the theologian (Crusius 1747: §32).

Crusius’ ethics is characterized by the principled separation ofthe will from the understanding as distinct powers, and are-orientation of his moral theory with respect to the former. Thehuman will depends on the understanding to supply it with ideas inaccordance with which it acts, but Crusius is clear that the will isnot solely determined to its action through some cognition (i.e., ofperfection) in the act itself; rather, the goodness of an actionconsists more generally in its being conformable to the will (Crusius1745: §26; Schneewind 1998: 447), and in any case the human willis always free to act or to omit to act in accordance with theunderstanding’s ideas. The human will is possessed of threebasic desires—the first is for our own perfection, in accordancewith which the talents of the intellect among others are promoted(Crusius 1745: §117); for unification with objects perceived asperfect, from which proceeds a drive to moral love through which wedesire to join with other rational beings without any further end(Crusius 1745: §125); and finally, the desire to recognize adivine law which, despite its abstract-sounding name, is identified byCrusius with the phenomenon of conscience (Gewissenstrieb).It is through conscience that we are able to recognize the divinelygiven moral law (Crusius 1745: §132), and conscience thereby alsodiscloses our dependence on God as divine lawgiver (Crusius 1745:§165). As such, conscience supplies us with a motivation toobedience where, according to Crusius, this obedience constitutes anessential component (the “form”) of virtue (Crusius 1745:§177). A derivation of our duties thus depends on a considerationof God and His aim in creating the world, which Crusius identifies asall human beings’ attainment of virtue, as opposed toknowledge or happiness in its own right, through their free actions(Crusius 1745: §213). On this basis, he proceeds to derive dutiesto God, to others, and to the self (for discussion, see Schneewind1998: 452–6).

6. Women and Other Under-Represented Thinkers

(Note: Treatment of these figures has not been integrated into theforegoing solely for the convenience of those interested primarily intheir contributions.)

A variety of circumstances—religious, political, andsocial—conspired to give women limited opportunities to engagein and with the contemporary intellectual culture, even compared totheir French- and English-speaking contemporaries. The German-speakinglands of Europe lacked a major cosmopolitan centre, like London orParis, to germinate progressive ideas and to propagate those developedabroad. Moreover, the fact that, in spite of Thomasius’ andWolff’s efforts, German intellectuals continued to publish (andteach) in Latin through the first half of the eighteenth century,meant that women’s access to these ideas remained limited. Therewere a handful of notable attempts by reformers (including Francke) toredress the general oversight of girls’ education, but by andlarge their education was a private matter and in any case guided bythe traditional conception of women’s threefoldBestimmung asGattin,Mutter, andHausfrau (wife, mother, and housewife).

Despite these substantial obstacles, however, women did engage withthe figures and debates of the time, and indeed they contributed invarious and integral ways to the history of German philosophythroughout the eighteenth century. Similar to the British and Frenchcontexts, women in Germany exerted an important influence onintellectual culture directly through the publication of conventionaltreatises, but also indirectly through their correspondence withwell-known philosophers, through provoking and mediating intellectualdisputes, and (particularly in the second half of the eighteenthcentury) through hosting salons that attracted leading philosophersand scientists, among others. And, likewise comparable to the Britishand French contexts (cf. O’Neill 1997), these contributions havebeen widely overlooked in subsequent histories of German philosophy,both for familiar reasons having to do both with the narrowness of theconception of the philosophical canon (Shapiro 2016), but also due tothe concerted efforts among nineteenth-century German academics toexclude women from the academy (Ebbersmeyer 2020).

6.1 Women and the Thomasian Philosophy

Women played crucial roles in the conception, refinement, andpopularization of the key ideas and systems of the GermanEnlightenment, as can be seen by considering their contributions toand connections with the two major early philosophical schools of theperiod already discussed: the Leibnizian-Wolffian and theThomasian(-Pietist). With respect to Thomasius, it should be notedthat he makes quite clear himself that his intention in publishing hisworks in logic and ethics in the vernacular was to reach a wideraudience, including women. Thus, the subtitle of hisIntroductionto the Doctrine of Reason indicates that it will show

in an intelligible manner [how] to distinguish the true, probable, andfalse from one another and to discover new truths, all withoutsyllogistics, for all reasonable people of whatever estate or genderthey might be.

Among those women impacted by Thomasius’ logic is DorotheaChristiane Erxleben (née Leporin, 1715–62), whowould later receive the first doctorate in medicine in Germany fromthe university in Halle in 1753. In 1742 she published a treatiseentitledGründliche Untersuchung der Ursachen, die dasweibliche Geschlecht vom Studiren abhalten (RigorousInvestigation of the Causes that Obstruct the Female Sex fromStudy). While Erxleben there draws on a variety of sources,including Wolffian thought (cf. Stiening 2020), she makes good use oftwo aspects of Thomasius’ logic, namely, hispractically-oriented account oflearnedness, and the doctrineof prejudice presented in the concluding chapter (cf. Dyck 2021c). So,in theRigorous Investigation, Erxleben defines learnedness(“Gelehrsamkeit”) as

a grounded knowledge of such necessary and useful truths wherebythe understanding and will, and consequently true human happiness, areimproved. (Erxleben 1742: §21 [2019: 44]; italics inoriginal)

Proceeding from this, she contends that it is important that andentirely possible for women to be able to attain such learnedness forsake of the concerns of ordinary life.

Further, Erxleben identifies the widespread conviction that theattainment of learnedness is unsuitable for women as the result ofprejudice, of which Erxleben distinguishes four principal types: thatwomen are unsuited (in virtue of their natural capacities) to attainlearnedness; that its attainment could not be useful for them; thatlearnedness could only be misused by women; and that women would onlyseek to attain learnedness to distinguish themselves from their peers.By way of rebutting these prejudices, Erxleben draws on an array ofsources, including theological, philosophical, and medicalauthorities, and argues generally that whatever disparities mightcurrently obtain between the apparent talents and achievements on thepart of each sex are not the result of a difference in naturalcapacities but instead only evidence of the salutary effect ofeducation on the human being (cf. Erxleben 1742: §71).

6.2 Women and the Leibnizian-Wolffian Philosophy

With respect to the Leibnizian-Wolffian philosophy, there issignificant evidence of women’s extensive engagement with thesystem already at its origins. Leibniz exchanged letters with a numberof women, but his correspondence with his patroness Electress Sophieof Hanover (1630–1714), who happened to be the sister ofElisabeth of Bohemia, and her daughter Queen Sophie Charlotte ofPrussia (1668–1705), is particularly significant as itfrequently turned to philosophical topics. In his letters, and hispersonal exchanges with “the two Sophies”, Leibniz can beseen to refine and develop key doctrines, including his conception ofsubstance and his attempted theodicy (Strickland 2011: 35–48),where Leibniz himself claimed that hisTheodicée foundits beginnings in his conversations with Sophie Charlotte. Sophie ofHanover likewise supplied Leibniz with one of his favourite pieces ofempirical evidence for the principle of the identity of indiscernables(when she challenged a courtier to find two identical leaves during agarden stroll). Sophie of Hanover was no dogmatic Leibnizian however,as she maintained her commitment to physical influence between themind and the body, and hosted controversial figures such as FrancisMercury Van Helmont (1614–1699) and John Toland(1670–1722) at her court. It is, however, debated whether Sophieshared the materialist views of these thinkers when it comes to themind (de Careil 1876; Strickland 2009 and 2011: 49–64) orinstead upheld a metaphysically agnostic view regarding the nature ofthe soul (Leduc 2021).

As for the other founder of the Leibnizian-Wolffian philosophy, Wolffdoes not seem to have been similarly influenced by interaction withwomen in the development of his system. Through adopting thevernacular for his initial series of textbooks, however, he did atleast indirectly contribute to making the latest innovations inmetaphysics, ethics, politics, and physics accessible to a widerliterate audience including women. Indeed, this hardly seems to havebeen an undesired consequence as, at one point, at the urging of theSaxon nobleman and Wolffian devotée Ernst Christoph Graf vonManteuffel (1676–1749), Wolff drafted the beginning of anintroduction to Wolffian philosophy intended specifically for women(cf. Ostertag 1910). In the 1740s and 1750s in particular, Wolffianphilosophy had gained such a following among women of society that onecommentator quipped that it was as if “an actuallycanthropy” had broken out (Edelmann 1740: 108). Among thosewomen so influenced was Émilie du Châtelet(1706–49), who made use of foundational Wolffian metaphysicalprinciples in her presentation of Newton’s physics in herInstitutions de physique—Wolff and du Châteletengaged in correspondence for a time, and he commended her mastery ofhis system to others and appraised her as a more talented philosopherthan her companion Voltaire.

In addition to du Châtelet, a number of women took up the taskof defending and developing Leibnizian-Wolffian ideas. None were moreactive in this than Luise Adelgunde Viktorie Gottsched(née Kulmus, 1713–62), whose husband JohannChristoph (§4.2 above) was a Wolffian disciple who made contributions to philosophy(metaphysics and aesthetics), as well as to literary theory and thedevelopment of German letters. In virtue of her ambitious education(especially in languages), Luise Gottsched contributed extensively toJohann Christoph’s efforts to promote German letters andtheatre, and was a prolific translator, both in the context of herhusband’s ambitious projects and in her own right. Thus, shemade substantial contributions to Johann Christoph’stranslations of Leibniz’sTheodicée (J. C.Gottsched 1744) and of Bayle’sDictionaire historique etcritique (1741–44) (for other philosophical translations,see Brown 2012). She also translatedRéflexions nouvellessur les femmes (1727; L. A. V. Gottsched 1731) by the Parisiansalonnière Anne-Thésèse, Marquise deLambert and produced a translation of and an original response toMadeleine Angélique Poisson de Gomez’sLe triomphe del’éloquence (1730; L. A. V. Gottsched 1739), whichemphasized the importance of education (including philosophy) forwoman’s cultivation of virtue.

Another notable figure in this respect is Johanna Charlotte Unzer(née Ziegler, 1725–82), who was raised in anintellectual family in Halle: her uncle J. G. Krüger(1715–59) was a well-known Wolffian scientist, andBaumgarten’s student G. F. Meier was a close family friend.Unzer herself would become a renowned poet, though she produced ahighly original philosophical contribution to Wolffian thought in herGrundriß einer Weltweisheit für das Frauenzimmer(Outline of a Philosophy for the Lady) of 1751. In that text,Unzer seeks to present the doctrines of Leibnizian-Wolffian logic andmetaphysics in an aesthetically perfect manner, often making use ofpoetry to provide a moving illustration of an otherwise abstrusetheorem. In the process, Unzer grants German women access to the mostchallenging and controversial philosophical debates of her time(including Wolff’s account of scientific reasoning, thechallenge of materialism, and the Leibnizian doctrine of monads) withthe express intention of equipping her female readers to engage inspeculative and scientific investigations themselves. At the sametime, she offers a dynamic revision and re-orientation of the Wolffianphilosophy which, significantly, attempts to carve out a space for the(as yet unfounded) discipline of aesthetics (Buchenau 2021).

6.3 Anton Wilhelm Amo

A final figure worthy of mention in this context is Anton Wilhelm Amo,the first African-born professor of philosophy in Germany. Amo wasborn in Axim in present-day Ghana around 1700, but was brought to theNetherlands as a small boy in 1707 through the Dutch West IndiaCompany. Shortly after, he was given to the young Anton Ulrich, Dukeof Wolfenbüttel-Braunschweig, and baptized on 29 July 1708. Amoevidently worked as a servant in the Duke’s court inWolffenbüttel, though he would also receive an education whichprepared him sufficiently for study at the Friedrichs-Universitätin Halle, where he matriculated on 9 June 1727. There, Amo studiedphilosophy and law, and it is reported that he presented a (now lost)disputation in November 1729 entitledDe jure maurorum inEuropa (On the Rights of Moors in Europe), in which hecontended (according to a contemporary account) against the legalityof slavery in the Holy Roman Empire given that the privileges grantedto African kings by the (old) Roman Emperor meant that they werevassals of the Empire, and entitled to consideration under thelaw.

Amo matriculated at the university in nearby Wittenberg the followingyear, and was promptly awarded aMagister in philosophy.While in Wittenberg, Amo wrote a dissertation, entitledDe humanaementis apatheia (On the Impassivity of the Human Mind)in 1734, which qualified him to teach, and later in the same year hesupervised a dissertation which he is also thought to have had a hand(at least) in writing (Menn & Smith 2020: 68–71). Amo wouldreturn to teach philosophy at Halle, and in 1738 published awide-ranging manual for his philosophical lectures,Tractatus dearte sobrie et accurate philosophandi (Treatise on the Art ofPhilosophizing Soberly and Accurately). Not long after, however,Amo applied for a position at the University of Jena, claimingindigence, and was granted permission to lecture there in 1740. Forreasons that we can only speculate about, Amo would request passage ona ship to return to Africa in 1746 (Menn & Smith 2020: 38), and itwas in Axim that a Swiss doctor would report encountering Amo in theearly 1750s. Amo is thought to have died not long after.

In his principal philosophical work, the dissertation onImpassivity, he argues against the claim that the soul can beendowed with a passive faculty of sensation, a position he identifiesas stemming from Descartes (Amo 1734a: 13–14 [2020: 179]). Amounderstands the human mind to be a species of spirit, which is purelyactive and immaterial. Were the mind to be endowed with a capacity tosense, it would have to be able to receive ideas, and in one of threeways: by “communication” (i.e., in the manner that fire“communicates” its heat to an object), by penetration(i.e., through interposition of another entity), or by direct contact(Amo 1734a: 5 [2020: 161]). Amo argues that it is impossible toconceive of the mind receiving ideas in any of these ways as it wouldviolate its essence as a spontaneous being and its immaterial natureprecludes transmission through contact (for discussion, see Walsh2019). Perplexingly, in spite of contending for the soul’simpassivity, Amo endorses the Aristotelian dictum that “nothingis in the intellect that was not first in the senses” (Amo1734b: 6). Amo also affirms the mind’s capacity to influence thebody (Amo 1734a: 8 [2020: 169]), though without accounting for how hetakes this to be possible or explicitly engaging with the debaterelating to the pre-established harmony. Nonetheless, in his lifetimeAmo was identified by at least one influential historian as a Wolffianthinker (Ludovici 1738: §202).

Bibliography

Primary Literature

By Author

• Amo, Anton Wilhelm, 1734a [2020],Dissertatio InauguralisPhilosophica, de humane mentis apatheia (On the Impassivityof the Human Mind), Wittenberg. Translated inAnton WilhelmAmo’s Philosophical Dissertations on Mind and Body, StephenMenn and Justin Smith (eds. and trans.), Oxford: Oxford UniversityPress, 2020. doi:10.1093/oso/9780197501627.001.0001
• –––, 1734b,Disputatio Philosophicacontinens Ideam Distinctam eorum quae competunt vel menti vel corporinostro vivo et organico, Wittenberg.
• –––, 1738,Tractatus de arte sobrie etaccurate philosophandi (Treatise on the Art of PhilosophizingSoberly and Accurately), Halle.
• Baumgarten, Alexander Gottlieb, 1735 [1954],Meditationesphilosophicae de nonnullis ad poema pertinentibus, Halle.Translated asReflections on Poetry, Karl Aschenbrenner andWilliam B. Holther (trans.), Berkeley: University of California Press,1954.
• –––, 1739 [2014],Metaphysica, Halle.Translated asMetaphysics, C. D. Fugate and J. Hymers(trans./eds). London: Bloomsbury, 2014.
• –––, 1740,Ethica philosophica(Philosophical Ethics), Halle.
• –––, 1750/58,Aesthetica, Halle.
• –––, 1760,Initia philosophiae practicaeprimae (Elements of First Practical Philosophy),Halle.
• Bayle, Pierre, 1741–44,Historisches und CritischesWörterbuch: nach der neuesten Auflage von 1740 ins Deutschübersetzt […] auch mit einer Vorrede und verschiedenenAnmerkungen versehen von Johann Christoph Gottsched, 4 vols;reprint, Olms, Hildesheim.
• Breitinger, Johann Jakob, 1740,Critische Abhandlung von derNatur, den Absichten und dem Gebrauche der Gleichnisse,Zürich.
• Budde, Johann Franz, 1697,Elementae philosophiaepracticae, Halle.
• –––, 1703,Institutiones philosophiaeeclecticae, 2 parts, Halle.
• –––, 1717,Theses theologicae de atheismo etsuperstitione, Jena.
• Crusius, Christian August, 1743,Dissertatio philosophica deusu et limitibus principii rationis determinantis, vulgosufficientis (Philosophical Dissertation on the Use andLimits of the Principle of Determining Reason, commonly called thePrinciple of Sufficient Reason), Leipzig. Extracts translated inDyck 2019: ch. 8.
• –––, 1744,Anweisung vernünftig zuleben (Guide to Rational Living), Leipzig. Selectiontranslated in Schneewind 2003: 569–584.
• –––, 1745,Entwurf der nothwendigenVernunftwahrheiten (Sketch of the Necessary Truths ofReason), Leipzig.
• –––, 1747,Weg zur Gewißheit undZuverlässigkeit (Path to the Certainty and Reliabilityof Human Cognition), Leipzig.
• –––, 1964ff,Die philosophischenHauptwerke (The Main Philosophical Works), 4 volumes,Giorgio Tonelli (ed.), Hildesheim: Georg Olms.
• Erxleben, Dorothea Christiane, 1742 [2019],GründlicheUntersuchung der Ursachen, die das weibliche Geschlecht vom Studirenabhalten (Rigorous Investigation of the Causes that Obstructthe Female Sex from Study), Berlin. Extracts translated in Dyck2019: ch. 2.
• Gottsched, Johann Christoph, 1730,Versuch einer critischenDichtkunst vor die Deutschen (Attempt at a Critical Poetryfor the Germans), Leipzig.
• –––, 1733–34,Erste Gründe dergesamten Weltweisheit, darinn alle philosophische Wissenschaften inihrer natürlichen Verknüpfung abgehandelt werden, 2volumes, Leipzig.
• ––– (trans.), 1744,Theodicee, das ist,Versuch von der Güte Gottes, Freyheit des Menschen, und vomUrsprunge des Bösen, by Gottfried Wilhelm Leibniz, Hannover& Leipzig.
• Gottsched, Luise Adelgunde Viktorie, 1731,Der FrauMarggräfin von Lambert Neue Betrachtungen über dasFrauenzimmer, Leipzig.
• –––, 1739,Triumph der Weltweisheit, nachArt des französischen Sieges der Beredsamkeit der Frau vonGomez, Leipzig.
• Hoffmann, Adolph Friedrich, 1737,Vernunftlehre,Leipzig.
• Lange, Joachim, 1704,Medicina mentis (Medicine ofthe Mind), Halle.
• –––, 1723,Caussa Dei et religionisnaturalis adversis atheismum, Halle.
• –––, 1724,Bescheidene undausführlicheEntdeckung der falschen und schädlichenPhilosophie in dem Wolfianischen Systemate metaphysico (AModest and Detailed Disclosure of the False and Harmful Philosophy inthe Wolffian Metaphysical System), Halle. Extracts translated inDyck 2019: ch. 6.
• Lau, Theodor Ludwig, 1717,Meditationes Philosophicae de Deo,mundo, et homine (Philosophical Meditations concerning God,the World, and the Human Being), Frankfurt M. Extracts translatedin Dyck 2019: ch. 4.
• Leibniz, Gottfried W. and Christian Wolff, 1963,Briefwechselzwischen Leibniz und Christian Wolff (Correspondence betweenLeibniz and Christian Wolff), C. I. Gerhardt (ed.), Hildesheim:Georg Olms Verlagsbuchhandlung.
• Rüdiger, Andreas, 1716,Physica divina, recta via,eademque inter supersttionem et atheismum media ad ultramque hominisfelicitatem, naturalem, atque moralem ducens, Frankfurt.
• –––, 1722,De sensu vedri et falsi,Leipzig.
• Stosch, Friedrich Wilhelm, 1692,Concordia rationis et fidei,sive harmonia philosophicae moralis et religionis christianae(Concord of Reason and Faith), Amsterdam.
• Thomasius, Christian, 1685,Dissertationem juridicam decrimini bigamiae, Leipzig.
• –––, 1688a,Institutiones jurisprudentiaedivinae (Institutes of Divine Jurisprudence), Leipzig.Translated in Thomasius 2011.
• –––, 1688b,Instruductio ad philosophiamauliam (Introduction to Court Philosophy), Leipzig.
• –––, 1691a,Einleitung zurVernunftlehre (Introduction to the Doctrine of Reason),Halle. Extracts translated in Dyck 2019: ch. 1.
• –––, 1691b,Ausübung derVernunftlehre (Application of the Doctrine of Reason),Halle.
• –––, 1692,Einleitung zur Sittenlehre(Introduction to the Doctrine of Morals), Halle.
• –––, 1696,Ausübung derSittenlehre (Application of the Doctrine of Morals),Halle.
• –––, 1705,Fundamentum iuris naturae etgentium, (Foundations of the Law of Nature and Nations).Selections translated in Thomasius 2011.
• –––, 1709,Versuch von Wesen desGeistes (Essay on the Essence of Spirit), Halle.
• –––, 2011,Institutes of DivineJurisprudence, with Selections from Foundations of the Law of Natureand Nation, Thomas Ahnert (ed. and trans), Indianapolis: LibertyFund. [Thomasius 2011 available online]
• Unzer, Johanna Charlotte, 1751,Grundriß einerWeltweisheit für das Frauenzimmer (Outline of aPhilosophy for the Lady), Halle.
• [GL] Wolff, Christian, 1713,Vernünftige Gedanken von denKräften des menschlichen Verstandes und ihrem richtigen Gebrauchin der Erkenntnis der Wahrheit (Rational Thoughts on thePowers of the Human Understanding and its Propert Use in the Cognitionof Truth), Halle.
• [GM] –––, 1720a [2019],VernünftigeGedanken von Gott, der Welt und der Seele des Menschen, auch allenDingen überhaupt (Rational Thoughts on God, the Worldand the Soul of Man, and on All Things in General), Halle.Extracts translated in Dyck 2019: ch. 5
• [GE] –––, 1720b,Vernünftige Gedankenvon der Menschen Thun und Lassen zur Beförderung ihrerGlückseligkeit (Rational Thoughts on Human Actions forthe Promotion of their Happiness), Halle. Selection translated inSchneewind 2003: 333–347.
• –––, 1721,Vernünftige Gedanken von demgesellschaftlichen Leben der Menschen, und insonderheit dem gemeinenWesen, Halle.
• –––, 1723,Vernünftige Gedanken von denWirkungen der Natur, Halle.
• –––, 1724,Vernünftige Gedanken von denAbsichten der natürlichen Dingen, Frankfurt andLeipzig.

Collections (English)

• (Unless noted otherwise, all translations in the foregoing entryare the authors’.)
• Dyck, Corey W. (ed. and trans.), 2019,Early Modern GermanPhilosophy, 1690–1750, Oxford: Oxford University Press.Includes extracts from Christian Thomasius, Dorothea ChristianeErxleben, Theodor Ludwig Lau, Christian Wolff, Joachim Lange,Christian August Crusius, and Georg Friedrich Meier.
• Schneewind, J. B. (ed. and trans.), 2003,Moral Philosophyfrom Montaigne to Kant, Cambridge: Cambridge University Press.Includes extracts from works by Christian Wolff and Christian AugustCrusius. doi:10.1017/CBO9780511811579
• Watkins, Eric (ed. and trans.), 2009,Kant’s Critique ofPure Reason: Background Source Materials, Cambridge: CambridgeUniversity Press. Includes works by Christian Wolff, AlexanderBaumgarten, and Christian August Crusius.doi:10.1017/CBO9780511809552

Secondary Literature

Following is a general bibliography listing histories of philosophyand reference works focusing on this period. Subsequent bibliographiescontain, for each section of the entry, works cited as well asadditional recommended secondary literature in English and German.

General

• Albrecht, Michael, 1994,Eklektik. Eine Begriffsgeschichte mitHinweisen auf die Philosophie- und Wissenschaftsgeschichte,Stuttgart: frommann-holzboog.
• Beck, Lewis White, 1969,Early German Philosophy: Kant and HisPredecessors, Cambridge, MA: Harvard University Press.
• Cassirer, Ernst, 1951,The Philosophy of theEnlightenment, Boston: Beacon Press.
• Erdmann, Johann Eduard, 1866 [1897],Grundriss der Geschichteder Philosophie, 2 volumes, Berlin. Part translated asAHistory of Philosophy, Volume 2, fourth edition, Williston S.Hough (ed./trans.), New York: Macmillan & Co., 1897.
• Klemme, Heiner F. and Manfred Kuehn (eds.), 2010,TheDictionary of Eighteenth-Century German Philosophers, London:Continuum.
• Schneewind, Jerome B., 1998,The Invention of Autonomy: AHistory of Modern Moral Philosophy, Cambridge: CambridgeUniversity Press. doi:10.1017/CBO9780511818288
• Ueberweg, Friedrich and Helmut Holzhey (eds.), 2001,DiePhilosophie des 17. Jahrhunderts, Vol. 4.2: Das Heilige RömischeReich Deutscher Nation, Nord- und Ostmitteleuropa, Basel:Schwabe.
• –––, 2015,Die Philosophie des 18.Jahrhunderts, Vol. 5.1: Heiliges Römisches Reich DeutscherNation, Schweiz, Nord- und Ostmitteleuropa, Basel: Schwabe.
• Wundt, Max, 1945,Die deutsche Schulphilosophie im Zeitalterder Aufklärung, Tübingen.
• Zenker, Kay, 2012,Denkfreiheit. Libertas philosophandi in derdeutschen Aufklärung, Hamburg: Felix Meiner.

Section 1: Christian Thomasius

• Ahnert, Thomas, 2006,Religion and the Origins of the GermanEnlightenment: Faith and the Reform of Learning in the Thought ofChristian Thomasius, Rochester, NY: Boydell & Brewer.
• Barnard, Frederick M., 1971, “The ‘PracticalPhilosophy’ of Christian Thomasius”,Journal of theHistory of Ideas, 32(2): 221–246. doi:10.2307/2708278
• –––, 1988, “Fraternity and Citizenship:Two Ethics of Mutuality in Christian Thomasius”,The Reviewof Politics, 50(4): 582–602.doi:10.1017/S0034670500041966
• Bottin, Francesco and Mario Longo, 2015, “ChristianThomasius (1655–1728)”, inModels of the History ofPhilosophy, volume 2: From the Cartesian Age to Brucker, GregorioPiaia and Giovanni Santinello (eds), Dordrecht: Springer, pp.315–323.
• Hochstrasser, T. J., 2000,Natural Law Theories in the EarlyEnlightenment, Cambridge: Cambridge University Press.doi:10.1017/CBO9780511490552
• Hunter, Ian, 2001,Rival Enlightenments: Civil andMetaphysical Philosophy in Early Modern Germany, Cambridge:Cambridge University Press. doi:10.1017/CBO9780511490583
• Kühnel, Martin, 2001,Das politische Denken von ChristianThomasius: Staat, Gesellschaft, Bürger, Berlin: Duncker& Humblot.
• Lutterbeck, Klaus-Gert, 2002,Staat und Gesellschaft beiChristian Thomasius und Christian Wolff, Stuttgart:Fromann-holzboog.
• Schneiders, Werner (ed.), 1989,Christian Thomasius1655–1728. Interpretationen zu Werk und Wirkung, Hamburg:Felix Meiner.

Section 2: Radical Philosophy

• Dyck, Corey W., 2016a, “Materialism in the Mainstream ofEarly German Philosophy”,British Journal for the History ofPhilosophy, 24(5): 897–916.doi:10.1080/09608788.2016.1154007
• Israel, Jonathan, 2001,Radical Enlightenment: Philosophy andthe Making of Modernity 1650–1750, Oxford: OxfordUniversity Press. doi:10.1093/acprof:oso/9780198206088.001.0001
• Mulsow, Martin, 2002 [2015],Moderne aus dem Untergrund :radikale Frühaufklärung in Deutschland 1680–1720,Hamburg: F. Meiner. Translated asEnlightenment Underground:Radical Germany, 1680–1720, H. C. Erik Midelfort (trans.),Charlottesville, VA: University of Virginia Press, 2015.
• Rumore, Paola, 2016, “Mechanism and Materialism in EarlyModern German Philosophy”,British Journal for the Historyof Philosophy, 24(5): 917–939.doi:10.1080/09608788.2016.1149691
• Schröder, Winfried, 1987,Spinoza in der deutschenFrühaufklärung, Würzburg: Könighausen &Neumann.
• Stiehler, Gottfried (ed. and trans.), 1966,Materialisten derLeibniz-Zeit: Ausgewählte Texte, Berlin: Deutscher Verlagdes Wissenschaften.

Section 3: The Controversy between Wolff and the Pietists

• Albrecht, Michael, 1985, “Einleitung”, inChristian Wolff, Rede über die praktische Philosophie derChinesen, Hamburg: Felix Meiner, p. ix.
• Albrecht, Ruth, 2004, “Frauen”, inGeschichte desPietismus, Band 4: Glaubenswelten und Lebenswelten, HartmutLehmann (ed.), Göttingen: Vandenhoeck & Ruprecht, pp.522–555.
• Beutel, Albrecht, 2001, “Causa Wolffiana. Die VertreibungChristian Wolffs aus Preußen 1723 als Kulminationspunkt desthelogisch-politischen Konflikts zwischen halleschem Pietismus undAufklärungsphilosophie”, inWissenschaftliche Theologieund Kirchenleitung. Beiträge zur Geschichte einerspannungsreichen Beziehung, U. Köpf (ed.), Tübingen:Mohr Siebeck, pp. 159–202.
• Bianco, Bruno, 1989. “Freiheit gegen Fatalismus. Zu JoachimLanges Kritik an Wolff”, inZentren der Aufklärung.Halle: Aufklärung und Pietismus, vol. I, N. Hinske (ed.),Berlin: De Gruyter, pp. 111–155.
• Chance, Brian A., 2018, “Wolff’s Empirical Psychologyand the Structure of the Transcendental Logic”, inKant andHis German Contemporaries, Volume 1: Logic, Mind, Epistemology,Science and Ethics, Corey W. Dyck and Falk Wunderlich (eds.),Cambridge: Cambridge University Press, pp. 17–34.doi:10.1017/9781316493229.002
• Corr, Charles A., 1975, “Christian Wolff and Leibniz”,Journal of the History of Ideas, 36(2): 241–262.doi:10.2307/2708926
• Dunlop, Katherine, 2013, “Mathematical Method and NewtonianScience in the Philosophy of Christian Wolff”,Studies inHistory and Philosophy of Science Part A, 44(3): 457–469.doi:10.1016/j.shpsa.2012.10.008
• Dyck, Corey W., 2021a, “Before and Beyond Leibniz:Tschirnhaus and Wolff on Experience and Method”, inTheExperiential Turn in 18th Century German Philosophy, Karin deBoer and Tinca Prunea-Bretonnet (eds.), London: Routledge, pp.17–36.
• École, Jean, 1979, “En quel sens peut-on dire queWolff est rationaliste?”Studia Leibnitiana, 11:45–61.
• Frketich, Elise, 2019, “Wolff and Kant on the MathematicalMethod”,Kant-Studien, 110(3): 333–356.doi:10.1515/kant-2019-2011
• Gava, Gabriele, 2019, “Kant, Wolff and the Method ofPhilosophy”,Oxford Studies in Early Modern Philosophy,Volume VIII, Daniel Garber and Donald Rutherford (eds.), Oxford:Oxford University Press, 271–303.
• Gierl, Martin, 2015, “Pietism, Enlightenment, andModernity”, inA Companion to German Pietism,1660–1800, Douglas H. Shantz (ed.), Leiden: Brill, pp.349–392.
• Grote, Simon, 2017,The Emergence of Modern Aesthetic Theory:Religion and Morality in Enlightenment Germany and Scotland,Cambridge: Cambridge University Press. doi:10.1017/9781316275559
• Hartmann, Georg Volckmar, 1737,Anleitung zur Historie derLeibnizisch-Wolffischen Philosophie, Frankfurt &Leipzig.
• Hinrichs, Carl, 1971,Preußentum und Pietismus: DerPietismus in Brandenburg-Preußen als religiös-sozialeReformbewegung, Göttingen: Vanderheck & Ruprecht.
• Hinske, Norbert (ed.), 1989,Halle: Aufklärung undPietismus, Heidelberg: Verlag Lambert Schneiders.
• Kertscher, Hans-Joachim, 2018,“Er brachte Licht undOrdnung in die Welt”. Christian Wolff – eineBiographie, Halle: Mitteldeutscher Verlag.
• Leduc, Christian, 2018, “Sources of Wolff’sPhilosophy: Scholastics/Leibniz”, in Theis and Aichele 2018:35–54. doi:10.1007/978-3-658-14737-2_2
• Ludovici, Carl Günther, 1737–8,Entwurf einervollständigen Historie der Wolffschen Philosophie, 3 volumes(I–II, 1737; III, 1738), Leipzig.
• Neveu, Sébastien, 2018, “Secondary Authors’Influence on the Formation of the Wolffian ‘System ofTruths’”, in Theis and Aichele 2018: 55–72.doi:10.1007/978-3-658-14737-2_3
• Podczeck, Otto, 1962,August Hermann Franckes Schriftüber eine Reform des Erziehungs- und Bildungswesens [DerGroße Aufsatz], Berlin: Akademie.
• Rumore, Paola, 2019, “Between Spinozism and Materialism:Johann Franz Budde and the Early German Enlightenment”,Archivio di Filosofia, 87(1): 39–56.
• Schönfeld, Martin, 2010, “Lange, Joachim(1670–1744)”, in Klemme and Kuehn 2010:456–460.
• Theis, Robert and Alexander Aichele (eds), 2018,HandbuchChristian Wolff, Wiesbaden: Springer Fachmedien Wiesbaden.doi:10.1007/978-3-658-14737-2
• Watkins, Eric, 1998, “From Pre-established Harmony toPhysical Influx: Leibniz’s Reception in Eighteenth CenturyGermany”,Perspectives on Science, 6(1/2):136–203.
• –––, 2005,Kant and the Metaphysics ofCausality, Cambridge: Cambridge University Press.doi:10.1017/CBO9780511614217
• Wallmann, Johannes, 1990,Der Pietismus, Göttingen:Vandenhoeck & Ruprecht.
• Wilson, Catherine, 1994, “The Reception of Leibniz in theEighteenth Century”, inThe Cambridge Companion toLeibniz, Nicholas Jolley (ed.), Cambridge: Cambridge UniversityPress, pp. 442–474. doi:10.1017/CCOL0521365880.013
• Wuttke, Heinrich (ed.), 1841,Christian Wolffs eigeneLebensbeschreibung, Leipzig: Weidemann.

Section 4: Alexander Gottlieb Baumgarten

• Bacin, Stefano, 2015, “Kant’s Lectures on Ethics andBaumgarten’s Moral Philosophy”, inKant’sLectures on Ethics: A Critical Guide, Lara Denis and OliverSensen (eds.), Cambridge: Cambridge University Press, pp. 15–33.doi:10.1017/CBO9781139567527.004
• Beiser, Frederick C., 2009,Diotima’s Children: GermanAesthetic Rationalism from Leibniz to Lessing, Oxford: OxfordUniversity Press. doi:10.1093/acprof:oso/9780199573011.001.0001
• Buchenau, Stefanie, 2013,The Founding of Aesthetics in theGerman Enlightenment: The Art of Invention and the Invention ofArt, Cambridge: Cambridge University Press.doi:10.1017/CBO9781139225281
• Dyck, Corey W., 2012, “Chimerical Ethics and FlatteringMoralists: Baumgarten’s Influence on Kant’s Moral Theoryin the Observations and Remarks”, inKant’sObservations and Remarks: A Critical Guide, Susan Meld Shell andRichard Velkley (eds.), Cambridge: Cambridge University Press, pp.38–56. doi:10.1017/CBO9781139028608.004
• –––, 2018, “Between Wolffianism andPietism: Baumgarten’s Rational Psychology”, in Fugate andHymers 2018: 78–93.
• Fugate, Courtney D. and John Hymers (eds.), 2018,Baumgartenand Kant on Metaphysics, Oxford: Oxford University Press.doi:10.1093/oso/9780198783886.001.0001
• Look, Brandon, 2018, “Baumgarten’s Rationalism”,in Fugate and Hymers 2018: 10–22.
• McQuillan, J. Colin, 2021,Baumgarten’s Aesthetics:Historical and Philosophical Perspectives, Lanham, MD: Rowman& Littlefield.
• Nannini, Alessandro, 2020, “The Six Faces of Beauty.Baumgarten on the Perfections of Knowledge in the Context of theGerman Enlightenment”,Archiv Für Geschichte DerPhilosophie, 102(3): 477–512.doi:10.1515/agph-2017-0034
• Schwaiger, Clemens, 2009, “The Theory of Obligation inWolff, Baumgarten, and the Early Kant”, inKant’sMoral and Legal Philosophy, Karl Ameriks and Otfried Hoffe(eds.), Cambridge: Cambridge University Press, pp. 58–74.doi:10.1017/CBO9780511581618.004
• –––, 2011,Alexander Gottlieb Baumgarten.Ein Intellektuelles Porträt, Stuttgart:Frommann-holzboog.
• Thorndike, Oliver, 2008, “Ethica Deceptrix: TheSignificance of Baumgarten’s Notion of a Chimerical Ethics forthe Development of Kant’s Moral Philosophy”, inRechtund Frieden in der Philosophie Kants, Valerio Rohden, Ricardo R.Terra, Guido A. de Almeida, and Margit Ruffing (eds.), Berlin/NewYork: Walter de Gruyter, pp. 451–462.doi:10.1515/9783110210347.3.451

Section 5: Christian August Crusius

• Benden, Magdalene, 1972,Christian August Crusius. Wille undVerstand als Prinzipien des Handelns, Bonn: Bouvier.
• Dyck, Corey W., 2016b, “Spontaneitybefore theCritical Turn: The Spontaneity of the Mind in Crusius, thePre-Critical Kant, and Tetens”,Journal of the History ofPhilosophy, 54(4): 625–648. doi:10.1353/hph.2016.0073
• Gava, Gabriele, 2019, “Kant and Crusius on Belief andPractical Justification”,Kantian Review, 24(1):53–75. doi:10.1017/S1369415418000523
• Heimsoeth, Heinz, 1926,Metaphysik und Kritik bei Chr. A.Crusius. Ein Beitrag zur ontologischen Vorgeschichte der Kritik derreinen Vernunft im 18. Jahrhundert, Berlin: DeutscheVerlagsgesellschaft für Politik und Geschichte.
• Hogan, Desmond, 2009, “Three Kinds of Rationalism and theNon-Spatiality of Things in Themselves”,Journal of theHistory of Philosophy, 47(3): 355–382.doi:10.1353/hph.0.0130
• Rumore, Paola, 2018, “Kant and Crusius on the Role ofImmortality in Morality”, inKant and His GermanContemporaries, Volume 1: Logic, Mind, Epistemology, Science andEthics, Corey W. Dyck and Falk Wunderlich (eds.), Cambridge:Cambridge University Press, pp. 213–231.doi:10.1017/9781316493229.012

Section 6: Women and Other Under-Represented Thinkers

• Brentjes, Burchard, 1976,Anton Wilhelm Amo. Der schwarzePhilosoph in Halle, Leipzig: Koehler & Amelang
• Brown, Hilary, 2012,Luise Gottsched the Translator,Rochester, NJ: Camden House.
• Buchenau, Stefanie, 2021, “A Modern Diotima: JohannaCharlotte Unzer on Wolffianism and Aesthetics”, in Dyck 2021b:29–48. doi:10.1093/oso/9780198843894.003.0003
• de Careil, Foucher, 1876,Leibniz et les deux Sophies,Paris: Germer-Baillière.
• Dyck, Corey W. (ed.), 2021b,Women and Philosophy inEighteenth-Century Germany, Oxford: Oxford University Press.doi:10.1093/oso/9780198843894.001.0001
• –––, 2021c, “On Prejudice and the Limitsto Learnedness: Dorothea Christiane Erxleben and theQuerelle desFemmes”, in Dyck 2021b: 51–71.doi:10.1093/oso/9780198843894.003.0004
• Ebbersmeyer, Sabrina, 2020, “From a ‘MemorablePlace’ to ‘Drops in the Ocean’: On theMarginalization of Women Philosophers in German Historiography ofPhilosophy”,British Journal for the History ofPhilosophy, 28(3): 442–462.doi:10.1080/09608788.2019.1677216
• Edelmann, Johann Christian, 1740,Moses mit aufgedecktenAngesichte, Frankfurt.
• Leduc, Christian, 2021, “Sophie of Hanover on the Soul-BodyRelationship”, in Dyck 2021b: 11–28.doi:10.1093/oso/9780198843894.003.0002
• O’Neill, Eileen, 1997, “Disappearing Ink: Early ModernWomen Philosophers and Their Fate in History”, inPhilosophyin a Feminist Voice: Critiques and Reconstructions, J. Kourany(ed.), Princeton: Princeton University Press, pp. 17–62.
• Ostertag, Heinrich, 1910,Der philosophische Gehalt desWolff-Manteuffelschen Briefwechsels, Leipzig.
• Prunea-Bretonnet, Tinca, 2019, “Émilie, Friedrich derGroße und die ‘Leibniz-Wolff’sche’Metaphysik”, inEmilie Du Châtelet und die deutscheAufklärung, Ruth Hagengruber and Hartmut Hecht (eds.),(Frauen in Philosophie und Wissenschaft. Women Philosophers andScientists), Wiesbaden: Springer Fachmedien Wiesbaden, pp.295–321. doi:10.1007/978-3-658-14022-9_10
• Shapiro, Lisa, 2016, “Revisiting the Early ModernPhilosophical Canon”,Journal of the American PhilosophicalAssociation, 2(3): 365–383. doi:10.1017/apa.2016.27
• Stiening, Gideon, 2020, “Feministische Vorurtheilskritik.Dorothea Christiane Leporins Argumente wider das Verbot desFrauenstudiums”, inFeministische Aufklärung in Europa/ The Feminist Enlightenment across Europe, I. Karremann & G.Stiening (eds.), Hamburg: Meiner.
• Strickland, Lloyd, 2009, “The Philosophy of Sophie,Electress of Hanover”,Hypatia, 24(2): 186–204.doi:10.1111/j.1527-2001.2009.01038.x
• –––, 2011,Leibniz and the Two Sophies: ThePhilosophical Correspondence, Toronto: Iter.
• Walsh, Julie, 2019, “Amo on the HeterogeneityProblem”,Philosophers’ Imprint, 19 (41):1–28. [Walsh 2019 available online]

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