Oken's early years in Würzburg and Göttingen

In a speech given in Jena in 1809, entitled ‘Über den Wert der Naturgeschichte besonders für die Bildung der Deutschen’ (On the value of natural history, especially for the education of the Germans), Oken explicitly objected to the natural history of his time, which he considered to be based on a senseless enumeration and description of animals. Instead, he called for a natural history integrated with the new Naturphilosophie, which should provide the scientific foundations of animal classification.

This idea should be read having in view the complex semantics of the notion of ‘science’ in the context of classical German philosophy, and particularly its convergence with the idea of ‘system’. In the Architectonic of Pure Reason, Kant claims, for instance, that ‘systematic unity is that which first makes ordinary cognition into a science, i.e. makes a system out of a mere aggregate of it’. In fact, true knowledge cannot ‘constitute a rhapsody but must constitute a system, in which alone one can support and advance its essential ends’. He went on: ‘I understand by a system … the unity of the manifold cognitions under one idea. This is the rational concept of the form of a whole’. This whole

In the last decade of the eighteenth century, this idea had been fully developed at the University of Jena, first in Fichte's Grundlage der gesamten Wissenschaftslehre (Foundations of the Science of Knowledge (1794/95)), and then by Schelling, especially in the Erster Entwurf eines System der Naturphilosophie (First Outline of a System of Philosophy of Nature (1799)) and the System der tranzendentalen Idealismus (System of Transcendental Idealism (1800)). Both thinkers called for a scientific methodology characterized by systematic unity and transcendental deduction. This understanding of scientific method involves the assumption of a first principle (Grundsatz). Once this principle has been established, a comprehensive account of the system requires the content of science to be deduced as a consequence of that same principle.

Oken attempted to set out such a natural history in the Lehrbuch der Naturphilosophie, the Lehrbuch der Naturgeschichte (Handbook of Natural History (1813–1826)), and the monumental seven-volume series Naturgeschichte für alle Stände (Natural History for All Levels (1839–1841)). The Lehrbuch der Naturphilosophie combines an elaborate dialectical construction of nature, similar to Schelling's, with a ‘plethora of often apparently weird analogies’.Footnote ⁹ The work opens with a ‘mathesis’ in which gravity, light, heat and fire are considered direct manifestations of God. This is an ontology which combines elements of Schelling's cosmogony and his account of the formation of the solar system, Earth, and principal rock formations and mineral types. Oken's account of living beings starts with the primordial units of life, the ‘Infusoria’, and then reconstructs the emergence of all animal classes, which are formed by the addition and reduplication of successively more complex organs. This culminates in human beings, who possess all organs in their higher form. In outlining this reconstruction, Oken formulates a clear statement of what Ernst Haeckel would later define as the theory of recapitulation (according to which ontogeny recapitulates phylogeny). This statement was supposed to account for how, in its development from fertilized egg to adult, an animal of a given class progresses through all the stages of all the classes that rank below it. From this viewpoint,

In this sense, Oken's system is an extraordinary feat of synthesis. It takes a decisive stand on every major controversial issue in the natural history of the period: the basis of the process of generation, the method of classification, the relation between form and function. Moreover, his system ‘tightly integrates the description, classification, anatomy, physiology, and chemistry of living beings’.Footnote ¹¹ It is thus not surprising that Oken defines his account of living beings as ‘biology’, a notion used since 1802 (when it appeared as the title of Gottfried Reinhold Treviranus's work) to describe integrated inquiry into the phenomena of organic nature.

This remarkable integration had constituted the hallmark of Oken's work since his lectures in Jena, which comprehensively covered natural philosophy, natural history, zoology, comparative anatomy and physiology. Oken had obtained a professorship in Jena after concluding his studies in Würzburg (1804–1805) and a period as Privatdozent at the University of Göttingen (1805–1807). His time in Würzburg was dominated by a close relationship with Schelling and his circle. During this period, Schelling had surrounded himself with a group of philosophers, physicians and naturalists, including Ignaz Döllinger, Karl August Eschenmeyer, Dietrich Georg Kieser, Heinrich Steffens, Wilhelm Ritter and Gotthilf Heinrich Schubert. This group carried out a research programme dedicated to organic nature that was founded on analogies between animal classes across the animal kingdom, tracing the development of nature in terms of successive levels of complexity.Footnote ¹²

Oken arrived in Würzburg in 1804 to complete the medical studies he had begun in Freiburg. As a student, Oken had already composed the Übersicht des Grundrisses des Systems der Naturphilosophie (Sketch of an Outline for a System of Nature-Philosophy (1802)), a short work strongly inspired by Schelling, in which he laid out his general research programme for natural history. In this earlier work, Oken holds that the animal classes are nothing other than an index of the sense organs and that they should therefore be arranged in accordance with them. Thus, strictly speaking, there are only five animal classes: Dermatozoa, or the Invertebrata; Glossozoa, the Fishes, the first animals to appear with a true tongue; Rhinozoa, or Reptiles, which first exhibit a nose that opens into the mouth and inhales air; Otozoa, or Birds, in which the ear for the first time opens externally; and Ophthalmazoa, or Thricozoa, in which all the sense organs are present and complete and the eyes are moveable and covered with two palepebrae, or lids. As we shall see in the following, this general idea of classifying animals according to the dominant organ in their plan of organization will remain a constant element and overall principle of Oken's natural history, even if this precise schema was partially altered in later elaborations.

In addition to hearing Schelling's lectures, in the autumn semester of 1804–1805 the young Oken also attended the lectures of the physiologist Ignaz Döllinger, under whose supervision he conducted research on a classic Wolffian subject: the formation of the intestines in the embryo. This also constituted the topic of the essay he wrote to obtain his professorial qualification in Göttingen, where he was sent by Schelling to study under Blumenbach's patronage. In this essay, ‘Die Zeugung’ (The generation (1805)), Oken argues that all organic beings originate from and consist of vesicles or cells, and that these vesicles are the infusoria according to which all larger organisms fashion themselves. The Göttingen programme of lectures of 1805 reports that Oken lectured on two topics: ‘Die Lehre von der Zeugung’ (The doctrine of generation) and ‘Biologie, gegründed auf den gesamten Organismus der Natur’ (Biology, grounded on the overall organism of nature). The latter was also turned into a monograph entitled Abriß der System der Biologie (Outline of a System of Biology (1805)). As Oken himself acknowledged, behind this Biologie stands his attempt to formulate a system of comparative physiology of animals, or to elaborate his ‘theory of the senses’ (Theorie der Sinne), which was already present in his earlier writings. This theory was to be part of a theoretical framework, grounded upon Naturphilosophie, capable of turning natural history into a science by providing a compelling principle of classification – a principle that, in Oken's view, was completely missing from Blumenbach's natural history.

Blumenbach was known for his work on natural history especially after the publication of his Handbuch der Naturgeschichte, which also appeared in several editions, the first being in 1779. The specific feature of Blumenbach's approach is the description of the ‘total-habitus’, the specific lifestyle of each animal, which takes into account factors like the breeding period of birds and the role of the female in the building of the nest, or the unique reproductive faculties of amphibians. In fact, Blumenbach's Handbuch der Naturgeschichte is full of descriptive natural history which provides an index of animal characteristics – beginning with the traits common to the whole animal kingdom and moving through to those particular to single classes.

In a letter dated May 1805, Oken reports to Schelling his impressions of Blumenbach's lectures:

Again in July, Oken claims that Blumenbach is ‘the worst professor … I have ever heard in my life, and that's saying a lot’. On the other hand, in a passage from Die Zeugung, Oken argues that Blumenbach ‘was the first and only scholar with the courage and spirit to stand against the crude mechanics that … had entered physiology, and was able to cut that mechanics off even if it had taken firm roots everywhere’.Footnote ¹³ In fact, a careful reading of Oken's various writings presents us with several shades of grey: his relation to Blumenbach seems variable, rather than a distinct opposition. In this latter passage, for instance, Oken demonstrates explicit appreciation of Blumenbach's physiology, despite his criticism of the latter's natural history. As I argue in the following section, Oken's scientific project in fact constituted an attempt to provide the scientific foundation of natural history that Blumenbach lacked, through the a priori method of Naturphilosophie.

Oken's programme for a scientific systematics and its development in Jena

A good example of Oken's programme for animal classification is found in a short essay contained in the Beiträge zur vergleichenden Zoologie, Anatomie und Physiologie titled ‘Entwicklung der wissenschaftliche Systematik der Tiere’ (Development of a scientific classification of animals (1806)). Here Oken characterizes every animal class according to the exclusive possession of specific organs. Animals are nothing but ‘natural functions attained to the highest vital degree’ and each of these functions ‘bestows [the animal] with its own form and its proper mode of action’.Footnote ¹⁴ Therefore ‘all the differences among animals are based on the excessive formation of a system at the expense of the others’. Since differences among animals result from the uneven growth of organs, the criterion for classification that Oken proposes consists in individuating the dominating organ of every organism: ‘if all the difference in animals resides in the inequality of organs, then every classification must be grounded on the same principle’.Footnote ¹⁵ Classificatory systems must highlight the central organ of every animal class.

In Oken's view, whoever endeavours to establish an animal system on the basis of external traits is left with a mere description of the envelope, which leads to mistakes because it does not take into account the essential character of organs. We can achieve an animal classification system only by considering the totality of animal anatomy, i.e. by surpassing the mere description of individual organs and instead considering their specific functional roles in the whole organism. Oken finds it is necessary to know which organs develop individually in the animal kingdom and become the characteristic of each class.

The fundamental organs of Oken's animal kingdom, the organs around which all the other organs are positioned, are the respiratory, digestive and cerebral systems. These three systems have an identical anatomical basis, the vesicle, which served as the essential embryological idea in Oken's work from Die Zeugung. The pulmonary vesicle is situated in the lowest area of the animal; the stomach vesicle is on top of it, and the brain vesicle on top of both. Together these three form the principal parts of the body: the thorax, the abdomen and the head – which Oken identifies as the three pillars of animal structure. Accordingly, there are three animal groups in which the respiratory, digestive and cerebral systems have a supremacy over the others. The animal kingdom is thus divided in three kingdoms, conceptually ranged not alongside one another, but one above the other: ‘that of respiration, that of digestion and that of cerebral action; these sub-kingdoms are defined in a clear and precise way, they are so well placed one above the other that it is difficult to suppose another relation among them’.Footnote ¹⁶

The first animal kingdom, respiration, is inhabited by invertebrate animals; the middle kingdom, digestion, is inhabited by birds, fishes and amphibians, which are more complex than the former; and finally, the superior kingdom, cerebral action, is inhabited by mammals, the most perfect animal organisms. The lower the kingdom, the less developed are its organs, and the more one of them dominates over the others. The higher the kingdom, the more developed the organs, since higher animals develop more complex organs than the simple ones displayed by inferior species.

As an example of Oken's system of classification I report some of his statements concerning the lower classes of the animal kingdom. The kingdom of respiration has three main organs: epidermis, dermis and lungs. Animals characterized by these systems are provided especially with these organs, and since they are the lowest of the lower kingdom, they are deprived of the organs characterizing mature animals in other classes. The first class of this kingdom is produced along a line and simply confined to a prolonged epidermis. This constitutes the character of the lowest class, i.e. worms, ‘in which all the organs are covered with epidermis: it is the animal-epidermis’. On the other hand, ‘the animal class whose characteristic organ is the dermoid system is that of the insects’.Footnote ¹⁷ In contrast with worms, which are composed of one single section, insects are animals of the inferior kingdom with a separated epidermic system, articulated in circles, wings, legs and abdominal rings: ‘the epidermic system dominated by the dermis is the insect, the latter is thus the animal-skin’.Footnote ¹⁸ On the other hand, the mollusc is nothing but a respiratory organ: ‘the mollusc is thus the animal where the epidermis and dermis are dominated by the lung: it is the animal-lung’.Footnote ¹⁹ As a result, the lowest kingdom, characterized by the respiratory system, is divided by Oken into three classes, according to the dominating organ of each: worms (epidermis), insects (skin), molluscs (lung.)

The second kingdom, digestion, is also divided into three main organs, i.e. bones, liver and stomach: ‘the bone system has become the bird, the hepatic system has become the fish, the digestive system, the most alive, the most considerable, unfolds under the form of an amphibian’.Footnote ²⁰ In birds, everything else is organized in the service of the bones, even the respiratory function itself is subordinated to them, thus ‘they should be called bone-animal’.Footnote ²¹ In fishes, everything is displaced to make space for the liver. The liver pushes the heart towards the head and extends from there through the entire trunk of the animal. The whole body is thus formed around the liver, while all the organs that do not harmonize with it are excluded: ‘they must be called liver-animals’.Footnote ²² Conversely, the digestive system is the principal organ among amphibians, and, as in the other classes, here the whole body is harmonized with this predominant trait; this class is thus defined as stomach-animal.Footnote ²³ Consequently, the middle kingdom is also divided into three classes, according to the dominating organ: birds (bone), fish (liver), amphibians (stomach).

Oken's analysis of the dominating organs of each animal class concludes with the six inferior classes, because the objective of the paper was not to build an entire system but only to formulate a new classificatory framework, in which every animal class can be subdivided according to differences in how its principal organ organizes the organism. Still, he argues that the third kingdom is marked by the presence of sensory organs. The fundamental difference between the animals of the third kingdom and those of the former two is the fact that the latter are organized around one single organ and must thus be called animalia monorganica, which can be distinguished from mammals, which are animalia panorganica.

Since, in Oken's system, each animal has an organ system that dominates its life, Oken envisions the entire animal kingdom as one great animal. Each animal class, from infusoria to amphibians and mammals, corresponds to a different organ of the universal organism. The tendency of the schema culminates in human beings, in which every organ is developed to the highest degree of perfection. This analogy is synthesized in the opening statements of the Abriß des Systems der Biologie, where Oken declares, ‘what else is the animal kingdom than the anatomy of humans, the macrozoon of microzoons?’ In this sense, humans gather in one individual organism all the organs expressed across the whole animal kingdom.

Another peculiar aspect of Oken's comparative anatomy is the vertebrate theory of the skull. In his inaugural lecture at Jena, ‘Über die Bedeutung der Schädelknochen’ (On the meaning of cranial bones (1807)), Oken argues that ‘the skeleton is just an awakened, branched and repeated vertebra; and the vertebra is the preformed germ [Keim] of the skeleton’.Footnote ²⁴ A single generalized vertebra constitutes for Oken the basic unit of animal design (equivalent to Goethe's primal leaf), and a sequence of such units constitutes the Urtypus of vertebrates. Carl Gustav Carus synthesized the ideas of Goethe and Oken in his Von den Ur-theilen des Knochen- und Schalengerüstes (On the Original Division of Bones and Shell Scaffolding (1828)). There he provided a sketch of the archetype of the vertebrate skeleton and its elementary part, the vertebra. Similarly to Oken, Carus conceives of the latter as the fundamental building block of vertebrate organization: the primitive vertebra (Urwirbel) can be multiplied and transformed to form the backbone and the head, ribs and limbs. This idea is a fundamental tenet of the Goethean notion of ‘metamorphosis’ and of German ‘transcendental morphology’ more generally. This current was characterized especially by the portrayal of the whole of organic nature as the metamorphosis of one and the same archetype as the template of all vertebrate organization.

Oken's Lehrbuch der Naturphilosophie brings all his doctrines into mutual connection, trying to show that the mineral, vegetable and animal classes cannot be arbitrarily arranged in accordance with single or isolated characters but are instead based on cardinal organs or anatomical systems, from which a firmly established number of classes result. In the Lehrbuch der Naturgeschichte and in the Allgemeine Naturgeschichte für alle Stände, Oken arranges genera and species in accordance with these principles, in an attempt to frame a scientific natural history. In his introduction to the last edition of the Lehrbuch der Naturphilosophie, he explicitly argues that ‘natural history is not a closed department of human knowledge, but presupposes numerous other sciences, such as anatomy, physiology, chemistry and physics, with even medicine, geography and history’.Footnote ²⁵ This synthetic attitude was an important character of emerging German biology, which implied the unification of several disciplinary matrices into one discipline concerned with the phenomena of organic nature. Its paradigmatic example is Gottfried Reinhold Treviranus's Biologie, oder Philosophie der lebenden Natur für Naturforscher und Aerzte (Biology, or Philosophy of Living Nature for Naturalists and Physicians (1802–1822)).

Other studies have stressed the strong connection between Naturphilosophie and later transcendental morphology. Indeed, the conceptual proximity linking Oken to Geoffroy and Owen is by now well known.Footnote ²⁶ A great wave of transcendentalism passed over biological thought in the early nineteenth century. This transcendental approach arose mainly in Germany, but powerfully affected also the thought of Geoffroy and his followers, such as Etienne Serres (1786–1868). Many ideas were shared between the French and German schools of transcendental anatomy: the belief that there existed a unique plan of structure, the idea of the scale of beings and the concept of a parallelism between the development of the individual and the evolution of the species.

As Jardine has already argued, it is tempting to reduce these developments to a more general process of secularization, in which God's plan becomes a purposiveness immanent in nature. One may also seek to relate these transcendental natural histories to the global episteme change that took place around 1800, which Michel Foucault saw as leading natural history from static concern with classification and external characteristics towards a more dynamic concern with inner development, function and structure.Footnote ²⁷ In this sense, if we approach the work of the Naturphilosophen from the right perspective, namely with an eye towards the questions they pose and the epistemological field those questions created, the work of these thinkers can also be appreciated for its historical significance. For Naturphilosophie transformed the paradigm of classification, moving it from a descriptive natural history based on the idea of the immutability of species (although admitting degeneration) to an explanatory comparative anatomy based on a unitary type which constitutes, as it were, the condition of all possible forms. In short, it marked a shift from discrete enumeration of differences to laws regulating expressions of continuity.