Leibniz (from) to Kant

From Leibniz to Kant Lewis White Beck INTRODUCTION Had Kant not lived, German philosophy between the death of Leibniz in 1716 and the end of the eighteenth century would have little interest for us, and would remain largely unknown. In Germany between Leibniz and Kant there was no world-class philosopher of the stature of Berkeley, Hume, Reid, Rousseau, Vico, or Condillac. The life and philosophy of Kant, however, raised some not-quite-first-class philosophers to historical importance. 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 we can best orient ourselves in a brief account of eighteenth-century German philosophy by seeing it as a preparation for Kant. Leibniz was the last great philosophical system-builder of the seventeenth century, and his bold speculations and systematic wholeness were more characteristic of the seventeenth- than of the eighteenthcentury philosophers. His peers were Descartes, Malebranche, Arnauld, Hobbes, Locke, and Spinoza, and in comprehensiveness and variety of genius he surpassed each of them. His system had an answer to almost every question put to it; he was said to be “an academy of science all by himself,” and the principal objection to his grand baroque philosophical system was that it was—simply unbelievable. To accept it all would have required a speculative faith and a blind confidence in the metaphysical powers of the human mind that few philosophers of the eighteenth century could muster. Christian Wolff, his most important disciple, did not make a summa of Leibniz’s philosophy, but both his followers and opponents saw Wolff as doing precisely that. They accordingly called his philosophy the “Leibniz-Wolffian philosophy,” a name which has become fixed in spite of both Leibniz and Wolff ’s renunciation of it. Modern scholarship shows the degree to which this tide is inappropriate,1 yet the Leibniz-Wolffian philosophy was the dominant intellectual system and movement in Germany from about 1720 to about 1754, the death of Wolff, and it provided the main opposition to Kant’s philosophy until near the end of the century. The rise and fall of the Leibniz-Wolffian philosophy in its controversies with its opponents is the subject matter of this chapter. I deal almost exclusively with topics now important chiefly for an understanding of Kant and German Idealism. But before we turn to these topics, something must be said about the general climate of opinion in Germany at this time. In all Protestant countries of western Europe, there was an intellectual awakening called the Enlightenment. “Enlightenment,” Kant wrote, “is man’s release from his self-incurred tutelage.” Tutelage is allowing or requiring someone else to do one’s thinking, and it is self-incurred because most human beings do not develop the skill and the courage to use their own reason. They surrender their freedom to those who will think for them in matters political, religious, and moral. Kant did not believe he lived in “an enlightened age,” but did say he lived in an “age of enlightenment” when progress was being made to independent thought. But the specific forms that Enlightenment took varied from country to country; it depended upon the particular form of tutelage in each country, from which thinkers strove to emancipate themselves. The German Enlightenment took place in a feudal environment of scores of small absolute monarchies in which Lutheran passive obedience and the eye of the local monarch ensured that the established order of things was regarded with sacred awe by the Bürger.2 While the philosophes of France were not merely anti-clerical but also antireligious (materialists, atheists, freethinkers, skeptics), what was unique to the German Enlightenment was that it originally had a profoundly religious motive. Pietism was a religious awakening at the end of the seventeenth century which had much in common with the persecuted Jansenist sect in France and the Methodist movement still to come in England. Pietism meant a return to a simpler form of Lutheranism, emphasizing the emotional and moral rather than the ritual and dogmatic aspects of the established churches. Instead of churches, there were evening gatherings in the homes of individual Pietists for communal devotion; every man was a priest, drawing inspiration from his own reading of scripture and applying its lessons to everyday life. Though the movement was not free of irrational elements, it was enlightened in encourag-ing its members not to defer to someone else who would do their thinking for them. Naturally all this produced plurality of opinion and diversity of faith, but its emphasis upon good works (establishing schools and orphanages, for instance) brought it in line with the Enlightenment movement in other countries where the motivation was perhaps more intellectual and political. There were, in fact, two Enlightenments in Germany. Besides the intellectual Enlightenment pursued by the Leibniz-Wolffian philosophers, there was also a Pietistic Enlightenment. Surprisingly they both originated in the same place, the University of Halle, a Pietistic institution founded by the Elector of Brandenburg primarily for the training of the bureaucracy required 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 of education was that it raise not the cloistered scholar but the honnête homme, imitating France in “polite learning, beauty of mind, good taste, and gallantry.” In order to reach a larger audience, he lectured and wrote most of his books in German, not Latin. He claimed academic freedom, taught religious toleration, and attempted to reform legal practices by outlawing torture and removing heresy and witchcraft from the reach of the law. As a Pietist he did not doubt the authority and authenticity of revelation, but he established the basis of law in ethics, ultimately in reason and experience. Pietism is almost always associated with an occult and quasi-mystical philosophy of nature, and this kept the German Enlightenment Pietists from participating in the great scientific revolution at the end of the seventeenth century. Unfortunately Wolff and Thomasius were on a collision course. Intellectually they were not in serious disagreement on most substantive questions (though their interests were widely divergent). Personally their relations were correct, though not close. Thomasius apparently took no part in the ignoble campaign which drove Wolff from Halle just as he had himself been driven from Leipzig. But their disciples carried on a running controversy for the next forty years, and it was marked by odium theologicum and general nastiness on both sides. WOLFF Life and works Christian Wolff was born in Breslau in 1679. With support from Leibniz he was appointed lecturer in mathematics at the University of Leipzig in 1702 and, four years later, professor of mathematics at the University of Halle. Wolff was no creative mathematician, but he found in mathematics the model for rigorous thinking in other fields. In this he simply followed the lead of Descartes and Leibniz. Soon Wolff was teaching and writing philosophy, philosophy then meaning both the natural sciences and the subject which is today called philosophy. He published copiously on the experimental sciences and also on logic, metaphysics, cosmology, psychology, political theory, and natural theology in a series of large German books, most of which were entitled Vernünftige Gedanken (“Rational Thoughts”) on the different areas of knowledge.3 The contents and expository skill of these books led to their widespread acceptance as textbooks. His successes in publishing extensively used books, and his victories in the annual competition for paying students, incited intense rivalry between Wolff and the less successful Thomasian Pietist professors. They seized the opportunity to charge Wolff with heresy when he held, in a public lecture as rector of the university, that the resemblances between Chinese and Western ethics showed that ethics was based on universal human reason and human nature, not on divine revelation vouchsafed only to Western civilization. They represented to the King of Prussia, Frederick William I, that Wolff ’s determinism and fatalism meant that he should not punish deserters from his army because, being determined, they could not have helped doing what they had in fact done. Enraged by this lèse-majesté, the choleric King dismissed Wolff and threatened 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 by an international student body, more of whom could understand Latin than German, he repeated and expanded his series of Vernünftige Gedanken into large volumes of scholastic Latin addressed to an international readership. So great was his fame, and so scandalous had been the behavior of Frederick William I and his “Tobacco Cabinet,” that efforts were repeatedly made to recall him to Prussia. He returned only in 1740 when the new King, Frederick the Great, made him chancellor of the University of Halle and granted him a patent of nobility and a large stipend. At the time of his death in 1754 he was certainly the best-known thinker in Germany, fully deserving the honorific title of Praeceptor Germaniae. The mathematical ideal in philosophy4 Hobbes, Descartes, Spinoza, and Leibniz all shared a common ideal for philosophy, that it should attain the clarity and certainty hitherto available only in mathematics. Wolff is quite explicit about the relation of mathematics to philosophy. “The rules of mathematical method,” he says,5 are the same as the rules of philosophical method…. The identity of philosophical and mathematical method will be a surprise only to one who does not know the common source from which the rules of both mathematics and philosophy are derived. This common source is “true logic” or “natural logic” of the workings of the human mind, not a finished logic which is itself a science. Lest the identity of philosophy and mathematics appear to be wholly quixotic, it is essential to remember that “philosophy” and “mathematics” did not then mean exactly what they mean now. Philosophy, well into the eighteenth century, included the sciences; and though work of the highest kind in pure mathematics was being performed by Leibniz and Lambert and others, the mathematics that was the cultural model for the Enlightenment was applied (or, as it was then called, “mixed”) mathematics. Wolff’s mathematical works contain far more information about astronomy, meteorology, geodesies, and even architecture than they do topics in pure mathematics. The root idea of the mathematical model is that computation and measurement are essential to any body of advanced scientific knowledge. In the true method, formulated by Descartes and followed with little change by Wolff, everything certain in our thoughts depends upon the order of our thoughts, a step-wise procedure of moving from the simplest and 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). The product of a définition is a clear and distinct idea, evident to attention and communicable to others. Mathematical theorems are demonstrated by analysis of the contents of definitions and axioms, demonstration taking the form of showing that an alternative to a true theorem is selfcontradictory or contradictory to another established truth. In the syllabus for his mathematics lectures in 17316 Wolff tried to show both the importance and the inadequacy of mathematical knowledge. Mathematics deals only with the observable phenomena in space and time (which are subjective), and it operates with images; ontology, on the other hand, deals with being qua being and replaces images with exact concepts. How well did the mathematical ideal stand? In 1762 the Royal Academy of Sciences in Berlin offered a prize for the best essay on the question: ‘Whether metaphysical judgments generally, and in particular the fundamental principles of natural theology and morals, are capable of proofs as evident as those of geometry?” A disciple of Wolff, Moses Mendelssohn, took the prize with an essay giving an affirmative answer, with which Wolff would have agreed. The runner-up, with a negative answer, was the unknown Immanuel Kant. In this respect history has followed Kant, not Wolff and Mendelssohn. The marriage of reason and experience One of the perennial problems of philosophy is to determine the roles of reason and experience in knowing. In the seventeenth and eighteenth centuries it was the subject of controversy between philosophers we now call rationalists and those we call empiricists. Among the empiricists we count Locke, Berkeley, Hume, Reid, and Condillac; among the rationalists, Descartes, Malebranche, Spinoza, and Leibniz. Wolff is sometimes considered the arch-rationalist, but we must enquire into the kind of rationalist he was.7 A rationalist like those just listed believes that reason alone, or rational intuition, is able to discover truths that are independent of experience and that could not be learned from experience, but that necessarily apply to experience. Such truths have been called, 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; he says that there is no human pure reason devoid of sense content; he agrees with the Scholastic teaching, “There is nothing in the intellect that was not first in sense.” He rejects the theory of innate ideas, which has always been one of the principal tenets of the rationalist school. Hence Wolff may seem to be no rationalist at all; he is not a rationalist in the strictly defined sense of the preceding paragraph, but his style and vocabulary give a rationalistic veneer to his thoughts because he seems to generate a priori knowledge by improving upon empirical knowledge. He attempted (successfully, in his own judgment) to derive the principle of sufficient reason from the law of contradiction.8 Leibniz had attempted to keep these two principles separate and independent of each other, and had ascribed each to a very different metaphysical source (respectively the will and the intellect of God). Wolff, on the contrary, contends that it is a logical truth that every true judgment has a sufficient reason for being true. Though Wolff does not claim to derive empirical truths from the principle of sufficient reason (and, ultimately, from the law of contradiction), he does claim (and makes good his claim) to be able to give a 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 in parallel with Aristotle’s distinction (Posterior Analytics, Book I, ch. 13) between knowledge of fact and knowledge of reasoned fact. Historical knowledge is knowledge based on the perception of a raw fact, something existing or happening. But by memory, classification, measurement, hypothesis-formation, and perhaps simple experiments we clarify our knowledge of a fact by seeing it as a “certain kind” of fact. The ideas of sense become ideas of reason (the vernünftige Gedanken of Wolff’s book titles), reason being the capacity for “seeing with the mind’s eye” the connections of ideas and their sufficient conditions. All the knowledge that reason has or produces comes from experience - historical knowledge is the basis of philosophical knowledge—but it is so processed by reason into definitions, principles, axioms, probable hypotheses, and well-tested laws of nature that a subtle change is introduced into our historical knowledge of fact: knowledge of fact becomes knowledge of reasoned fact. Going beyond what has been actually observed, knowledge of reasoned fact extends to facts not yet experienced. Wolff likes to say that there is a marriage 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 of fact to principles and reasons is the analytical method of Descartes (Kant’s regressive method); the descent from reason to experience is Descartes’s synthetic (Kant’s progressive) method. The knowledge of reasoned fact was commonly in Wolff’s day called a priori knowledge10 (knowledge from reason, not experience), even though for Wolff its ultimate and irreplaceable source is experience. We can now summarize Wolff’s kind of rationalism. He is not a rationalist in the sense of the belief that pure reason without need of experience can produce a priori knowledge (in mathematics and metaphysics, for example). He is a rationalist in a loose sense in that he emphasizes the function of reason in converting raw data of the senses into reasonable knowledge. With his armies of syllogisms in valiant array, Wolff demonstrated everything from the existence of God to theories in astronomy; he proves that German coffee houses should be modeled after those of England. No wonder Wolff is generally thought of as a rationalist! Ontology and special metaphysics The keystone of Wolff’s stupendous edifice is his First Philosophy, or Ontology, published in Latin in 1729. In 1720 he had published a volume sometimes known as the German Metaphysics whose accurate and instructive 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, demonstrative knowledge of what it is that makes something possible if it is possible and actual if it is actual. It is like Aristotle’s “First Philosophy” which deals with being qua being (Metaphysics, Book IV, ch.1). Ontology deals with questions and concepts common to all branches of knowledge. Questions about the various kinds of being are reserved for the several volumes on special metaphysics, viz., the being of God, the existence of whom follows only from his possibility (the ontological argument), the being of the soul, and the being of the world. The actual world and the actual soul are made actual by “a complement of possibility”11 which renders possible things actual. Kant destroyed this connection of possibility and actuality by asking the question: Is the complement possible? If it is not, it is impossible and cannot serve the purpose. If it is, it is just another possibility and contributes nothing toward actuality. There is no valid inference from possibility 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 of metaphysical 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, and compared in an almost mechanical procedure. One of the most important concepts is that of substance, defined as follows: “What contains in itself a principium [roughly: a cause] of changes is a substance.”12 Each substance contains in itself a sufficient condition for a change in itself or in other substances. If the change is motion, the monad is a physical substance; if the change is mental, the monad is a spiritual substance. Only one substance contains the cause of its own being, and that substance is God. Thus arise the three divisions of special metaphysics: rational theology, rational psychology, and rational cosmology. It will be noticed that Wolff is closer to Descartes than to Leibniz, who had asserted that all substances are spiritual and had denied that one substance could cause a change in another. Wolff, very tentatively, holds the doctrine of pre-established harmony only for the case of relations between mind and body monads. Wolff follows Leibniz in denying absolute Newtonian space, and agrees with Leibniz that space is a subjective order of appearances of substances. He holds a mechanical view of nature, which consists of simple unextended physical monads interacting by contact with each other, the whole showing intelligent design and especially purposiveness for human benefit.13 The soul is a simple substance with a vis repraesentativa or a power of being conscious; the soul is immortal and the will free. Like Leibniz in his Theodicy, Wolff strove to reconcile freedom and necessity, but with equal ill-success. Moral philosophy Wolff wrote more on practical philosophy (ethics and law) than on any other subject. There is little new in Wolff’s theory, but it is superbly organized and undoubtedly influenced Kant’s articulation of ethical theory in his Metaphysics of Morals. Kant cites Wolff as the exemplary representative of the best of the four types of heteronomous ethics, the ethics of perfection.14 The intellect conceives of a perfection, which is the value aspect of truth as the perfect harmony and interconnection of the essential attributes of a thing following from its intrinsic essence. True being (as object of knowledge) and true good (as object of desire) are identified. The will necessarily strives for a perfection which the intellect has discerned. Rational willing is definitive of morality. The achievement of a perfection is attended with pleasure, but the test for an action is not its consequent pleasure, but its rational motivation and justification. Natural law requires that each person strive to achieve their own perfection and also that of others. Revelation is not required to teach men their duties, nor is the promise of divine reward needful to move people to do the good. The completion of Wolff’s system in aesthetics A great gap in Wolff’s system was the lack of a theory of beauty and fine art. The last decade of Wolff’s life was a time of extensive literary dispute concerning matters of taste. There were controversies between defenders of the classical forms and harbingers of the romanticism that was yet to come. There was great competition between those who would emulate French drama and those in favor of English models, and still others (e.g. Lessing) who wanted to develop a native drama with German themes. It is easy to see why a comprehensive philosophical movement like Wolffianism should be concerned to develop a theory of art, in spite of the fact that there certainly are few philosophical theories less likely than Wolff’s to be fruitful concerning beauty and art. Wolffian theories of art were produced by two disciples, Alexander Baumgarten of Halle (later Frankfurt on the Oder) and Moses Mendelssohn of Berlin. . Baumgarten15 In Leibniz-Wolffian philosophy the perfection of sense would be achieved when a sensuous idea was so clarified and rendered so distinct that it would become an abstract intellectual idea. Indeed the entire Wolffian program may be summed up in Wolff’s efforts to replace facts given in sense with reasoned facts from which the unique, ineffable content of sense had been evaporated. The perfection of sense is reason, and there is only a difference of degree between the clarity of reason and obscurity of sense. To raise the perfection of sense means: to replace percepts with concepts. This feature of Wolffian rationalism made it indifferent to the arts, for the artist is one whose skill makes it possible to achieve a perfection of sense which is the object of a perfect, direct intuition, not object of abstract thought got at by omitting the specificities of a singular perception. According to Baumgarten sensation can be perfected by so enhancing its vividness and clarity that there will be pleasure in its mere contemplation. The irreducible sensory component in such a perception is called the aesthetic and the intuitive by Baumgarten. Sense, which is the lower cognitive faculty, is the higher faculty in the contemplation of beauty. A perfection (of form, color, sound) apprehended by sense instead of by reason is beauty. Aesthetics is the “science of the beautiful.” Mendelssohn In 1755 Moses Mendelssohn published On Feelings (Empfindungen), a modification of Baumgarten’s views which marks a sharp advance in the direction of Kant’s mature aesthetic theory and the aesthetic theory of the later idealists and romantics. The human mind, he holds, is too limited to be able to sensuously observe the variety-in-unity of ontological perfections, which is discernible only by reason. Thus far Mendelssohn stands with Wolff and Baumgarten, but he now adds: we can sensuously contemplate the variety in unity of the mind’s own acts and passions, sensations, thoughts, and emotions. He calls this the “harmony of the powers of the soul.” The directly felt perfection of perceiving, not the perception of an antecedent perfection in the perceived object, gives rise to disinterested aesthetic pleasure in the harmonious play of our faculties. Mendelssohn here makes an important and permanent contribution to the history of art and aesthetic theory. He teaches that beauty is not predicated upon an objective perfection (of color, design, morals, or whatever is found in the work of art); it is a perfection of perception, not a perception of perfection. Pleasure usually accompanies the satisfaction of some previously existing desire, but art and beauty are not normally enjoyed because of the pleasure they afford by satisfying some antecedent desire. In addition to perception and will, each with its own attendant pleasure, there is another faculty of the mind which has its own peculiar pleasure. This faculty Mendelssohn calls feeling or approval (Billigungsvermögen) by which we experience “disinterested pleasure,” a pleasure different from that of satisfied desire or curiosity. Mendelssohn explains this pleasure by our satisfaction in the harmonious function of all the Seelenkräfte, when feeling and willing and perceiving go together to produce a delectable state of mind. Each person’s taste will be affected by their physical and even physiological make-up, but with the advance of education and general culture more pervasive satisfactions will replace the doctrine of à chacun son gout. This harmony of the powers of the soul is involved in both the enjoyment of art and its creation by genius. Genius is an “imitator of divinity,” a “second creator.” CRUSIUS The Pietist campaign against Wolff was fought on two levels. Motivated by odium theologicum, envy, and nepotism as well as by genuine concern incited by Wolff ’s apparent affinity with Spinozistic pantheism and fatalism, the Halle Thomasians Budde, Lange, and Walch conducted a dirty campaign that continued even after Wolff had been banished. But these Thomasians, like Thomasius himself, were not systematic philosophers of Wolff’s caliber; they found fault with Wolff, but offered no interesting alternative. The most important alternative was that of Crusius. 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 were Lutheran clergymen, and he held professorships in both philosophy and theology and was a pastor holding important posts in the Lutheran hierarchy. About 1750 he gave up philosophical work altogether and devoted himself to theological and biblical studies and the care of souls. In place of mathematics,16 Crusius thought of theology as the science whose relations to philosophy must be understood. Philosophy, according to him, is not a sufficient ground for religious faith and human virtue; it is not even essential to the conceptualization of theological truth, since the truths established in philosophy may be overturned by the greater authority of theology. “We cannot think something” was the mark for the impossible among most Enlightenment philosophers, but for Crusius there were conditions under which the inference from inconceivability to impossibility may be suspended: if the thing inconceivable by us may be conceivable by a more perfect mind, or if “We recognize an obligation to regard something inconceivable as possible or actual in order not to act contrary to the most important rules of human perfection” (which include, of course, revelations of the commands of God).17 From all this it is easily seen how opposed Crusius was to Wolff. Wolff as a leader of the intellectual Enlightenment was bent upon extending the scope and power of human reason and denying any constraints upon it; Crusius as a leader of Pietistic thought was more concerned to restrain the ambition to explain everything; he tried to determine and fix the boundaries of human intellect when dealing with the brute facticity of the contingent world and the mysteries of religion. That he did so without the obscurantism of the early Thomasians, by developing a sophisticated epistemology as an alternative to Wolff, is a mark of near greatness in this almost forgotten man. Ontology and theory of knowledge For Crusius existence, not possibility, is the fundamental concept. In this he differs markedly from Wolff, who asks what is the ground of the possibility of something prior to asking what it is that makes it actual if it is actual. Wolff’s answer to this question concerns logical possibility, i.e. non-self-contradictoriness. Crusius’s ontology is to challenge Wolff’s account of the role of logical possibility in the explanation of existence. We reach the concept of possibility by first finding existent things and then, by “an abstraction from existence” (the reverse of the “complement of possibility”), we find that whatever exists is also possible, but not the converse. If nothing existed, nothing would be even possible. The concept of possibility requires the concept of existence, but not the converse.18 Crusius is here speaking, obviously, of what he calls real possibility, not ideal possibility (i.e. possibility of being thought, because noncontradictory). Real possibility is the possibility inhering in things that might exist outside and beyond our thought of something merely noncontradictory. There can be this real possibility only if there are in the world existing things with forces adequate to bring about the actualization of this possibility. Understanding has the inexplicable faculty of being conscious of ideas. Reason is the perfection of understanding, consciously recognizing truth as truth. Two activities of reason are to be distinguished; reason in concreto, which is the capacity functioning in a single individual with their various quirks and dispositions; and reason in abstracto, which is the “complex” of the essential forces of human understanding in general. Only reason in abstracto is capable of objective knowledge.19 By a kind of denudation we find simplicity and clarity in sensations and other representations. We remove in thought all accidental properties of things, and we are left only with the essential relations that things necessarily bear to one another. Besides noncontradiction and identity there are relations that show the ultimate unanalyzable real forces of things. There is intuitive knowledge of simple, clear, and necessary relations of ideas stated by Crusius as basic laws of thought. Instead of Wolff’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 without something else cannot exist without that other (Metaphysics, § 15); (b) The law of incompatibles: Whatever cannot be thought in connection with another 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 of contingence: That whose nonbeing may be conceived may at some time have not existed (§ 33).20 These laws are based upon “the nature of human ” which is “the supreme criterion of possible and actual things.”21 Kant thinks that Crusius’s epistemological principles can correspond to ontological truths only if there is a pre-established harmony between the knower and the known.22 Crusius, of course, will not accept this Leibnizian theory, but he states repeatedly that God has “placed the marks of truth in the human understanding.”23 Freedom and the principle of sufficient reason The principle of sufficient reason is not listed among the basic laws of thought. Though a valid principle it is not an independent principle; it is, rather, a corollary deduced from the law of the inseparable. Crusius, who certainly had not read Hume, states that we cannot think of a happening or a coming-to-be without associating it, in intuition, with some other precedent event. (Hume, of course, about the same time flatly denied this impossibility.)24 But Crusius says: “Anyone who observes himself clearly sees that nothing that comes to be may be thought except when one at the same time admits that there is another thing that has power sufficient to produce it.”25 He concludes, like Hume, that causation is neither analytically necessary nor an empirical generalization, but he does not draw Hume’s skeptical conclusion. For any coming-to-be we search for a substance or thing that has the force or power (otherwise inscrutable) to bring this about. Reason must accept the forces and powers it empirically discovers in nature without thinking that they are logically necessary.26 The law of efficient causation shown in the previous paragraphs to be a corollary of the law of the inseparable has several corollaries of its own, and they may be collectively called the law of sufficient reason. Crusius’s Latin Dissertation on the Use and Limits of the Principle of Determining Reason, Commonly Called Sufficient Reason (1743) is based on his unwavering adherence to the freedom of the will, but uncompromising rejection of any theory of freedom of the will compatible with the Wolffian principle of sufficient reason. He distinguishes between determining reason and sufficient reason. The former is a reason which makes its consequence uniquely necessary, and that principle underlies determinism and fatalism. But that principle, he holds, is not demonstrable by the principle of contradiction, and therefore is not universally valid. A sufficient reason,27 on the contrary, may have diverse consequences, and is compatible with freedom of the will. Crusius’s “solution” to the problem of free will is one of the standard ones: nature is the realm of strict determinism, but man is an exception to this rule of the law of determining reason. He believed that the will is free and therefore believed he had to relax the strict principle of determinant reason and accept the looser condition of sufficient reason. Then the same conditions may be “sufficient” for me to do A or to do B, and whichever I do I freely do because these reasons for A or B are supplemented by a free human 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 epistemological conclusions when they conflict with faith and morals. This was not the first time, nor will it be the last, when moral conviction takes precedence over logical analysis. Virtue is the agreement of human actions with the commands of God.28 Hence Kant correctly lists Crusius as the exemplary representative of “theological moralists” who hold (correctly) that there is an objective standard of morality but also (incorrectly) that the standard lies in the will of God instead of in the rational will of man.29 Having established (to his satisfaction) the freedom of the will as the capacity for absolute spontaneity of action, Crusius believed that he had established the only possible foundation for imputing responsibility and for 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 pure moral motive, like respect for the moral law in Kant. For guidance in morality man has an inborn conscience and a will to virtue. Since mankind and its moral perfection are the final end of God, we human beings can believe 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 the young Crusius gave up his philosophical career after only twelve years. Theology’s gain was philosophy’s loss. LAMBERT Johann Heinrich Lambert was born in Mühlhausen, Alsace, in 1728. Unlike Wolff he was a creative mathematician; he was the first to demonstrate that e and (pi) are irrational numbers, and he was a pioneer in non-Euclidian geometry. He is generally regarded as the father of the science of photometry, and his name is commemorated in the “Lambert- Beer law” of the absorption of light, and in the name of a fundamental unit of illumination, the “lambert.” Mathematics and simple ideas Lambert speaks as an almost fanatical mathematician when he says: “What cannot be weighed and calculated doesn’t concern me. I understand nothing 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 a matter of bringing the other half.”32 The half Wolff had brought in was the method of definition and proof, but he did not bring to philosophy the part of mathematics which concerns intuition, postulation, hypothesis, and construction; by taking arbitrary definitions “as it were, gratis,” “without noticing it he hid all the difficulties in them.”33 When Lambert first read Euclid, long after he had studied Wolff’s theory of geometry, he was astonished, he says,34 to find that Euclid had begun with simple, clear, and distinct intuitions of lines, points, and angles, and not (as Wolff had done) with nominal definitions, the applicability of which to figures in space was at least questionable. He thought that Wolff had done nothing to establish die truth of his premises and correspondence between theorems and the actual structure of figures in space. Still, “The honor of bringing the right method into philosophy was reserved for Wolff,” he says. “Whoever wants to profit most from Wolff’s writings should begin with them, and then survey writings which more or less diverge from his. I do not hesitate to include here [the works of] Darjes35 and Crusius.” But the most Wolff could establish was the possibility, not the necessity and objective reference, of mathematical knowledge. 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 and scientific knowledge of things.36 Scientific knowledge establishes clear and distinct ideas of experience and supplements them with hypothetical Lehrbegriffe. Lambert then asks: to what extent can scientific knowledge be a priori?, using the term a priori in a stricter sense than Wolff, and approximating Kant’s usage to refer to concepts that could not have arisen out of experience.37 Experience is only the occasion of our having a priori knowledge,38 but it is experience that gives existential reference to a priori knowledge which, without experience, is limited to the possible and the necessary. Though we suppose that it applies to the actual, the specificities of the actual - i.e. which possibilities are actual in this world—are not known 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, and by means of which, Lambert believes we have a priori knowledge. Simple ideas are said to have only one (atomic) predicate; they are equivalent 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 the mind of a solipsist, and so are not dependent on the real existence of their objects. What is most important about simple ideas is not their identities but their necessary and possible connections such as “what is solid is extended” and “cogito ergo sum.” It is by virtue of these relations that we escape from an endless series of mere tautologies and, through combining them, formulate the sets of simple ideas which underlie, a priori, the various sciences. In true Leibnizian spirit of the ars characteristica, the more we can analyze empirical concepts into simple ones and empirical judgments into tautologies or possible combinations, the more our knowledge is a priori. The relations of simple ideas through comparison and combination are submitted to the criterion of thinkability (Gedenkbarkeit, like Crusius’s inseparability—which Lambert calls combinability—and incompatibility), and each combination can be the a priori foundation of some science; each actual science can be submitted to the analytical discovery of what its simple, a priori ideas are. These simple ideas are called Grundbegriffe. Geometry is the science of simple ideas of extension 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 on simple ideas of a thinking being and Locke’s ideas of reflection. This gives rise to metaphysical knowledge which in point of certainty is on a par with geometry.39 Lambert and Crusius were the first among our philosophers to see the problematic aspect, yet also the extreme importance, of understanding necessary relations between simple ideas. No longer can the Wolffians equate impossibility with logical contradictoriness. Not all opposition is opposition of contradictories.40 The necessity dependent upon the principle of contradiction is confined to the components of complex ideas, established by arbitrary definitions. It was the Wolffians’ goal to show that all necessity was logical necessity, and all impossibility was logical incompatibility; 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 the possibility of combining two [simple] ideas) has not been fully discovered.”41 It had hardly even been noticed, and it will not have been “fully discovered” until Kant will have generalized the problem into the question: How are synthetic judgments a priori possible? Lambert himself attempted to find the fons of the necessary connections among simple ideas. There is in our minds, he held, an actus reflexus, a comparing of simple ideas which, in some unexplained way, gives rise to knowledge of their possible and/or necessary connections and combinations. Comparison is the fundamental actus reflexus of mind which is involved in analysis and synthesis of ideas.42 In ways Lambert does not explain, out of the similarity and difference of simple ideas there issue necessary relational ideas, which indicate which simple ideas are validly synthesizable with others. This is not logical inference (where “synthesizable with” means “not contradictory to”); it involves an intuition, and in so concluding Lambert makes little or no progress beyond Crusius. Nor were Lambert’s efforts to avoid phenomenalism (and indeed solipsism) any more successful. Holding that possibility presupposes the actual existence of something, Lambert fallaciously thinks that it must be existence extra mentem.43 He eventually follows Malebranche in calling upon God to give metaphysical status to some of our ideas.44 In spite of the influence of Locke and his proximity to Kant, Lambert is a metaphysician in the grand style, and his epistemological acuteness does not restrain his speculative passions. Lambert’s correspondence with Kant Lambert published his Cosmological Letters in 1761. It has a rather curious history. It was a product of a sudden aperçu which Lambert had into the structure of the heavens. He saw analogies between planetary systems and galaxies. Kant had presented somewhat the same plan in his Universal Natural History and Theory of the Heavens (1755) but had introduced a cyclical evolutionary dimension on the origin and dissolution of astronomical structures. This theory is now known as the Kant-LaPlace hypothesis on the origin of the solar system. This classic in the history of astronomy was almost unknown at the time because of the bankruptcy of Kant’s publisher. When Lambert read Kant’s Only Possible Premise for a Demonstration of the Existence of God (1764), which contained a brief account of Kant’s astronomical views, he wrote to Kant exculpating himself for the apparent plagiary, expressed contempt for the belletrist philosophers in Berlin, and invited Kant to enter a philosophical correspondence with him. Lambert really does philosophy in his letters and is anxious to involve Kant in his plans; Kant, always a reluctant letter writer, fills his letters with politesse but does not engage with Lambert in any serious philosophical rumination. In September 1770, Kant sent Lambert a copy of his Inaugural Dissertation, On the Form and Principles of the Sensible and Intelligible World. 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 letter which shows that he had a good understanding of Kant’s Inaugural Dissertation. In it he disagreed with Kant on the nature of time and on the method 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 in themselves (noumena). It is an error in philosophy to apply predicates of sensible knowledge to objects of intellectual representation; there is (in Lambert’s terminology) an absolute gap between ontology and phenomenology. Time and space are a priori forms of both pure and empirical sensible knowledge; therefore neither space nor time nor any predicates presupposing space or time may be applied to the reality of things as they are in themselves. Lambert’s most explicit objection was to the “unreal” state to which time was condemned in the Dissertation.45 He tells Kant: “If time is unreal, then no change can be real…. Till now I have not been able to deny all reality to time and space, or to consider them mere images and Schein.”46 To his regret, Kant did not answer Lambert’s letter, but after Lambert’s death in 177747. he replied, in § 7 of the Critique of Pure Reason, saying: “I grant the whole argument. Certainly time is something real, namely die real form of inner intuition.” If, on the other hand, we take time and space to be transcendentally real, the status of bodies in time and space is “degraded to mere illusion (Schein)” and “the good Berkeley cannot be blamed” for so degrading diem.48 Kant’s response to lambert in the Critique is to show that the transcendental reality of time, which lambert desiderated, leads to subjective idealism (illusionism) which lambert rejected. Lambert’s second major objection to the Inaugural Dissertation anticipated a major shift of view between the Dissertation and the first Critique. Anticipated, yes; occasioned, perhaps not, though we do not know. Lambert’s assertion of continuity between phenomenology and ontology conflicted with what Kant called “the all-important rule” in metaphysical thinking: “Carefully prevent the principles proper to sensitive cognition from passing their boundaries and affecting intellectual cognition.”49 This rule was rescinded in the Critique of Pure Reason in the famous sentence: “Thoughts without content are empty, intuitions without concepts are blind.”50 Here “content” means sensible intuitions, and Kant is here saying that no exertion of thought can produce knowledge if there is no sensible intuition. The most decisive factor in this reversal was Kant’s discovery (aided no doubt by his reading of Tetens) that without sensible intuition there can be no synthesis of concepts and hence no judgments. The Inaugural Dissertation had kept separated what the first Critique would tightly bind together. So much, then, for Kant’s thinking that he would never have to change what he thought in 1770! Whether Lambert’s obiter dicta had anything to do with this turnabout in Kant’s thinking is doubtful, yet the weighty remark of a man Kant so much admired may have had an influence on him. Lambert says: It is also useful in ontology to take up concepts borrowed from appearance (Schein), since the theory must finally be applied to phenomena again. For that is how the astronomer begins, with the phenomenon: deriving his theory of the construction of the world from phenomena, he applies it again to phenomena and their predictions in his ephemerides. In metaphysics, where the problem of appearance (Schein) is so essential, the method of the astronomer will surely be the safest.51 Could there here lie the seed of Kant’s Copernican analogy? TETENS Johann Nicolaus Tetens was born in Schleswig in 1736 or 1738. His teacher at the University of Kiel, Johann Christian Eschenbach, was the German translator of Berkeley, and from him must have come much of the extensive knowledge of, and sympathy for, British philosophy which Tetens so obviously shows. Tetens was professor at Kiel from 1776 to 1789, when he entered the service of the King of Denmark. He had a distinguished career as a minister of finance until his death in 1807. Tetens’s empiridstic orientation Tetens was sometimes alluded to as “the German Locke.” He repeatedly says that “We must go back to the path trodden by Locke” and build on his “physiology (Physic) of the human understanding.”52 He thought that Locke’s “plain, historical method” must be practiced, deriving all our ideas from experience. But he also thought that the British (especially Bacon, Locke, and Hume) had interpreted empirical knowledge as a mere collection of observations, had minimized the role of theory and logical form in their theories of knowledge, and had never been able to develop a systematic speculative philosophy or ontology. Reid, Oswald, and Beattie likewise had failed to develop an ontology which would enable them to systematize their common-sense philosophy, and this had kept them from penetrating very deeply into explanations of the mental process underlying common-sense knowledge and everyday practice. Tetens does not oppose the common-sense philosophers as he does Hume, but sees his own task rather to be that of securing and clarifying the philosophy of common sense. He is so committed to Locke, however, that he never concerns himself with Reid’s opposition to “the new way of ideas,” which is Reid’s preeminent claim to historical importance. Tetens writes contentedly of impressions and ideas just as if Reid had never thrown doubt on the entire movement from Descartes to its denouement in Berkeley, Hume, and unnamed “solipsists” in France.53 The possibility of metaphysics In his Universal Speculative Philosophy Tetens asked the fundamental Kantian question: Is metaphysics possible? He asked: “Are the times right for systems of philosophy? Can one be more than an observing philosophical raisonneur?”54 Since Wolff, special metaphysics had been about either spiritual substances (God and the soul) or material substance. Rational theology, rational psychology, and rational cosmology each has its own fundamental concepts and principles, but they share some in common. Tetens calls the study of these common elements transcendent philosophy because it transcends the three divisions of special metaphysics.55 It is first philosophy, ontology, Grundwissenschaft. Transcendent philosophy, however, is no longer to be the abstract, formal, almost lexicographical ontology of Wolff. It is, rather, epistemology (though the word did not exist in Tetens’s lifetime). It is an empirical science, even though practiced in the armchair. What begins in the empirical sciences may end up in the a priori science of ontology. When Tetens says, for instance, that “Nothing comes from nothing,” he is formulating an objectively necessary principle of transcendent philosophy. But he sees the same judgment as an assertion of his reason, and he interprets it as an empirical proposition asserting only that his reason cannot think that something comes from nothing.56 How can this empirical, contingent judgment (even if true) serve (as it did for Crusius and Lambert as well as for Tetens) as a warrant for the objective principle expressed in the same words? For Tetens, the determination of the conditions of knowledge of the objective principle is itself an explicitly empirical task. Tetens believed that necessities of our mental operations, though discovered empirically, became necessities of transcendent philosophy. He asks us to consider whether “Nothing comes from nothing” is just a quirk of his individual mind; do others agree with him in asserting that nothing comes from nothing? These are all empirical questions that can be answered; but it is not obvious how a true and favorable answer to these questions has any standing when it is a question of ontology: Can something come from nothing? Neither Crusius, Lambert, nor Tetens seems to have seen the problematical character of efforts to base the a priori claims of our cognitions upon contingent facts of psychology. Kant characterizes such efforts as “getting water from a pumice stone.” Let us see how Tetens proceeds. The cognitive faculties Tetens draws a line between the active and the receptive powers of the soul. The active power is the will and the faculty of thought; the receptive faculty is feeling or sense. Cognition occurs only when the former works upon the latter. The first product of this working is the capacity to form representations and concepts; there are already impressions of sense and feeling, but these are brought to consciousness as representations only by the basic power of making representations and concepts; a representation is the first object of consciousness, but it is not an impression or a copy of an impression. Thought is necessary to form a representation as a sign of sensation; the sensations must be “run through” and “held together” in a certain way57 by thought before they become representations of an object. The power of imagination (Dichtkraft) creates generic images of sensible abstracta such as space and time. When representations refer to things in space and time which resumably give rise to them, we are said to perceive objects, and we il to notice that we have only representations of objects, not objects themselves. We identify and reidentify objects, associate them with one another, make abstractions from and classify them. In short, we obtain or form a concept of an object that can function in knowing in a way that a mere image cannot. When representations become distinct concepts and their original felt association is replaced by a connection which is thought, there arises a concept of relation (Verhältnissbegriff) between concepts. Relational concepts are not confined to specific pairs of representations but may remain the same even when the specific content of the representations is different. Such concepts are the fundamental concepts of transcendent philosophy. Among them are sameness and difference, coexistence and succession (space and time), inherence of a property in a substance, and dependence of one thing on another (echoes of Hume’s list of “philosophical relations,” anticipations of Kant’s categories). The relations among these concepts are a priori, because they are not restricted as to the empirical content of the representations related to each other. Since they are relations implicit in the formal structure of judgments and inferences, they are found in and apply to all knowledge. We have seen repeatedly how Crusius and Lambert recognized a class of necessary judgments which are not based on logical necessity according to the laws of identity and contradiction. They tried to establish the objectivity of such judgments. Generally, they tried to do so by appealing to the fact (if it is a fact) that these judgments express a necessity of thought, not a logical necessity: one just must see that some things cannot be thought to coexist. That, however, is a fallible, contingent truth if it is true at all. What they needed was a proposition with the apodeictic certainty of the law of contradiction yet one that could not be proved by the law of contradiction. (In a word, they needed to recognize what Kant will later call synthetic a priori judgments.) Tetens was keenly aware of the problem in 1776. The truths of geometry are necessarily true, but not because they depend on identity and contradiction; they are necessarily true of space as we constitute the abstracta of space by the functioning of our cognitive faculties. The laws of identity and contradiction are “mere ways of thinking without reference to what is peculiar to the ideas related,”58 but the laws of mathematics deal with what is peculiar to space and time. Where the necessity of a judgment does not depend on the merely formal relationship between subject and predicate or the particular empirical content of the two concepts, it must depend upon “what is, in respect to certain general classes of representations (or objects), necessary and natural to the understanding.”59 What the features are that are necessary and natural to the understanding must be discovered, according to Tetens, empirically, though the relations themselves are a priori necessary. The objective reference of perception It is a quite different thing to show that a judgment is an expression of thought natural to our understanding, and to show that the judgment is objectively true. Tetens made an original and significant change in the mode 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 being ingredient in representations, representations in our consciousness being representations of something. Tetens claims that this is a better account of the origin of our belief in external, independent objects than the different ones offered by Hume and Reid. But he also confesses,60 however, that it does not touch the question: Is objective reference veridical? Tetens does not have an answer to the demand for justification of objective knowledge-claims, regarded as a question of metaphysics. Epistemologically, however, he gives a criterion of objectivity which is independent of the ontological status of minds and objects. Tetens examines the way some ideas are endowed with objective reference without presupposing an answer to the question of the ontology of subject and object. He empirically distinguishes the unchangeable subjective and the changeable subjective,61 and sees that the former captures the empirical and methodological, if not the ontological, meaning of “objective.” Similarly there is the distinction between the intersubjective and the subjective, where the former is ordinarily called the objective. This is as close as a writer of an empirical theory of knowledge can come to the Kantian divisons between judgments of perception and judgments of experience and between unattainable knowledge of transcendent objects and attainable knowledge of objects immanent in experience. Kant’s friend Hamann said that Kant had Tetens open upon his desk while writing the Critique of Pure Reason. Kant regretted that this powerful and original thinker did not review his Critique of Pure Reason when 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’s criticisms. There is a certain melancholy in some of Kant’s remarks about Tetens—how close he had come to what Kant saw as truth, and yet how far 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 the possibility of such a priori knowledge [ingredient in and presupposed by empirical knowledge] although Herr Tetens could have given rise to it.62 THE MENDELSSOHN-JACOBI CONTROVERSY The philosophers we have been studying raised objections to Wolff’s philosophy, but with the possible exception of Crusius they did not bring much against his Weltanschauung. They were all men of the Enlightenment. They all were quite “safe” on the big issues of philosophy—God, freedom, and immortality—while they disputed technical points such as the logical status of the principle of sufficient reason. A little after 1780 the pax philosophica was shattered by a controversy that left its mark on Kant, Herder, Goethe, and the early German Idealists such as Schelling. It was a turning point in German philosophy and cultural life. If one decides that Jacobi was the “victor,” one can say that the Enlightenment in Germany was finished. Moses Mendelssohn was a faithful disciple of Wolff and won the prize essay contest of the Berlin Academy by defending the Wolffian mathematical ideal, defeating Immanuel Kant. Kant praised the elegance of his literary style, and in fact he is the best stylist among German philosophers before Schopenhauer. He was an intimate friend of Lessing’s and was the model of the wise man in Lessing’s drama, Nathan der Weise. Friedrich Heinrich Jacobi was born into a rich Pietistic family in Düsseldorf in 1743. He reacted against the naturalistic, empiricistic education 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, a destructive critic of Scripture who denied its authority, and a revolutionary political thinker was almost universally accepted in Germany. Wolff wrote extensively in criticism of Spinoza,64 but nonetheless he was accused of Spinozism by his Pietist colleagues at Halle. Mendelssohn in his Philosophical Conversations (1763) pleaded for a better and more fairminded appraisal of “the accursed atheist of Amsterdam,” without, of course, taking any step that committed him to Spinozism and without effecting any change in the almost unanimous condemnation of Spinozism. Imagine the shock, then, when it became known shortly after his death in 1781 that Lessing had been a Spinozist. Lessing—Germany’s greatest man of letters, Germany’s greatest thinker between Leibniz and Kant, a man whose character after more than two centuries still awakens feelings of affection and respect—a Spinozist? In conversations with Jacobi, Lessing had made this confession. Through mutual friends Jacobi imparted this information to Mendelssohn, ostensibly to contribute to a biography of Lessing that Mendelssohn was working on. Naturally the secret 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 there were publications in which spleen was hardly covered by civility: Jacobi’s On 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), and Jacobi’s Against Mendelssohn’s Accusations in his “To the Friends of Lessing” (1786). To these should be added David Hume on Belief (1787) since it develops Jacobi’s “philosophy of faith and feeling” which underlies the conversations with Lessing and the correspondence with Mendelssohn. Nothing shows better the ill-nature of this controversy than the accusations that Jacobi was responsible for Mendelssohn’s death in 1786 at the climax of the debate. For three reasons what might have been a quiet Auseinandersetzung between two scholars was raised to the level of a public scandal. The first was the eminence of the recently deceased Lessing. Any surprising secrets about that good and famous man were bound to be objects of public curiosity. Second, there were many who hoped it was true that Lessing had been a Spinozist. These crypto-Spinozists were more numerous than anyone had reckoned, and with Lessing’s Spinozism established they could come out of the closet. Then there were the personal motives and traits of the principals. Fritz Jacobi was a name-dropper and a tuft-hunter. He prided himself on knowing everybody. (Goethe told Eckermann that Jacobi lacked something necessary for a poet or philosopher, but that he would have made a good ambassador.) Pride and snobbery were mixed in him with a genuine 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 of thirty years, should have concealed his Spinozism from him and revealed it to some young man he hardly knew. At first he doubted the truth of what Jacobi said about Lessing; then he doubted the truth of what Lessing may have 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 dodged by Mendelssohn who was laying traps of his own, etc. Neither of the principals came out with clean hands. The stakes were too high for either man to be punctilious about the ethics of publication of personal documents. The stakes were the validity of the whole philosophical enterprise. Jacobi saw the issue as a choice between the nihilistic Spinoza-Leibniz- Wolffian Enlightenment and the absolute but irrationalistic claims of faith and feeling. Jacobi’s target was something even bigger and grander than Lessing and Spinoza: he aimed to overthrow the Enlightenment’s rationalism and intellectualism and ideal of demonstrable metaphysical and theological truth. He tried to show that any system of demonstrations had to go in the direction of Spinozism; minor criticisms of Wolff had to give way to a frontal assault on the entire enterprise of philosophy as an intellectual discipline. Mendelssohn’s strategy was to construct a form of Spinozism which Lessing might have held and which did not have the fatal consequences that Jacobi had found in his interpretation of Spinoza. In this 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 think nothing about it doesn’t imply its impossibility,” Jacobi replied: “You go even farther than Spinoza. For him understanding is worth more than anything.” Lessing replied: “For men only. Spinoza was far from thinking our miserable human acting for purposes was the best method, and far from making thought supreme.”65 After an excursus in which Jacobi tries to show that Leibniz and hence the Leibniz-Wolffians were in essential agreement with Spinoza, Jacobi returns to his theme of the impotence and inferiority of abstract thought: In my judgment the greatest service of the enquirer is to uncover and reveal being (Daseyn). Explanation is only the means and the way to the goal; it is neither the next nor the ultimate goal. The final goal is what does not let itself be explained: the irresolvable, the immediate, the simple…. Since we only put together and hang together what is explainable in things, there is a certain illusion (Schein) in the soul which blinds more than it reveals…. [When we enquire] we close the eye of the soul with which the soul sees itself and God, so that by greater concentration it can see with the eye of the body.66 We do not, therefore, approach truth by rational thinking; rather, we embrace it in spite of rational thinking. A mortal leap (salto mortale) is needed. (An almost exactly parallel move can be found in Kierkegaard’s distinction between approximation to the truth and appropriation of the truth.) But Jacobi was unable to persuade Lessing with his “tired head and old legs” to take the plunge; Lessing remained a Spinozist. Others who professed adherence to Spinozism, however, embraced a very different Spinozism from that of rationalism and geometrical rigor. For men like Herder,67 Schelling, and Goethe, an organic, holistic, romantic conception of oneness replaced the quasi-mathematical perfection of Spinoza’s substance. Spinoza came into his own, paradoxically, when rationalism was on the wain. Having held Spinozistic nihilism (Jacobi’s own word) to be the natural and inevitable last stage in the evolution of Enlightenment, it was to be expected that Kant’s Critique of Pure Reason, published the year of Lessing’s death, should come under criticism from Jacobi. But instead of appealing directly to religious “faith and feeling,” he allied himself with David Hume. He appealed to Hume and to Hume’s critic, Thomas Reid, to justify his doctrine of the impotence of reason even in the simplest actions of everyday life. Hume substituted belief for unattainable knowledge, and Reid found belief essential in establishing the existence of external objects when all that analytical reason could show was only impressions and ideas. In his Morning Lessons (Morgenstunden) (1785) Mendelssohn does two things. First, he reasserts the correctness of Wolff ’s deism and its superiority over Spinoza’s pantheism. He points out what seems to him to be a myriad of errors in Spinoza’s philosophy. He shows, to his own satisfaction, that the demonstrative method does not necessarily produce the Spinozistic conclusions of pantheism and fatalism.68 Second, he formulates, in the name of his friend Lessing, a system of “purified pantheism” which Lessing might have held and which would not have the evil consequences that Jacobi thought were indigenous in Spinozism. Specifically, in the fourteenth Lesson he makes of substance a spiritual being endowed with intellect and will but not extension. Then the question whether God is the world (pantheism) or the world stands outside God (deism) does not have the portentous consequences which follow from identifying the human mind with a mode of substance whose essence is necessity, extension, and oneness. In his To the Friends of Lessing (1786) Mendelssohn tries a new gambit. He commends “sound human understanding” (common sense in the Scottish philosophy) when high speculations like Spinozism or purified pantheism, formulated by fallible human reason, conflict or do not carry conviction. He says: When I speak of rational conviction… I am not speaking of metaphysical argumentation…or of scholastic demonstrations which have stood the test of the most subtle skepticism; rather, I speak of the expressions and judgments of simple and sound human understanding which directly grasps and contemplates things. I certainly respect demonstrations in metaphysics… but my conviction of religious truths does not depend so completely upon metaphysical argumentations that it would have to stand or fall with them. One can raise doubts about my arguments and show fallacies in them, and yet my conviction remains unshaken…. For the true and genuine conviction of natural religion…these artificial methods [of metaphysical speculation] are of no use. The man whose reason is not debauched by sophistry needs only to follow his own good sense.69 This 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 in common sense. On both sides, reason has taken a beating. That is how it appeared to one man, Immanuel Kant, in an apostrophe to Jacobi and Mendelssohn: Men of intellectual power and broad minds! I honor your talents and love your feeling for humanity. But have you considered what you do, and where you will end, with your attacks on human reason?…Friends of the human race and of that which is holiest to it!…do not wrest from reason that which makes it the highest good on earth, the prerogative of being the ultimate touchstone of truth.70 German Idealism proper may be said to have begun when leading philosophers heeded Kant’s words and made reason “the highest good on earth” and “the ultimate touchstone of truth.” NOTES 1 See, for instance, C.A.Corr, “Christian Wolff and Leibniz,” Journal of the History of Ideas, 36 (1975): 241–62. 2 W.H.Bruford, Germany in the Eighteenth Century (Cambridge: Cambridge University 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 in English. There is Preliminary Discourse on Philosophy in General, trans. R.G.Blackwell (Indianapolis: Bobbs-Merrill, 1963); selections from Vernünftige Gedanken von Gott, der Welt, der Seele des Menschen, auch allen Dingen überhaupt in Eighteenth Century Philosophy, trans. L.W.Beck (New York: Free Press, 1966); selections from Vernünftige Gedanken von der Menschen 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 on the 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?” Studia Leibnitiana, 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 not worthwhile 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 the power of the intellect.” “Whatever becomes known to us by ratiocination is said 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 Pure Reason, A 231, B 284. On this difficult point, see C.A.van Peursen, “Wolff’s Philosophy 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 the sun’s existence, e.g. without the sun there could be no sundials and we could not detect compass deviations. What about suns (i.e. stars) that do not benefit earth-dwellers? There must be inhabitants of their planets, who do benefit from their suns. See also the exciting chapter on the benefits we have from the existence of air. Vemünftige Gedanken von der Ahsicht der natürlichen Dingen, in Gesammelte Werke, op. cit., §§ 28, 44, 46, 60, 85, 91, et passim. 14 Kant, Critique of Practical Reason, trans. L.W.Beck (New York: Macmillan, 1993), P. 41.s 15 Baumgarten’s Latin Wolffian textbooks were used by Kant in his lectures. One book has been translated into English under the name Reflections on Poetry, trans. K.Aschenbrenner and W.B.Holtker (Berkeley: University of California Press, 1954). 16 Crusius, Weg zur Gewissheit und Zuverlässigkeit der menschlichen Erkenntnis (1747), §§ 5, 9, 10 (hereafter referred to as Logic); Entwurf der notwendigen Vernunftwahrheiten (1745), § 234 (hereafter referred to as Metaphysics). All citations 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 the precritical Kant in his Only Possible Premise for a Demonstration of the Existence of God, trans. G.Treash, Part I, Observation 2 (New York: Abaris, 1979), p. 69; also New Exposition of the First Principles of Metaphysical Knowledge, 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 Crusian distinction permits an escape from psychological subjectivity. 20 All of these laws except the first two are rejected as “subreptitious axioms” in Kant’s Inaugural Dissertation. They result from the application of sensible concepts 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 Philosophical Correspondence, 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, “Kant and Crusius: epigenesis and preformation,” Proceedings of the Sixth International 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 grant another thing from which one thing comes” (Metaphysics, op. cit., § 63) but does not draw Hume’s skeptical conclusion. 25 Crusius, Metaphysics, op. cit., § 31. 26 This is the principal theme of Kant’s Essay towards Introducing Negative Magnitudes into Philosophy (1764), the work that shows more than any other the Crusian influence on Kant. 27 Crusius, Dissertatio philosophica de usu et limitibus principii rationis determinantis, 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’s aid in 1765, aimed to be an ontology for all the sciences, but it lacks the architectonic, systematic order which might have come from the successful application of Lambert’s adaptation of Leibniz’s ars characteristica. It is to be found 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 paper Lambert apparently intended to submit to the Berlin Academy in the prize competition of 1762. It was first published as the Kant-Studien Ergänzungsheft (1918). It shows some remarkable kinship with Kant’s prize essay. 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 in Kant-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. The quotation is from Lambert, Anlage zur Architektonic, op. cit., § 11. 36 Lambert, Neues Organon, Dianoiologie, §§ 601–5. This work was published in two volumes in 1764 and is reprinted as Lambert’s Philosophische Schriften, 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 of Negative Magnitudes in Philosophy, written under the Crusian influence before 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 of Time,” 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 of Pure 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 in this volume. 53 The pervasive influence of the Scots on Tetens has been studied by M.Kuehn in his 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 (Neues Organon, 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 marked resemblance 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 in intuition and that belonging to “the transcendent principles of reason.” Thus he is at one with Kant in asserting the discontinuity of mathematical and metaphysical 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. 527 62 Kants gesammelte Schriften, 29 vols, ed. Deutsche (formerly Königliche Preussische) Akademie der Wissenschaften (Berlin: de Gruyter [and predecessors], 1902–), Reflexion 4901, and Vol. 23, pp. 23, 57. 63 The best collection of documents is H.Scholz (ed.), Die Hauptschriften zum Pantheismusstreit (Berlin: Kant Gesellschaft, 1916). Selections from Scholz have been translated as The Spinoza Conversations between Lessing and jacobi, 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 Practical Reason and Other Writings in Moral Philosophy (Chicago: University of Chicago Press 1949), PP. 303, 305. BIBLIOGRAPHY 1.1 Allison, H.E. Lessing and the Enlightenment, Ann Arbor: University of Michigan 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 des achtzehnten Jahrhunderts. Darmstadt: Wissen-schaftliche Buchgesellschaft, 1967. (Originally published as Kant’s Kritik der Urtellskraft, 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 Background of the Literary Revival, Cambridge: Cambridge University Press, 1935 (reprinted 1965). 1.9 Cassirer, E. Das Erkenntnisproblem in der Philosophie und Wissenschaft der neueren Zeit, Darmstadt: Wissenschaftliche Buchgesellschaft, 1971. Volume II. 1.10 Cassirer, E. The Philosophy of the Enlightenment, princeton: Princeton University 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 scholarly articles and bibliographies on all the philosophers mentioned in this chapter.) 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’s Death, New York: Holt, 1880. 1.15 Kantzenbach, F.W. Protestantisches Christentum im Zeitalter der Aufklärung, Gütersloh: Mohm, 1965. 1.16 Kuehn, M. Scottish Common Sense in Germany, 1768–1800, Kingston and Montreal: McGill-Queen’s University Press, 1987. 1.17 Petersen, P. Geschichte der aristotelischen Philosophie im protestantischen Deutschland, 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 la Philosophie, ed. Y.Beleval, vol. ii, pp. 728–85. Paris: Encylopédie de la 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.