Other Callings: Philosophers

Specimen of Rosa eglanteria from a herbarium made for Mademoiselle Julie Boy-de-la-Tour by Jean-Jacque Rousseau, Zurich Central Library.

In the last post, I discussed members of the clergy who were also avid plant collectors and in many cases made substantial contributions to botany.  Now I want to deal with another group, much smaller in number, but interesting nonetheless:  philosophers who liked plants.  I am hardly the first to consider this connection.  Michael Marder, himself a philosopher, wrote The Philosopher’s Plant: An Intellectual Herbarium (2014), in which he discussed how thinkers from Plato to Hegel used plant metaphors in exploring deep questions of existence.  It is a fascinating approach, yet none of the philosophers I want to write about here, all of whom kept herbaria, are given more than a mention.  Marder’s thinkers seem to have been more involved with conceptual rather than real plants, though some of their work is definitely based on close observation of nature.

I’ll begin my survey with John Locke (1632-1704) who maintained correspondence with several botanist/gardeners, including Jacob Bobart the Younger, who had succeeded his father as head gardener at the Oxford University Botanic Garden and also taught there.  Bobart assisted Locke in identifying plants, and Locke, while in France, served as a go-between with Pierre Magnol at the Montpelier botanical garden, which had long been a center for botanical research in France.  Among the items passed among these men were seed lists:  what would be available for sharing.  Locke was particularly interested in fruit trees and vines.  He had number of botanical reference works, and kept specimens for reference (Harris, 2009).

As the years went by, Locke’s interest in botany dwindled, but the opposite was true for Jean-Jacques Rousseau.  While exiled in Switzerland in the early 1760s, he was tutored by the physician and botanist Abraham Gagnebin who joined him on plant collecting trips.  Rousseau was focused on the plants he found around him rather than on exotics and horticultural “monstrosities.”  Botany became an important manifestation of his interest in nature, and he considered studying plants a way to calm the emotions by focusing the mind on something outside itself.   He was drawn to meditating on plant form and became absorbed in learning about plant structures, comparing one species with another.  Carl Linnaeus’s books were among his guides.  As with many others, Linnaean classification made plant identification accessible to him.  He even learned to press plants and began an herbarium, guided by Gagnebin who had a massive collection (Cook, 2012).

Since Rousseau had spent his life writing, it’s not surprising that he began to write about botany.  Madeleine Delessert, the wife of a French financier, sought his advice on teaching her daughter about plants.  In response, he sent her eight letters focusing on the art of observation and how to compare plant forms, then ending with a letter on creating a herbarium; these were later published.  Rousseau came to appreciate a plant collection as a way to reinforce information about a plant.  By this time, Rousseau was creating beautiful specimens, including ones mounted on pages framed with red ink borders (see image above).  He gave some to his patrons, to Delessert and also to the Duchess of Portland for whom he made two portable collections.

Among those influenced by Rousseau’s botanical work was the German writer Johann Wolfgang von Goethe.  He became involved with plants as an administrator in Weimar with responsibility for agriculture and forestry management.  Then, as happened with so many others, he grew fascinated by plants for their own sake.  Goethe read Carl Linnaeus’s works and, like Rousseau, tried to puzzle out the similarities and differences among species.  He started a herbarium and also began sketching plants and plant structures.  The turning point in Goethe’s interest came when he traveled south to Italy and was struck by the new and intriguing species he encountered (Arber, 1946).  They had some similarities with those in Germany, but there were also significant differences, especially greater variety, a diversity of variations on botanical forms.  When he visited the botanical garden in Padua, one of the oldest in Europe, he had an epiphany that somehow leaf forms were related to each other, and all leaves to a basic form.

This unity in diversity led Goethe still further to posit a fundamental plant form, based on the leaf, to which all plant structures were related.  This might seem to have evolutionary implications, but not for Goethe.  He considered the relationship purely conceptual and finally came to accept that this idea could not be visualized and had to remain a mental construct.  Goethe worked on his botanical ideas referencing the drawings he made or had made for him as well as his herbarium specimens.  These included plants he collected and other herbaria he purchased in order to broaden his study material.  His The Metamorphosis of Plants (Goethe & Miller, 2009) presents his argument on form, and while some see him as influential in the history of plant morphology, others consider him an amateur who added little to the field.

Probably the most long-term collector among philosophers was John Stuart Mill, who was interested in botany throughout his life in part because he saw the hierarchical classification of living things as a model for ordering many aspects of human affairs such as law.  Mill collected mainly in the British Isles and had such an extensive herbarium that his daughter-in-law outfitted a room for his specimens (Curtis, 1988).  His collecting broadened after his wife’s death when he moved to Provence and befriended the French naturalist Henri Fabre.  They often botanized together.  Mill also went on collecting trips through Eastern Europe and Greece.  Numbering in the many thousands, his specimens are in several collections in both Europe and the United States (Pearce, 2006).


Arber, A. R. (1946). Goethe’s botany: The Metamorphosis of plants, 1790, and Tobler’s ode to nature, 1782. Waltham, MA: Chronica Botanica.

Cook, A. (2012). Jean-Jacques Rousseau and Botany: The Salutary Science. London: Voltaire Foundation.

Curtis, S. (1988). The philosopher’s flowers: John Stuart Mill as botanist. Encounter, 80(2), 26–33.

Goethe, J. W., & Miller, G. L. (2009). The Metamorphosis of Plants. Cambridge, MA: MIT Press.

Harris, S., & Anstey, P. (2009). John Locke’s seed lists: A case study in botanical exchange. Studies in the History and Philosophy of Science Part C: Studies in History and Philosophy of Biological and Biomedical Sciences, 40, 256–264.

Marder, M. (2014). The Philosopher’s Plant: An Intellectual Herbarium. New York: Columbia University Press.

Pearce, N. R. (2006). John Stuart Mill’s botanical collections from Greece (a private passion). Phytologia Balcanica, 12(2), 149–164.

The 18th-Century Passion for Botany: Philosophy

4 Rousseau Gentiana filiformis

Gentiana filiformis specimen from the Rousseau herbarium, Jean-Jacques Rousseau Museum, Montmorency, France

The argument I am making in this series of posts (1,2,3) is that in the 18th century there was an interest in natural history, and particularly in plants, that was both intense and pervasive among European educated classes.  Statesmen like the British Prime Minister, Lord Bute, merchants such as George Clifford, and noblewomen including the Duchess of Portland were fascinated by, if not obsessed with, the plant world.  This extended well beyond enjoying gardens or just decorating with plants; they studied botany, learning as much as they could about plant taxonomy with the help of the Linnaean method.  They went so far as to dissect flowers, coax exotic species into bloom, attempt hybridization experiments, and of course, keep herbaria.  With this cultural background, it is hardly surprising that two of the most influential writers of the day were also fired with botanical zeal:  Jean-Jacques Rousseau and Johann Wolfgang von Goethe.

Rousseau became serious about botany around 1764 while he was living in Switzerland (Cook, 2012).  This fit with his philosophy of humans being linked to nature.  Like many of that era, as soon as he became interested, he had a thirst to learn more and more about plants, including how to identify them.  Rousseau was not particularly taken with the Linnaean system, though he studied it.  He was instructed in it by two Swiss physicians as mentors who went on plant collecting tours with him and taught him to press plants for a herbarium.  Rousseau really took to the practice and created beautiful specimens mounted on pages framed in red ink (see figure above).  He also corresponded with the botanist, Joseph Dombey, who sent him over 1500 rare specimens to study.  Rousseau was fascinated by plant form, by the visible similarities and differences among species.  He saw botany as a way to calm the emotions by focusing the mind on something outside itself.

Rousseau was closely tied to the intelligentsia of the day and corresponded with a number of well-educated women of the elite.  He visited the Duchess of Portland (see earlier post) when he went to Britain in 1767 and botanized with her.  He had already been in correspondence with her and sent her two small herbaria.  He also was in contact with Madeleine Delessert, the wife of a financier.  She prevailed on him to give her instruction on how to teach her daughter about plants.  This was the origin of his book of eight letters on botany.  It is a lovely little work, especially because the final chapter is on how to create a herbarium—what more could you ask for in botanical instruction?  In 1785, the British botanist Thomas Martyn translated the letters into English, but gave them a more Linnaean slant than Rousseau had.  In the early 19th century, the letters were published with illustrations by none other than the great botanical artist Pierre-Joseph Redouté, a beautiful tribute to the philosopher (Rousseau, 1979).

One of those influenced by Rousseau’s botanical work was Johann Wolfgang von Goethe.  He became interested in plants when he was made an administrator in Weimar and had to deal with agricultural and forestry management.  As with so many others, he then grew fascinated by plants for their own sake.  He read Linnaeus’s books as well as Rousseau’s botanical writings and tried to work out the similarities and differences among species.  Goethe started a herbarium and also began sketching plants and plant structures (Schulze, 2006).  The turning point in his interest came when he traveled south to Italy and was struck by all the new and intriguing plants he encountered.  They had some similarities with those in Germany, but there were also tremendous differences, especially in the greater variety of species, the number of variations on botanical forms.

As he tried to make sense of this multiplicity, Goethe had a flash of insight when he visited the botanical garden in Padua.  There he saw a palm tree and studied the variations in the forms of its leaves.  He became fixated on leaves and the idea came to him that all plant structures on a stem: leaves, flowers, and the parts of flowers were variations on a basic leaf form.  He came to realize that it was impossible to visualize this Urblatt, as he called it, or to draw it; it was an ideal, a mental construct.  This was also the case with what he termed the Urpflanze or basic plant from which derived all the different plant forms.  He was not thinking in evolutionary terms but more Platonically of an ideal form.  Goethe developed his concept in a book on plant metamorphosis.  While some consider it of little importance in the development of modern botany, others see it as seminal in that he examined questions of relationships among forms that are still relevant today.  One in the second group was Agnes Arber, a noted plant morphologist of the first half of the 20th century who published an English translation of Metamorphosis (Arber, 1946) and wrote The Natural Philosophy of Plant Form (1950) that built on Goethe’s ideas.  Arber saw the basic plant unit as the leaf-as-partial-shoot, and her work received some vindication at the end of the 20th century when the genes responsible for flower structures were discovered and the ABC model of flower development form was published (Haughn & Somerville, 1988).  To me, this is a wonderful story of how fundamental ideas can resurface in new ways as science develops.  It’s another example of where the passion for plants can lead.


Arber, A. R. (1946). Goethe’s botany. Chronica Botanica, 10, 63–126.

Arber, A. R. (1950). The Natural Philosophy of Plant Form. Cambridge: University Press.

Cook, A. (2012). Jean-Jacques Rousseau and Botany: The Salutary Science. Oxford, UK: Voltaire Foundation.

Haughn, G. W., & Somerville, C. R. (1988). Genetic control of morphogenesis in Arabidopsis. Developmental Genetics, 9(2), 73–89.

Rousseau, J.-J. (1979). Botany: A Study of Pure Curiosity (K. Ottevanger, Trans.). London: Michael Joseph.

Schulze, S. (2006). The Painter’s Garden: Design, Inspiration, Delight. Frankfurt, Germany: Hatje Cantz.