Emil du Bois-Reymond’s Reflections on Consciousness

Abstract

The late nineteenth-century Ignorabimus controversy over the limits of scientific knowledge has often been characterized as proclaiming the end of intellectual progress, and by implication, as plunging Germany into a crisis of pessimism from which Liberalism never recovered. My research supports the opposite interpretation. The initiator of the Ignorabimus controversy, Emil du Bois-Reymond, was a physiologist who worked his whole life against the forces of obscurantism, whether they came from the Catholic and Conservative Right or the scientistic and millenarian Left. Du Bois-Reymond’s doubt that scientists would ever elucidate consciousness must therefore be seen as an endorsement, and not a rejection, of his faith in reason.

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10.1 The Limits of Science

You are right in demanding that an artist approach his work consciously, but you are confusing two concepts: the solution of a problem and the correct formulation of a problem. Only the second is required of the artist.

Anton Chekhov to Alexei Suvorin, 27 October 1888

Emil Heinrich du Bois-Reymond (1818–1896) grew up divided. His father was Swiss and poor, but his mother came from one of Berlin’s most celebrated families. At home he learned art, music, and conversation, but his parents encouraged exercise, exploration, and experiment. A lifelong enthusiast of literature, history, and philosophy, he trained in geology, physics, and physiology. He enjoyed the respect of colleagues at the University of Berlin and the Prussian Academy of Sciences, but most of his friends were Jews and foreigners. During the term he worked in Berlin, but on weekends he commuted to Potsdam where he spoke German to his family, English to his servants, and French to his guests. Even his house was diverse: an Italian villa designed by a Prussian architect, it showcased Roman statues, Dutch paintings, German furniture, French books, and English vegetables. Such a cosmopolitan existence allowed him to see farther than most.

Du Bois-Reymond’s perspicacity informed “The Limits of Science”, a keynote address that he delivered to the Congress of German Scientists and Physicians in Leipzig on 14 August 1872. In this, the most famous of his speeches, du Bois-Reymond aimed to show that even the empire of science could not expand indefinitely.¹ To do so he first defined what he meant by natural knowledge. The reduction of events to the “apodictic certainty” of physics offered the only form of understanding that satisfied our desire for causal explanation.² The task of science, as du Bois-Reymond described it, was to construct a mathematical model of reality.

The astronomer Pierre-Simon Laplace first spelled out the implications of this project. “A mind which at a given instant should know all the forces acting in nature, as also the respective situation of the beings of which it consists—provided its powers were sufficiently vast to analyze all these data—could embrace in one formula the movements of the largest bodies in the universe as well as those of the smallest atom; nothing would be uncertain for such a mind, and the future, like the past, would be present to its eyes.”³ It could tell us, as du Bois-Reymond envisioned, “the day when the Greek cross shall glitter from the mosque of St. Sophia, or when England shall have burnt the last of her coals”, or alternatively, “who was the Man in the Iron Mask, or how the President was lost”.⁴ To such a mind all things would become “one single fact and one great truth”.⁵

Of course, du Bois-Reymond never expected science to reach this degree of perfection. To do so presumed that we could resolve natural events into the “vibrations of a primitive, undifferentiated matter”—a transmutation still awaiting the philosopher’s stone.⁶ There was also the practical impossibility of gathering all the necessary facts and tracing their infinite ramifications. Nevertheless, our ignorance was more a question of degree than of kind. If we did know the disposition of every atom, we could indeed calculate the fate of the universe with the confidence expressed by Laplace. Such an “astronomical intelligence” represented the fullest possible understanding of the world, since any information barred to it would necessarily be foreclosed to us.⁷

Having laid the foundation of his argument, du Bois-Reymond identified two bounds of understanding that even his “Laplacian demon” could not cross. The first was the essence of matter. Material atoms supplied a “useful fiction” for many considerations of physics, but volume-elements made more sense of continuous fields.⁸ Metaphysical atoms presented similar difficulties. On the one hand, they were presumed to be inert points; on the other, they occupied space and interacted with the world.⁹ What was worse, these contradictions appeared inevitable. Metaphysical atoms did little more than import into “the minute and the invisible the qualities of the gross and the visible”; the same went for material atoms, which could not be expected to develop novel properties simply because they were small.¹⁰ On either conception matter remained a riddle.

The origin of life might appear to set the other limit, but du Bois-Reymond assured his audience that this problem did not amount to an impenetrable mystery. The Laplacian demon could determine the precise conditions that produced the first living things. Organic matter was composed of common atoms; the puzzle was how they remained in dynamic equilibrium. Since the supernatural was excluded, biology translated to an “exceedingly difficult mechanical problem” that science might someday expect to solve. “For the rest”, du Bois-Reymond wrote, “the most luxuriant picture of a jungle ever sketched by Bernardin de St. Pierre, Alexander von Humboldt, or Eduard Pöppig offers to the view of theoretical science nothing more than matter in motion”.¹¹

Instead, the second limit was consciousness. Having arisen at some point in the evolution of life, it was the one aspect of nature that could not be reduced to a material substrate. This held as true for plain sensations as for complex ideas: the “first awakenings of pleasure or pain in simple organisms” confronted the world with “an impassable gulf that rendered it doubly incomprehensible”.¹² As du Bois-Reymond recounted, no philosophical reflection had come close to explaining how the mind interacted with the body—not Descartes’ invocation of the pineal gland, nor Malebranche’s appeal to divine assistance, nor Leibniz’s assumption of perfect harmony. The best one could do was to regard consciousness as an effect of matter.¹³

With this du Bois-Reymond arrived at the heart of his argument. It certainly would be a “lofty triumph” if science could correlate mental phenomena with physiological activity. We could note with interest “what play of carbon, hydrogen, nitrogen, oxygen, and phosphorus corresponds to the bliss of hearing music, what whirl of such atoms answers to the climax of sensual enjoyment, what molecular storm coincides with the raging pain of trigeminal neuralgia.” But even perfect knowledge of the brain would tell us nothing about experience, for “no imaginable movement of material particles could ever transport us into the realm of consciousness”.¹⁴ The same could be said of attempts to address the question psychologically, since perception, association, and memory could never substitute for awareness. In a famous passage, du Bois-Reymond laid out the difficulty: “What conceivable connection exists between definite movements of definite atoms in my brain on the one hand, and on the other hand such primordial, indefinable, undeniable facts as these: I feel pain or pleasure; I taste something sweet, or smell a rose, or hear an organ, or see something red, and the certainty that immediately follows: Therefore I am?” Even if the atoms of the brain were mindful of their own existence, science would be at a loss to explain how consciousness followed from their combined action.¹⁵ “In a world made up of matter in motion”, he declared, “the movements of the cerebral molecules are like a dumb show”.¹⁶

At this point in his address du Bois-Reymond advanced a pair of theological considerations. The first was that the unconscious mind held no secrets for the Laplacian demon—the brain of a “dreamless sleeper” was as intelligible to it as were the orbits of the planets. This did not mean that identity was rooted in the will; sensation clearly preceded desire, a fact that implied that sin was subordinate to perception.¹⁷ This led du Bois-Reymond to his second point: religion held no authority over science. Our knowledge was indeed “imprisoned by two limits”, but between these “the man of science is lord and master; he can analyze and synthesize, and no one can fathom the extent of his knowledge and power.” Science therefore could safely ignore “myth, dogma, or time-honored philosophy”.¹⁸

As du Bois-Reymond saw it, the mind depended entirely on the brain. Ideas derived from the senses, morbid states altered thought, and animals experienced the world, all of which indicated that intelligence had emerged as a consequence of natural selection. In this regard the scholastic presumption that separated mental phenomena from material conditions was “so plainly in conflict with reality” that it supplied an “apagogical demonstration of the falsity of its premises”.¹⁹ The mystery of consciousness could not excuse the error of dualism.

Du Bois-Reymond brought his address to a surprising conclusion. Leibniz once conceived a superior intelligence “constructing a body capable of mimicking the actions of person.” However, he considered this automaton to lack the “monad of the soul.” Du Bois-Reymond pictured the Doppelgänger more classically:

Imagine all the atoms of which Caesar consisted at any given moment, say, as he stood at the Rubicon, to be brought together by mechanical artistry, each in its own place and possessed of its own velocity in its proper direction. In our view Caesar would then be restored mentally as well as bodily. This artificial Caesar would have the same sensations, ambitions, and ideas as his prototype on the Rubicon, and would share the same memories, inherited and acquired abilities, and so forth.

“Suppose several artificial figures of the same model”, he continued, “to be simultaneously formed out of a like number of other atoms of carbon, hydrogen, etc. What would be the difference between the new Caesar and his duplicate, beyond the differences in the places where they were formed? But the mind imagined by Leibniz, after fashioning the new Caesar and his many Sosiae, could never understand how the atoms he had arranged and set into motion could lead to consciousness”.²⁰

Du Bois-Reymond recalled Carl Vogt’s assertion that “thought is to the brain what bile is to the liver or urine is to the kidneys.”²¹ The weakness of the comparison was less aesthetic than intellectual: it suggested that consciousness could be explained by the structure of the nervous system in the same way that secretion could be explained by the structure of a gland.²² Monism might offer the most practical philosophy of science, du Bois-Reymond conceded, but “whether we shall ever understand mental phenomena from their material conditions is a very different question from whether these phenomena are the product of their material conditions”.²³ He doubted the prospect of a solution. Scientists were used to admitting their ignorance, “but as regards the enigma of matter and force, and how they are capable of thought, we must resign ourselves once and for all to the far more difficult verdict: Ignorabimus”—we shall never know.²⁴

10.2 The Seven Enigmas

When I was in Berlin I met du Bois-Reymond, and, wagging the end of my finger, I said to him, “What is that? What moves the finger?” He said he didn’t know; that investigators have for twenty-five years been trying to find out. If anybody could tell him what wagged this finger, the problem of life would be solved.

Thomas Edison, “What is Life?” 1891

Du Bois-Reymond’s speech created a furor. Contemporaries likened it to an “unexpected explosion of a mine”, coming as it did from “the center of the center of science”.²⁵ Darwinists placed him in league with the “evil horde” of the Catholic Church.²⁶ Catholics regarded his argument as a challenge to the divinity of God.²⁷ Philosophers resented his trespass on grounds they considered their own.²⁸ And critics subjected him to abuse, sneering at his “incompetent ramblings”, branding him as “the professor of national limitation”, and charging him with offering the public “bisexual religious retrogressions, mysticisms, and multidimensional inanities”.²⁹ For a long time du Bois-Reymond ignored his attackers, but after 8 years he had enough and answered them in a discourse titled “The Seven Enigmas”.³⁰ The setting was significant: du Bois-Reymond addressed the Prussian Academy of Sciences on his home ground in Berlin. As one of the four permanent secretaries of the venerable institution he knew that his remarks would carry all the weight of his office.

Du Bois-Reymond opened the speech with an attack on the ignorance of his detractors. He confessed that he had hesitated before addressing his colleagues at Leipzig: the limits of science were well known to anyone familiar with the history of philosophy, and he had felt almost ashamed to offer them “so stale a draft”.³¹ His doubts had been misplaced. Most of his philosophical critics had assumed him to be a Kantian, a mistake in judgment that was A result of academic specialization.³² “Since Kant transformed the discipline”, du Bois-Reymond explained, “philosophy has taken on so esoteric a character, has so forgotten the language of common sense and plain thought, has so evaded the questions that most deeply stir our youth, or treated them condescendingly as officious speculations, and finally, has so opposed the rise of science, that it is not surprising that even the recollection of its earlier achievements has been lost”.³³ In addition to forgetting the history of their own subject, philosophers also ignored metaphysics and religion, leaving many scientists to conclude that the field was empty.³⁴

This condescending attitude blinkered the thinking of naturalists unacquainted with du Bois-Reymond’s arguments. “Fanatics who should have known better” (meaning the morphologist Ernst Haeckel) “denounced me as belonging to the Black Band and demonstrated once again how near radicalism is to despotism. More temperate heads” (meaning the botanist Carl von Nägeli) “betrayed the weakness of their dialectics” in confusing the view that he endorsed, that consciousness was linked to material processes, with the view he opposed, that consciousness could be explained on a mechanical basis.³⁵

The theologian David Friedrich Strauss was more insightful. Apart from saving du Bois-Reymond the trouble of “having to dash the hopes of those who mistakenly saw me as a champion of dualism”, Strauss identified three questions that appeared to be insoluble:

• (A) How has the living arisen out the lifeless?

• (B) How has the sensible arisen out of the insensible?

• (C) How has the conscious arisen out of the unconscious?

Du Bois-Reymond viewed the second question as crucial, whereas Strauss inclined to the first and the third.³⁶ Here Strauss missed the point. Astronomical knowledge could indeed reveal the origin of life, since only the “wholly childish” insisted on successive periods of creation. The Almighty, du Bois-Reymond joked, was not some kind of amateur artist in continual need of improvement. Moreover, du Bois-Reymond had never asserted that sensation could explain consciousness; rather, he had asserted that the incomprehensibility of all higher mental processes “followed from it by an a fortiori argument.” This accounted for why the “gap in our understanding” appeared at the second stage in Strauss’s series and not after.³⁷

Strauss thought that only time would tell if du Bois-Reymond’s Ignorabimus would be the last word on the subject.³⁸ Du Bois-Reymond conceded that it was not, since Haeckel had taken his ironic suggestion that atoms were sentient and had spun it into a theory of inheritance that proposed the transmission of unconscious memories by means of “vivified atom-complexes”.³⁹ At the very least, Haeckel’s updated doctrine of anamnesis was obscure—one of his friends had studied it six times and still could not make sense of it.⁴⁰ It also lacked motivation. What was the point of attaching souls to atoms if mechanics explained our minds? Haeckel’s error reminded du Bois-Reymond of the critics of Newton who associated gravity with will. “Whoever arrives at such nonsense”, he scoffed, “and instead of humbly withdrawing, nails his colors to the mast and works himself into a frenzy of strident bombast, has indeed met success where Newton could only concede defeat”.⁴¹

Having addressed the objections to his previous speech at Leipzig, du Bois-Reymond moved on to his current subject, “the seven shortcomings” of science.⁴² He deemed the first two, the essence of matter and the origin of motion, to be inscrutably mysterious.⁴³ Continued investigation might well discover the origin of life, despite Pasteur’s experience to the contrary, leaving a fourth problem in the apparently teleological arrangement of nature. Since morphological laws were inconsistent with the mechanical view, du Bois-Reymond regarded natural selection as the best answer to this conundrum.⁴⁴ By contrast, the fifth difficulty of the origin of sensation was quite transcendent.

Here du Bois-Reymond paused his discussion to review Leibniz’s treatment of the issue. According to the German philosopher, “we are constrained to confess that perception and whatever depends upon it are inexplicable on mechanical principles; that is, by reference to forms and movements.” “Imagine a machine”, Leibniz continued, “which manufactured thoughts, feelings, and perceptions, and think of it as enlarged in all its proportions, so that we could go into it as one might a mill. Even then we would find nothing but parts jostling each other, and never anything by which perception could be explained.”⁴⁵ Du Bois-Reymond had followed the same line of reasoning in his essay on “The Limits of Science”; however, time had changed his mind. After all, it made a great difference whether charcoal, sulfur, and saltpeter were combined in large lumps or in a fine powder. He therefore rejected Leibniz’s analogy and affirmed that consciousness could not be explained “as the result of any arrangement or motion of atoms”—a position, he added, that no one had attempted to challenge.⁴⁶ Instead, his denigrators had contented themselves with making contradictory assertions, like Haeckel’s charge that he had not considered the evolution of the human mind. This may have been the case, du Bois-Reymond allowed, but then Haeckel had failed to realize that our species had not altered since the time of Homer, that the world would freeze long before the advent of any super-beings, and that however much our brains might develop they could never surpass the powers of the Laplacian demon. “If anyone has sinned against evolution”, du Bois-Reymond averred, “it is the Prophet of Jena”.⁴⁷

Du Bois-Reymond named the origin of intelligent thought and language as his sixth difficulty. He recognized the vast chasm between an amoeba and a person, but he expected the gap to be bridged in stages.⁴⁸ The “theory of knowledge” required only “memory and the power of generalization” to fashion complex thoughts out of simple sensations, and as great as was the intellectual divide between species, it paled in comparison with the rift between mechanics and mind. “To use to Strauss’s notation again”, he wrote, “if problem B is solved, problem C does not seem transcendent”.⁴⁹

With this du Bois-Reymond arrived at the final and the most important of the difficulties faced by science. Whereas the other problems in his list had been the concern of only a few intellectuals, the question of whether our actions were free—“touching everyone, apparently accessible to everyone, implicated with the fundamental conditions of society, impinging on the deepest religious convictions”—had played a part of “immeasurable moment in the history of ideas and civilization, and the stages of the development of the human mind” were plainly reflected in the discussion of it.⁵⁰ The earliest of these, classical antiquity, saw no contradiction between choice and necessity. Rather, it was Christian theology that complicated the question. If God was omnipotent, we were not free. But then how could He hold us responsible for His will?⁵¹ Du Bois-Reymond heaped scorn on the Church’s reply.

The doctrine of original sin, the questions of redemption through merit or through the blood of the Savior, by faith or by works, and of the different kinds of grace, were complicated in a thousand ways with that dilemma itself, already fruitful in subtleties, and the cloisters of Christendom resounded from the fourth to the seventeenth century with disputations about determinism and indeterminism. There is perhaps no subject of human consideration about which so many rows of untouched folios lie moldering away. But the controversy was not always confined to books. The bitter accusations of heresy that the ruling sect hurled at dissenters, with all their attendant horrors, hung all the more on such abstruse controversies the less they had to do with reason and the honest pursuit of truth.⁵²

Science imagined freedom in altogether different terms. Force was neither created nor destroyed, which meant that everything was determined, including the molecules of our brains. The universe made most sense as a machine.⁵³

Du Bois-Reymond pointed out that Leibniz had been the first to conceive of the world in this way. Freedom did not concern the philosopher, since God had ordained all things, including our experiences. However, Leibniz refused to accept we could ever find ourselves in the predicament of Buridan’s ass (which starved because it could not choose between two equally distant piles of food) on the grounds that angels would tip the balance one way or the other. He also justified atrocities with the excuse that God had been forced to permit their existence in this best of all possible worlds.⁵⁴ Du Bois-Reymond found such metaphysics peculiar, to say the least, and endorsed only the objective side of Leibniz’s determinism. Here he joined a long line of fatalists who regarded free will as an illusion, noting that we felt free in our dreams, that our waking thoughts seemed to come and go of themselves, and that much of the activity underlying purposeful movement went on beneath the level of our awareness.⁵⁵ Were our conscious actions really that much more deliberate?⁵⁶

None of this seemed especially worrisome as long as we considered matters of minor importance. The trouble came when we imagined our ethical choices to be determined. “Even the most decided monist”, du Bois-Reymond granted, “could hardly adhere to the earnest purposes of practical life in the face of the idea that all of human existence is a fable convenue in which mechanical necessity awards to Caius the part of a traitor, and to Sempronius that of a judge; and therefore Caius is taken to execution, while Sempronius goes to his breakfast. We are not bothered that so many letters in every hundred thousand miscarry because they are not addressed”, “but it shocks our moral feelings to think that, according to Quetelet, so many persons in every hundred thousand are to become thieves, murderers, and arsonists; for it is disconcerting to have to think that we are not criminals only because others, instead of ourselves, have drawn the black lots that might have fallen to our share”.⁵⁷

Du Bois-Reymond pointed out that most people—scientists, historians, judges, poets, dreamers, even those who just “sleepwalk through life”—saw no alternative but to ignore this dilemma.⁵⁸ Metaphysicians throughout history had attempted to reconcile morality with the mechanical view of the world; had they succeeded in squaring this circle, their attempts would have ceased. There was little hope of arriving at any solution sub specie aeternitatis: “only unconquerable problems tend to be this immortal”.⁵⁹

In the last section of his speech du Bois-Reymond appraised recent attempts to explain the interaction of mind and matter in terms of the singular solutions of certain differential equations. Three Catholic mathematicians had postulated that the soul could affect the motion of atoms in unstable equilibrium much as small disturbances could trigger avalanches.⁶⁰ Du Bois-Reymond countered that argument with the observation that even slight perturbations required the mind to perform work, an act that violated the conservation of energy. He therefore dismissed the claims of his French colleagues as a recrudescence of superannuated metaphysics, the atoms of the brain playing the part of Buridan’s ass and the “directing principle” of the soul, whatever that might be, playing the part of Leibniz’s angel.⁶¹

The seventh difficulty vanished if we denied free will; otherwise, it remained transcendent.⁶² Du Bois-Reymond deemed it a poor consolation to monism to see dualism caught in the same net, “tangled all the more helplessly the more it struggles with ethics.”⁶³ At one time he had thought that individual freedom was only a question of mechanics.⁶⁴ But later—and he made no secret of it—he experienced a Damascene moment.⁶⁵ During the winter of 1861 he came to believe “that at least three transcendental problems precede the problem of free will, namely, the nature of matter and force, the origin of motion, and the origin of sensation”.⁶⁶ The enumeration of seven separate enigmas was merely an effect of the scientific division of labor. They might just as easily have been consolidated into “the enigma of the universe.” Leibniz thought that he had resolved this problem, but had he listened to du Bois-Reymond’s deliberations he would surely have agreed with his judgment of “Dubitemus”: let us leave the question open.⁶⁷

10.3 Sources and Significance

The Saturnian once more took up the little mites, and Micromegas addressed them again with great kindness, though he was a little disgusted in the bottom of his heart at seeing such infinitely insignificant atoms so puffed up with pride. He promised to give them a rare book of philosophy, written in minute characters, for their special use, telling all that can be known of the ultimate essence of things, and he actually gave them the volume ere his departure. It was carried to Paris and laid before the Academy of Sciences; but when the old secretary came to open it, the pages were blank.

“Ah!” said he. “Just as I expected.”

Voltaire, Micromegas, 1753

“The Seven Enigmas” caused a groundswell of outrage even larger than “The Limits of Science.” Du Bois-Reymond met with obloquy from all across the world: scientists recoiled at his doubt, ecclesiastics castigated his usurpation, socialists decried his insolence, journalists slighted his language, writers parodied his arguments, and philosophers dismissed his logic.⁶⁸ The last response was particularly telling. There was no need to worry about the mystery of consciousness, Ernst Mach informed the Austrian Academy of Sciences, since “the problem was not a problem.”⁶⁹ In this light the advent of positivism, pragmatism, and idealism at the end of the century can be seen as an effort to sweep du Bois-Reymond’s argument under the rug.

Still, it would be a mistake to interpret the intensity of feeling generated by “The Limits of Science” and “The Seven Enigmas” as evidence that du Bois-Reymond wrote for his critics. In truth he did not think much of philosophy. He believed that it had much more to learn from science than science had to learn from it: experiments, as he wrote to a friend, had taught him to attend to fundamental incomprehensibility of the world.⁷⁰ The task of science was to reduce events to equations; where that failed, it was to delineate the limits of knowledge. As far as du Bois-Reymond was concerned his essays had done so satisfactorily, and he had come to a caesura in his thinking, “like a mathematician who demonstrates the impossibility of solving a problem”.⁷¹ Any additional metaphysical speculation was on a par with astrology and alchemy.⁷²

Neither were du Bois-Reymond’s essays intended as a sop to the Church. Since Haeckel’s allegations of Ultramontane conspiracy, critics had construed du Bois-Reymond’s Ignorabimus as a gambit for independence, or even worse, a Walk to Canossa.⁷³ Evidence points away from this. If du Bois-Reymond cared about the Church’s opinion of science, he would not have remarked that his opponents included “Catholic Jesuits fighting with open visors, and easily recognizable Protestant Jesuits fighting with closed”, nor would he have characterized Bishop Weber’s position as “one of a supernatural dualism which throws itself into the arms of Christian doctrine to the point of the Trinitarian dogma”.⁷⁴ Du Bois-Reymond’s lectures appear conciliatory only in the context of the Kulturkampf; viewed against the background of his career, they exhibit his abiding commitment to “Pyrrhonism in a new guise”.⁷⁵ Expressing doubt does not equate to admitting surrender. As Friedrich Lange remarked in his History of Materialism,⁷⁶ the rhapsodies of theologians and philosophers only denoted their conceit:

Force and matter are inexplicable, models of atoms are only a “substitute” for true knowledge; therefore materialism is rejected—rejected by one of our top scientists. Why, then, can’t speculation and theology saunter onto the abandoned field and teach with great authority what science doesn’t know? (That they have no idea either doesn’t come into question). The celebrated physiologist has declared consciousness—indeed, the simplest sensation—inaccessible to research: why, then, shouldn’t good old metaphysics and faculty psychology drag out their puppets and set them dancing on the vacant field? The dreaded bugbear is gone; the scientist has sworn not to interfere; so the subject is ours again! Everything will carry on as if science didn’t exist.

Du Bois-Reymond did not need to add anything to this rejoinder.

The origins of “The Limits of Science” remain unclear. Some commentators identify Kant’s antinomies, Goethe’s sayings, or Müller’s agnosticism as German sources, but to my mind, Friedrich Schlegel’s analysis of irony with its use of paradox, its study of rhetoric, and its equation of actor and spectator, seems just as likely.⁷⁷ Themes of intellectual limitation appear in English. In 1860 John Tyndall wrote that

when we endeavor to pass from the phenomena of physics to those of thought, we meet a problem which transcends any conceivable expansion of the powers which we now possess. We may think over the subject again and again, but it eludes all intellectual presentation. The territory of physics is wide, but it has its limits for which we look with vacant gaze into the region beyond. Let us follow matter to its utmost bounds, let us claim it in all its forms—even in the muscles, blood, and brain of man himself it is ours to experiment with and to speculate upon. Casting the term “vital force” from our vocabulary, let us reduce, if we can, the visible phenomena of life to mechanical attractions and repulsions. Having thus exhausted physics, and reached its very rim, a mighty Mystery still looms beyond us.⁷⁸

This sounds a lot like the introduction to du Bois-Reymond’s 1848 treatise, Investigations in Animal Electricity.⁷⁹ Tyndall claimed to have gotten the idea in Normandy while sitting under an elm, but his story seems about as plausible as the one about Newton’s apple.⁸⁰ Du Bois-Reymond spent a day with Tyndall in London on 9 May 1855, just a few weeks before Tyndall’s French reverie, and they could have discussed the limits of science then or at any time during their previous encounters.⁸¹ To complicate matters further, the title of du Bois-Reymond’s 1872 address recalled both Charles Kingsley’s lecture on “The Limits of Exact Science as Applied to History” (1860) and Henry Longueville Mansel’s meditations on The Limits of Religious Thought (1859). The whole question of English influence is vexed.⁸²

Moreover, an equally good case can be made for French sources. The theme of intellectual limitation had been explored by Diderot, who was one of du Bois-Reymond’s favorite authors, and by Voltaire, a bust of whom he kept in his living room.⁸³ It also had been mentioned by Bayle, La Mettrie, Condorcet, d’Alembert, and Rousseau, all of whom du Bois-Reymond read and cited, not to speak of Pascal, whose Pensées drew attention to both the incomprehensibility of matter and the “ataraxia, doubt, and perpetual suspension of judgment” of the Pyrrhonists.⁸⁴ Finally, it should be remembered that du Bois-Reymond’s literary model, Sainte-Beuve, discussed all these luminaries in his Causeries de lundi (1948).

Du Bois-Reymond left one clue to the provenance of his determinism. In a letter to his parents dated 26 July 1838, written during the summer he discovered Lucretius, du Bois-Reymond recounted a debate with classmates in which he claimed that chance could not exist in a universe governed by physical law, and that anything that we perceived as random was merely a transference of our own feelings of freedom onto a world of necessity.⁸⁵ A decade later he developed that idea in the introduction to his Investigations in Animal Electricity, arguing that force and matter were nothing other than anthropomorphic projections of ignorance, figures of speech that hypostatized “the same dualism which presents itself in the notions of God and the world, of soul and body, the same want which once impelled men to people bush and fountain, rock, air, and sea with creatures of their imagination”.⁸⁶ It was here that he first addressed the problem of scientific limits:

If we ask what is left if neither force nor matter possesses reality, those who stand with me at this point answer as follows: It is simply not granted to the human mind to get beyond a final contradiction in these things. We therefore prefer, instead of turning in circles of fruitless speculation, or hewing the knot asunder with the sword of self-delusion, to hold to the intuition of things as they are, to content ourselves, to use the poet’s phrase, with the “wonder of what is there.” For we cannot bring ourselves, by the simple reason that a true explanation eludes us in one direction, to shut our eyes to the defects of another, solely because no third alternative seems possible; and we possess enough renunciation to accept the idea that ultimately the one goal appointed to science may be not to comprehend the nature of things, but to comprehend that it is incomprehensible.⁸⁷

This passage contains all the elements of du Bois-Reymond’s later argument. The only difference between it and his mature philosophy was that in 1848 he still thought he could reconcile choice and constraint. That changed in the winter of 1861, when he began to assert there was no room for caprice in “the world of Epicurus,” and that either one could look on history as Voltaire did, as an absurd fable convenue, or one could accept the harsh logic of Calvin’s election of grace, which preserved the idea of providence at the cost of condemning apostates to be burned.⁸⁸

10.4 The Famous Old Bear

It is true that around every man a fatal circle is traced beyond which he cannot pass; but within the wide verge of that circle he is powerful and free.

Alexis de Tocqueville, Democracy in America, 1835

Du Bois-Reymond should not have been surprised by the reaction to his speeches. The theme of forbidden knowledge had been handled in myth from the Garden of Eden to the Flight of Icarus, in literature from Dante’s Inferno to Shelley’s Frankenstein, and in philosophy from the Skeptics to the agnostics.⁸⁹ Du Bois-Reymond brought it up himself at least three times after the introduction to his Investigations: in his 1868 lecture on “Voltaire as a Scientist”, where he referred to the limits of his understanding, in his 1870 lecture on “Leibnizian Ideas in Modern Science”, where he mentioned the impossibility of comprehending even simple sensations, and in his 1872 lecture on the “History of Science”, where he pointed out the areas in which science had reached the frontiers of its territory.⁹⁰ This did not mean that anyone took notice. Du Bois-Reymond’s words hit home only after the creation of the state of Germany in 1871. There is nothing quite as unsettling as success.

Du Bois-Reymond’s perceptions have stood up well. He questioned the possibility of understanding consciousness at a time when physiologists assumed that it arose naturally from the nervous system, he recognized the strengths and weaknesses of atomic models before they won general acceptance, he characterized life as a dynamic equilibrium at every level of organization, and he understood that science was necessarily flawed.⁹¹ Indeed, the sophistication of his views has generally escaped historians of ideas, most notably Ernst Cassirer, whose Determinism and Indeterminism in Modern Physics caricatured his arguments as a muddle of contradictions.⁹² What Cassirer failed to grasp was that quantum events are not necessarily random, and whereas some mathematicians believe that calculation cannot substitute for intuition, others suspect that intuition rests on an irremediable inconsistency in our thinking. Modern science does not entail Platonism.⁹³

Du Bois-Reymond understood his critics far better than they understood him. His insight that metaphysics would cease to exist if consciousness were mechanically comprehensible refuted the idealist assumption that the mind lies beyond understanding.⁹⁴ Neither did he see any point in the phenomenalist program of reducing knowledge to sensation, since the ability to intuit things was precisely what was forbidden in a world without qualities. Moreover, the nominalist emphasis on the growing diversity of science only replaced coherent knowledge with an incongruous mess.⁹⁵ In contrast, du Bois-Reymond viewed mechanics as a heuristic. As Stephen Gaukroger has noted about Descartes, it was not that he thought that the world was a machine, rather that it was best imagined as a machine.⁹⁶ This is a subtle distinction, just as subtle as the politics of du Bois-Reymond’s observation that the arbitrariness of history would disappear in a determinist universe.⁹⁷

The impact of du Bois-Reymond’s essays was so great that it is only now coming into view. His arguments raised an outcry that shaped debates over foundations in mathematics, measurement in physics, activity in neuroscience, will in psychology, and mind in philosophy.⁹⁸ Moreover, variants of his ideas showed up throughout modern culture – for example in Jean-Paul Sartre’s meditation on the impossibility of self-knowledge, in Frederick Jackson Turner’s thesis of the closing of the American frontier and in Henry Adams’s search for unity as he wandered “through the forests of ignorance” and “necessarily fell upon the famous old bear that scared children at play”.⁹⁹ In literature, du Bois-Reymond inspired Theodor Fontane, Heinrich Mann, Arthur Schnitzler, Hermann Broch, Robert Musil, Pío Baroja, Miguel de Unamuno, and, Gustave Flaubert, whose Bouvard et Pécuchet can be read as a rumination on the limits of knowledge.¹⁰⁰ Even the planet in Stanislaw Lem’s Solaris is an embodiment of the Laplacian mind.¹⁰¹

A good deal of the difficulty of interpreting du Bois-Reymond’s essays is conceptual. Du Bois-Reymond’s faith in mechanism and liberalism trusted in the rule of law. Still, it does not follow that a decline in one ideology heralded a decline in the other, or that mechanism and liberalism declined at all.¹⁰² As many narratives of change as there were at the end of the nineteenth century—and the shrillness of du Bois-Reymond’s critics makes such announcements of revolution hard to ignore—there were also narratives of continuity. Instrumental approaches to science did not begin with Wilhelm Wundt and Ernst Mach. Emil du Bois-Reymond was perfectly aware of the elision of description and explanation.¹⁰³ By the same token, there is as much evidence for the strength of liberal values at the fin-de-siècle as there is for weakness.¹⁰⁴ Science never went bankrupt.

Ernst Cassirer identified du Bois-Reymond as the inventor of the doctrine of determinism.¹⁰⁵ Ian Hacking proved this wrong: Charles Renouvier discussed the concept in the 1850s, and if we consider Laplace’s religious training a century earlier, the demon was nothing more than a variant of the Arminian belief in divine omniscience.¹⁰⁶ What is more, the idea that everything follows from natural causes dates back to Lucretius, or at the very least, to 1417, when Poggio discovered a copy of De rerum natura at Fulda. Contemporary philosophers continue to wrangle over the “hard problem of consciousness” without realizing that their arguments differ little from du Bois-Reymond’s.¹⁰⁷

Du Bois-Reymond said that the only thing to be learned from history is that there is nothing to learn. His doubt seems axiomatic to any study of the past. People who think there is a point to things tend to view history as a record of error, whereas those who are conscious of their ignorance tend to take the dead more seriously. Such an attitude of humility generally arises in the course of research. But it is also possible to come to this opinion by thinking. As du Bois-Reymond explained to his students, history was just the cosmic formula solved for negative values of time—a solution, he might have added, beyond the ken of all but a perfect mind.¹⁰⁸ Not that this was any great concern. “If the Laplacian demon should find anything in the cosmic formula obscure”, du Bois-Reymond wrote to Carl Ludwig, “he need only take the train and come to Berlin”.¹⁰⁹