From Leibniz to KantLewis White BeckINTRODUCTIONHad Kant not lived, German philosophy between the death of Leibniz in1716 and the end of the eighteenth century would have little interest forus, and would remain largely unknown. In Germany between Leibniz andKant there was no world-class philosopher of the stature of Berkeley,Hume, Reid, Rousseau, Vico, or Condillac. The life and philosophy ofKant, however, raised some not-quite-first-class philosophers to historicalimportance. The fame of these men is parasitic upon Kant’s greater fame.There were philosophers who did not achieve even this derivative fame,for not all roads led from Leibniz to Kant. I think, nevertheless, that wecan best orient ourselves in a brief account of eighteenth-century Germanphilosophy by seeing it as a preparation for Kant.Leibniz was the last great philosophical system-builder of theseventeenth century, and his bold speculations and systematic wholenesswere more characteristic of the seventeenth- than of the eighteenthcenturyphilosophers. His peers were Descartes, Malebranche, Arnauld,Hobbes, Locke, and Spinoza, and in comprehensiveness and variety ofgenius he surpassed each of them. His system had an answer to almostevery question put to it; he was said to be “an academy of science all byhimself,” and the principal objection to his grand baroque philosophicalsystem was that it was—simply unbelievable. To accept it all would haverequired a speculative faith and a blind confidence in the metaphysicalpowers of the human mind that few philosophers of the eighteenth centurycould muster.Christian Wolff, his most important disciple, did not make a summa ofLeibniz’s philosophy, but both his followers and opponents saw Wolff asdoing precisely that. They accordingly called his philosophy the“Leibniz-Wolffian philosophy,” a name which has become fixed in spite ofboth Leibniz and Wolff ’s renunciation of it.Modern scholarship showsthe degree to which this tide is inappropriate,1 yet the Leibniz-Wolffianphilosophy was the dominant intellectual system and movement inGermany from about 1720 to about 1754, the death of Wolff, and itprovided the main opposition to Kant’s philosophy until near the end ofthe century. The rise and fall of the Leibniz-Wolffian philosophy in itscontroversies with its opponents is the subject matter of this chapter. I dealalmost exclusively with topics now important chiefly for an understandingof Kant and German Idealism.But before we turn to these topics, something must be said about thegeneral climate of opinion in Germany at this time. In all Protestantcountries of western Europe, there was an intellectual awakening calledthe Enlightenment. “Enlightenment,” Kant wrote, “is man’s release fromhis self-incurred tutelage.” Tutelage is allowing or requiring someone elseto do one’s thinking, and it is self-incurred because most human beings donot develop the skill and the courage to use their own reason. Theysurrender their freedom to those who will think for them in matterspolitical, religious, and moral. Kant did not believe he lived in “anenlightened age,” but did say he lived in an “age of enlightenment” whenprogress was being made to independent thought. But the specific formsthat Enlightenment took varied from country to country; it dependedupon the particular form of tutelage in each country, from which thinkersstrove to emancipate themselves.The German Enlightenment took place in a feudal environment of scoresof small absolute monarchies in which Lutheran passive obedience and theeye of the local monarch ensured that the established order of things wasregarded with sacred awe by the Bürger.2 While the philosophes of Francewere not merely anti-clerical but also antireligious (materialists, atheists,freethinkers, skeptics), what was unique to the German Enlightenment wasthat it originally had a profoundly religious motive.Pietism was a religious awakening at the end of the seventeenth centurywhich had much in common with the persecuted Jansenist sect in Franceand the Methodist movement still to come in England. Pietism meant areturn to a simpler form of Lutheranism, emphasizing the emotional andmoral rather than the ritual and dogmatic aspects of the establishedchurches. Instead of churches, there were evening gatherings in the homesof individual Pietists for communal devotion; every man was a priest,drawing inspiration from his own reading of scripture and applying itslessons to everyday life. Though the movement was not free of irrationalelements, it was enlightened in encourag-ing its members not to defer tosomeone else who would do their thinking for them. Naturally all thisproduced plurality of opinion and diversity of faith, but its emphasis upongood works (establishing schools and orphanages, for instance) brought itin line with the Enlightenment movement in other countries where themotivation was perhaps more intellectual and political.There were, in fact, two Enlightenments in Germany. Besides theintellectual Enlightenment pursued by the Leibniz-Wolffian philosophers,there was also a Pietistic Enlightenment. Surprisingly they both originatedin the same place, the University of Halle, a Pietistic institution founded bythe Elector of Brandenburg primarily for the training of the bureaucracyrequired by this largest and most important German state.The father of the Pietistic Enlightenment was Christian Thomasius(1655–1728), who had been banished from Saxony on religious grounds.Thomasius was an active reformer but not a deep philosopher. His ideal ofeducation was that it raise not the cloistered scholar but the honnêtehomme, imitating France in “polite learning, beauty of mind, good taste,and gallantry.” In order to reach a larger audience, he lectured and wrotemost of his books in German, not Latin. He claimed academic freedom,taught religious toleration, and attempted to reform legal practices byoutlawing torture and removing heresy and witchcraft from the reach ofthe law. As a Pietist he did not doubt the authority and authenticity ofrevelation, but he established the basis of law in ethics, ultimately inreason and experience. Pietism is almost always associated with an occultand quasi-mystical philosophy of nature, and this kept the GermanEnlightenment Pietists from participating in the great scientific revolutionat the end of the seventeenth century.Unfortunately Wolff and Thomasius were on a collision course.Intellectually they were not in serious disagreement on most substantivequestions (though their interests were widely divergent). Personally theirrelations were correct, though not close. Thomasius apparently took nopart in the ignoble campaign which drove Wolff from Halle just as he hadhimself been driven from Leipzig. But their disciples carried on a runningcontroversy for the next forty years, and it was marked by odiumtheologicum and general nastiness on both sides.WOLFFLife and worksChristian Wolff was born in Breslau in 1679. With support from Leibnizhe was appointed lecturer in mathematics at the University of Leipzig in1702 and, four years later, professor of mathematics at the University ofHalle. Wolff was no creative mathematician, but he found in mathematicsthe model for rigorous thinking in other fields. In this he simply followedthe lead of Descartes and Leibniz.Soon Wolff was teaching and writing philosophy, philosophy thenmeaning both the natural sciences and the subject which is today calledphilosophy. He published copiously on the experimental sciences and alsoon logic, metaphysics, cosmology, psychology, political theory, and naturaltheology in a series of large German books, most of which were entitledVernünftige Gedanken (“Rational Thoughts”) on the different areas ofknowledge.3 The contents and expository skill of these books led to theirwidespread acceptance as textbooks. His successes in publishingextensively used books, and his victories in the annual competition forpaying students, incited intense rivalry between Wolff and the lesssuccessful Thomasian Pietist professors. They seized the opportunity tocharge Wolff with heresy when he held, in a public lecture as rector of theuniversity, that the resemblances between Chinese and Western ethicsshowed that ethics was based on universal human reason and humannature, not on divine revelation vouchsafed only to Western civilization.They represented to the King of Prussia, Frederick William I, that Wolff ’sdeterminism and fatalism meant that he should not punish deserters fromhis army because, being determined, they could not have helped doingwhat they had in fact done.Enraged by this lèse-majesté, the choleric King dismissed Wolff andthreatened to hang him in forty-eight hours if he was still on Prussian soil.Wolff had already received a call from the Calvinist University of Marburg,which he now accepted. He taught in Marburg for seventeen years. Heard byan international student body, more of whom could understand Latin thanGerman, he repeated and expanded his series of Vernünftige Gedanken intolarge volumes of scholastic Latin addressed to an international readership. Sogreat was his fame, and so scandalous had been the behavior of FrederickWilliam I and his “Tobacco Cabinet,” that efforts were repeatedly made torecall him to Prussia. He returned only in 1740 when the new King, Frederickthe Great, made him chancellor of the University of Halle and granted him apatent of nobility and a large stipend. At the time of his death in 1754 he wascertainly the best-known thinker in Germany, fully deserving the honorifictitle of Praeceptor Germaniae.The mathematical ideal in philosophy4Hobbes, Descartes, Spinoza, and Leibniz all shared a common ideal forphilosophy, that it should attain the clarity and certainty hitherto availableonly in mathematics. Wolff is quite explicit about the relation ofmathematics to philosophy. “The rules of mathematical method,” he says,5are the same as the rules of philosophical method…. The identity ofphilosophical and mathematical method will be a surprise only toone who does not know the common source from which the rules ofboth mathematics and philosophy are derived.This common source is “true logic” or “natural logic” of the workings ofthe human mind, not a finished logic which is itself a science.Lest the identity of philosophy and mathematics appear to be whollyquixotic, it is essential to remember that “philosophy” and “mathematics”did not then mean exactly what they mean now. Philosophy, well into theeighteenth century, included the sciences; and though work of the highestkind in pure mathematics was being performed by Leibniz and Lambertand others, the mathematics that was the cultural model for theEnlightenment was applied (or, as it was then called, “mixed”)mathematics. Wolff’s mathematical works contain far more informationabout astronomy, meteorology, geodesies, and even architecture than theydo topics in pure mathematics. The root idea of the mathematical model isthat computation and measurement are essential to any body of advancedscientific knowledge.In the true method, formulated by Descartes and followed with littlechange by Wolff, everything certain in our thoughts depends upon theorder of our thoughts, a step-wise procedure of moving from the simplestand most indubitable to the less certain and more problematical.Mathematics begins with définitions, proceeds to fundamental principles(axioms), and thence to theorems and problems (constructions). Theproduct of a définition is a clear and distinct idea, evident to attention andcommunicable to others. Mathematical theorems are demonstrated byanalysis of the contents of definitions and axioms, demonstration takingthe form of showing that an alternative to a true theorem is selfcontradictoryor contradictory to another established truth.In the syllabus for his mathematics lectures in 17316 Wolff tried toshow both the importance and the inadequacy of mathematicalknowledge. Mathematics deals only with the observable phenomena inspace and time (which are subjective), and it operates with images;ontology, on the other hand, deals with being qua being and replacesimages with exact concepts.How well did the mathematical ideal stand? In 1762 the RoyalAcademy of Sciences in Berlin offered a prize for the best essay on thequestion: ‘Whether metaphysical judgments generally, and in particularthe fundamental principles of natural theology and morals, are capable ofproofs as evident as those of geometry?” A disciple of Wolff, MosesMendelssohn, took the prize with an essay giving an affirmative answer,with which Wolff would have agreed. The runner-up, with a negativeanswer, was the unknown Immanuel Kant. In this respect history hasfollowed Kant, not Wolff and Mendelssohn.The marriage of reason and experienceOne of the perennial problems of philosophy is to determine the roles ofreason and experience in knowing. In the seventeenth and eighteenthcenturies it was the subject of controversy between philosophers we nowcall rationalists and those we call empiricists. Among the empiricists wecount Locke, Berkeley, Hume, Reid, and Condillac; among therationalists, Descartes, Malebranche, Spinoza, and Leibniz.Wolff is sometimes considered the arch-rationalist, but we must enquireinto the kind of rationalist he was.7 A rationalist like those just listedbelieves that reason alone, or rational intuition, is able to discover truthsthat are independent of experience and that could not be learned fromexperience, but that necessarily apply to experience. Such truths have beencalled, especially since Kant, a priori, in contrast to truths a posteriori, i.e.truths learned only from experience.Wolff frequently insists that there are no a priori truths in this sense; hesays that there is no human pure reason devoid of sense content; he agreeswith the Scholastic teaching, “There is nothing in the intellect that was notfirst in sense.” He rejects the theory of innate ideas, which has alwaysbeen one of the principal tenets of the rationalist school. Hence Wolff mayseem to be no rationalist at all; he is not a rationalist in the strictly definedsense of the preceding paragraph, but his style and vocabulary give arationalistic veneer to his thoughts because he seems to generate a prioriknowledge by improving upon empirical knowledge.He attempted (successfully, in his own judgment) to derive the principleof sufficient reason from the law of contradiction.8 Leibniz had attemptedto keep these two principles separate and independent of each other, andhad ascribed each to a very different metaphysical source (respectively thewill and the intellect of God). Wolff, on the contrary, contends that it is alogical truth that every true judgment has a sufficient reason for beingtrue. Though Wolff does not claim to derive empirical truths from theprinciple of sufficient reason (and, ultimately, from the law ofcontradiction), he does claim (and makes good his claim) to be able to givea rational account of what was originally perceived empirically.He does so by drawing a distinction between two kinds of knowledge,which he calls historical and philosophical knowledge.9 He does so inparallel with Aristotle’s distinction (Posterior Analytics, Book I, ch. 13)between knowledge of fact and knowledge of reasoned fact. Historicalknowledge is knowledge based on the perception of a raw fact, somethingexisting or happening. But by memory, classification, measurement,hypothesis-formation, and perhaps simple experiments we clarify ourknowledge of a fact by seeing it as a “certain kind” of fact. The ideas ofsense become ideas of reason (the vernünftige Gedanken of Wolff’s booktitles), reason being the capacity for “seeing with the mind’s eye” theconnections of ideas and their sufficient conditions. All the knowledge thatreason has or produces comes from experience - historical knowledge isthe basis of philosophical knowledge—but it is so processed by reason intodefinitions, principles, axioms, probable hypotheses, and well-tested lawsof nature that a subtle change is introduced into our historical knowledgeof fact: knowledge of fact becomes knowledge of reasoned fact. Goingbeyond what has been actually observed, knowledge of reasoned factextends to facts not yet experienced. Wolff likes to say that there is amarriage of reason and experience (connttbium rationis et experientiae)which he does not wish to disturb.There are two movements in knowledge. The ascent from knowledge offact to principles and reasons is the analytical method of Descartes (Kant’sregressive method); the descent from reason to experience is Descartes’ssynthetic (Kant’s progressive) method. The knowledge of reasoned factwas commonly in Wolff’s day called a priori knowledge10 (knowledge fromreason, not experience), even though for Wolff its ultimate andirreplaceable source is experience.We can now summarize Wolff’s kind of rationalism. He is not arationalist in the sense of the belief that pure reason without need ofexperience can produce a priori knowledge (in mathematics andmetaphysics, for example). He is a rationalist in a loose sense in that heemphasizes the function of reason in converting raw data of the senses intoreasonable knowledge. With his armies of syllogisms in valiant array, Wolffdemonstrated everything from the existence of God to theories inastronomy; he proves that German coffee houses should be modeled afterthose of England. No wonder Wolff is generally thought of as a rationalist!Ontology and special metaphysicsThe keystone of Wolff’s stupendous edifice is his First Philosophy, orOntology, published in Latin in 1729. In 1720 he had published a volumesometimes known as the German Metaphysics whose accurate andinstructive title is Rational Thoughts on God, the World, the Soul of Man,and All Things in General.The subject matter of ontology is being in general, demonstrativeknowledge of what it is that makes something possible if it is possible andactual if it is actual. It is like Aristotle’s “First Philosophy” which dealswith being qua being (Metaphysics, Book IV, ch.1). Ontology deals withquestions and concepts common to all branches of knowledge.Questions about the various kinds of being are reserved for the severalvolumes on special metaphysics, viz., the being of God, the existence ofwhom follows only from his possibility (the ontological argument), the beingof the soul, and the being of the world. The actual world and the actual soulare made actual by “a complement of possibility”11 which renders possiblethings actual. Kant destroyed this connection of possibility and actuality byasking the question: Is the complement possible? If it is not, it is impossibleand cannot serve the purpose. If it is, it is just another possibility andcontributes nothing toward actuality. There is no valid inference frompossibility to actuality. The converse inference, from existence to possibility,is explored by Lambert, Crusius, and Kant.Many of the 964 articles in the Ontology give definitions ofmetaphysical terms such as being, existence, possibility, essence, condition,thing, attribute, simplicity, substance, space, time, cause, quality, etc.These concepts are shuffled, combined and separated, contrasted, andcompared in an almost mechanical procedure.One of the most important concepts is that of substance, defined asfollows: “What contains in itself a principium [roughly: a cause] ofchanges is a substance.”12 Each substance contains in itself a sufficientcondition for a change in itself or in other substances. If the change ismotion, the monad is a physical substance; if the change is mental, themonad is a spiritual substance. Only one substance contains the cause ofits own being, and that substance is God. Thus arise the three divisions ofspecial metaphysics: rational theology, rational psychology, and rationalcosmology. It will be noticed that Wolff is closer to Descartes than toLeibniz, who had asserted that all substances are spiritual and had deniedthat one substance could cause a change in another. Wolff, verytentatively, holds the doctrine of pre-established harmony only for the caseof relations between mind and body monads.Wolff follows Leibniz in denying absolute Newtonian space, and agreeswith Leibniz that space is a subjective order of appearances of substances.He holds a mechanical view of nature, which consists of simpleunextended physical monads interacting by contact with each other, thewhole showing intelligent design and especially purposiveness for humanbenefit.13 The soul is a simple substance with a vis repraesentativa or apower of being conscious; the soul is immortal and the will free. LikeLeibniz in his Theodicy, Wolff strove to reconcile freedom and necessity,but with equal ill-success.Moral philosophyWolff wrote more on practical philosophy (ethics and law) than on anyother subject. There is little new in Wolff’s theory, but it is superblyorganized and undoubtedly influenced Kant’s articulation of ethical theoryin his Metaphysics of Morals. Kant cites Wolff as the exemplaryrepresentative of the best of the four types of heteronomous ethics, theethics of perfection.14The intellect conceives of a perfection, which is the value aspect of truthas the perfect harmony and interconnection of the essential attributes of athing following from its intrinsic essence. True being (as object ofknowledge) and true good (as object of desire) are identified. The willnecessarily strives for a perfection which the intellect has discerned.Rational willing is definitive of morality. The achievement of a perfectionis attended with pleasure, but the test for an action is not its consequentpleasure, but its rational motivation and justification.Natural law requires that each person strive to achieve their ownperfection and also that of others. Revelation is not required to teach mentheir duties, nor is the promise of divine reward needful to move people to dothe good.The completion of Wolff’s system in aestheticsA great gap in Wolff’s system was the lack of a theory of beauty and fineart. The last decade of Wolff’s life was a time of extensive literarydispute concerning matters of taste. There were controversies betweendefenders of the classical forms and harbingers of the romanticism thatwas yet to come. There was great competition between those who wouldemulate French drama and those in favor of English models, and stillothers (e.g. Lessing) who wanted to develop a native drama withGerman themes.It is easy to see why a comprehensive philosophical movement likeWolffianism should be concerned to develop a theory of art, in spite of thefact that there certainly are few philosophical theories less likely thanWolff’s to be fruitful concerning beauty and art. Wolffian theories of artwere produced by two disciples, Alexander Baumgarten of Halle (laterFrankfurt on the Oder) and Moses Mendelssohn of Berlin. .Baumgarten15In Leibniz-Wolffian philosophy the perfection of sense would be achievedwhen a sensuous idea was so clarified and rendered so distinct that it wouldbecome an abstract intellectual idea. Indeed the entire Wolffian programmay be summed up in Wolff’s efforts to replace facts given in sense withreasoned facts from which the unique, ineffable content of sense had beenevaporated. The perfection of sense is reason, and there is only a differenceof degree between the clarity of reason and obscurity of sense. To raise theperfection of sense means: to replace percepts with concepts.This feature of Wolffian rationalism made it indifferent to the arts, forthe artist is one whose skill makes it possible to achieve a perfection of sensewhich is the object of a perfect, direct intuition, not object of abstractthought got at by omitting the specificities of a singular perception.According to Baumgarten sensation can be perfected by so enhancing itsvividness and clarity that there will be pleasure in its mere contemplation.The irreducible sensory component in such a perception is called theaesthetic and the intuitive by Baumgarten. Sense, which is the lowercognitive faculty, is the higher faculty in the contemplation of beauty. Aperfection (of form, color, sound) apprehended by sense instead of byreason is beauty. Aesthetics is the “science of the beautiful.”MendelssohnIn 1755 Moses Mendelssohn published On Feelings (Empfindungen), amodification of Baumgarten’s views which marks a sharp advance in thedirection of Kant’s mature aesthetic theory and the aesthetic theory of thelater idealists and romantics.The human mind, he holds, is too limited to be able to sensuouslyobserve the variety-in-unity of ontological perfections, which is discernibleonly by reason. Thus far Mendelssohn stands with Wolff and Baumgarten,but he now adds: we can sensuously contemplate the variety in unity ofthe mind’s own acts and passions, sensations, thoughts, and emotions. Hecalls this the “harmony of the powers of the soul.” The directly feltperfection of perceiving, not the perception of an antecedent perfection inthe perceived object, gives rise to disinterested aesthetic pleasure in theharmonious play of our faculties. Mendelssohn here makes an importantand permanent contribution to the history of art and aesthetic theory. Heteaches that beauty is not predicated upon an objective perfection (ofcolor, design, morals, or whatever is found in the work of art); it is aperfection of perception, not a perception of perfection.Pleasure usually accompanies the satisfaction of some previouslyexisting desire, but art and beauty are not normally enjoyed because of thepleasure they afford by satisfying some antecedent desire. In addition toperception and will, each with its own attendant pleasure, there is anotherfaculty of the mind which has its own peculiar pleasure. This facultyMendelssohn calls feeling or approval (Billigungsvermögen) by which weexperience “disinterested pleasure,” a pleasure different from that ofsatisfied desire or curiosity.Mendelssohn explains this pleasure by our satisfaction in theharmonious function of all the Seelenkräfte, when feeling and willing andperceiving go together to produce a delectable state of mind. Each person’staste will be affected by their physical and even physiological make-up,but with the advance of education and general culture more pervasivesatisfactions will replace the doctrine of à chacun son gout. This harmonyof the powers of the soul is involved in both the enjoyment of art and itscreation by genius. Genius is an “imitator of divinity,” a “second creator.”CRUSIUSThe Pietist campaign against Wolff was fought on two levels. Motivatedby odium theologicum, envy, and nepotism as well as by genuine concernincited by Wolff ’s apparent affinity with Spinozistic pantheism andfatalism, the Halle Thomasians Budde, Lange, and Walch conducted adirty campaign that continued even after Wolff had been banished. Butthese Thomasians, like Thomasius himself, were not systematicphilosophers of Wolff’s caliber; they found fault with Wolff, but offered nointeresting alternative. The most important alternative was that ofCrusius.Christian August Crusius was born in Leuna near Merseburg (Saxony)in 1715 and died in Leipzig in 1775. Almost all the men in his family wereLutheran clergymen, and he held professorships in both philosophy andtheology and was a pastor holding important posts in the Lutheranhierarchy. About 1750 he gave up philosophical work altogether anddevoted himself to theological and biblical studies and the care of souls.In place of mathematics,16 Crusius thought of theology as the sciencewhose relations to philosophy must be understood. Philosophy, accordingto him, is not a sufficient ground for religious faith and human virtue; it isnot even essential to the conceptualization of theological truth, since thetruths established in philosophy may be overturned by the greaterauthority of theology. “We cannot think something” was the mark for theimpossible among most Enlightenment philosophers, but for Crusius therewere conditions under which the inference from inconceivability toimpossibility may be suspended: if the thing inconceivable by us may beconceivable by a more perfect mind, or if “We recognize an obligation toregard something inconceivable as possible or actual in order not to actcontrary to the most important rules of human perfection” (which include,of course, revelations of the commands of God).17From all this it is easily seen how opposed Crusius was to Wolff. Wolffas a leader of the intellectual Enlightenment was bent upon extending thescope and power of human reason and denying any constraints upon it;Crusius as a leader of Pietistic thought was more concerned to restrain theambition to explain everything; he tried to determine and fix theboundaries of human intellect when dealing with the brute facticity of thecontingent world and the mysteries of religion. That he did so without theobscurantism of the early Thomasians, by developing a sophisticatedepistemology as an alternative to Wolff, is a mark of near greatness in thisalmost forgotten man.Ontology and theory of knowledgeFor Crusius existence, not possibility, is the fundamental concept. In thishe differs markedly from Wolff, who asks what is the ground of thepossibility of something prior to asking what it is that makes it actual if itis actual. Wolff’s answer to this question concerns logical possibility, i.e.non-self-contradictoriness. Crusius’s ontology is to challenge Wolff’saccount of the role of logical possibility in the explanation of existence.We reach the concept of possibility by first finding existent things andthen, by “an abstraction from existence” (the reverse of the “complementof possibility”), we find that whatever exists is also possible, but not theconverse. If nothing existed, nothing would be even possible. The conceptof possibility requires the concept of existence, but not the converse.18Crusius is here speaking, obviously, of what he calls real possibility, notideal possibility (i.e. possibility of being thought, becausenoncontradictory). Real possibility is the possibility inhering in things thatmight exist outside and beyond our thought of something merelynoncontradictory. There can be this real possibility only if there are in theworld existing things with forces adequate to bring about the actualizationof this possibility.Understanding has the inexplicable faculty of being conscious of ideas.Reason is the perfection of understanding, consciously recognizing truth astruth. Two activities of reason are to be distinguished; reason in concreto,which is the capacity functioning in a single individual with their variousquirks and dispositions; and reason in abstracto, which is the “complex”of the essential forces of human understanding in general. Only reason inabstracto is capable of objective knowledge.19By a kind of denudation we find simplicity and clarity in sensations andother representations. We remove in thought all accidental properties ofthings, and we are left only with the essential relations that thingsnecessarily bear to one another. Besides noncontradiction and identitythere are relations that show the ultimate unanalyzable real forces ofthings. There is intuitive knowledge of simple, clear, and necessaryrelations of ideas stated by Crusius as basic laws of thought. Instead ofWolff’s single supreme condition (law of contradiction) and its corollary(law of sufficient reason), Crusius states five laws:(a) The law of inseparables: Whatever cannot be conceived withoutsomething else cannot exist without that other (Metaphysics, § 15); (b)The law of incompatibles: Whatever cannot be thought in connection withanother thing cannot exist with that thing (§ 15); (c) The law of space:Everything that is is somewhere in space (§ 48); (d) The law of time:Everything that is is somewhen or at some time (§ 48); (e) The law ofcontingence: That whose nonbeing may be conceived may at some timehave not existed (§ 33).20These laws are based upon “the nature of human ” which is “thesupreme criterion of possible and actual things.”21 Kant thinks thatCrusius’s epistemological principles can correspond to ontological truthsonly if there is a pre-established harmony between the knower and theknown.22 Crusius, of course, will not accept this Leibnizian theory, but hestates repeatedly that God has “placed the marks of truth in the humanunderstanding.”23Freedom and the principle of sufficient reasonThe principle of sufficient reason is not listed among the basic laws ofthought. Though a valid principle it is not an independent principle; it is,rather, a corollary deduced from the law of the inseparable. Crusius, whocertainly had not read Hume, states that we cannot think of a happeningor a coming-to-be without associating it, in intuition, with some otherprecedent event. (Hume, of course, about the same time flatly denied thisimpossibility.)24 But Crusius says: “Anyone who observes himself clearlysees that nothing that comes to be may be thought except when one at thesame time admits that there is another thing that has power sufficient toproduce it.”25 He concludes, like Hume, that causation is neitheranalytically necessary nor an empirical generalization, but he does notdraw Hume’s skeptical conclusion.For any coming-to-be we search for a substance or thing that has theforce or power (otherwise inscrutable) to bring this about. Reason mustaccept the forces and powers it empirically discovers in nature withoutthinking that they are logically necessary.26The law of efficient causation shown in the previous paragraphs to be acorollary of the law of the inseparable has several corollaries of its own,and they may be collectively called the law of sufficient reason. Crusius’sLatin Dissertation on the Use and Limits of the Principle of DeterminingReason, Commonly Called Sufficient Reason (1743) is based on hisunwavering adherence to the freedom of the will, but uncompromisingrejection of any theory of freedom of the will compatible with theWolffian principle of sufficient reason. He distinguishes betweendetermining reason and sufficient reason. The former is a reason whichmakes its consequence uniquely necessary, and that principle underliesdeterminism and fatalism. But that principle, he holds, is not demonstrableby the principle of contradiction, and therefore is not universally valid. Asufficient reason,27 on the contrary, may have diverse consequences, and iscompatible with freedom of the will.Crusius’s “solution” to the problem of free will is one of the standardones: nature is the realm of strict determinism, but man is an exception tothis rule of the law of determining reason. He believed that the will is freeand therefore believed he had to relax the strict principle of determinantreason and accept the looser condition of sufficient reason. Then the sameconditions may be “sufficient” for me to do A or to do B, and whichever Ido I freely do because these reasons for A or B are supplemented by a freehuman decision. But it is patently wrong to call the conditions “sufficient”when they must be supplemented by a free act of will.Here we have a fine example of Crusius’s modifying epistemologicalconclusions when they conflict with faith and morals. This was not thefirst time, nor will it be the last, when moral conviction takes precedenceover logical analysis.Virtue is the agreement of human actions with the commands of God.28Hence Kant correctly lists Crusius as the exemplary representative of“theological moralists” who hold (correctly) that there is an objectivestandard of morality but also (incorrectly) that the standard lies in the willof God instead of in the rational will of man.29Having established (to his satisfaction) the freedom of the will as thecapacity for absolute spontaneity of action, Crusius believed that he hadestablished the only possible foundation for imputing responsibility andfor justifying reward and punishment. The duty of man is to obey God,not directly to seek perfection and pleasure.30 The love of God is the puremoral motive, like respect for the moral law in Kant. For guidance inmorality man has an inborn conscience and a will to virtue. Since mankindand its moral perfection are the final end of God, we human beings canbelieve that obedience to and love of God will in fact lead to blessedness,even if only in another world.With these views and his Pietist habitus it is not hard to see why theyoung Crusius gave up his philosophical career after only twelve years.Theology’s gain was philosophy’s loss.LAMBERTJohann Heinrich Lambert was born in Mühlhausen, Alsace, in 1728.Unlike Wolff he was a creative mathematician; he was the first todemonstrate that e and (pi) are irrational numbers, and he was a pioneerin non-Euclidian geometry. He is generally regarded as the father of thescience of photometry, and his name is commemorated in the “Lambert-Beer law” of the absorption of light, and in the name of a fundamentalunit of illumination, the “lambert.”Mathematics and simple ideasLambert speaks as an almost fanatical mathematician when he says:“What cannot be weighed and calculated doesn’t concern me. I understandnothing of it.” “One will not give the name of ‘perfect scientific knowledge’to philosophy when it is not at the same time completely mathematical.”31“Wolff brought about half of mathematics into philosophy; now it is amatter of bringing the other half.”32 The half Wolff had brought in was themethod of definition and proof, but he did not bring to philosophy the partof mathematics which concerns intuition, postulation, hypothesis, andconstruction; by taking arbitrary definitions “as it were, gratis,” “withoutnoticing it he hid all the difficulties in them.”33When Lambert first read Euclid, long after he had studied Wolff’stheory of geometry, he was astonished, he says,34 to find that Euclid hadbegun with simple, clear, and distinct intuitions of lines, points, andangles, and not (as Wolff had done) with nominal definitions, theapplicability of which to figures in space was at least questionable. Hethought that Wolff had done nothing to establish die truth of his premisesand correspondence between theorems and the actual structure of figuresin space. Still, “The honor of bringing the right method into philosophywas reserved for Wolff,” he says. “Whoever wants to profit most fromWolff’s writings should begin with them, and then survey writings whichmore or less diverge from his. I do not hesitate to include here [the worksof] Darjes35 and Crusius.” But the most Wolff could establish was thepossibility, not the necessity and objective reference, of mathematicalknowledge. There was a gap between logical truth and experience,between possibility and existence.How is a priori knowledge possible?To fill this gap Lambert, like Wolff, distinguished between ordinary andscientific knowledge of things.36 Scientific knowledge establishes clear anddistinct ideas of experience and supplements them with hypotheticalLehrbegriffe. Lambert then asks: to what extent can scientific knowledgebe a priori?, using the term a priori in a stricter sense than Wolff, andapproximating Kant’s usage to refer to concepts that could not have arisenout of experience.37 Experience is only the occasion of our having a prioriknowledge,38 but it is experience that gives existential reference to a prioriknowledge which, without experience, is limited to the possible and thenecessary. Though we suppose that it applies to the actual, the specificitiesof the actual - i.e. which possibilities are actual in this world—are notknown a priori. But we have a priori knowledge of the contents (objects)of simple ideas and not just of their formal relations to each other.In giving the “mechanism,” so to speak, of a priori knowledge, that is,in explaining how we know anything a priori, Lambert turns to the“anatomist of ideas,” Locke, for the theory of simple ideas of which, andby means of which, Lambert believes we have a priori knowledge.Simple ideas are said to have only one (atomic) predicate; they areequivalent to their Merkmal (sign or criterion) with no hidden predicates,and they have insufficient complexity to be liable to self-contradiction(and for that reason they are possible). Simple ideas are clear even in themind of a solipsist, and so are not dependent on the real existence of theirobjects. What is most important about simple ideas is not their identitiesbut their necessary and possible connections such as “what is solid isextended” and “cogito ergo sum.” It is by virtue of these relations that weescape from an endless series of mere tautologies and, through combiningthem, formulate the sets of simple ideas which underlie, a priori, thevarious sciences. In true Leibnizian spirit of the ars characteristica, themore we can analyze empirical concepts into simple ones and empiricaljudgments into tautologies or possible combinations, the more ourknowledge is a priori. The relations of simple ideas through comparisonand combination are submitted to the criterion of thinkability(Gedenkbarkeit, like Crusius’s inseparability—which Lambert callscombinability—and incompatibility), and each combination can be the apriori foundation of some science; each actual science can be submitted tothe analytical discovery of what its simple, a priori ideas are. These simpleideas are called Grundbegriffe. Geometry is the science of simple ideas ofextension in space; chronometry the science of simple ideas in duration;phoronomy the science of simple ideas in both space and duration; etc.The Vernunftlehre—science of the operations of the mind—depends onsimple ideas of a thinking being and Locke’s ideas of reflection. This givesrise to metaphysical knowledge which in point of certainty is on a parwith geometry.39Lambert and Crusius were the first among our philosophers to see theproblematic aspect, yet also the extreme importance, of understandingnecessary relations between simple ideas. No longer can the Wolffiansequate impossibility with logical contradictoriness. Not all opposition isopposition of contradictories.40 The necessity dependent upon theprinciple of contradiction is confined to the components of complex ideas,established by arbitrary definitions. It was the Wolffians’ goal to showthat all necessity was logical necessity, and all impossibility was logicalincompatibility; but they failed to achieve it. To have seen the problem,which arises in trying to account for all necessities by means of identities,was the eminent contribution of Crusius and Lambert. Lambert confesses“that the fons possibilitatis duos ideas combinandi (the origin of thepossibility of combining two [simple] ideas) has not been fullydiscovered.”41 It had hardly even been noticed, and it will not have been“fully discovered” until Kant will have generalized the problem into thequestion: How are synthetic judgments a priori possible?Lambert himself attempted to find the fons of the necessary connectionsamong simple ideas. There is in our minds, he held, an actus reflexus, acomparing of simple ideas which, in some unexplained way, gives rise toknowledge of their possible and/or necessary connections and combinations.Comparison is the fundamental actus reflexus of mind which is involved inanalysis and synthesis of ideas.42 In ways Lambert does not explain, out ofthe similarity and difference of simple ideas there issue necessary relationalideas, which indicate which simple ideas are validly synthesizable withothers. This is not logical inference (where “synthesizable with” means “notcontradictory to”); it involves an intuition, and in so concluding Lambertmakes little or no progress beyond Crusius.Nor were Lambert’s efforts to avoid phenomenalism (and indeedsolipsism) any more successful. Holding that possibility presupposes theactual existence of something, Lambert fallaciously thinks that it must beexistence extra mentem.43 He eventually follows Malebranche in callingupon God to give metaphysical status to some of our ideas.44 In spite ofthe influence of Locke and his proximity to Kant, Lambert is ametaphysician in the grand style, and his epistemological acuteness doesnot restrain his speculative passions.Lambert’s correspondence with KantLambert published his Cosmological Letters in 1761. It has a rathercurious history. It was a product of a sudden aperçu which Lambert hadinto the structure of the heavens. He saw analogies between planetarysystems and galaxies. Kant had presented somewhat the same plan in hisUniversal Natural History and Theory of the Heavens (1755) but hadintroduced a cyclical evolutionary dimension on the origin and dissolutionof astronomical structures. This theory is now known as the Kant-LaPlacehypothesis on the origin of the solar system. This classic in the history ofastronomy was almost unknown at the time because of the bankruptcy ofKant’s publisher. When Lambert read Kant’s Only Possible Premise for aDemonstration of the Existence of God (1764), which contained a briefaccount of Kant’s astronomical views, he wrote to Kant exculpatinghimself for the apparent plagiary, expressed contempt for the belletristphilosophers in Berlin, and invited Kant to enter a philosophicalcorrespondence with him. Lambert really does philosophy in his lettersand is anxious to involve Kant in his plans; Kant, always a reluctant letterwriter, fills his letters with politesse but does not engage with Lambert inany serious philosophical rumination.In September 1770, Kant sent Lambert a copy of his InauguralDissertation, On the Form and Principles of the Sensible and IntelligibleWorld. In his covering letter (2 September 1770) he spoke of having“arrived at a position that, I flatter myself, I shall never have to change.”Little did he know!Lambert replied on 13 October in a long, somewhat repetitious letterwhich shows that he had a good understanding of Kant’s InauguralDissertation. In it he disagreed with Kant on the nature of time and on themethod to be followed in metaphysics.The Kantian position to which Lambert objected was very briefly this.We have sensible representations of things as they appear to us(phenomena) and intellectual representations of things as they are inthemselves (noumena). It is an error in philosophy to apply predicates ofsensible knowledge to objects of intellectual representation; there is (inLambert’s terminology) an absolute gap between ontology andphenomenology. Time and space are a priori forms of both pure andempirical sensible knowledge; therefore neither space nor time nor anypredicates presupposing space or time may be applied to the reality ofthings as they are in themselves.Lambert’s most explicit objection was to the “unreal” state to which timewas condemned in the Dissertation.45 He tells Kant: “If time is unreal, thenno change can be real…. Till now I have not been able to deny all reality totime and space, or to consider them mere images and Schein.”46To his regret, Kant did not answer Lambert’s letter, but after Lambert’sdeath in 177747. he replied, in § 7 of the Critique of Pure Reason, saying:“I grant the whole argument. Certainly time is something real, namely diereal form of inner intuition.” If, on the other hand, we take time and spaceto be transcendentally real, the status of bodies in time and space is“degraded to mere illusion (Schein)” and “the good Berkeley cannot beblamed” for so degrading diem.48 Kant’s response to lambert in theCritique is to show that the transcendental reality of time, which lambertdesiderated, leads to subjective idealism (illusionism) which lambertrejected.Lambert’s second major objection to the Inaugural Dissertationanticipated a major shift of view between the Dissertation and the firstCritique. Anticipated, yes; occasioned, perhaps not, though we do notknow. Lambert’s assertion of continuity between phenomenology andontology conflicted with what Kant called “the all-important rule” inmetaphysical thinking: “Carefully prevent the principles proper tosensitive cognition from passing their boundaries and affecting intellectualcognition.”49This rule was rescinded in the Critique of Pure Reason in the famoussentence: “Thoughts without content are empty, intuitions withoutconcepts are blind.”50 Here “content” means sensible intuitions, and Kantis here saying that no exertion of thought can produce knowledge if thereis no sensible intuition. The most decisive factor in this reversal was Kant’sdiscovery (aided no doubt by his reading of Tetens) that without sensibleintuition there can be no synthesis of concepts and hence no judgments.The Inaugural Dissertation had kept separated what the first Critiquewould tightly bind together. So much, then, for Kant’s thinking that hewould never have to change what he thought in 1770!Whether Lambert’s obiter dicta had anything to do with this turnaboutin Kant’s thinking is doubtful, yet the weighty remark of a man Kant somuch admired may have had an influence on him. Lambert says:It is also useful in ontology to take up concepts borrowed fromappearance (Schein), since the theory must finally be applied tophenomena again. For that is how the astronomer begins, with thephenomenon: deriving his theory of the construction of the worldfrom phenomena, he applies it again to phenomena and theirpredictions in his ephemerides. In metaphysics, where the problem ofappearance (Schein) is so essential, the method of the astronomerwill surely be the safest.51Could there here lie the seed of Kant’s Copernican analogy?TETENSJohann Nicolaus Tetens was born in Schleswig in 1736 or 1738. Histeacher at the University of Kiel, Johann Christian Eschenbach, was theGerman translator of Berkeley, and from him must have come much of theextensive knowledge of, and sympathy for, British philosophy whichTetens so obviously shows. Tetens was professor at Kiel from 1776 to1789, when he entered the service of the King of Denmark. He had adistinguished career as a minister of finance until his death in 1807.Tetens’s empiridstic orientationTetens was sometimes alluded to as “the German Locke.” He repeatedlysays that “We must go back to the path trodden by Locke” and build onhis “physiology (Physic) of the human understanding.”52 He thought thatLocke’s “plain, historical method” must be practiced, deriving all ourideas from experience. But he also thought that the British (especiallyBacon, Locke, and Hume) had interpreted empirical knowledge as a merecollection of observations, had minimized the role of theory and logicalform in their theories of knowledge, and had never been able to develop asystematic speculative philosophy or ontology. Reid, Oswald, and Beattielikewise had failed to develop an ontology which would enable them tosystematize their common-sense philosophy, and this had kept them frompenetrating very deeply into explanations of the mental process underlyingcommon-sense knowledge and everyday practice. Tetens does not opposethe common-sense philosophers as he does Hume, but sees his own taskrather to be that of securing and clarifying the philosophy of commonsense. He is so committed to Locke, however, that he never concernshimself with Reid’s opposition to “the new way of ideas,” which is Reid’spreeminent claim to historical importance. Tetens writes contentedly ofimpressions and ideas just as if Reid had never thrown doubt on the entiremovement from Descartes to its denouement in Berkeley, Hume, andunnamed “solipsists” in France.53The possibility of metaphysicsIn his Universal Speculative Philosophy Tetens asked the fundamentalKantian question: Is metaphysics possible? He asked: “Are the times rightfor systems of philosophy? Can one be more than an observingphilosophical raisonneur?”54Since Wolff, special metaphysics had been about either spiritualsubstances (God and the soul) or material substance. Rational theology,rational psychology, and rational cosmology each has its own fundamentalconcepts and principles, but they share some in common. Tetens calls thestudy of these common elements transcendent philosophy because ittranscends the three divisions of special metaphysics.55 It is firstphilosophy, ontology, Grundwissenschaft. Transcendent philosophy,however, is no longer to be the abstract, formal, almost lexicographicalontology of Wolff. It is, rather, epistemology (though the word did notexist in Tetens’s lifetime). It is an empirical science, even though practicedin the armchair. What begins in the empirical sciences may end up in the apriori science of ontology.When Tetens says, for instance, that “Nothing comes from nothing,” heis formulating an objectively necessary principle of transcendentphilosophy. But he sees the same judgment as an assertion of his reason,and he interprets it as an empirical proposition asserting only that hisreason cannot think that something comes from nothing.56How can this empirical, contingent judgment (even if true) serve (as itdid for Crusius and Lambert as well as for Tetens) as a warrant for theobjective principle expressed in the same words? For Tetens, thedetermination of the conditions of knowledge of the objective principle isitself an explicitly empirical task. Tetens believed that necessities of ourmental operations, though discovered empirically, became necessities oftranscendent philosophy. He asks us to consider whether “Nothing comesfrom nothing” is just a quirk of his individual mind; do others agree withhim in asserting that nothing comes from nothing? These are all empiricalquestions that can be answered; but it is not obvious how a true andfavorable answer to these questions has any standing when it is a questionof ontology: Can something come from nothing?Neither Crusius, Lambert, nor Tetens seems to have seen theproblematical character of efforts to base the a priori claims of ourcognitions upon contingent facts of psychology. Kant characterizes suchefforts as “getting water from a pumice stone.” Let us see how Tetensproceeds.The cognitive facultiesTetens draws a line between the active and the receptive powers of thesoul. The active power is the will and the faculty of thought; the receptivefaculty is feeling or sense. Cognition occurs only when the former worksupon the latter. The first product of this working is the capacity to formrepresentations and concepts; there are already impressions of sense andfeeling, but these are brought to consciousness as representations only bythe basic power of making representations and concepts; a representationis the first object of consciousness, but it is not an impression or a copy ofan impression. Thought is necessary to form a representation as a sign ofsensation; the sensations must be “run through” and “held together” in acertain way57 by thought before they become representations of an object.The power of imagination (Dichtkraft) creates generic images of sensibleabstracta such as space and time. When representations refer to things inspace and time which resumably give rise to them, we are said to perceiveobjects, and we il to notice that we have only representations of objects,not objects themselves. We identify and reidentify objects, associate themwith one another, make abstractions from and classify them. In short, weobtain or form a concept of an object that can function in knowing in away that a mere image cannot.When representations become distinct concepts and their original feltassociation is replaced by a connection which is thought, there arises aconcept of relation (Verhältnissbegriff) between concepts. Relationalconcepts are not confined to specific pairs of representations but mayremain the same even when the specific content of the representations isdifferent. Such concepts are the fundamental concepts of transcendentphilosophy. Among them are sameness and difference, coexistence andsuccession (space and time), inherence of a property in a substance, anddependence of one thing on another (echoes of Hume’s list of“philosophical relations,” anticipations of Kant’s categories). Therelations among these concepts are a priori, because they are not restrictedas to the empirical content of the representations related to each other.Since they are relations implicit in the formal structure of judgments andinferences, they are found in and apply to all knowledge.We have seen repeatedly how Crusius and Lambert recognized a classof necessary judgments which are not based on logical necessity accordingto the laws of identity and contradiction. They tried to establish theobjectivity of such judgments. Generally, they tried to do so by appealingto the fact (if it is a fact) that these judgments express a necessity ofthought, not a logical necessity: one just must see that some things cannotbe thought to coexist. That, however, is a fallible, contingent truth if it istrue at all. What they needed was a proposition with the apodeicticcertainty of the law of contradiction yet one that could not be proved bythe law of contradiction. (In a word, they needed to recognize what Kantwill later call synthetic a priori judgments.)Tetens was keenly aware of the problem in 1776. The truths ofgeometry are necessarily true, but not because they depend on identity andcontradiction; they are necessarily true of space as we constitute theabstracta of space by the functioning of our cognitive faculties. The lawsof identity and contradiction are “mere ways of thinking withoutreference to what is peculiar to the ideas related,”58 but the laws ofmathematics deal with what is peculiar to space and time. Where thenecessity of a judgment does not depend on the merely formal relationshipbetween subject and predicate or the particular empirical content of thetwo concepts, it must depend upon “what is, in respect to certain generalclasses of representations (or objects), necessary and natural to theunderstanding.”59 What the features are that are necessary and natural tothe understanding must be discovered, according to Tetens, empirically,though the relations themselves are a priori necessary.The objective reference of perceptionIt is a quite different thing to show that a judgment is an expression ofthought natural to our understanding, and to show that the judgment isobjectively true. Tetens made an original and significant change in themode of examining this question of subjectivity and objectivity.Sensations and impressions are not normally objects of consciousness.They lack referentiality or intentionality. They get intentionality from beingingredient in representations, representations in our consciousness beingrepresentations of something. Tetens claims that this is a better account ofthe origin of our belief in external, independent objects than the differentones offered by Hume and Reid. But he also confesses,60 however, that itdoes not touch the question: Is objective reference veridical?Tetens does not have an answer to the demand for justification ofobjective knowledge-claims, regarded as a question of metaphysics.Epistemologically, however, he gives a criterion of objectivity which isindependent of the ontological status of minds and objects.Tetens examines the way some ideas are endowed with objectivereference without presupposing an answer to the question of the ontologyof subject and object. He empirically distinguishes the unchangeablesubjective and the changeable subjective,61 and sees that the formercaptures the empirical and methodological, if not the ontological, meaningof “objective.” Similarly there is the distinction between theintersubjective and the subjective, where the former is ordinarily called theobjective.This is as close as a writer of an empirical theory of knowledge can cometo the Kantian divisons between judgments of perception and judgments ofexperience and between unattainable knowledge of transcendent objectsand attainable knowledge of objects immanent in experience.Kant’s friend Hamann said that Kant had Tetens open upon his deskwhile writing the Critique of Pure Reason. Kant regretted that thispowerful and original thinker did not review his Critique of Pure Reasonwhen it was published in 1781. We can be sure that the second edition(1787) would have been improved if Kant had had the benefit of Tetens’scriticisms. There is a certain melancholy in some of Kant’s remarks aboutTetens—how close he had come to what Kant saw as truth, and yet howfar short of it he had fallen. He wrote:Tetens investigated the concepts of reason subjectively, I objectively.His analysis is empirical, mine transcendental. No one considered thepossibility of such a priori knowledge [ingredient in and presupposedby empirical knowledge] although Herr Tetens could have given riseto it.62THE MENDELSSOHN-JACOBI CONTROVERSYThe philosophers we have been studying raised objections to Wolff’sphilosophy, but with the possible exception of Crusius they did not bringmuch against his Weltanschauung. They were all men of theEnlightenment. They all were quite “safe” on the big issues ofphilosophy—God, freedom, and immortality—while they disputedtechnical points such as the logical status of the principle of sufficientreason.A little after 1780 the pax philosophica was shattered by a controversythat left its mark on Kant, Herder, Goethe, and the early German Idealistssuch as Schelling. It was a turning point in German philosophy andcultural life. If one decides that Jacobi was the “victor,” one can say thatthe Enlightenment in Germany was finished.Moses Mendelssohn was a faithful disciple of Wolff and won the prizeessay contest of the Berlin Academy by defending the Wolffianmathematical ideal, defeating Immanuel Kant. Kant praised the eleganceof his literary style, and in fact he is the best stylist among Germanphilosophers before Schopenhauer. He was an intimate friend of Lessing’sand was the model of the wise man in Lessing’s drama, Nathan der Weise.Friedrich Heinrich Jacobi was born into a rich Pietistic family inDüsseldorf in 1743. He reacted against the naturalistic, empiricisticeducation he received in Switzerland and became a religious enthusiast(Schwärmer). Faith and feeling were the watchwords of his philosophy.The conception of Spinoza as an atheist or pantheist, a blind fatalist, adestructive critic of Scripture who denied its authority, and a revolutionarypolitical thinker was almost universally accepted in Germany. Wolff wroteextensively in criticism of Spinoza,64 but nonetheless he was accused ofSpinozism by his Pietist colleagues at Halle. Mendelssohn in hisPhilosophical Conversations (1763) pleaded for a better and more fairmindedappraisal of “the accursed atheist of Amsterdam,” without, ofcourse, taking any step that committed him to Spinozism and withouteffecting any change in the almost unanimous condemnation of Spinozism.Imagine the shock, then, when it became known shortly after his deathin 1781 that Lessing had been a Spinozist. Lessing—Germany’s greatestman of letters, Germany’s greatest thinker between Leibniz and Kant, aman whose character after more than two centuries still awakens feelingsof affection and respect—a Spinozist? In conversations with Jacobi,Lessing had made this confession. Through mutual friends Jacobiimparted this information to Mendelssohn, ostensibly to contribute to abiography of Lessing that Mendelssohn was working on. Naturally thesecret could not be kept; party lines were drawn.There was a complicated exchange of letters through intermediaries,some of whom egged on one or the other of the protagonists. Finally therewere publications in which spleen was hardly covered by civility: Jacobi’sOn the Doctrine of Spinoza, in Letters to Moses Mendelssohn (1785),Mendelssohn’s Morning Lessons or Lectures on the Existence of God(1785), Mendelssohn’s To the Friends of Lessing (posthumous, 1786), andJacobi’s Against Mendelssohn’s Accusations in his “To the Friends ofLessing” (1786). To these should be added David Hume on Belief (1787)since it develops Jacobi’s “philosophy of faith and feeling” which underliesthe conversations with Lessing and the correspondence with Mendelssohn.Nothing shows better the ill-nature of this controversy than theaccusations that Jacobi was responsible for Mendelssohn’s death in 1786at the climax of the debate.For three reasons what might have been a quiet Auseinandersetzungbetween two scholars was raised to the level of a public scandal. The firstwas the eminence of the recently deceased Lessing. Any surprising secretsabout that good and famous man were bound to be objects of publiccuriosity. Second, there were many who hoped it was true that Lessing hadbeen a Spinozist. These crypto-Spinozists were more numerous thananyone had reckoned, and with Lessing’s Spinozism established they couldcome out of the closet.Then there were the personal motives and traits of the principals. FritzJacobi was a name-dropper and a tuft-hunter. He prided himself onknowing everybody. (Goethe told Eckermann that Jacobi lackedsomething necessary for a poet or philosopher, but that he would havemade a good ambassador.) Pride and snobbery were mixed in him with agenuine religious concern.Mendelssohn was not shocked by Spinozism, as we have already seen.But it was a personal wound to him that Lessing, his intimate friend ofthirty years, should have concealed his Spinozism from him and revealed itto some young man he hardly knew. At first he doubted the truth of whatJacobi said about Lessing; then he doubted the truth of what Lessing mayhave said about himself, citing as explanation Lessing’s love of paradox,irony, and persiflage.Much has been written about the strategy and tactics of the contestants,detailing how Jacobi laid traps for Mendelssohn, how these were dodgedby Mendelssohn who was laying traps of his own, etc. Neither of theprincipals came out with clean hands. The stakes were too high for eitherman to be punctilious about the ethics of publication of personaldocuments. The stakes were the validity of the whole philosophicalenterprise.Jacobi saw the issue as a choice between the nihilistic Spinoza-Leibniz-Wolffian Enlightenment and the absolute but irrationalistic claims of faithand feeling. Jacobi’s target was something even bigger and grander thanLessing and Spinoza: he aimed to overthrow the Enlightenment’srationalism and intellectualism and ideal of demonstrable metaphysicaland theological truth. He tried to show that any system of demonstrationshad to go in the direction of Spinozism; minor criticisms of Wolff had togive way to a frontal assault on the entire enterprise of philosophy as anintellectual discipline. Mendelssohn’s strategy was to construct a form ofSpinozism which Lessing might have held and which did not have the fatalconsequences that Jacobi had found in his interpretation of Spinoza. Inthis way he could free the Leibniz-Wolffian philosophy of the atheism,pantheism, nihilism, and fatalism that Jacobi said it shared with Spinoza.When Lessing remarked of Spinoza’s substance “that we can thinknothing about it doesn’t imply its impossibility,” Jacobi replied: “You goeven farther than Spinoza. For him understanding is worth more thananything.” Lessing replied: “For men only. Spinoza was far from thinkingour miserable human acting for purposes was the best method, and farfrom making thought supreme.”65After an excursus in which Jacobi tries to show that Leibniz and hencethe Leibniz-Wolffians were in essential agreement with Spinoza, Jacobireturns to his theme of the impotence and inferiority of abstract thought:In my judgment the greatest service of the enquirer is to uncover andreveal being (Daseyn). Explanation is only the means and the way tothe goal; it is neither the next nor the ultimate goal. The final goal iswhat does not let itself be explained: the irresolvable, the immediate,the simple…. Since we only put together and hang together what isexplainable in things, there is a certain illusion (Schein) in the soulwhich blinds more than it reveals…. [When we enquire] we close theeye of the soul with which the soul sees itself and God, so that bygreater concentration it can see with the eye of the body.66We do not, therefore, approach truth by rational thinking; rather, we embraceit in spite of rational thinking. A mortal leap (salto mortale) is needed. (Analmost exactly parallel move can be found in Kierkegaard’s distinctionbetween approximation to the truth and appropriation of the truth.) ButJacobi was unable to persuade Lessing with his “tired head and old legs” totake the plunge; Lessing remained a Spinozist. Others who professedadherence to Spinozism, however, embraced a very different Spinozism fromthat of rationalism and geometrical rigor. For men like Herder,67 Schelling,and Goethe, an organic, holistic, romantic conception of oneness replaced thequasi-mathematical perfection of Spinoza’s substance. Spinoza came into hisown, paradoxically, when rationalism was on the wain.Having held Spinozistic nihilism (Jacobi’s own word) to be the naturaland inevitable last stage in the evolution of Enlightenment, it was to beexpected that Kant’s Critique of Pure Reason, published the year ofLessing’s death, should come under criticism from Jacobi. But instead ofappealing directly to religious “faith and feeling,” he allied himself withDavid Hume. He appealed to Hume and to Hume’s critic, Thomas Reid,to justify his doctrine of the impotence of reason even in the simplestactions of everyday life. Hume substituted belief for unattainableknowledge, and Reid found belief essential in establishing the existence ofexternal objects when all that analytical reason could show was onlyimpressions and ideas.In his Morning Lessons (Morgenstunden) (1785) Mendelssohn doestwo things. First, he reasserts the correctness of Wolff ’s deism and itssuperiority over Spinoza’s pantheism. He points out what seems to him tobe a myriad of errors in Spinoza’s philosophy. He shows, to his ownsatisfaction, that the demonstrative method does not necessarily producethe Spinozistic conclusions of pantheism and fatalism.68Second, he formulates, in the name of his friend Lessing, a system of“purified pantheism” which Lessing might have held and which would nothave the evil consequences that Jacobi thought were indigenous inSpinozism. Specifically, in the fourteenth Lesson he makes of substance aspiritual being endowed with intellect and will but not extension. Then thequestion whether God is the world (pantheism) or the world standsoutside God (deism) does not have the portentous consequences whichfollow from identifying the human mind with a mode of substance whoseessence is necessity, extension, and oneness.In his To the Friends of Lessing (1786) Mendelssohn tries a newgambit. He commends “sound human understanding” (common sense inthe Scottish philosophy) when high speculations like Spinozism or purifiedpantheism, formulated by fallible human reason, conflict or do not carryconviction. He says:When I speak of rational conviction… I am not speaking ofmetaphysical argumentation…or of scholastic demonstrations whichhave stood the test of the most subtle skepticism; rather, I speak of theexpressions and judgments of simple and sound human understandingwhich directly grasps and contemplates things. I certainly respectdemonstrations in metaphysics… but my conviction of religious truthsdoes not depend so completely upon metaphysical argumentationsthat it would have to stand or fall with them. One can raise doubtsabout my arguments and show fallacies in them, and yet myconviction remains unshaken…. For the true and genuine convictionof natural religion…these artificial methods [of metaphysicalspeculation] are of no use. The man whose reason is not debauched bysophistry needs only to follow his own good sense.69This was the state of things at the end of the Mendelssohn-Jacobi dispute:the proponent of faith and feeling sees his rationalist enemy take refuge incommon sense. On both sides, reason has taken a beating. That is how itappeared to one man, Immanuel Kant, in an apostrophe to Jacobi andMendelssohn:Men of intellectual power and broad minds! I honor your talentsand love your feeling for humanity. But have you considered whatyou do, and where you will end, with your attacks on humanreason?…Friends of the human race and of that which is holiest toit!…do not wrest from reason that which makes it the highest goodon earth, the prerogative of being the ultimate touchstone oftruth.70German Idealism proper may be said to have begun when leadingphilosophers heeded Kant’s words and made reason “the highest good onearth” and “the ultimate touchstone of truth.”NOTES1 See, for instance, C.A.Corr, “Christian Wolff and Leibniz,” Journal of theHistory of Ideas, 36 (1975): 241–62.2 W.H.Bruford, Germany in the Eighteenth Century (Cambridge: CambridgeUniversity Press, 1965), p. 222.3 Wolff’s Gesammelte Werke, ed. J.Ecole, J.E.Hofmann, et al. (Hildesheim:Olms, 1962–), are currently being published, but there is little Wolff inEnglish. There is Preliminary Discourse on Philosophy in General, trans.R.G.Blackwell (Indianapolis: Bobbs-Merrill, 1963); selections fromVernünftige Gedanken von Gott, der Welt, der Seele des Menschen, auch allenDingen überhaupt in Eighteenth Century Philosophy, trans. L.W.Beck (NewYork: Free Press, 1966); selections from Vernünftige Gedanken von derMenschen Thun und Lassen in Moral Philosophy from Montaigne to Kant,trans. J.B.Schneewind (Cambridge: Cambridge University Press, 1990).4 See T.Frangsmyr, “Christian Wolff’s Mathematical Method and its Impact onthe Eighteenth Century,” Journal of the History of Ideas, 36 (1975): 653–68.5 Wolff, Preliminary Discourse on Philosophy in General, op. cit., §139.6 Wolff, Von dem Unterschiede metaphysischer und mathematischer Begriffe…,in Gesammelte Werke, op. cit., Series I, Vol. 22, pp. 286–343, esp. § 14.7 J.Ecole, “En quel sens peut-on dire que Wolff est rationalist?” StudiaLeibnitiana, XI (1979): 45–61.8 Wolff, Prima Philosophic sive Ontologia, in Gesammelte Werke, op. cit.,Series I, Vol. 2, §§ 70, 288–319; Vernünftige Gedanken von Gott…, op. cit., §30. Wolff’s “deductions” are so patently question-begging that it is notworthwhile repeating them.9 Wolff, Preliminary Discourse on Philosophy in General, op. cit., §§ 7 ff.10 Wolff defines a priori as follows: “Whatever is known a priori is elicited by thepower of the intellect.” “Whatever becomes known to us by ratiocination issaid to be known a priori.” Psychologia Empirica, in Gesammelte Werke, op.cit., §§ 438, 434.11 Wolff, Ontologia, op. cit., § 174; Vernünftige Gedanken von Gott…, op. cit.,§14. Kant’s rejection of the complement of possibility is in Critique of PureReason, A 231, B 284. On this difficult point, see C.A.van Peursen, “Wolff’sPhilosophy of Contingent Reality,” Journal of the History of Philosophy, 25(1987): esp. 75–6.12 Wolff, Ontologia, op. cit., § 872.13 Wolff tediously recites the benefits that earth-dwellers enjoy by virtue of thesun’s existence, e.g. without the sun there could be no sundials and we couldnot detect compass deviations. What about suns (i.e. stars) that do not benefitearth-dwellers? There must be inhabitants of their planets, who do benefitfrom their suns. See also the exciting chapter on the benefits we have from theexistence of air. Vemünftige Gedanken von der Ahsicht der natürlichenDingen, in Gesammelte Werke, op. cit., §§ 28, 44, 46, 60, 85, 91, etpassim.14 Kant, Critique of Practical Reason, trans. L.W.Beck (New York: Macmillan,1993), P. 41.s15 Baumgarten’s Latin Wolffian textbooks were used by Kant in his lectures. Onebook has been translated into English under the name Reflections on Poetry,trans. K.Aschenbrenner and W.B.Holtker (Berkeley: University of CaliforniaPress, 1954).16 Crusius, Weg zur Gewissheit und Zuverlässigkeit der menschlichen Erkenntnis(1747), §§ 5, 9, 10 (hereafter referred to as Logic); Entwurf der notwendigenVernunftwahrheiten (1745), § 234 (hereafter referred to as Metaphysics). Allcitations are to C.A.Crusius, Die philosophischen Hauptwerke, ed. G.Tonelli,4 vols (Hildesheim: Olms, 1987).17 Crusius, Metaphysics, op. cit., § 14.18 Ibid., §§ 56, 57. This startling thesis was accepted by Lambert and by theprecritical Kant in his Only Possible Premise for a Demonstration of theExistence of God, trans. G.Treash, Part I, Observation 2 (New York: Abaris,1979), p. 69; also New Exposition of the First Principles of MetaphysicalKnowledge, in Kant’s Latin Writings, 3rd edn (New York: P.Lang, 1993), p.52.19 Crusius, Logic, op. cit., § 62. Kant does not believe that the Crusiandistinction permits an escape from psychological subjectivity.20 All of these laws except the first two are rejected as “subreptitious axioms” inKant’s Inaugural Dissertation. They result from the application of sensibleconcepts to intelligible objects and are therefore invalid.21 Crusius, Metaphysics, op. cit., §15.22 Kant’s letter to Herz, 21 February 1772, in Kant’s PhilosophicalCorrespondence, ed. A.Zweig (Chicago: University of Chicago Press, 1967),pp. 72–3. Crusius may have been the target of Kant’s attack on“preformationism” in Critique of Pure Reason, B 167–8; see G.Treash, “Kantand Crusius: epigenesis and preformation,” Proceedings of the SixthInternational Kant Congress, II (1989): 95–108.23 Crusius, Logic, op. cit., § 185.24 Crusius is closer to Hume when he speaks of “feeling a compulsion to grantanother thing from which one thing comes” (Metaphysics, op. cit., § 63) butdoes not draw Hume’s skeptical conclusion.25 Crusius, Metaphysics, op. cit., § 31.26 This is the principal theme of Kant’s Essay towards Introducing NegativeMagnitudes into Philosophy (1764), the work that shows more than any otherthe Crusian influence on Kant.27 Crusius, Dissertatio philosophica de usu et limitibus principii rationisdeterminantis, vulgo sufficientis, §§ II, III.28 Crusius, Anweisung vernünftig zu Leben (1744), § 175.29 Kant, Critique of Practical Reason, op. cit., p. 41.30 Crusius, Anweisung vernünftig zu Lehen, § 176.31 Lambert, Anlage zur Architektonic, § 683. This work, published with Kant’said in 1765, aimed to be an ontology for all the sciences, but it lacks thearchitectonic, systematic order which might have come from the successfulapplication of Lambert’s adaptation of Leibniz’s ars characteristica. It is to befound in Lambert’s Philosophische Schriften, ed. H.W.Arndt (Hildeshcim:Olms, 1965), Vols 3 and 4.32 Lambert, “On the Improvement of Method of Proof in Metaphysics,Theology, and Morals,” p. 5. This was an uncompleted draft of a paperLambert apparently intended to submit to the Berlin Academy in the prizecompetition of 1762. It was first published as the Kant-StudienErgänzungsheft (1918). It shows some remarkable kinship with Kant’s prizeessay.33 Lambert to Kant, 3 February 1766, in Kant’s Philosophical Correspondence,op. cit., p. 51.34 Lambert, Abhandlung von Criterium veritatis (1761), § 79, first published inKant-Studien Ergänzungsheft, 36 (1915).35 Joachim Georg Darjes (1714–63), professor in Jena and later in Frankfurt/Oder; originally a disciple of Wolff, he was influenced by Crusius. Thequotation is from Lambert, Anlage zur Architektonic, op. cit., § 11.36 Lambert, Neues Organon, Dianoiologie, §§ 601–5. This work was publishedin two volumes in 1764 and is reprinted as Lambert’s PhilosophischeSchriften, op. cit., Vols 1 and 2.37 Ibid., § 639.38 Ibid., §§ 656–7.39 Ibid., Dianoiologie, § 662.40 This is the subject matter of Kant’s Essay towards the Introduction ofNegative Magnitudes in Philosophy, written under the Crusian influencebefore Kant had read Lambert.41 Lambert, On the Improvement of the Method…, op. cit., § 19 μ; see Lambert,Abhandlung von Criterium veritatis, op. cit., § 92.42 Ibid., notanda 4.43 Lambert, Anlage zur Architektonic, op. cit., § 297.44 Lambert, Neues Organon, op. cit., Alethiologie, § 234a.45 See L.Falkenstein, “Kant, Mendelssohn, Lambert, and the Subjectivity ofTime,” Journal of the History of Philosophy, 29 (1991): 227–52.46 Kant’s Philosophical Correspondence, op. cit., pp. 63, 66.47 Until Lambert’s death it had been Kant’s intention to dedicate the Critique ofPure Reason to him.48 Quotations from Kant, Critique of Pure Reason, A 37, B 53, B 71.49 Kant, On the Form and Principles of the Sensible and the Intelligible World, §24, in Kant’s Latin Writings, op. cit., p. 148.50 Kant, Critique of Pure Reason, A 51=B 75.51 Kant’s Philosophical Correspondence, op. cit., p. 65.52 Tetens, On Universal Speculative Philosophy (1775), pp. 57, 66–7, in Tetens,Philosophische Versuche über die menschliche Natur und ihre Entwickelung(Berlin: Kant Gesellschaft, 1913). Both of Tetens’s works cited are included inthis volume.53 The pervasive influence of the Scots on Tetens has been studied by M.Kuehn inhis comprehensive Scottish Common Sense in Germany, 1768–1800(Montreal: McGill-Queen’s University Press, 1987), ch. 7.54 Tetens, On Universal Speculative Philosophy, op. cit., p. 66.55 Ibid., p. 40. A like use of “transcendent” is found in Lambert (NeuesOrganon, op. cit., Alethiologie, § 48; Anlage zur Architektonic, op. cit., §301). “Transcendent” is not to be confused with Kant’s “transcendental.”56 Tetens, On Universal Speculative Philosophy, op. cit., p. 27. There is a markedresemblance to Crusius here.57 Kant, Critique of Pure Reason, A 99.58 Tetens, On Universal Speculative Philosophy, op. cit., pp. 33–4.59 Ibid., p. 28. Tetens accepts Kant’s distinction between the necessity inherent inintuition and that belonging to “the transcendent principles of reason.” Thushe is at one with Kant in asserting the discontinuity of mathematical andmetaphysical reasoning, citing Kant’s Inaugural Dissertation. See ibid., pp.21–2 n.60 Tetens, Philosophical Essays (1777), in Philosophische Versuche…, op. cit., p.393.61 Ibid., p. 52762 Kants gesammelte Schriften, 29 vols, ed. Deutsche (formerly KöniglichePreussische) Akademie der Wissenschaften (Berlin: de Gruyter [andpredecessors], 1902–), Reflexion 4901, and Vol. 23, pp. 23, 57.63 The best collection of documents is H.Scholz (ed.), Die Hauptschriften zumPantheismusstreit (Berlin: Kant Gesellschaft, 1916). Selections from Scholzhave been translated as The Spinoza Conversations between Lessing andjacobi, trans. G.Vallée et al. (Canham, Md: University Press of America,1988).64 Wolff, B.von S.Sittenlehre widerleget von…Christian Wolff (Leipzig, 1744);Theologia naturalis (1749), Vol. II, §§ 671–716.65 The Teaching of Spinoza in Letters to Moses Mendelssohn, in Scholz, op. cit.,pp. 82–3.66 Ibid., p. 91.67 See, for example, Herder’s God, Some Conversations (1787) (New York:Hafner, 1940).68 Mendelssohn, Morgenstunden, Lesson XIV; Scholz, op. cit., p. 15.69 Scholz, op. cit., p. 307.70 Kant, “What is Orientation in Thinking?” in Kant’s Critique of PracticalReason and Other Writings in Moral Philosophy (Chicago: University ofChicago Press 1949), PP. 303, 305.BIBLIOGRAPHY1.1 Allison, H.E. Lessing and the Enlightenment, Ann Arbor: University ofMichigan Press, 1968.1.2 Anchor, R.E. The Enlightenment Tradition, New York: Harper & Row,1967.1.3 Baeumler, A. Das Irrationalitätsproblem in der Aesthetik und Logik desachtzehnten Jahrhunderts. Darmstadt: Wissen-schaftlicheBuchgesellschaft, 1967. (Originally published as Kant’s Kritik derUrtellskraft, Ihre Geschichte und Systematik, Halle, 1923.)1.4 Beck, L.W. Early German Philosophy: Kant and His Predecessors,Cambridge: Harvard University Press, 1969. Chs XI–XVI.1.5 Beck, L.W. Essays on Kant and Hume, Yale University Press, 1978. Ch. 5:“Analytic and Synthetic Judgments before Kant.”1.6 Beiser, F.C. The Fate of Reason. German Philosophy from Kant to Fichte,Harvard University Press, 1987.1.7 Bossenbrook, W.J. The German Mind, Detroit: Wayne State University Press,1961.1.8 Bruford, W.H. Germany in the Eighteenth Century. The Social Backgroundof the Literary Revival, Cambridge: Cambridge University Press, 1935(reprinted 1965).1.9 Cassirer, E. Das Erkenntnisproblem in der Philosophie und Wissenschaft derneueren Zeit, Darmstadt: Wissenschaftliche Buchgesellschaft, 1971.Volume II.1.10 Cassirer, E. The Philosophy of the Enlightenment, princeton: PrincetonUniversity Press, 1951.1.11 Copleston, F. A History of Philosophy, London: Burns & Oates, 1960.Volume 6: Wolff to Kant.1.12 Edwards, P. (ed.) The Encyclopedia of Philosophy, New York:Macmillan and Free Press, 1967, 8 volumes. (Contains scholarlyarticles and bibliographies on all the philosophers mentioned in thischapter.)1.13 Gawlik, G. and Kreimendahl, L. Hume in der deutschen Aufklärung,Stuttgart: Fromman Hoolzboog, 1987.1.14 Hillebrand, K. German Thought from the Seven Years’ War to Goethe’sDeath, New York: Holt, 1880.1.15 Kantzenbach, F.W. Protestantisches Christentum im Zeitalter derAufklärung, Gütersloh: Mohm, 1965.1.16 Kuehn, M. Scottish Common Sense in Germany, 1768–1800, Kingston andMontreal: McGill-Queen’s University Press, 1987.1.17 Petersen, P. Geschichte der aristotelischen Philosophie im protestantischenDeutschland, Leipzig: Meiner, 1921.1.18 Philipp, W. Das Werden der Aufklärung in theologiegeschichtlicher Sicht,Göttingen: Vanderhoek aund Ruprecht, 1957.1.19 Philipp, W. (ed.) Das Zeitalter der Aufklärung, Bremen: Schünemann, 1963.1.20 Sutton, C. The German Tradition in Philosophy, London: Weidenfeld &Nicolson, 1974.1.21 Tonelli, G. “La Philosophie Allemande de Leibniz á Kant.” In Histoire de laPhilosophie, ed. Y.Beleval, vol. ii, pp. 728–85. Paris: Encylopédie dela Pléiade, 1973.1.22 Wolff, H.M. Die Weltanschauung der deutschen Aufklärung, Bern: Francke,1949.1.23 Wundt, M. Die deutsche Schulmetaphysik im Zeitalter der Aufklärung,Tübingen: Mohr, 1945.1.24 Zeller, E. Geschichte der deutschen Philosophie seit Leibniz,München, 1873.