Form as Movement in Goethe's

 'The Metamorphosis of Plants'[*]


Zemplén Gábor

PhD Student

Techincal University of Budapest



"Genoß ich die schönsten Augenblicke meines Lebens zu gleicher Zeit, als ich der Metamorphose der Pflanzen nachforschte, als mir die Stufenfolge derselben klar geworden, begeistete mir diese Vorstellung den Aufenthalt von Neapel und Sizilien, gewann ich diese Art des Pflanzenreich zu betrachten immer mehr und mehr lieb, übte ich mich unausgesetzt daran auf Wegen und Stegen…."

J. W. Goethe[[1]]


The aim of the paper is to introduce and interpret a little booklet, written by J. W. Goethe and containing not more than 123 paragraphs: The Metamorphosis of Plants [[2]](1789). It is considered to be one of the best examples of Goethe's method of science, by no means a 'mere side glance of the poet into a strange field' as Augustine Pyrame de Candolle (1778-1841) stated [[3]]; its investigation can yield to a better understanding of Goethe's conception of Science. It undoubtedly became the best known and probably most famous of Goethe's scientific endeavours [[4]].


The Metamorphosis of Plants

Die Urpflanze

Goethe's essay is the result of a thorough, laborious study of a topic that had intrigued him well before his famous Italian journey in 1786-1788[†]. By that time, his knowledge of plants and contemporary botany was anything, but negligible. It was here, that he realized the effect of the climate on certain plant species (see entry on the 8th of October 1786, Venice), and started to develop the concept of his archetypal plant, Die Urpflanze. The concept gradually developed and was modified during his journey, as is clear from his diary entries [[5]]:

"Here where I am confounded with a great variety of plants, my hypothesis that it might be possible to derive all plant forms from one original plant becomes clear to me and more exciting. Only when we have accepted this idea will it be possible to determine genera and species exactly. So far this has, I believe, been done in a very arbitrary way. At this state of my botanical philosophy, I have reached an impasse, and I do not see how to get out of it. The whole subject seems to me to be profound and of far-reaching consequence." (Padua Botanical Gardens, September 27, 1786)

"…Seeing such a variety of new and renewed forms, my old fancy suddenly came back to mind: among this multitude might I not discover the Primal Plant [Urpflanze]? There certainly must be one. Otherwise, how could I recognize that this or that form was a plant if all were not built on the same basic model?" (Botanical Gardens, Palermo, Sicily, April 17, 1797)

"… The Primal Plant is going to be the strangest creature in the world, which Nature herself shall envy me. With this model and the key to it, it will be possible to go on forever inventing plants and know that their existence is logical; that is to say, if they do not actually exist, they could, for they are not the shadow phantoms of vain imagination, but possess an inner necessity and truth." (Naples, May 17, 1787)

"While walking in the Public Gardens of Palermo, it came to me in a flash that in the organ of the plant which we are accustomed to call the leaf lies the true Proteus who can hide or reveal himself in vegetal forms. From first to last, the plant is nothing but leaf, which is so inseparable from the future germ that one cannot think of one without the other." (Rome, July 31, 1787)

The Urpflanze was a historical ancestor first, later an underlying scheme, the 'plantness' of a plant.

His Italian wanderings and observations are the bases of the essay on The Metamorphosis of Plants. Here, contrary to the fragments of his diary, there is no mentioning of the Urpflanze. Instead, a different approach is used.


An Essay on Plants

In the foreword of the 1829 French translation of The Metamorphosis of Plants by M. Frédéric de Gingins-Lassaraz we read:

 "There are two very different methods of studying plants. The most common is to compare with one another all the individual plants making up the entire world of vegetation. The other method compares the various organs comprising the individual plant and searches there for the characteristic symbol of plant life. The first of these two methods of study leads us to knowledge of the plants that exist throughout the world, and of their environment, mode of life, and uses. The second method acquaints us with the organs of the plant, with their physiological functions and the roles that they must play in the plant economy. It studies the course of development, the metamorphoses to which the individual parts must adjust themselves; it allows us to see the plant as an organism, which is born, grows, reproduces, and dies. In brief: the one method is the history of the plants; the other, the history of the plant" [3]

Goethe is mainly concerned with the second approach. Many of his contemporaries (like Humboldt) stress the importance of the first one. His aim is "to follow as circumspectly as possible in the steps of Nature, accompanying the plant through all its outward transformations, from its development out of the seed to re-formation of the seed." (§ 84) He does not claim "to be revealing the origin and mainsprings of Nature's processes", wants no causal explanations, only phenomenological ones.

The style of the essay is somewhat unusual[‡]. In the first few chapters Goethe sets up his task, 'determines his area of research' within the broader meaning of metamorphosis (the numbers refer to the paragraphs):

5. This metamorphosis may be of three different types: regular, irregular, and accidental.

6. Regular metamorphosis we might also call progressive, for it is this type that may be observed at work step by step from the first seed leaves to the final development of the fruit. By transmutation of one form into another, it ascends as though on the rungs of an imaginary ladder to that climax of Nature, reproduction through two sexes. It is this type of metamorphosis which I have been studying attentively for several years and now undertake to explain in this essay. In the following demonstration, we shall therefore consider the plant only insofar as it is an annual, advancing continuously from seed to fructification.

After the straightforward introduction Goethe sets out to describe the different 'leaves' of the plant, starting from seed leaves, through stem leaves, to the formation of calyx, corolla, the staminal organs, the style and finally the fruit. He explains the change in form of the different organs with 'expansion' and 'contraction', while there is a general 'rectification of sap'[§]. This explanation, using the changing quality of the 'sap', is typical for 18th century scientific discourse and was probably the best theory available [[6]]. He considers the refinement of the sap as a process that is partly dependent on the surroundings30).

One of the most ground-breaking aspects of Goethe's attitude to botany is that, contrary to the general view, he did not condemn malformations as 'freaks of nature', discarding them as useless for scientific studies, rather, he collected them and used them to 'test his hypothesis'. He believed that these 'exceptions' are only exceptional insofar as they are unusual; but if there is a rule governing the formation of ordinary forms, these rules must apply to the extraordinary rules as well (§102-103).

Why did Goethe choose simple, annual, flowering plants, and did not even attempt to encompass the whole of the Plant Kingdom? This is one of the 'mysteries' of the Metamorphosis of Plants, but is explained when we read what he writes about Linneaus and his theory of anticipation (§109-110). His aim was not to explain the secrets of the plant world, but to give a tool, with which the reader can carry out similar investigations. And the easiest way to teach this method is by reducing the notion 'plant' to 'annual, flowering dicotyledoneus plant'. He claims to have found a new way of seeing in Italy (to have seen the Urpflanze), and believes this to be teachable and applicable to the rest of the plant kingdom. After understanding the method "the conceptions established above - of expansion and contraction, compression and anastomosis - would have to be manipulated as expertly as algebraic formulae, and would have to be applied in the right places" (§102).

While this reduction helped him to tackle a problem in its own right very well, another reduction brought about the serious misunderstanding of his endeavour. Many have mistaken his concept of the Leaf ('Blatt') for a simple leaf (i.e. that all organs of the plant can be derived from the 'leaf', an organ that is still visible on most plants as vegetative leaf). If this is true, and by saying "Blatt", Goethe means nothing more than a vegetative leaf, then his idea carries nothing new in itself; he becomes just one of the many before and after him. First Theophrastos, later Nehemiah Grew (1672, 1682), Malphigi (1671), C. Fr. Wolff (1768), and Augustine Pyrame de Candolle all treated the leaf as a universal organ [6, [7], 8]. This - to my belief - mistaken notion leads to the 'weak' interpretations of Goethe's ideas. But Goethe explicitly states that "we might equally well say that a stamen is a contracted petal, as that a petal is a stamen in a state of expansion; or that a sepal is a contracted stem leaf" (§120) and that the transformations must be run in both directions. This will prove to be a very significant difference when interpreting Goethe's views, paving the way for the 'strong' interpretation [see e.g. [8]].


'Weak' Interpretations

The essay itself became a part of the scientific canon. By the middle of the 19th century the concept that 'all the organs of the higher flowering plants can be derived from a simple leaf' had been accepted. There is a reference to Goethe's botanical studies even in Darwin's Origin of Species:

"It is familiar to almost every one, that in a flower the relative position of the sepals, petals, stamens, and pistils, as well as their intimate structure, are intelligible in the view that they consist of metamorphosed leaves, arranged in a spire" [[9]]

This notion of Darwin can be taken as the received opinion of most of his contemporaries, and, in general, the scientifically educated minds about Goethe's concept of the Metamorphosis of Plants. According to this view, Goethe becomes one of the many scientists preparing the final triumph of 19th century biology: the theory of evolution. Goethe's Urpflanze, the mysterious archetypal plant, is thus to be discarded as the product of Romantic imagination, something that has no scientific significance, unless it be meant as a vague term for "the ancient progenitor, the archetype as it may be called"[9], as Darwin later expressed it.

Some modern theories give even more justice to Goethe by openly or implicitly accepting the correctness of his theory. Walter Zimmermann's theory about the evolution of plant organs from primitive ferns (Psilopsida) stresses that the vegetative and generative functions of the 'leaf' were not always separated, and that all the different types of leaves (vegetative leaves, sepals, petals, stamens, and styles) have a common origin, a leaf-progenitor that had both vegetative and generative functions.

Besides, in recent years answers have begun to emerge from genetic studies of mutant flowers similar to those which exercised Goethe's mind, and it seems that a single gene triggers the growth of flowers in plants, which sets off the cascade of changes needed to produce a flower. "The discovery is part of a wider series of breakthroughs in the study of flower development which have confirmed the theory, originally put forward by the poet Johann Wolfgang von Goethe more than 200 years ago, that the different organs in a flower, such as petals and stamens, are all variations on a single theme." [[10], see also [11]]

It is very tempting to stop here, and claim that Goethe was a respectable though undervalued member of the scientific community; that his ideas have been incorporated into the mainstream of science. This would be the safer route. However, I believe that Goethe's concept is not that of an evolutionary precursor, or his vision is not the foretelling of recent results concerning the flo gene in flowering plants. This would be the 'weak' interpretation of Goethe's morphology. I will attempt to sketch the 'strong' - and in my opinion more faithful - interpretation of Goethe's morphological ideas. I will argue that both the Darwinian and the more modern theories are incorrect interpretations of the Metamorphosis of Plants. It accommodates the Goethean way of thinking to the later emerging evolutionary paradigm. (The corruption of meaning is not Darwin's fault, he only used concepts and interpretations of Owen, Carus, and Oken, see [[12], [13]].)


'Strong' Interpretations


In the following, I will attempt to make the 'strong case' approachable[**]. For this the problem of homology has to be tackled first, then Goethe's attitude to the 'weak' interpretations. In modern taxonomy, biologists assume a common plan underlying certain taxa. The actual classification, however, is according to only a few general characters. This has been the accepted method since the time of Owen (separation of birds and reptiles based on minor osteological differences). Whether an animal belongs to one taxon or another depends on the existence or lack of these few (not necessarily macroscopic) 'distinguishing' features. Identification of these general characters implies the rest as a context, but this is not how the process of classification is carried out. The relationship between forms is established first, and this is followed by the search for a 'missing link'. The first step is done without any possibility of 'proving' whether it is a correct step or not. It assumes the common plan, which infers the grouping, but the existence of the plan is an object of speculation.

Taking an example: the limbs of fish and tetrapods have supposedly the same origin, but, as yet, there is no good (meaning close) series of transitional forms between the two. To find our hypothesis well grounded, we have to see the 'missing link'. To solve the problem, we can either imagine an intermediary, that establishes a connection between the two forms, or find a generalized schema, on which both can be mapped. This latter might also be called a progenitor, or an Archetype, usually something simple, and not yet specialized. The search for these forms have begun well before the time of Darwin[††], but even for him one of the questions to be answered by his evolutionary theory was the existence and emergence of these progenitors.

The strategy of finding speculative progenitors and homologizing dissimilar organs is used even today when there is not enough evidence for seeing the connection between forms.  It must be remembered, however, that in these cases evidence is mixed with theory; an idealization is homologized with actual features or forms through abstract transformations. This dubious practice compares empirical and hypothetical forms, but the "procedure treats the invention as if it were an empirical discovery, and results in the determinations that would follow from such a discovery."[7] Obviously, the devised intermediary forms (or hypothetical progenitors) will differ from scientist to scientist, it is unlikely to find two forms that are the same. Does this mean that there are many progenitors? How many, then?  Of course we all agree that (if our hypothesis about the common origin is right) there should be only one. But we can invent an infinite number of intermediaries and they may all be non-existent. How are we to choose or recognize from this multitude of hypothetical forms the one, the 'real' one? The case is the same with the hypothetical ancestor as with the intermediary form. Thus the "mediating form was created because the data in itself was inconclusive without it. The known forms are now interpreted by the hypothetical. The theory of the particular homology is therefore tested (and found true) using artefacts of that same theory in its hypothesis-form."[7]

But Goethe did not even attempt to find such a progenitor and was strongly against mixing facts with theory; his concept of form was dynamic, generative and empirical, not speculative. As Cassirer states, the "theory of metamorphosis has nothing to do with this question of the historic sequence of the appearance of life. It is quite separate from every 'theory of descent' not only in its content but in the posing of the question and method. Goethe's concept of 'genesis' is dynamic, not historical; "It is not a broadening but a deformation of the sciences," said Kant, "when their boundaries are allowed to run together." It would be such a deformation if we were to confound Goethe's biological idea of knowledge with that of Darwin or Haeckel."[[14]]

If Goethe's ideas are incommensurable with a search for a historical (evolutionary) progenitor, the other plausible assumption is to treat it together with Romantic notions about a blueprint, "Bauplan" of a taxon. Against the background of Naturphilosophie, Goethe's notion seems to stem from the same source as Owen's general homology of the vertebrates. This can be summarized as follows: (a) there is a general homology of all organs of the shoot. (b) the leaf is a generalized plan for the underlying organ, (c) by repetitive transformation of the underlying organ a generalized plan of the whole shoot can be built. Goethe could have provided a form that is the common schema (much like Owen's archetypal vertebra) but he deliberately did not. His solution is radically different, as I will try to show.

But many critics agree, that Goethe's concept of type is different from most of his contemporaries. As Cassirer writes:

 "To Cuvier or Candolle 'type' was an expression of definite and basic constant relationships in the structure of living things that are fixed and unalterable and upon which all knowledge of them depends. … But this view was not Goethe's. He did not think geometrically or statically, but dynamically throughout. He did not reject permanence, but he recognized no other kind than that which displays itself in the midst of change, which alone can discover it to us."[14].

The identification of plant parts is based on common recognition and there is no valid strict positional schema, the topography is not determining (tulips, and monocots in general, have no sepals, yet this does not deter us from calling the petals 'petals', the stamen 'stamen'). Instead, plant nodal points are multivalent, and the outcome depends on several factors. Although we can usually guess right as to what comes next, sometimes we see double flowers, foliage leaves instead of the corolla (Goethe clearly noted this). This proves the multivalency and thus the underlying identity, and the question is how one can find an 'underlying' element that is not a mere reduction of the visible forms to the simplest possible structure.

By subscribing to the view that 'everything is leaf' means a simple foliage leaf we misinterpret Goethe's views, as, exactly for this, he criticizes Wolff's (seemingly very similar see 3, 6, 8) theory:

"… Excellent as this [Wolff's] method is, and however much he may have accomplished with it, the worthy man nevertheless failed to realize that there is a difference between seeing and seeing; he failed to realize that the intellectual eye must work in constant and spirited harmony with the bodily eye, for otherwise the scholar might run the risk of looking and yet overlooking." [3]

He clearly distinguishes between his theory and Wolff's, stating that something has to appear in front of the 'intellectual eye' when seeing with the 'bodily eye' - a statement just as mysterious as the original notion of the Urpflanze. To understand this it is probably the easiest to start from the simplest case. I will only venture to arrive at a better understanding of the Urorgan, the 'Leaf' here, and not even attempt to find the underlying schema of the whole plant world, Goethe's Urpflanze.


Form as Movement

The leaves of a plant usually resemble each other. In fact, for a trained botanist, most of the species can be identified by a single leaf, regardless of the leaf's origin. This implies the existence of general homology among leaves. That we are able to find a  'theme' behind the 'variations' (and say that a leaf is the leaf of a beech tree, for example) is the result of our working, ever-searching intellect. For modern theory of science this can only be hypothetical. Goethe, on the other hand, clearly talks of finding an underlying schema that is not hypothetical. If we arrange the separated leaves of a flowering plant in a semicircle, where the oldest ones (near the base) are on the left, and the youngest ones (near the top of the plant, right under the flower) are on the right, we might understand his puzzling statement better[‡‡].

Looking at the leaf-series, it is easy to conclude that they resemble each other. But how can we find the 'theme'? By taking the simplest forms on either end of the series we see that it gives us no information about the complex ones. By taking one of the complex ones we only reach the others through deletion. In either case the obvious progression is lost. By starting with any one of the forms the 'movement' cannot be detected. Any scheme seems painfully arbitrary. There is no reason why we should take one leaf and not the other as the basis. Picking one and 'explaining' the others using it does not allow us to grasp the underlying unity.

Another way of tackling the problem is starting from the progression itself. That there is positional information within the series can be seen if we mix up the leaves. For someone, who has never seen these leaves before, it is not hard to reshuffle them and find their correct order (he might begin with the end, but the order is not changed by this). Taking this route the forms of a graded series appear to be arrested stages, 'snapshots' of a continuous movement. The more 'missing pictures' we have, the more continuous the movement is. An infinite number of logically possible leaves could be inserted, just like an infinite number of pictures can be the intermediaries of two pictures of a running athlete. No particular scheme is present, however, as the connections themselves are transformed.

Owen and many others thought that similarity makes the series. In the Romantic Naturphilosophie it was generally accepted that though forms are 'on the surface' different, they really aren't, that there is a general Bauplan or blueprint on which the forms are variations. This view stresses the importance of similarity, while in Goethe's method the difference is just as crucial, and the two, similarity and difference, have the same importance in understanding the movement. The movement enables us to include or exclude potential new members. It is perfectly continuous, specifying forms by generating them. Individual pieces do not show the movement by themselves, but are governed by it. The mobile governs the static. In this sense the movement works as a law, that can be used to generate new forms that follow it.

 Each individual form thus turns out to be an arrested stage of the transformation; the independence of forms are cancelled, they become manifestations of something that is not visible, but traceable. This something is, in itself, never visible, however, this invisible form unites all pictures. Seeing only the pictures the intellect can not arrive at the movement. In the 'movement', though it cannot be drawn or sketched, all the forms are given, and the viewer is not forced to make any unfounded steps to acquire it. The only hypothetical step is accepting that the series 'makes sense', that is, it is a manifestation of something objective, yet unperceivable by the senses.

By making this Goethean leap of faith, a new level of investigation is opened, just as making the important, crucial step, that by using mathematics we can explain some parts, aspects, and phenomena of the world. By not taking the step we remain in the realm of isolated signs, phenomena, hypotheses, conjectures about the form of the plants, which cannot be proven to be real, existing rules of the world. They might seem logical according to our intellect. Their structure follows certain rules, but these rules are that of our reason or intellect. They are logical. But this intellect, the mathematical capacities we develop have no connection to the realm of the phenomena outside. [see for details [15], [16], [17]]

By taking the Goethean step, we attribute the same lawfulness to the outer world as to our intellect. We can still misunderstand these laws, but, according to Goethe, these faculties can be trained, just as the faculty of mathematical understanding, and a gradual correction of the mistakes is possible here, too. This knowledge might be called generative, as knowing the movement can be used to generate new forms. The apprehension of movement here depicted about one single plant can be extended over several plants in a species, over related species, and the plant kingdom in general. We dealt exclusively with spatial movement, but the same laws apply for the study of temporal movement.

The above example tried to show the basis of Goethe's method, and that, in principio, it is not less grounded than other approaches to make plant form intelligible. His method was justifiable in his time, as the generally accepted notions of homology in Goethe's time were unable to give a more correct answer as to how the morphe of plants can be grasped. (as in botany the number of organs can change, and, as we have seen, it is arbitrary which form is picked as the scheme). Goethe chooses to investigate movements rather than forms; in the outcome his approach is similar to the 'schematic one': simple difference of forms is reduced to intelligible difference, using descriptive concepts. His 'Leaf' is not any sort of simplification; it has no form at all: it is the movement itself. The organs are the same but not because of positional or compositional identity, and it is not a schematic archetype as it can't take on any form. The consequences are far-reaching:

"If we take this approach, the dynamic aspect of the forms becomes little more than an artefact of perception, and should we choose to call it generative, in that it specifies all forms potential to the series, there would seem less reason to suppose it causal. After all, a mathematical differential, however predictive of future forms, is not a productive power but a specification of relations. It shows us how the finished product is structured, but not how it was caused."[7]

 Or, as expressed by one of the leading biologists working with the Goethean approach: "The leaves are like footprints of a plant which develops in the realm of the invisible" [16].


[*] I would like to thank Jochen Bockemühl, Márta Fehér, György Kampis and the Invisible College for their help and support.

[†] In 1777 October 31, he requested all sorts of mosses from Frau von Stein, but this interest is not yet that of a professional scientist. It is in 1782, when we first hear about his studies of Linneaus, whose classification of plants he found invaluable. In 1785 he wrote to his friend Friedrich Jacobi (1743-1819), the later president of the Academy of Sciences in Munich: "A microscope is set up in order, when spring arrives, to reobserve and verify the experiments of von Gleichen, called Russwurm". He read Russwurm's Special Microscopic Discoveries about Plants, and he was intrigued to find out the validity of the descriptions in the book. Goethe's interest in mosses, lichens, and microscopic structures seems to contradict the generally accepted view, that he ignored that plants have less aesthetically pleasing aspects under the ground – namely roots, and that this is why they are not treated in his botanical writings.


[‡] Closely resembling Linneaus' Fundamenta Botanica, a book that Goethe was well acquainted with, containing 365 aphorisms.

[§] Goethe's explanation is doubly polar. It contains a polar element, i.e. the 'contraction' and 'expansion', expressions, that are clearly visible on the plant, but opposed to this polarity is a one-way, gradual development, an 'enhancement'. This mode of explanation reappears in Goethe's later writings. In his Farbenlehre he will talk of a 'strengthening' (Steigerung), of the two basic colours (polarity again).

[**] Here I try to support and possibly further elaborate one view of Goethe's morphological works shared by numerous scholars, a significant minority still (to name a few: Rudolf Steiner, Ernst Cassirer, Agnes Arber, Jochen Bockemühl, Ronald H. Brady).

[††] Robinet and Diderot wanted to find a prototype for all natural forms; Oken, Owen, Carus, and others have made efforts to find the common progenitor of one taxon.

[‡‡] Several plants are suitable for this, mostly ones where leaf-shapes vary significantly, like thistles, buttercups, poppies, etc.

[1] GOETHE, J. W. von . Glückliches Ereignis. in Johann Wolfgang Goethe Sämtliche Werke, Briefe, Tagebücher und Gespräche. Vierzig Bände. Deutsche Klassiker Verlag. Frankfurt am Main 24:434

[2] GOETHE, J. W. von 1790. Versuch die Metamorphose der Pflanzen zu erklären Gotha: Carl Wilhelm Ettinger

[3] Goethe’s Botanical Writings. 1989. Ox Bow Press, Connecticut (trans: Bertha Mueller) p. 165 fn, 208, 180

[4] WENZEL, Manfred. 1982. Goethe und Darwin (Goethes Morphologische Schriften in ihrem naturwissenschafthistorischen Kontext). Ruhr-Univesitat Bochum. p.71

[5] GOETHE, J. W. von 1969. Italian Journey. Schocken. New York. There is a currently available (and, contrary to the Hungarian translation, full) version of the diary published by Penguin Books.

[6] PORTMANN, Adolf. 1987. Goethe and the Concept of Metamorphosis. Reidel Publishing Comp., Boston (in: Goethe and the Sciences BSPS 97) pp. 133-145.

[7] BRADYrady, Ronald H. 1987. Form and Cause in Goethe’s Morphology. Reidel Publishing Comp., Boston (in: Goethe an the Sciences BSPS 97)

[8] BORTOFT, Henri. 1996. The Wholeness of Nature: Goethe’s Way of Science. Floris Books

[9] DARWIN, Charles. 1958. The Origin of Species. Penguin [1981] Introduction, Ch. 1, 13.

[10] COEN, Enrico; CARPENTER, Rosemary. 1992 ‘The power behind the flower: What makes a plant flower?’ in: New Scientist, 25 April 1992, Vol.134 No.1818

[11] BOWN, William. 1991. ‘Flowers start from a single gene’ in: New Scientist, 06 July 1991, Vol.131 No.1776

[12] WEBSTER Stephen. 1994 ‘Review: The truth about Darwin's old foe’ in: New Scientist, 3 September 1994, Vol.143 No.1941

[13] RUPKE, Nicolas A. 1994. Richard Owen. Victorian Naturalist. Yale Univ. Press. New Haven and London

[14] CASSIRER, Ernst. 1950. The Problem of Knowledge. Yale Univ. Press, New Haven

[15] AMRINE, Frederick. 1987. Goethean method in the work of Jochen Bockemühl. Reidel Publishing Comp. Boston (In: Goethe an the Sciences BSPS 97)

[16] BOCKEMÜHL, Jochen. 1997. Aspekte der Selbsterfahrung im phänomenologischen Zugang zur natur der Pflanzen, Gesteine, Tiere und der Landschaft Manuscript for a lecture for „Phänomenologie der Natur – ein Projekt“ by Gernot Böhme.

[17] BOCKEMÜHL, Jochen. 1992. Awakening to Landscape. Goetheanum, Naturwissenschaftliche Sektion. Dornach/Schweiz