The Second Adam: Linnaeus and His Systema Naturae

May 13, 2014 by

So out of the ground the LORD God formed every animal
of the field and every bird of the air, and brought them to the man to see
what he would call them; and whatever the man called every living
creature, that was its name. Gen 2.19

 

One of the major themes of what is commonly called the Scientific Revolution is the engagement of “natural philosophers” (the precursor to modern day scientists) with the works of classical philosophers and mathematicians.  Because many of these natural philosophers were classically trained, it is natural that they would use this education as a backdrop to their studies.  One ancient philosopher who was frequently referenced, Aristotle, stands out simply because his work was so vast and varied that it was practically impossible to not respond to it in some way.

Carl Linnaeus, the father of modern taxonomy

Carl Linnaeus, the father of modern taxonomy

Carl Linnaeus, who lived in Sweden from 1707 to 1778, is credited with being the “father of modern taxonomy” (the study of the classification of animals and plants)[1] and has even been nicknamed by some as “The Second Adam.”[2] This is because he is the scientist who formalized the organization of living organisms into the hierarchy from kingdom to species and developed the method of binomial nomenclature- that is, referring to an organism by its genus and species.[3]  An example of this would be homo sapiens, or canis familiaris.  Yet he was not the first person to think of living beings hierarchically, nor was he even the first to discuss organisms through their genus and species.  Aristotle discusses both of these in several of his writings.  In the scheme of the history of science, Linnaeus’ work presupposes Aristotle’s hierarchical theories and had an influence on later studies of Darwinian evolution.

Most historiographical studies of the history of taxonomy have been conducted by taxonomists themselves rather than historians.  Although this research is by no means inclusive or exhaustive, most historiographical works on Linnaeus focus on his biography and what he did to a greater extent than his place in the history of scientific inquiry or how he did it.  Because of this, this research includes secondary works by both taxonomists and historians, as well as a study of primary sources by Aristotle and Linnaeus.  This research also refer to commentaries on Aristotle’s writings for clarification.

Aristotle is more commonly known as a philosopher, but his work in the discipline of science is considerable.  Living in Greece in the fourth century B.C.E., he began his works on categories and natural sciences with an introductory analysis of the philosophy of science.  This philosophy begins with Aristotle’s treatises on logic:  Analytica Priora and Analytica Posteriora.[4]  These works discuss Aristotle’s philosophy of syllogisms, or the idea of using deductive reasoning to figure out new information from facts already known.  For example, if we know that A is equal to B, and that B is equal to C, then we can deductively conclude that A is equal to C.  This is important in the study of categorization because it allows us to deduce that if a poodle is a type of dog and a dog is a type of animal, then a poodle must be a type of animal.

Is this poodle a dog?  No one really knows.

Is this poodle a dog? No one really knows.

In order for this deductive logic to work, one must know the definitions of the things from which he or she is trying to reach a conclusion.  One cannot deduce that a poodle is type of dog without knowing what a dog is and then seeing if a poodle satisfies this definition.  One of Aristotle’s biggest ideas is the idea of nature being teleological, meaning that it operates towards a specific goal.  Therefore, one can define a thing by what its purpose is (e.g., a poodle is a dog because it fulfills the function of a dog).  Because of this, Aristotle discusses in his De Generatione Animalium (On the Generation of Animals) the four causes which are the root of everything:

First, the final cause, that for the sake of which a thing exists; secondly, the formal cause, the definition of its essence (and these two we may regard pretty much as one and the same); thirdly, the material; and fourthly, the moving principle or efficient cause.[5]

For Aristotle, the final cause is the same as the definition of a thing’s essence because of his teleological interpretation of nature.  The material of a thing is rather obvious:  That which a thing is made of.  The efficient cause is whatever thing or event caused that thing to come into being.  In the case of a watch, the efficient cause is the watchmaker who made the watch.[6]  But when it comes to living plants and animals, the efficient cause is not so clear.  Aristotle investigates this by discussing how semen in sexual creatures could be the efficient cause (one must keep in mind when reading this section that Aristotle did not have the benefit of a modern sexual education when he was in school).  The fact that plants and animals generate in different ways is one way to distinguish their definitions because one teleological purpose of a species is to propagate its own species.  Thus one is able to categorize the species into different categories.

Stafleu in his monograph Linnaeus and the Linnaeans:  The Spreading of their ideas in systematic botany, 1735-1789 discusses Aristotle’s logical influence on Linnaeus.  He notes that while Linnaeus was in school he excelled in Aristotelian logic.[7]  The trick to using Aristotelian logic to organize nature in a hierarchical way is separating the essential characteristics of a thing from its accidental characteristics.  A poodle may have the accidental characteristics of being black or white, but this does not determine whether or not it is a dog.  On the other hand, if a thing is not carnivorous nor has four legs nor the correct dental characteristics (a major defining characteristic for Linnaeus in his Systema Naturae), then the thing may not be a dog.

drawing of plants for taxonomy purposes

drawing of plants for taxonomy purposes

It can be hard to determine the difference between essential and accidental characteristics at times.  Some dogs are born with three legs or perhaps have some defect that does not allow the teeth to form properly.  Does this mean it is not a dog?  The intuitive answer is no.  This raises the question of how many essential characteristics can one take away before a thing is not the thing we claim it is.  To state the issue another way:  it is hard to determine logically the distinctions we give to things.  One of Linnaeus’ big struggles as a devout Christian was to figure out how humans were different from apes.  He knew from a theological viewpoint that man alone was endowed with God’s special grace, but from a scientific standpoint he had to admit, “I know scarcely one feature by which man can be distinguished from apes, if it be not that all the apes have a gap between their fangs and their other teeth.”[8]  If one wanted to suggest that this gap between the teeth is the fundamental reason why humans are different from apes, he or she would have a hard time proving this.  Modern scientists today are still studying apes and humans (mostly through brain scans and other experiments) to determine what separates man from animals.

Through knowing the definitions of things, one can categorize a group of things into a hierarchical order, starting with what all the things have in common and then working down to the specific differences.  For Aristotle, the substance of a thing is of the utmost importance because it tells us what the essence, or definition, of a thing is.  Studtmann, a professor of philosophy, collected information on Aristotle’s writings on substance and compiled it into a hierarchical structure of which he thinks Aristotle would have approved:

I. Substance
A. Immobile Substances — Unmoved Mover(s)
B. Mobile Substances — Body
1. Eternal Mobile Substances — Heavens
2. Destructible Mobile Substances — Sublunary bodies
a. Unensouled Destructible Mobile Substances — Elements
b. Ensouled Destructible Mobile Substances — Living things
i. Incapable of Perception — Plants
ii. Capable of Perception — Animals
• Irrational — Non-Human Animals
• Rational — Humans[9]

From this chart we can learn a lot about Aristotle’s view of the universe, particularly the difference between minerals (i.e., earth:  one of Aristotle’s four earthly elements), plants, animals, and humans.  Even though scientists today may not agree with Aristotle’s particular method for categorization (we now know that the heavens are not indestructible), it is still useful for the basic premise of categorization and organization.

These distinctions between the different types of substances were used for centuries by subsequent natural philosophers, including Carl Linnaeus.  Carl Linnaeus wrote in his Systema Naturae:

… the Reign of Nature has been divided into three… Stone bodies brought together, nor alive nor feeling; Vegetable bodies having been cultivated and alive, not feeling; Animal bodies having been cultivated and alive and feeling.[10]

Furthermore, next to Linnaeus’ categorization of the genus homo is the phrase “nosce te ipsum”  which translates to ‘know thyself,’ (the first step towards wisdom, as Linnaeus clarifies in a footnote).[11] This means that the genus homo is defined by its rational nature.  Even though humans are listed as primates along with apes, what separates man from other animals according to Linnaeus (and Aristotle) is the ability to reason.

The name of a thing was very important to Aristotle, for a name symbolizes the essence of a thing.  He stated in his Categories that “it is by stating the species or the genus that we appropriately define any individual man; and we shall make our definition more exact by stating the former than by stating the latter.”[12]  Linnaeus also understood that taxonomy is important because “indeed if they destroy the names, knowledge of the things also dies.”[13]  This is because if we do not have the name, the symbol of the essence, we do not know what a thing is.  This is where Linnaeus both gets his system of binomial nomenclature and yet at the same time diverges from Aristotle’s assertions.  Whereas Aristotle favored the species over the genus, Linnaeus favored the genus over the species.[14]  This is obvious when we consider Linnaeus’ method of binomial nomenclature.

Linnaeus' botanical garden in Uppsala, Sweden

Linnaeus’ botanical garden in Uppsala, Sweden

Originally a tool used to help taxonomists remember the hierarchical order of a species, Linnaeus’ system of classification is completely dependent on knowledge of the genus of a species.  If one labelled man as simply sapiens, or a dog as familiaris, it would be difficult to understand what one was talking about.  In Aristotle’s time, when fewer species of plants and animals were known, it was easier to identify a thing by its species name.  But Carl Linnaeus lived in the eighteenth century, after the discovery of the New World and the Age of Exploration.  The influx of new specimens and the different taxonomists’ methods for organizing these specimens made taxonomy messy and highly disorganized.[15]  This is why Linnaeus’ work is so important, because he both standardized and simplified the existing system of taxonomy.

Linnaeus’ work is still important to us today in its own right, but it is also important for the influence it had on another famous biologist:  Charles Darwin.  Without Linnaeus’ ordering of the species, it would have been immensely difficult for Darwin to develop his own theories.  Darwin knew that he had also to thank Aristotle, though.  He once wrote, “Linnaeus and Cuvier have been my two gods, though in very different ways, but they were mere schoolboys to old Aristotle.”[16]

In a world where only as little as ten percent of all species are known to man, the study of taxonomy is still very important.[17]  Both Aristotle and Linnaeus knew that to name a thing was to know it, and since “all men by nature desire to know,” it is our duty to give names to the marvels of the world around us.[18]  Even the Christian Bible takes care to note Adam’s duty to name “every animal of the field and every bird of the air,” a duty that one could say has been passed down to us, from Aristotle to Linnaeus to present-day taxonomists.[19]

 

[1] “Taxonomy.” Merriam-Webster.com. Accessed December 9, 2013. http://www.merriam-webster.com/dictionary/taxonomy.

[2] Frans Antonie Stafleu, Linnaeus and the Linnaeans:  The Spreading of Their Ideas in Systematic Botany, 1735-1789 (Utrecht, Netherlands:  A. Oosthoek’s Uitgeversmaatschappij N.V., 1971), 19.

[3] Edward O. Wilson, “The Major HIstorical Trends of Biodiversity Studies,” in Systema Naturae 250:  The Linnaean Ark, ed. Andrew Polaszek (Florida:  CRC Press, 2010), 1.

[4] The Stanford Encyclopedia of Philosophy (Fall 2011), s.v. “Aristotle’s Biology,” by James Lennox.

[5] Aristotle, De Generatione Animalium, trans. Arthur Platt, in The Basic Works of Aristotle, ed Richard McKeon (New York: Random House, 1941), 665.

[6] “Three Minute Philosophy: Aristotle (the new version!),” YouTube video, 3:55, posted by “CollegeBinary,” May 7, 2012, http://www.youtube.com/watch?v=tbgHbzrL3d0.

[7]  Stafleu, 25.

[8]  Sten Lindroth, Gunnar Eriksson, and Gunnar Broberg, Linnaeus, the Man and His Work, ed. Tore Frängsmyr (Berkeley: University of California, 1983), 167.

[9] The Stanford Encyclopedia of Philosophy (Fall 2011), s.v. “Aristotle’s Categories,” by Paul Studtmann.

[10]  Caroli Linnaei, Systema Naturae, trans. by myself (London: British Museum, 1956), 6.

[11] Ibid., 20.

[12] Aristotle, Categoriae, trans. E. M. Edghill, in The Basic Works of Aristotle, ed Richard McKeon (New York: Random House, 1941), 10.

[13]  Linnaei, 7.

[14] Stafleu, 79.

[15] Wilson, 1.

[16]  Charles Darwin, “Letter to W. Ogle,” in The Life and Letters of Charles Darwin, vol. 2, ed. Charles Darwin and Francis Darwin (London:  John Murray, 1896), 427.

[17] Wilson, 2.

[18] Aristotle, Metaphysica, trans. W. D. Ross, in The Basic Works of Aristotle, ed Richard McKeon (New York: Random House, 1941), 689.

[19] Gen 2.19 NRSV.

 

 

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