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Darwin's Man in BrazilThe Evolving Science of Fritz Müller$

David A. West

Print publication date: 2016

Print ISBN-13: 9780813062600

Published to Florida Scholarship Online: January 2017

DOI: 10.5744/florida/9780813062600.001.0001

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The Development of Fritz Müller’s Worldview, 1822–1852

The Development of Fritz Müller’s Worldview, 1822–1852

(p.8) 1 The Development of Fritz Müller’s Worldview, 1822–1852
Darwin's Man in Brazil

David A. West

University Press of Florida

Abstract and Keywords

Chapter 1 presents Müller’s family background, education, university studies, intellectual development, and early writings. At Frederick William University of Berlin he studied anatomy, mathematics, natural history, physics, physiology, and zoology, completing a PhD dissertation on leech systematics under zoologist Johannes Müller. He also studied botany at Greifswald University. One topic of particular interest for Müller during his university studies was the mutability of species. Müller was preoccupied with freedom of conscience in the oppressive Prussian state. He became a freethinker and antireligious atheist with leftist political leanings. To avoid a loyalty oath that presupposed commitment to Christianity, he abandoned a high school teaching career and returned to Greifswald to pursue an M.D., hoping to become a ship’s doctor (which required no such oath), but he refused to sit for required exams that required a similar oath. This strong independence of mind reflects a lifelong pattern of advocacy at great personal cost, of unpopular views in politics, religion, science, and social matters.

Keywords:   education, botany, zoology, natural history, species mutability, freedom of conscience, Prussia, independence

Early Life

Fritz Müller, as he was known throughout his life, was born Johann Friedrich Theodor Müller on 31 March 1822 in the village of Windischholzhausen, near Erfurt in the central German province of Thuringia. He was the first of five surviving children of the Protestant pastor Johann Friedrich Müller and Caroline née Trommsdorff, both of whom were from old Erfurt families. Caroline’s father was Johann Bartholomäus Trommsdorff, a well-known manufacturing pharmaceutical chemist in that city. Fritz’s father started his career in 1818 with a poorly paid position in Windischholzhausen and some neighboring parishes, but despite the low salary, his children remembered happy childhoods without deprivation, both there and later in Mühlberg, a larger town southwest of Erfurt to which the family moved in 1828.

Fritz’s father was fond of natural history, alert to interesting plants and insects “even while practicing his sermon” on his way to one of his other parishes, and as a “keen student of the rich local flora,” he encouraged his children’s interest in the subject. Müller had early memories of walking with his parents through the woods and fields around Windischholzhausen, and of the orchids, irises, and other native plants that they found. After the move to Mühlberg, his father formed his own herbarium, and the children helped out, especially Fritz and his brother Hermann. Years later a visitor remembered how Fritz’s father guided the children in observing and understanding “nature and its creations.”1

(p.9) Pastor Müller evidently had independent religious views, perhaps inclining to rationalism, although holding to the “tenets of the Christian faith. It was undoubtedly his enthusiasm for precise observations of nature and his feeling for living nature that awakened his children’s interest in the natural sciences. For him nature and God were united, such that several of his children moved farther and farther away from their father’s Christian worldview.”2 Rational theology had its roots in the seventeenth century, after the successes of science, especially Newton, and recognized “the necessity that all things be tested by reason.”3 By the early nineteenth century the rationalists in Germany “made it their special mission to take the offensive against traditional supernaturalism.”4 Fritz’s father would not have carried things that far, but Müller’s later rejection of religion, although driven primarily by his training in science, probably owed something to his father’s liberal views; his brothers August (1825–1904) and Hermann (1829–83) followed similar paths. As Rainer Friese wrote, “The proximity and love of nature in many Thuringian parsonages evidently provided fertile ground for the systematic study of nature.”5

The early formal education of Fritz and his brothers was at their father’s knee and then in the Mühlberg village school, which Müller remembered years later for its stimulating instruction. When he returned from Berlin University to a probationary teaching position in Mühlberg in 1845, he was said by a young cousin, Richard Mensing, to have introduced “the first proper course in natural science.” Former teachers, whatever their specialties, had used a text giving only “a classification of the animal, plant and mineral kingdoms,” an indication of the parlous state of the field when Müller was a student there.6

In 1835, thirteen years old and already well founded in natural history, Fritz transferred to the Gymnasium in Erfurt, where he lodged with his uncle Hermann Trommsdorff’s family. Müller tells something of his courses in mathematics and languages in Erfurt, but nothing about sciences. He might have become a linguist rather than a naturalist, he told his brother Hermann years later, if the school had given him any help in learning “Italian, Russian, Syriac and Arabic.”

Müller found stimulating activity in the natural sciences, however, in the company of the apprentices and shop assistants in his grandfather Trommsdorff’s Swan Pharmacy and in other Erfurt pharmacies, with whom he went on botanical excursions. He also had an experience while he was living with the Trommsdorff family that revealed something of his indifference (p.10) to religion even in his early teens. He remembered hearing “from grandfather’s mouth” the fact that Konrad Sprengel, the pioneering pollination biologist of the late eighteenth century, had “neglected church over his flower observations, and I drew out the moral that it wouldn’t matter if I, too, sometimes missed church while [plant-hunting] on the Steiger or the Schwellenburg.”7 Herman Trommsdorff, who took over the pharmaceutical business after the death of the grandfather in 1837, was also a botanist with his own herbarium, and Müller had a close association with him while he was a student in Erfurt. All of these people encouraged his interest in pharmacy as a profession.8 Such a professional course, combining botany and chemistry, could lead into pure science or perhaps to an appointment abroad in an interesting tropical country, and Müller was already thinking about emigration.9 Before finishing at the Gymnasium, Müller applied for a pharmaceutical apprenticeship (which would have meant dropping out of school), but was rejected, and it was only after he finished school in 1840 that he was successful. The appointment allowed him to join his friend Ernst Biltz, and the two of them went plant-hunting together and even corresponded with scholarly botanists.

University Years

Müller’s thoughts, however, were turning toward a career in pure science, pharmacy becoming too inflexible a subject for him. He had also been developing an independent streak and decided to get a university degree in natural sciences and mathematics and to become a teacher. He left the apprenticeship in February 1841 and entered the Frederick William University of Berlin that spring.10 Müller was well prepared both academically and practically for the broad university education that Berlin could provide.

The university had been founded in 1809 by a group of “neo-humanists” who wished to restore the preeminence of the philosophical faculty (arts and sciences) over theology, law, and medicine then dominant in German universities, using the city’s collections and research labs and the members of the Prussian Academy of Science as inexpensive resources. In addition, because it was the first German university in a large city, its students would not be “as free to lead the licentious and often terroristic life-style they had sometimes enjoyed in small university towns in the eighteenth century,” and in these respects the founders were successful.11 (p.11) But they also hoped that most of the students would take up subjects in Wissenschaft (science or scholarship) rather than Brotstudium (career-oriented curricula), and in this respect they were unsuccessful; Brotstudenten were probably in the majority.12 By 1841, however, the Faculty of Philosophy had achieved the aim of imparting its own research results rather than handing down “accepted truths,” and was cultivating the “scholars, who were … a guarantee that the ideals of Wissenschaft would live on into the next generation.”13 Müller was clearly going to be one of those, and the direction of his interests shifted under the stimulating lectures, seminars, and research opportunities available to him. As for his fellow students, however, when Max Sagemehl, a young zoologist in Amsterdam, complained to Müller in 1885 that few university students there were interested in pure science, Müller replied that the same had been true in Berlin forty years earlier: “Most students divided their time between the bars and Brotstudium,” despite the “matchless men whom Berlin possessed as teachers.”14

The first of Müller’s professors in the natural sciences were Jules Lichtenstein (1816–1866), a French-German entomologist and naturalist, who gave him an excellent introduction to zoology, and the botanist Karl Sigismund Kunth (1788–1850), who had spent sixteen years in Paris working up the vast South American plant collection brought back by Alexander von Humboldt.15 He also met Johannes Peter Müller (1801–58), a legendary professor of anatomy and physiology, who had broad research interests in embryology, nervous systems, comparative anatomy, and marine zoology, and whose Handbuch der Physiologie of 1833–40 was a milestone in experimental medicine. “[Johannes Müller] required of empirical research that it be carried out ‘with seriousness of purpose and thoughtfulness, with incorruptible love of truth and perseverance…. Almost all German scientists who achieved fame at the middle of the 19th century considered themselves his students or adopted his methods or views.”16 Johannes Müller’s lectures on theoretical and practical anatomy in winter term 1841–42 were the beginning of a close scientific relationship between the two that would culminate in Fritz’s PhD in 1844.

Johannes Müller had studied medicine at the University of Bonn when natural-philosophical speculation was widespread in Germany, but a postdoctoral term in Berlin in the early 1820s brought him “under the influence of Carl Rudolphi, Germany’s most distinguished anatomist, … who sought to lead scientific research out of the ‘turbid mire of mysticism’ (p.12) and endow it with an exact method. Johannes Müller credited Rudolphi with having enabled him to escape the dangers” of Naturphilosophie. Fritz himself had begun seeing nature without theological underpinnings in the early 1840s, but Johannes Müller, who was then beginning to study larval forms and development in marine invertebrates, would have introduced him to Amphioxus (now Branchiostoma), then considered “the simplest model of the basic plan of the vertebrate subphylum,” and to “complex metamorphoses, including sea urchins from a bilateral larva.”17 These studies provided the foundation of Fritz Müller’s research on marine invertebrates in Brazil and were almost certainly the roots of his lifelong interest in development and its implications, the full flowering of which came two decades later when he met Darwin’s Origin. Johannes Müller is said to have begun studying marine invertebrates in 1845, as Fritz Müller was leaving Berlin, but if he began publishing on them that year he would certainly have been engaged in the research sometime earlier, while Fritz was still his student.

In 1842 Müller transferred to Greifswald University for a year, a common practice among German students simply seeking variety, but in Müller’s case probably in order to study the marine fauna of the nearby Baltic. There is no record of his academic work during that year, but he did meet another influential mentor and friend, the professor of botany Christian Friedrich Hornschuch (1793–1850), who treated talented undergraduates as colleagues and with whom Müller collaborated a few years later. Hornschuch’s specialty was mosses, and Müller helped to organize his collection.18

Müller’s mother died in February 1843 after a six-week illness, and he returned that summer to Berlin. There he attended lectures on the comparative physiology of the infusoria by Christian Gottfried Ehrenberg (1795–1876), whose specialty was single-celled marine and fossil organisms. The infusoria were originally a diverse assemblage of single-celled organisms that appeared in infusions of hay, hence the belief that they arose spontaneously from decaying organic matter; the name was later restricted to ciliated and flagellated protozoa. Ehrenberg was opposed to Lamarck’s “chain of being” and to spontaneous generation, but he favored “a philosophical system that presupposed the spiritual origin and constancy of the world order and therefore resisted materialistic and evolutionary interpretations.”19 Müller never commented on Ehrenberg’s ideas, but the man’s extensive travel experience in the Near East and Siberia might have stimulated Müller’s (p.13) own future travel plans. Wilhelm Ferdinand Erichson (1809–1848), with a special interest in beetles, rounded out Müller’s term with lectures in entomology. In summer term 1844 he took his last science lectures, the natural history of mollusks, from Franz Hermann Troschel (1810–82), a curator at the Humboldt Museum, and both comparative anatomy and general physiology from Johannes Müller.

From his undergraduate professors in natural sciences he had acquired a strong background in botany and zoology, including entomology and marine and freshwater invertebrates, as well as anatomy and physiology. He had also attended lectures in astronomy, geology and mineralogy, mathematics, physics and meteorology, philology, philosophy, and the classics. It was probably a set of lectures on number theory, given by the brilliant mathematician Gustav Peter Lejeune Dirichlet (1805–1859), that led Müller to an interest in phyllotaxis, the arrangement of buds on a plant stem. With these riches from Berlin (and Greifswald) Müller received an education in arts and sciences nearly unobtainable at that time in Great Britain or the United States.

Müller’s later rejection of religion probably resulted in part from his encounter with the philosophy of Spinoza while at Berlin, although it is not clear whether through the lectures on the history of philosophy given by the Aristotelian philosopher Friedrich Adolf Trendelenburg (1802–1872) or from Johannes Müller himself. Heinrich Czolbe, one of Fritz’s contemporaries at Berlin and another student of Johannes Müller’s, was directed by his mentor to the importance of Aristotle and Spinoza during his own doctoral examination.20 A decade later, after two years in Brazil, Fritz asked his brother in Germany to send him Spinoza’s works, “in the original Latin, of course, I am opposed to translations.” It is no surprise that the Dutch philosopher Baruch Spinoza (1632–1677) would be Müller’s favorite, given Spinoza’s views. Steven Nadler encapsulates them as expressed in Spinoza’s Theological-Political Treatise, published anonymously in 1670: “The Treatise—with its rigorous depiction of the Bible as not of divine origin but a mere work of human literature; its attack on sectarian religion as organized superstition and a danger to the well-being of the state; its argument for the toleration of philosophical thinking; and its debunking of miracles, revelation, and divine providence as products of the imagination—was widely and vociferously condemned by ecclesiastic and political authorities … [and] was regarded as the work of an atheist and a libertine.”21 Those sentiments are in line with the point of view that (p.14) led to Müller’s declaration of atheism in 1846, and they remained paramount for the rest of his life.

In 1884, for example, having found that most of the chapters in Werden und Vergehen,22 a popular work on evolution, had Lucretian epigraphs, he asked Hermann for a copy of Lucretius’s On the Nature of Things, circa 50 B.C.E.23 Lucretius had materialist and atheist views that would have appealed to Müller, although his atheism was “more accurately [described as] the indifference of the gods.” Lucretius posed numerous challenges to society, for example, that “All living beings, from plants and insects to the higher mammals and man, have evolved through a long, complex process of trial and error”; that clearly “over the infinite expanses of time, some species grow, others disappear, generated and destroyed in the ceaseless process of change”; and that “All organized religions are superstitious delusions.”24

Johannes Müller, whom most students shunned because of his “stern inaccessibility,” recognized Fritz’s serious scientific interest, provided him with a microscope at their first meeting, and “almost never left without instruction and encouragement.”25 Fritz’s first published research was on the classification of two leeches from the Berlin region, correcting previous authors with a careful study of the animals not only in the living state but also through dissection. Although the work is purely descriptive, it already reveals the care with which Müller included information even about the habitats of the animals, a common feature of many future papers.

On 14 December 1844 the philosophical faculty of the University of Berlin conferred on Müller (not yet twenty-three) the PhD based on a dissertation approved by Johannes Müller: “On the Leeches of the Berlin Region.”26 It was a taxonomic work: chapter 1 a diagnosis of the family, chapter 2 the systematic treatment of the species of leeches in the genus Clepsine, and a third chapter not printed. This “Dissertatio inauguralis zoologica” was a sign of Müller’s independent scholarly achievement as well as a credential for a prospective Gymnasium teacher.27 Müller passed the secondary school teacher’s examination early in 1845 and completed his “philosophical” education.

There were seven theses appended to his dissertation, not published but apparently defended at his PhD examination. Whether they were set by his examiners or were his own ideas is not clear, but they seem to reflect the working of an independent mind and could well be the opinions of such a twenty-two-year-old:

  1. (p.15) 1. The peristome alone is not sufficient for determining the natural genera of mosses. [The peristome is a marginal ring of teeth around the opening of the sporangium of mosses, but some genera of mosses lack a peristome, and in very few genera is it a reliable single character.]28

  2. 2. The genus Andreaea should be included with the mosses, not with the true liverworts. [Andreaea and the liverworts have unique morphological features and have apparently never been thought connected. Müller could presumably have defended nos. 1 and 2 from his experience with Hornschuch’s mosses.]29

  3. 3. Neither Treviranus’s nor Henle’s theory about the genitalia of leeches is defensible. [Gottfried Reinhold Treviranus (1776–1837), German naturalist, and Friedrich Gustav Jacob Henle (1809–1885), German pathologist and anatomist, had published on the anatomy and histology of leeches. Müller’s careful dissections of several species of leeches convinced him that they were wrong in some details and would have provided the evidence for his refutation of their theories.]30

  4. 4. The study of languages is less suited than the study of mathematics and natural history for developing the power of judgment in children. [Although he was fascinated with languages, Müller’s broad experience in math and science would have supported this thesis.]

  5. 5. Lungs and gills are not clearly distinguishable.

  6. 6. There is no reason to consider some animals more perfect, others more imperfect. [It is tempting to think that Müller was on the threshold of a Darwinian idea—that the perfection of an organism is a relative matter. “If our reason leads us to admire with enthusiasm a multitude of inimitable contrivances in nature, this same reason tells us, though we may easier err on both sides, that some other contrivances are less perfect.” But is the stinger of a bee perfect, though its use “inevitably causes the death of the insect by tearing out his viscera?”31 Although Müller was not prescient about Darwin’s theories, the thoughts engendered by this thesis could have eased his acceptance of the Origin.]

  7. 7. There is no such thing as the so-called animalcules of animal semen. [Animalcules (tiny animals) were first observed by the Dutch microscopist Antonie van Leeuwenhoek (1632–1723); they (p.16) included a variety of single-cell organisms, bacteria, and blood corpuscles. But in 1677 he discovered them in his own semen and “speculated that those animalcules”—now called spermatozoa—“penetrated the egg and resulted in fertilization.”32 Although the egg was at that time widely accepted as the basis of a new organism, Leeuwenhoek insisted that the animalcule that he had discovered played that role and started a controversy that was not settled until the nineteenth century.33 Matthias Schleiden and Theodor Schwann’s discovery in the 1830s that organisms were made up of cells, and thus that eggs and sperms were cells, would presumably have persuaded Müller that spermatozoa were not “tiny animals,” at all.]

Müller was familiar with the work of the Danish biologist Otto Frederik Müller (1730–1784) through his studies of leeches and other “worms,” and in 1844 he selected as an epigraph for his dissertation a passage from O. F. Müller’s Vermium terrestrium et fluviatilium (1773) that typifies his lifelong approach to research: “I am echoing no one else’s ideas and have not depended in any way on the findings of others; I am setting forth here only what I have studied myself and observed repeatedly and at different times.”34 In the same year, after discovering a rare aquatic earthworm near Berlin, he wrote to his brother Hermann that looking only at external morphology, you “get but a dim view of the endless diversity of nature. The careful study of a single animal gives more pleasure than a whole zoological museum, as you observe its way of life, study its internal structure and can sense the infinite wisdom that fits the smallest part to the common purpose of the whole animal, … [and how] all work with and for one another!”35 Integrating ecology, structure, and physiology had already become Müller’s priority and remained so, although he would reject “infinite wisdom” even before he encountered Darwin and natural selection seventeen years later.

After Müller’s mother died, his father married Sophie Agnes Schmidt (1815–1899), the eldest daughter of a landowner in Kirchheim, not far from Mühlberg. They had six children, one of whom, Christian Gustav Wilhelm Müller (1857–1940) (known as Wilhelm Müller), would spend two years in research with Fritz in Brazil and became professor of zoology at Greifswald.36 Fritz and his siblings remained on cordial terms with their stepmother, and in the spring of 1845 he returned to the area to take up a probationary teaching position in his old school, the Erfurt Gymnasium, (p.17) with a full load of natural history and mathematics, introducing a modern approach to the teaching of natural history. The authoritarian Prussian state, however, of which the Erfurt region was a part, was cracking down on both secular and religious dissent, and Müller was edgy about the threat to the supposed guarantees of freedom of conscience. The official “intolerant propagandist line,” as he described it to a cousin in June 1845, meant that anyone who “does not hypocritically follow [that line] will be [un]able to depend on any forbearance from the State.”37 Müller realized that his intellectual freedom and his proposed teaching career were both seriously threatened, particularly because he was about to take the momentous step of renouncing religion; he knew that he would then truly lose all “forbearance” to teach in state schools.

With that realization, Müller left his teaching post after half a year and took to a new direction: pursuing a medical degree with the intention of becoming a ship’s doctor in order to travel and study natural history abroad. The medical course at Greifswald University was his choice, and in early October 1845 he headed north. He was already a fully rounded scientist, but late in his life he looked back to those years in Greifswald with gratitude, for it was there that his lifelong passion for truth and freedom matured.

Hornschuch greeted him once again with hospitality and botanical excursions, and for three years, until 1848, Müller made use of all the medical lectures and clinical work that the university offered. But natural history still occupied him, and on free afternoons he rambled the countryside and was able to publish a few zoological articles, though not a word in the medical literature.

In 1846 Hornschuch was asked by the Danish zoologist Johannes Iapetus Smith Steenstrup (1813–1897) to translate into German his work on the question of whether hermaphroditism was of natural occurrence in nature.38 Steenstrup had concluded that it was not, arguing that it “disagrees completely with the whole way in which nature works, as well as with the surest principles of physiology, comparative anatomy and development.” Since Hornschuch’s subject was mosses, he showed the work to Müller and to two of his closest zoologist friends, Max Schultze (1825–1874) and Anton Karsch (1822–1892). From their own experience they all thought that Steenstrup was wrong, and their observations on leeches and on hydra and snails, respectively, were published as an appendix to the translation.

Müller, in characteristic fashion, referred to his own detailed studies of leech anatomy and declared that Steenstrup’s description of the genitalia (p.18) of leeches was “based partly on an incomplete, and partly on an incorrect, understanding of the anatomical relationships.” In one species Steenstrup had not examined his material at the appropriate season and had dismissed as “dormant regions” what were actually ovaries. “Had these been carefully investigated in May or June, the author would have easily convinced himself that the eggs really are formed here, and not in [what are actually] the testicular vesicles.”39 Steenstrup had seen only one sort of complicated sexual apparatus and decided that in some individuals it produced eggs and in others sperm.

Müller’s Precursors

Müller’s research in the 1840s and 1850s was careful and detailed, largely descriptive and taxonomic, but even in 1844, in a letter to his brother Hermann, he speaks of species diversity, and through his teachers in Berlin and Greifswald he must have known of the controversies over whether species are mutable, what causes their diversity, and how they could be classified. Although he had undoubtedly learned about Naturphilosophie, a distinctly German view of the organic world developed by philosophers like F. W. J. Schelling (1775–1854) and derived in part from Spinoza, it was those controversies that would have engaged him, probably from French naturalists such as Lamarck, Cuvier, Étienne Geoffroy Saint-Hilaire, and Henri Milne-Edwards.

In his Philosophie zoologique of 1809, Lamarck (1744–1829) had supported mutability in contrasting two ways of looking at animal diversity. On the one hand there was what he called the current view, that “nature (or its Author) in creating the various animals foresaw all the possible kinds of circumstances in which they would have to live and gave to each species a constant organization, … obliging each … to live in the places and climates where it is found and to maintain there its characteristic habits.”40 That was the classic teleological creationist view, the position of Georges Cuvier (1769–1832), who, according to the historian Toby Appel, proposed “four basic body plans, his embranchements [branches]—vertebrate, articulate, mollusk, and radiate, and insisted that there were no transitions between” them. “Every part of an animal … was designed to contribute to the functional integrity of the animal or to adapt it to its environment,” and if a “new part is required for functional purposes, the Creator was free to fashion a new and appropriate organ. For Cuvier, species were unchanging creations, (p.19) and the animal’s needs sufficed to determine its structure.”41 In 1825, Cuvier “defined nature in the light of his teleological and religious preconceptions” and condemned all speculative theories as “based on a dangerous misunderstanding of this definition.”42

Lamarck’s own conclusion was that “nature, in producing successively all the species of animals, beginning with the most imperfect or most simple … has gradually made their organization more complex; and with these animals spreading generally throughout all the habitable regions of the globe, each species received from the influence of the circumstances in which it is found” its habits and the modifications of its parts.43 Richard Burkhardt points out that Lamarck allowed two causes of organic change: “the general series of increasing complexity formed by the animal classes,” which affected “internal structures that were in some measure removed from the direct influence of the environment,” and the classic Lamarckian explanation, “change through the inherited effects of environmentally inspired use and disuse,” which affected “external, less essential characters.”44 Müller himself later made a similar distinction and may have picked it up from exposure to Lamarck in Berlin. He thought that some characters, such as the venation of lepidopteran wings, are “inherited,” by which he meant deeply rooted in inheritance and fundamental, while others, such as mimetic patterns on butterfly wings, are “acquired,” that is, have arisen recently and are relatively changeable.45 Müller’s mechanism of acquisition, however, was not in the least Lamarckian, but rather natural selection.

Cuvier also believed that the extinctions evident in the fossil record were caused by periodic catastrophes, “by which all the forms of animal life in entire geographical areas were wiped out … and replaced by other forms of life.”46 In 1801 he had given “three possible explanations of the observed differences between fossil and living forms”: “the species that existed [had] been entirely destroyed, … they [had] been only modified in their form, or … they had been simply transported [migrated] from one climate to another.” Cuvier favored the first explanation. Lamarck accepted migration but “also embraced the idea that in the course of the Earth’s history organic forms have been modified.”47 From Lamarck’s uniformitarian view, neither extinction nor catastrophism was “compatible with the operations of nature.”48

According to Burkhardt, this explains some of the “inspiration of Lamarck’s belief in species mutability,” or of his evolutionary views, because “Lamarck’s understanding of evolution was not simply (or even primarily) (p.20) an extension of the idea of mutability that arose from his refusal to admit species extinction.” He did, however, endorse mutability when he wrote that the fact that many fossil shells are different from all the living ones “does not prove that the fossil species … were destroyed,” but only that they had changed over time and were now different from the fossils.49

Müller was familiar with Lamarck’s ideas and was clearly aware, after he read the Origin, that natural selection was an all-important break with the past, as we know from his correspondence with Alexander Agassiz in the 1860s. In his book Für Darwin of 1864, Müller recognized a broad acceptance of species mutability in simplified parasites that were clearly derived from barnacles, with no mention of Lamarck. Lamarck could have made him think about diversification, but Müller would certainly have rejected the idea that the “sovereign author” created organization and set the process of diversification in motion.50

Cuvier’s point of view pervaded the early nineteenth century, but a colleague in the Muséum d’histoire naturelle in Paris, Étienne Geoffroy Saint-Hilaire (1772–1844), developed very different ideas that could also have contributed to the intellectual environment of Müller’s university years. Those differences with Cuvier culminated in a famous debate reflecting the bitter dispute between those who believed that species do not change and those who believed that they could in the Academy of Sciences in 1830.51

In the debate, Geoffroy proposed what he called “philosophical anatomy” as the basis of the study of morphology. “Instead of describing each class of animals separately, using different names for different structures in each,” he sought a single generalized structural plan for all the vertebrates, based on the concept of what is now called homology, to discover the resemblances, “often obscured … by changes of form and function, between elements of animal structure. For the philosophical anatomists, animal organization appeared to have a constancy in the number and arrangement of parts that was independent of the form of the parts and the uses to which they are put.”52 He rejected some Lamarckian ideas, but he agreed that species were mutable. In further opposition to Cuvier, Geoffroy explicitly “refused to mix mysterious matters of faith with his work as a scientific investigator,” although he “reaffirmed his faith in a Christian God and the immortality of the soul.”53

The great debate of 1830 ended with no winner or loser, and Cuvier was dead within two years, but zoologists of the next generation divided in adopting parts of both sides of the controversy. The work of one of these, (p.21) Henri Milne-Edwards (1800–1885), an authority on the Crustacea and a student of Geoffroy’s, exemplifies one taxonomic framework of the 1830s and 1840s, when Müller was gaining experience in observation and interpretation, and Müller was familiar with Milne-Edwards’s work on the Crustacea. In the first volume of his Histoire naturelle des crustacés of 1834, Milne-Edwards stood for species mutability with his best-known evolutionary insight, the division of physiological labor. “As one ascended the scale of being [a pre-Lamarckian echo] … the parts of organisms became increasingly dissimilar. While at first the same organ felt, moved, respired, and absorbed nutrients, step by step each function acquired its own instrument,” leading to complexity.54

As Appel reports, Milne-Edwards “envisioned the external skeleton of [all] Crustacea as in essence a series of [twenty-one] ‘homologous’ segments,” and he chose a mantis shrimp, Squilla, as a starting point because it seemed to be the least modified form of Crustacea, with many distinct segments of similar structure. “As the division of physiological labor progressed, functions became localized, and the segments and their associated appendages became increasingly modified. Likewise, in the embryo the [appendages] at first all had the same form, but soon became dissimilar.”55

Milne-Edwards saw physiological anatomy as a way to achieve “Cuvier’s goal of a natural system of classification,” and Geoffroy’s “homologies [as] especially useful in classification when embryological evidence was brought to bear.”56 Differences in structure did not trouble Milne-Edwards, who wrote that “one includes in the group of crustacea all animals whose general organization … can be linked to that of the types of the class, and whose conformation recalls the transitory states through which the most perfect beings of the series have passed during the duration of their embryonic development.”57 His belief that “the closer the pattern of development of two animals, the closer they ought to appear in the natural system of classification”58 points the way to Müller. Milne-Edwards was a vitalist and advocated final causes. He “agreed with Cuvier that God’s conception of the function of an organ was prior to the assigned structure, but in practice he often gave primacy to structure.”59 But “while he did offer a few examples of possible new creations … he did not believe with Cuvier that God has unlimited freedom to create them,” but “only as a last resort.”60

With the exception of Milne-Edwards, these forerunners were dead before Müller finished university in 1844, but his teachers were certainly familiar with them. Unfortunately, we don’t know what his lecturers said, but (p.22) in one respect, as an atheist, Müller stood completely apart from them all. He did not renounce religion formally until 1846, when he turned twenty-four, and he gave only one clue, in 1844, that there was ever a deity in his universe, when he spoke of the “infinite wisdom” that arranges every part of an animal to its “common purpose.”61 After reading the Origin and accepting natural selection as a force that could bring about those new arrangements, Müller used the phrase “infinite wisdom” only ironically.62

The prominent scientific materialists were contemporaries of Müller’s and were also non-religious, but except for Carl Vogt (1817–1895) they were doubtfully naturalists. Vogt had contributed to Louis Agassiz’s work on fossil fishes and was the closest to being a practicing naturalist, but his Zoological Letters was a compendium, not his own work.

Louis Agassiz (1807–1873) overlapped those forerunners and was the most important figure bridging the years into the post-Origin period, and he deserves special mention here because, as a creationist and close adherent of Cuvier’s views, he was one of Müller’s principal targets. Müller distinguished between Agassiz’s facts, which he recognized as admirably worked out, and Agassiz’s philosophical framework, which he deplored, indicating that he could have had an open mind about some of the ideas of men like Lamarck and Geoffroy while rejecting their religious framework. Agassiz had worked on fossil fishes with Cuvier in Paris in the 1830s, and although he may have been somewhat of a scientific materialist in his youth,63 he soon adopted Cuvier’s four branches, the fixity of species, and the importance of extinction and catastrophism. In 1842, Agassiz declared that the time had come “when science … can recognise in nature God the Creator, the Author of all things.”64 Agassiz realized that the Earth had a history, but he saw the discontinuities in the fossil record as evidence of repeated mass extinctions followed by episodes of creation. Agassiz’s “creation” was not biblical, however, since there were many episodes, each marking an advance, and if apparent intermediates appeared in the fossil record, they were only “prophetic types” that the Creator got “right” on the next go-round. “The combination, in many extinct types, of characters, which, in later ages, appear disconnected in different types, exhibits thought, prophetic thought, foresight; combinations of thought preceding their manifestation in living forms.”65 Agassiz maintained these views to his death in 1873.

Müller and Agassiz had similar experiences growing up in the households of Protestant clergymen—an early introduction to natural history (p.23) (for Müller mostly plants, for Agassiz a variety of animals) and a lack of family pressure to enter the ministry—and yet the premises they developed in their teens and twenties were extraordinarily different. Müller attributed his rejection of religion to university science, suggesting that at least some of his teachers in the 1840s encouraged that view, but the expressions of independence in his teenage years suggest still earlier roots. He was also influenced by his reading of David Friedrich Strauss (1808–1874) and Ludwig Feuerbach (1804–1872) while in medical school. These factors may be enough to account for Müller’s premises as Darwin slid into his ken. For Agassiz, the idea that the natural world must have been formed by a “superior intelligence” on some sort of “premeditated plan” seems to have arisen principally from the successive appearance of different types of vertebrates in the fossil record.66 But other, unrecognized premises must underlie that obvious one.

Freedom of Conscience

The expansion of German universities after 1819 was accompanied by the rise of “reformed student fraternities” that reacted against the old dueling and drinking tradition with a sober and serious side and a “devotion to real discussion of political and university issues.” The possible consequences of those discussions, however, raised the suspicions of the government, which set up “a system for spying upon and punishing political activism” that eventually drove the student groups underground.67 By the mid-1840s “the freedom of the lectern was at no time so much at the mercy of ministerial despotism as it was [then].”68 The authorities of the Prussian state and the church were depriving freethinkers of their platforms, censoring the press, and arousing students, including Müller, who wrote to Rosalie, another of the Mensing cousins, in October 1845: “There are so wretchedly few men these days who … are really capable of sacrificing everything for their convictions.”69

Among scarcely 180 students in the university, 60 belonged to a student association that set up a reading room with the “latest and most liberal writings of the time,”70 including those of Strauss and Feuerbach, perhaps the two most influential writers on theology in that period. Strauss’s Life of Jesus (1835) raised a storm by accepting Jesus as a historical figure but stripping away all of the supernatural events in the Gospels as myths.71 In 1840–41 Strauss rejected the creation stories in Genesis on the basis of (p.24) advances in astronomy and geology with which Müller was already familiar.72 But Strauss also wrote something that may have promoted Müller’s tolerance toward other points of view: “We leave [the believers’] faith to them; let them leave our philosophy to us.”73 Feuerbach’s Essence of Christianity (1841) declared that God was only “the reflection of human thoughts and aspirations, … [an] idealized essence projected into a transcendental sphere,”74 the basis of scientific materialism in the 1850s.75 Müller was already affected by Feuerbach’s arguments in the religious sphere and expressed his admiration twenty years later in Brazil when he named a genus of orchids “Feuerbachia.”

Many years later Müller was not sure just how he came to be “regarded as a great Darwinist.” He thought it “neither surprising, nor much to my credit” that Brazil provided him with so many observations of living plants and animals that would not have been possible in European museums—“stuffed and impaled corpses or dry hay,” he wrote. But it was his Greifswald experience, not so much the radical readings as the “lively verbal sparring over those topics at nearly every meeting,” that led him to “probe the meaning of those [later] observations more deeply.”76 The other authors in that reading room were largely political, and although Müller had firm convictions about religion, in politics he was merely affected by the slogans of friends who shared his religious views.77

As a member of the reading society, Müller could keep up with all the religious and political controversies of the day, including the establishment of a national church. The idea was promoted by the liberal theologian Georg Gottfried Gervinus (1805–1871), who in 1845 “zealously took up the cause of the German Catholics,” hoping it would unite “all the Christian confessions” and lead to the formation of a national church.78 The German Catholics had dissented from the Roman Catholic Church in 1844 and adopted a creed that banned external authority and made the Bible the sole rule.79 That movement might have caught Müller’s interest by its repudiation of external authority, but there was still enough of the Nicene Creed in it to have kept him at a distance. Friedrich Theodor Vischer (1807–1887), a writer on the philosophy of art and active in the democratic movement of 1848–49, criticized Gervinus and the German Catholics, and, as Müller wrote, showed that “every dogma, however arrived at and however liberal-seeming, must always have some exclusiveness, always give rise to intolerance and be in irreconcilable conflict with religious freedom.”80

One group of dissident Protestants, the Friends of Light (Lichtfreunde), (p.25) did catch Müller’s eye. It had been founded in 1841 in protest against the government-backed Protestant harassment of rationalist clergy,81 and in 1844 it was taken over by the liberal Lutheran pastor Gustav Adolf Wislicenus (1803–1875). The group was outlawed by the Prussian government in 1845 as an agent of political opposition. Wislicenus protested that “our own inherent intellect,” not the Bible, should be “the standard of Protestant consciousness,” after which he was dismissed from the national (Lutheran) church in 1846. In January 1846 he started a monthly journal on church reform (Kirchliche Reform) for “free Protestants of all persuasions,” which changed its title and remained a step ahead of the authorities for the next seven years.82 Soon there were eighty Free Congregations, forming a party opposed to the government as well as to the national church.83

In 1853 Wislicenus published Der Bibel im Lichte der Bildung unsere Zeit (The Bible in the light of contemporary learning). Copies of the book were destroyed and he was found guilty of “mocking the Bible” and avoided a two-year imprisonment only by leaving Halle precipitously on 14 September 1853, the morning after the judgment, and escaping to England and then to Boston. He objected that if he were really “mocking” the Bible he must have been scorning it, but that he was merely stripping the stories of their supernatural content.84

In the first issue of Kirchliche Reform, Wislicenus expressed the aims of the Friends of Light in two principles: church reform will never come from above but rather from “the people and the whole community”; and not through “broken traditional beliefs” but only by “the universal application of reason.” He closed with an expression of tolerance, having recalled in part Strauss’s 1840 arguments and rejected biblical authority when he took over the Friends of Light in 1844. The Friends of Light trusted that their convictions would eventually prevail, but if they had the power to take away the free expression of opposing opinions they “could not use it, because by that practice [its] own belief must immediately crumble.”85 Müller had probably read that passage before an incident that demonstrated the same tolerance. The small Catholic community in Greifswald had not been allowed to use local churches for its occasional services, and petitioned the university for the use of its assembly hall. That too was rejected, and Müller joined with other students in asking the faculty to grant the petition, “in the interest … of the free practice of religion.”86

In January 1846 Müller faced a major intellectual crisis, writing to his brother August that he was rejecting his religious heritage. “Three of the (p.26) five medical men with whom I mainly associate, and I, are radical rationalists, in college life and in matters of religion, and draw our conclusions with inexorable consequences, painful though it may be to give up ideas to which we have clung fervently from childhood.”87 It was the hypocrisy of professing “an inwardly foreign belief, for fear of the opinion of the masses or of the powerful arm of authority” that he hated—and he added that “there is nothing Christian, but something human, about hating.” Believing that it would be better if people were frank about their convictions, he told August of his plan to “declare openly that I will not be a Christian, but rather a human being,” when he came legally of age on his twenty-fourth birthday, 31 March 1846.88

He said that he would explain everything to his father and stepmother, and to his mother’s brother-in-law, the Lutheran bishop of Prussian Saxony, who had presided over his confirmation, but aside from a letter to a cousin he apparently put those steps aside until late in 1846. Müller had by then seen Wislicenus’s new journal, and on 15 November 1846 he wrote to Wislicenus, declaring his agreement with the principles of the Halle Free Congregation. It was “a serious striving for truth” engendered by his university studies in natural sciences that led him to his freethinking point of view, and he could no longer be a hypocrite. “The Bible has been replaced by the intellect, the supernatural God by the eternal laws of nature, life hereafter as the end of all striving by life on earth as an end in itself. A Christian has become a human being!”89 Compare Feuerbach in 1841: “Unbelief has taken the place of belief, reason the place of the Bible, politics the place of religion and the church, earth the place of heaven, work the place of prayer, material want the place of hell, man the place of the Christian.”90

Müller’s letter appeared in Kirchliche Reform in December 1846. In aligning himself with the Friends of Light, Müller seemed to retain some sort of religion, but he had already become an atheist, or was rapidly moving toward becoming one, and he reiterated that point of view for the rest of his life. His Lutheran bishop uncle learned of Müller’s convictions from the letter and reacted in dismay and horror, and his favorite sister, Rosine, broke off contact, evoking a plea from Fritz that she remain a “loyal and sympathetic woman friend,” who could hear his laments and share his joys. He assured her that he would not “attack [her] beliefs with philosophical subtlety,” but recognized that she might be frightened by the candid expression of his thoughts and “afraid of being made miserable because of confusion about the rightness of [her] viewpoint.” There would then be no way (p.27) out but silence.91 Müller’s father and stepmother also broke off communication for a time, probably in sadness, and when August gave up theology that same year they not unfairly blamed his older brother’s influence. But time closed the rift, Rosine returned as a correspondent, and Fritz continued to unburden his thoughts to her.

In September 1847 Müller was anticipating graduation from his medical course, which would be followed by the state examination giving him the license to practice medicine. But he could also see a looming problem: the examination had to follow graduation, and to graduate he had to subscribe to an oath concluding with “so help me God and his sacred Gospel,” and that Müller refused to do. He petitioned to replace it with a simple promise, but after passing through the bureaucracy his request was turned down in February 1848 because he had “not joined a religious society whose members were excused from the rules regarding the wording of the oath.”92 He still had time before graduation to ask again, but now there was a major distraction: the March Revolution of 1848.

The Prussian monarch Frederick William IV came to the throne in 1840 promising to restore civil liberties and freedom of the press, but he quickly retracted those measures of liberalization, dashing Müller’s hopes, and in the autumn of 1847 there were popular calls for liberal reforms. In March 1848, with revolutionary stirrings in all the major capitals of Europe, the Prussian monarch lost control after brutally suppressing a workers’ demonstration in Berlin, and on 18 March he gave in to popular pressure and was then “entirely under the protection of his subjects.”93

There was elation in Greifswald, and the formation of the Democratic Party, and Müller “swam in a sea of happiness.”94 He was occupied in the obstetrical clinic until 1 July 1848 and had dysentery for several weeks in the late summer, but in September, on the “finest day of his life,” as he wrote to his brothers, he attended a congress in Greifswald of “all the democrats of Lower Pomerania,” meeting a host of “splendid people.”95 He was most concerned with how religious freedom was to be achieved, and the likelihood of that freedom was fast diminishing.

The problem of the Christian graduation oath remained, and Müller doubted that the revolution had gone far enough to allow him to graduate without it. His second petition to the medical faculty, in October 1848, asked that he be allowed, “like Jews, to take the oath without its concluding phrase,” and said that the denial of his request would be a “slap in the face” of the civil rights reinstated after the March Revolution. The faculty (p.28) responded that they had no authority to alter the rules, and his petition was rejected. It has been said that the rejection was based upon Müller’s political views, but the historian of pharmacy Irene Lauterbach corrects that claim and gives a full and accurate account based upon critical documents she found in the Greifswald University archives.96 Osvaldo Rodrigues Cabral was in error, she claims, when he said that Fritz had “forgotten … that the Christian God was the same as the Jewish one.”97 Jews did not have to say a religious formula. Lauterbach says that Müller’s stubbornness was his own fault, and that he could have graduated if he had compromised. Although his inflexibility is undeniable, her argument has something of “blaming the victim.”

In March 1849 Müller wrote to his cousin Wilhelm Mensing that the only employment left for him was as a private tutor, a writer, or a day laborer but that he would be “miserable forever were I to forswear a jot of my convictions for the sake of any superficial gain.”98 By the time Müller finished his medical training in 1849 he knew that reactionary forces had wiped out the religious reforms of the brief revolution, and early the next year the authoritarian state was once again in control.


(1) This account of Müller’s childhood and education is based on West 2003, chapter 1.

(p.257) (3.) New Encyclopaedia Britannica, 15th ed., 26:222.

(6) Richard Mensing to AM, November 1897, Life, 21.

(7) FM to HM, 23 December 1879, Letters, 393.

(8) Richard and Wilhelm Mensing to AM, 1 November 1897, Life, 10.

(9) Ernst Biltz to AM, 7 and 17 August 1897, Life, 10.

(10) Ernst Biltz to AM, 17 August 1897, Life, 10.

(12) Ibid., 200.

(13) Ibid., 201.

(14) FM to Max Sagemehl, 12 July 1885, Senckenbergische Bibliothek, Frankfurt am Main.

(18) FM to EK, 10 July 1882, Life, 17.

(23) FM to HM, 22 March 1881, Life, 123.

(25) FM to Max Schultze, 18 October 1860, Life, 19.

(28) Dr. Anne Mills, personal communication, 8 January 2009.

(30) FM’s evidence was published in Müller 1846a.

(34) Translation in part from Friesen 1999–2000.

(35) FM to HM, 24 September 1844, Life, 19.

(37) FM to Wilhelm Mensing, 10 June 1845, Life, 23.

(39) Müller quoted in Steenstrup 1846, 110–14.

(42) Ibid., 137.

(48) Ibid., 131.

(50) Ibid., 184, quoting Lamarck 1817, 10:443.

(52) Ibid., 4–5.

(53) Ibid., 141.

(56) Ibid., 219.

(59) Ibid., 221.

(60) Ibid., 222.

(61) FM to HM, 24 September 1844, Life, 19; West 2003, 27.

(69) FM to Rosalie Mensing, 30 October 1845, Life, 20.

(70) Oehlschläger to Alfred Möller, 10 October 1897, Life, 27.

(72) Ibid., 85.

(76) FM to Oehlschläger, 26 March 1893, Life, 27.

(78) Gervinus 1845; Encyclopaedia Britannica, 11th ed. (2011), s.v. “Gervinus.”

(79) Encyclopaedia Britannica, 11th ed. (2011), 770–71.

(80) Lauterbach 2000 identifies the critic as Vischer (1845, 3:1086–1114). FM to Hermann Trommsdorff, 19 February 1846, quoted in Lauterbach 2000, 262–63.

(82) Brockhaus Enzyklopädie, 17th ed. (2011), s.v. “Wislicenus.”

(83) Friesen 1999–2000 summarizes the fortunes of the Friends of Light.

(p.259) (87.) FM to August Müller, 2 January 1846, Life, 28–29. Compare “Take any three doctors and two will be atheists every time” in Gregory 1977, 29.

(88) FM to August Müller, 2 January 1846, Life, 28–29.

(89) FM to Wislicenus, 15 November 1846, Life, 31–32. Published as Müller 1846b. The version in the Life differs slightly from the published one and may have come from the original letter, now lost.

(90) Feuerbach 1957, quoted in translation, Gregory 1977, 5.

(91) FM to Rosine Müller, 15 October 1847, Life, 33–34.

(92) Lauterbach 2000 contains important documents relating to Müller’s “problem.”

(93) The summary of the Revolution of 1848 comes principally from Langer 1969.

(94) Oehlschläger to AM, 1897, Life, 36.

(95) FM to August and HM, 21 October 1848, Life, 36.

(98) FM to Wilhelm Mensing, 14 March 1849, Life, 35.