Mules, Species, and Other Problems in the Philosophy of Biology

Zachary G. Augustine

B.A. thesis under the direction of Robert J. Richards

History, Philosophy, and Social Studies of Science and Medicine (HIPS)

The University of Chicago

2016 April 22

ABSTRACT

Mules, Species, and Other Problems in the Philosophy of Biology

Zachary G. Augustine

The tree of life is in constant flux as organisms are reclassified. Yet the philosophy of biology

has struggled to define a species. A movement of pluralism has taken hold, leading philosophers

to doubt or deny the existence of ‘species’ as a category. I argue that pluralism is self-defeating,

and refining the species concept is paramount to science and philosophy. Finding flaws in

Mayr’s biological species concept, I examine three alternatives and pit them against each other

in a simulated form of competitive discourse. I define this risk-laden discursive practice as

competitive monism and propose it as a methodology for the philosophical community to resolve

paradigmatic debates. Using my method, I support Boyd’s homeostatic property cluster (HPC)

species concept as a resolution in the debate. Mules become members of their own species and

other species can be more easily classified. Beyond species, I draw parallels between the natural

selection of organisms and the competition of ideas in a more general theory of the evolution of

knowledge.

CONTENTS

ABSTRACT

PART I: THE NEED FOR ‘SPECIES’

The Mystifying Mule, or the Failures of the Biological Species Concept 1

Definitions 8

The Pluralistic Claim of Impossibility 11

PART II: FINDING A REPLACEMENT

Competitive Monism (Three Species Concepts) 17

The Mule, Newly Classified 29

Discursive Competition 29

CONCLUSION: KNOWLEDGE EVOLVES

BIBLIOGRAPHY

PART I: THE NEED FOR ‘SPECIES’

Scientists are striving to carve nature at her joints.

–David Hull1

Faced with the immense and spectacular diversity of natural forms, it is impossible to deny the

distinct character of that most fundamental of categories: species. Despite its apparent simplicity,

‘species’ is difficult to define as a category. Various definitions have been proposed, each one

their own ‘species concept’ (as distinct from the word alone). Most famously, Mayr’s 1940

biological species concept equates the category with the ability to reproduce and beget viable

offspring. This is still the established view, yet it does not stand up to more than a cursory

glance. The biological species concept must be replaced, or biology with continue to face

problems in classification: not only with regard to hybrid organisms such as mules, but also to

the numerous organisms to which it does not apply such as those asexual, rare, or extinct. The

endeavor to carve nature at her joints must overcome its outdated concepts through a new

discourse, a discourse limited, I argue, by the current batch of philosophical pluralists.

THE MYSTIFYING MULE, OR THE FAILURES OF THE BIOLOGICAL

SPECIES CONCEPT

The paradigmatic case of what is not a species is the mule, the sterile and short-lived

horse/donkey hybrid. The fact that a horse and a donkey cannot produce viable offspring

suggests that, although superficially similar, they are not members of the same species. This may

be correct in itself; yet the mule’s exclusion from the category of species raises philosophical

problems for biology. What is the mule – a species or not or something else?

1 David L Hull, The Metaphysics of Evolution (Albany: State University of New York Press, 1989), 161.

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I choose this example to illustrate what’s at stake: the concept of ‘species’ rests at the

heart of biological practice. Theoretically, species represents a base epistemological category

with which science can operate, much like how the category of ‘atom’ acts as the foundation for

chemistry. Species, likewise, is the base unit of biology, a definitional grounding for the

knowledge it supports in the discipline.

First is a question of life. As the Linnaean taxonomy is the systematic and total

categorization of all known forms of life. Its categories encompass the totality of all things

living. Each and every living thing is codified in its kingdoms and sub-categories. If the mule is

presumed to be living but denied status as a species, then one faces another contradiction. Either

the mule is living, included in the taxonomy, and assigned a species name, or denied a species

name, excluded from the taxonomy and considered nonliving. The classifications of life and

species hang together.

Second is a question of reproductive viability. Is the mule a member its own species, or

does it lack such a designation entirely? Assume the former: the sterile mule could nonetheless

constitutes its own species designation. One is then faced with a strange situation. Mules are

sterile so they cannot reproduce with other mules. Mules would not be recognized taxonomically

with other mules, even if they were assigned an arbitrary species name. Under the biological

species concept, strictly interpreted, each and every mule would be the sole member of a new

species, as no mule has any partners with which it could be viable. Thousands of distinct mule

species would then fail to link them together by their obvious similarities and common ancestry.

Given this problem, one questions the premises again: either the mule is not a species, or the

mule is not a thing i.e. nonliving in the former case, or nonexistent, or unable to be categorized in

the latter.

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Wikipedia provides three definitions of the mule, indicative of differing approaches to

classifying it. Relatively undisputed is the plain text definition, “A mule is the offspring of

a male donkey (jack) and a female horse (mare).”2 This is reasonable and appears correct in

terms of biology. However, vagueness in the word ‘offspring’ hides ambiguity with regard to the

mule’s taxonomic status. Interestingly enough, this vagueness is also reflected in the secondary

definition of mule, as a hybrid of any organism, especially those that are sterile.

Wikipedia’s table on mules (Figure 1) classifies a

mule as an animal, vertebrate, mammal, Perissodactyl

(odd-toed ungulates), equid, and equine in descending

taxonomic classification. When it comes to species,

however, there are three possibilities presented in

unadorned factual form.

First, and under ‘species’ in the taxonomic table,

is “Equus asinus x Equus caballus”, listing the donkey,

as the male of the hybrid pairing, first followed by that

of the modern domesticated horse.3 Second, the mule’s

binomial name is listed as ‘none’. The subtext states that

‘Most mules are sterile. Sterile hybrids are not species in

their own right.’4 The qualifying ‘most’ is interesting –

perhaps implying that only the sterile ones lack the

2 “Mule,” Wikipedia, the Free Encyclopedia, April 14, 2016, http://en.wikipedia.org/wiki/Mule. 3 Ibid. 4 Ibid.

Figure 1- Wikipedia’s table on mules

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species designation.5 The third classification in the same table is the fictional classification

‘Equus mulus’.

All three of these classifications raise other problems specific to the philosophy of

biology, in addition to the two problems of life and reproduction above. Do not confuse this case

study on mules as an extreme example – it is indicative of flaws in the more general

classification process. Allow me to follow each of these three possibilities to their logical

conclusions and so reveal those difficulties already present..

The first ‘hybrid’ classification is an ugly ‘x’ linking the binomial species names of both

parents. Indeed, this ‘x’ betrays the mission of the taxonomic endeavor, and its core tenant of

irreducibility. Species are the fundamental taxonomic unit, in the same way that atoms are

whole, fundamental, and unbreakable. Both fulfill an important epistemological role, which, if

abolished, would need to be filled by another term. To sidestep the issue here is to push the

burden onto other categories, either in the next most-specific category ‘genus’, or ‘offspring’, or

even ‘living’ itself. That is, if one can split species into even parts and take one-half of an

epistemological atom from each parent, then species is no longer the most basic unit of

taxonomy. To accommodate hybrid offspring using this piecemeal method, one must face other

problems: the nature of these species-parts, the status of their newly-implied essence, and rules

for their intermingling among offspring. To accommodate hybrids, it seems that one must

redefine standard inheritance among members of the same species as simply a limiting case of a

new, larger taxonomic model. Flubbing the binomial name with an ‘x’ between Equus asinus and

Equus caballus leads to prohibitive theoretical complexities.

The second classification is that, as a sterile hybrid, the mule is not a species and has no

5 This raises an accompanying question of what non-sterile mules, however rare, are. Does their fertility reclassify

them apart from sterile mules?

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species name. One immediately wonders if this denial of name also applies to sterile non-

hybrids, such as organisms that are old, injured, or celibate. What is more damning, however,

about this solution is the questionable ontological status of sterile hybrids like mules. Is the

denial of a species name a claim that the mule is non-living, much like how viruses are often

denied the same status? Probably not, for few deny that mules are living. Yet there is something

more at stake beyond answering the simple philosophical question of ‘what kind of thing is it’,

and that is the consistency and ubiquity of the taxonomic endeavor. As I have indicated above,

all living organisms are granted a species name to signify their inclusion in that grand tree of life.

The idea that all things living are classified means that those known and willfully unclassified

are non-living. There is a pressure, then, to classify the mule, so clearly living. This pressure

invalidates the second (non-)classification attempt that the mule is not a species.

The third classification is largely irrelevant at face value. Equus mulus finds its origin in

an outdated 1777 description by Johann Christian Polycarp Erxleben.6 However, the notion of

assigning the mule its own species name despite its sterility seems promising, as it allows one to

retain the whole of Linnaean taxonomy and avoid the implications of non-living mules.

Unfortunately, this is not feasible under the current framework of the biological species concept.

Other species concepts do, however, provide a promising way forward.

In summation, the current biological species concept forces an impossible situation when

it comes to classifying mules. An abundance of material has been written about the flaws and

foibles of the biological species concept often, admittedly, in support of an alternative. Allow me

then, to state the debate surrounding species in a novel way. Mules present us with four

independent claims, each of which appear true on their own but conflict when taken together,

6 F. Welter Schultes, “‘Mulus’ Erxleben, 1777 Described in Equus,” AnimalBase, April 21, 2010,

http://www.animalbase.uni-goettingen.de/zooweb/servlet/AnimalBase/home/speciestaxon?id=21799.

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P1) Mules live and breathe

P2) Mules are sterile

P3) Species can reproduce viably with members of the same

P4) All living organisms have a species name

All of these positions appear reasonable. One can infer an intermediate conclusion,

I5) Mules are not species (P2+P3)

Which leads to a conclusion that directly contradicts P1,

C6) Mules are non-living (I5+P4)

Facing this contradiction, one must dispute the reasoning or abandon the premises. It’s

unquestionable that mules are living (P1) and sterile (P2). Up for dispute, then, is the biological

species concept of reproductive viability (P3) or the use of species names to define living

organisms (P4). One must choose: either the mule is non-living, or the biological species concept

is broken.

EXTINCT, ELUSIVE, & ASEXUAL ORGANISMS

Mules are a particularly concrete and illustrative example in their own right. More valuable are

the questions they raise about classification more generally. The biological species concept’s

reliance on sexual reproduction for classification excludes huge swaths of nature.

The biological species concept does not apply to any organism which does not reproduce

sexually. So plants, bacteria, many invertebrates, and fungi – categories which dominate our

knowledge of life and its taxonomy – are out. For this so expansive and numerous of a category,

its members are afflicted by a philosophical problem far worse than that of the mule. The mule,

at the very least, fails the one condition of the biological species concept: it is unviable.

Asexually reproducing organisms, however, do not qualify for such a test. They do not pass or

fail the biological species concept – it does not even apply to them. Sticking to the biological

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species concept would be to abandon >95% of the living world, and its most fundamental and

important members.

Many organisms are poorly understood. We have a startling lack of information on the

reproductive habits, lifestyles, geographic ranges, or population size of the rarer species. Those

rarer still we may have yet to discover. In these cases of rare organisms, one is forced to

speculate whether or not they could have reproduced. It is fine to lack knowledge about these

elusive organisms, but we must have a good framework against which they can be classified.

Closely related is the final category of extinct organisms. Those organisms which we may

only know from the fossil record become indeterminate taxonomically, as one cannot figure out

if it were possible for, say, a fossilized Australopithecus to breed and produce fertile offspring

with Paranthropus. Again, taxonomy proceeds on using other methods such as phylogeny,

genetics, morphology, and so on. These other methods also require another definition of species.

The biological species concept is in need of a replacement. If the reader were already in

agreement on this point, the above examples do well to qualify what kind of replacement is

required. A species concept need apply to all of nature, not just the visible or sexually

reproducing spheres. It needs to make use of a variety of evidence, often scant, and it needs to

apply to extinct organisms.

A final note is the disqualification of species concepts which rely on largely genetic

modes of analysis. While the 1953 confirmation of a genetic basis of inheritance profoundly

transformed biology and has led to surprising evolutionary conclusions, a granular or exhaustive

taxonomy based on genetics is simply infeasible. A primary problem is the lack of genetic

evidence for extinct organisms. DNA is notoriously fragile and conditions for fossilized

specimens can be harsh. Even if a perfect DNA sample were to be found, one faces

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epistemological issues: genes vary greatly between members of the same species. While

humanity celebrates its diversity, humans are actually among the most homogenous of

organisms.7 Despite this uncharacteristically high degree of similarity to one another, there is no

singular ‘human genome’. There are as many genomes as there are individuals. Yet one cannot

deny that humans are all members of a singular species. But one makes this argument on

phenotypic, evolutionary, behavioral, and social grounds; genes offer little but confirmation.

Similarly, the concept of a ‘Neanderthal genome’ is absurd. Fossilized organisms we now call

Neanderthals have switched designations many times. Even if they were to remain stable, we

don’t have good genetic samples. Even if we did have good genetic samples, we could not

analyze them in such a way as to find a single ‘genome’ characteristic of the species.8 While

genes have changed much for evolutionary biology, one must dispel of the notion that they have

done anything for the definition of species.

DEFINITIONS

Philosophy, like all disciplines, proceeds according to a shared set of assumptions and

definitions. Particular to the debate surrounding species in the philosophy of biology, I identify

two primary dichotomies.

7 The homogeneity of humans is due to their novelty. Starting from one or two populations in Africa around 30,000

years ago, humans quickly globalized. Extremely adaptable to any climate, humans were able to lead longer,

healthier lives through technology, producing more children with similar genes and leading to a relaxation of natural

selection. In a way, humans have shifted the genetic adaptability that natural selection brought about through

differentiated reproductive success and death onto a kind of behavioral adaptability with far less risk. Unsuccessful

behaviors can be culled through learning and adaption instead of being eliminated through death. (This is a theme

that I explore in terms of the philosophical community in the final section of this paper.) Just how homogenous are

humans? I thank Professor Tuttle for sharing this insight: a single tribe of chimpanzees has more genetic diversity

than the entire human species. That is to say the genetic differences between Caucasian, African, and Asian humans

are far less significant than even the normal variation between, say, fish of the same school. Humans are one species.

Russell H. Tuttle, Apes and Human Evolution (Cambridge, Massachusetts: Harvard University Press, 2014), 29–32. 8 If we are to stake claim on the model for the human genome, Professor Tuttle has graciously volunteered.

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Realism is a philosophical stance that equates an object to its definition. Realists believe

that there are real distinctions between things. Realists argue that a definition of species reflects

real, meaningful divisions in nature. Nominalism is a philosophical stance that denies the reality

of definitions. Nominalists believe that definitions are arbitrary, and that things are merely given

names. Nominalists argue that our attempts to classify different parts of nature do not reflect

reality. Together, Realists and nominalists argue whether definitions can reflect reality.

Monism is a philosophical stance that argues for one valid definition. Monists wish to

define species in a singular way. Only some monists supply that definition, but all monists argue

that a valid definition exists. Pluralism is a philosophical position that rejects that one valid

definition is even possible. Dupré defines pluralism as, “the thesis that there is no uniquely

correct or natural way of classifying organisms and that a variety of classificatory schemes will

be best suited to the various theoretical and practical purposes of biology.”9 Pluralists necessitate

multiple definitions of species. Some pluralists may argue there is no valid definition of species.

Together, Monists and pluralists argue about the ability of science to make a singular claim as to

how nature works. Taken together, these two definitions form two distinct spectrums.

Nominalism stands opposed to realism. Pluralism stand opposed to monism. Yet the two

spectrums need not correspond. One can plot them to better visualize their independence (Figure

2).

Species (pl. species) is a scientific term from which we get the word ‘specific’. A species

is the smallest taxonomic category an organism can be classified as. (Perhaps one would say the

most specific category.)10 Genus (pl. genera) is a scientific term from which we get the word

9 John Dupré, “On the Impossibility of a Monistic Account of Species,” in Species: New Interdisciplinary Essays,

ed. Robert A. Wilson (Bradford Books, 1999), 4. 10 Species is also sometimes used a philosophical term, roughly meaning ‘essence’ or ‘category’. It is sometimes

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‘general’. A genus is the second smallest taxonomic category an organism can be classified as.

(More general in scope than a species, one might say.)

A species concept is a proposed definition that applies to all species. The concept that is

generally accepted is Ernst Mayr’s 1940 biological species concept. It defines a species as those

which can interbreed and produce viable offspring.11 Although Mayr’s species concept is well-

known among scientists, many philosophers believe it is incomplete or wrong. Many alternatives

have been proposed. In terms of these alternatives, realists and nominalists also differ. Realists

may propose particular species concepts, whereas nominalists are often less concerned with any

particular species concepts as opposed to their general impossibility. Likewise, pluralists tend to

point out the inadequacy of any one species concept, while monists strive for a unified, holistic

species concept.

used interchangeably with ‘natural kinds’ or ‘distinct categories’, with phrases like ‘carving nature at the joints’ or

‘historical (or temporally) distinct individuals’, or distinctions like un/real, un/natural, dis/continuous, ex/intrinsic,

un/essential. There is definite slippage between ‘species’ as a biological term and ‘specific’ as a categorical term,

which I will avoid wherever possible, excepting of course, the points at which this slippage itself is my focus. 11 “A species consists of a group of populations which replace each other geographically or ecologically and of

which the neighboring ones intergrade or hybridize wherever they are in contact or which are potentially capable of

doing so (with one or more of the populations) in those cases there contact is prevented by geographical or

ecological barriers.” Ernst Mayr, “Speciation Phenomena in Birds,” The American Naturalist 74, no. 752 (1940):

256. paraphrased in Ronald H Matson, “Species Concepts and the Definition of ‘Species,’” College of Science and

Mathematics at the Kennesaw State University, accessed July 4, 2015,

http://science.kennesaw.edu/~rmatson/Biol%203380/3380species.html.

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Figure 2 - Philosophical stances about definitions in science. The different shapes represent distinct yet valid

theoretical positions. Importantly, the two spectrums are independent .

THE PLURALISTIC CLAIM OF IMPOSSIBILITY

Scholars such as Dupré have argued that a singular definition of species is impossible.12 There

has been a growing resistance to traditional realism or a belief in essentialist notions of natural

kind. Instead, pluralists argue that one must accept multiple definitions or at least the possibility

12 Dupré, “On the Impossibility of a Monistic Account of Species.”

Philosophical stances about definitions in science

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of them. Dupré writes

There is no God-given, unique way to classify the innumerable and diverse products of

the evolutionary process. There are many plausible and defensible ways of doing so, and

the best way of doing so will depend on both the purposes of the classification and the

peculiarities of the organisms in question, whether those purposes belong to what is

traditionally considered part of science or part of ordinary life.13

Dupré claims that there is no singular definition, and that there can’t be one. Instead, he argues

that definitions must change when they are used in different disciplines or for different purposes.

Boyd names this the ‘accommodation’ thesis and offers a critique based on the different and

incompatible ways in which disciplines produce knowledge.14

More simply, however, one can ask: do the plants, animals, and bacteria exist and have

names when we are not looking at them? All but the most extreme anti-realists would agree that

those organisms do exist; they’re real in this way. However Pluralism is a problem for this

simple fact. Pluralism, as Boyd is correct to suggest, separates organisms that we recognize as

one and the same. Whereas I draw a conceptual link between an everyday definition of a rock (as

a hard, solid chunk of earth) and the geologic definition (of a heterogeneous mineral solid),

pluralism weakens any equivalence between the two. Pluralists’ definitions tend to exist

separately or weakly linked to each other, whereas realists and monists insist there is a thing

behind these two imperfect definitions. The reasonable belief in rocks then somewhat invalidates

the pluralist’s resistance to the reality of rocks. However, one must acknowledge the reality of

the pluralistic position that has since become the party line in the philosophy of biology.

A fundamental limitation of pluralism is its inability to produce results. Pluralists are not

concerned with finding a singular definition, because they don’t believe that one exists. Instead,

13 John Dupré, The Disorder of Things: Metaphysical Foundations of the Disunity of Science (Cambridge, Mass.:

Harvard University Press, 1993), 57. 14 Richard Boyd, “Homeostasis, Species, and Higher Taxa,” in Species: New Interdisciplinary Essays, ed. Robert A.

Wilson (Cambridge, Mass.: MIT Press, 1999), 160, http://pi.lib.uchicago.edu/1001/cat/bib/3909850.

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they posit multiple correct definitions or, as it has been more recently, the impossibility of any

definition. When faced with the inadequacy of current definitions, pluralists internalize this sense

and proclaim that the entire effort is impossible. So when it comes to the philosophy of biology

and the species concept debate, pluralists deny their intuition – that nature is divided into

different organisms we so readily observe – and instead insist on the unreality of the category.

As this defies intuition (how can one deny the tremendous diversity and distinction found in

categories as simple as ‘trees’) I struggle to understand the pluralistic position. Yet I’m

compelled to find a more rigorous denial of it.

My response and resolution is that science has, and always will, carry on in the face of

uncertainty. Indeed, it is this characteristic which gives science its unique strength and separates

it from those disciplines, including my own, which are less exact.

THREE SHIFTS IN THE DEBATE

The debate surrounding ‘species’ is a fertile ground for testing sociological or epistemological

claims. To my surprise, discourse about a rather straightforward philosophical issue – ‘what is a

species?’ – is routinely redirected to a more abstracted discourse about philosophy itself. This

common occurrence cannot be mere coincidence – indeed, there is something common, perhaps

categorical, about the claims of each level of argumentation. As methodological and disciplinary

themes come to drive arguments, discourse itself becomes a new object of inquiry.

Up until now, I have examined the species problem on two levels: its own terms, and that of

the philosophical positions and allegiances that inform the debate. I have weighed some of the

merits of different species concepts, and one can see how they follow from commitments to, say,

pluralism. Yet, the pattern of causal influence extends further. If one examines the debate itself

as the object of inquiry, then trends tend to emerge. That is, there is a definite evolution in the

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debate about species, just as the species themselves. Just as any given definition of species is

cyclical in structure, so, too, does discourse surrounding the subject revolve in a regular way

with standard, if not predictable, deviations.

Three quick moves outline the evolution of the debate, proper.

1) TRADITIONAL REALISM:

Most early philosophical positions were instances of the naïve traditional realist view. (Matson’s

list is a good example of this.15) Wilson claims that three assumptions govern the positions of a

traditional realist. 16 Commonality is the first realist assumption that “there is a common, single

set of shared properties that form the basis for membership in any natural kind”. Priority is the

second, with a belief that “the various natural kinds reflect the complexities one finds in nature

rather than our epistemic proclivities”. Ordering is the third and final assumption such that

“natural kinds are ordered so as to constitute a unity”.17 Together, the traditional realist paints a

picture of nature as consisting of universal and natural categories easily visible through human

inquiry. These three assumptions of the traditional realist come together to constitute a relatively

straightforward baseline position.

2) PLURALISM

Since Mayr, philosophers have increasingly argued against traditional realism and the essentialist

notion of natural kinds. Perhaps hyperbolically, Dupré argues that if one accepts Darwin’s theory

15 Matson, “Species Concepts and the Definition of ‘Species.’” 16 Robert A. Wilson, “Realism, Essence, and Kind: Resuscitating Species Essentialism?” in Species: New

Interdisciplinary Essays, ed. Robert A. Wilson (Cambridge, Mass.: MIT Press, 1999), 187–207,

http://pi.lib.uchicago.edu/1001/cat/bib/3909850. 17 Ibid.

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of organisms constantly changing, then one must abandon the notion of species.18 Sober argues

along similar lines, introducing a sense of nominalism.19 In this environment, Lewens feels

compelled to offer a defense of typological thinking.20 This is indicative of an ‘established’

position. As such, pluralists hold firm that nature does not offer categories that are either easily

discerned or real, and if they were, then there would necessarily be multiple. Since its adoption, a

position of fundamental doubt, beyond that of simple skepticism, has become the norm.

Pluralism has taken root.

3) BEYOND PLURALISM

Dissatisfied with agreement, Hull objects to the party-line of pluralism.21 Similarly, Wilson

argues that pluralism is too extreme of a reaction.22 Pluralism and the misguided notion that

species are individuals go too far and neglects to say much about nature at all. Instead of

rejecting all three above assumptions, Wilson seems to reject only the commonality assumption

and emphasizes the priority assumption.23 Wilson instead argues that the Wittgenstein-like

notion of ‘family resemblance’,24 for which commonality is not necessary, be applied to the

species debate. Views such as Sterelny25 and Boyd26 do so and settle upon a conception of

18 Dupré, “On the Impossibility of a Monistic Account of Species.” 19 Elliott Sober, “Evolution, Population Thinking, and Essentialism,” Philosophy of Science 47, no. 3 (September 1,

1980): 350–83. 20 Tim Lewens, “What Is Wrong with Typological Thinking?,” Philosophy of Science 76, no. 3 (July 1, 2009): 355–

71, doi:10.1086/649810; Tim Lewens, “Evo-Devo and ‘typological Thinking’: An Exculpation,” Journal of

Experimental Zoology Part B: Molecular and Developmental Evolution 312B, no. 8 (December 15, 2009): 789–96,

doi:10.1002/jez.b.21292. 21 David L Hull, “On the Plurality of Species: Questioning the Party Line,” in Species: New Interdisciplinary

Essays, ed. Robert A Wilson (Cambridge, Mass: MIT Press, 1999), 23–48. 22 Wilson, “Realism, Essence, and Kind: Resuscitating Species Essentialism?” 204. 23 Ibid., 200. 24 Ludwig Wittgenstein, Philosophical investigations, trans. G. E. M. Anscombe, Rev. 4th ed (Chichester, West

Sussex, U.K. ; Malden, MA: Wiley-Blackwell, 2009). 25 Kim Sterelny, “Species as Ecological Mosaics,” in Species: New Interdisciplinary Essays, ed. Robert A. Wilson

(Cambridge, Mass: MIT Press, 1999), 119–38. 26 Boyd, “Homeostasis, Species, and Higher Taxa.”

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species as ecological mosaics and homeostatic property clusters (HPC),27 respectively. Similarly

but distinctly, Hull28 and Griffiths29 take issue with another part of the definition: that species act

as traditionally ahistorical universals. Instead, they contextualize a species evolutionarily in local

time and space. In these ways, traditional realism is ‘loosened’ and qualified without devolving

into a position of passive pluralism.

27 Marc Ereshefsky, “Species as Homeostatic Property Cluster Kinds,” Stanford Encyclopedia of Philosophy,

January 27, 2010, http://plato.stanford.edu/entries/species/#SpeHomProCluKin. 28 David L Hull, “A Matter of Individuality,” Philosophy of Science, 1978, 335–60. 29 Paul E. Griffiths, “Squaring the Circle: Natural Kinds with Historical Essences,” in Species: New Interdisciplinary

Essays, ed. Robert A. Wilson (Cambridge, Mass.: MIT Press, 1999), 209–28,

http://pi.lib.uchicago.edu/1001/cat/bib/3909850.

PART II: FINDING A REPLACEMENT

The testing of classificatory statements is intimately connected to the testing of

the relevant theories, and testing is not a simple matter.

–David Hull30

These three shifts lead us to the current moment in the philosophy of biology. Through tracing

these concepts, one observes a kind of progression within the philosophical community. Tracing

the changing species concepts makes it obvious that there is a kind of intellectual competition in

operation. As philosophers posit different species concepts, those concepts compete in the

philosophical community. I examine three species concepts on their merits and pit them against

each other in a kind of competitive monism. The species problem – a debate about ‘categories’

and ‘kinds’ – necessarily leads to a more abstracted discourse, a discourse subject to its own

movements, patterns which mirror that of natural selection. Philosophy must embrace the method

already so familiar to science if it is to improve itself.

COMPETITIVE MONISM (THREE SPECIES CONCEPTS)

Matson has collected a list of species concepts and their appearances in the literature.31 The

biological species concept is listed first, both historically and in terms of importance. The

replacements vary from the ecological to the phylogenetic, historical, and cladistic. The

particulars are less important than the general trend: philosophers trying to fit the wonderful

diversity of nature into the narrow confines of scientific practice. Facing this frustration, some

eschew belief in species entirely. Yet the difficulty of the endeavor is precisely what makes it

30 Hull, The Metaphysics of Evolution, 161. 31 Matson, “Species Concepts and the Definition of ‘Species.’”

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worthwhile, especially in the face of the apparent obviousness of a solution. The contradictory

position is the pluralistic one, of which a more detailed discussion will follow.

For now, however, I wish to examine three alternatives to the biological species concept.

First, the evolutionary species concept defines species as the fundamental unit of descent within

the broader evolutionary system. Second, the ecological species concept defines species relative

to the behavioral niche it fulfills in its environment. Third and finally, the homeostatic property

cluster (HPC) species concept defines species as individuals which others relate to through the

notion of family resemblance. Each of these three concepts aim to improve the shortcomings of

the biological species concept, yet in doing so introduce different assumptions and dependencies

of their own. On this point, the pluralists may be right: no species concept has yet emerged

complete and unflawed.

With this in mind and lacking an answer, we, too, must operate from the same position of

ignorance. Yet here I will diverge from the pluralist methodology and carve a path forward. I

will establish some sample criteria which an ideal species concept must fulfill, then I will pit

these three potential replacements against each other. The specific criteria are not very important,

and neither are the specifics of the replacement concepts. What is important is the way in which

one approaches each theory and treats it philosophically. Rather than treating each as another

failed solution for an unsolvable problem, if one acknowledges the possibility of success, then

each and every new theory becomes valuable toward that end. Even and especially if a new

theory fails, its failure aids all the other theories yet unfalsified. Even better, the failures of each

theory point out lacking qualities that must be present in the successful theory. Like science,

philosophy is a fabric riddled with holes. Its past is a story of errors too numerous to count. In

spite of this, indeed, precisely because of this, one can have confidence in the present answer and

Augustine 19

an even greater confidence in the possibility of improvement. Through continual examination

and repair, science and philosophy cohere into a material ever-more watertight.

Opposed to pluralism is the belief that there is a singular, real answer to the question

‘What is a species?’. Such a position is monistic and traditionally realistic; it believes in essences

and natural kinds. Before pluralism took hold, scientists and philosophers would propose

different definitions and critique them all. Through this process, both science and philosophy

eliminated incorrect or conceptually weak ideas. As the more correct ideas survived and

continued to be discussed, the disciplines of science and philosophy experienced a kind of

progression in quality toward truthfulness. Once pluralism took hold, however, discussion shifted

away from actual proposals and critique and toward a more high-level and self-defeatist

conversation about the terms of the argument. In this climate, conceptual progress has remained

stagnant.

It is my belief that both science and philosophy need to return to the practice of taking

strong, risk-laden monistic positions – with full knowledge that nearly all of them will turn out to

be incorrect. Yet in no way does the unreality of, say, the four humors tarnish our current

knowledge of physiology. Similarly, the failures of the biological species concept, as I have

outlined above, do nothing to eliminate the possibility, or the potential, for a better definition.

Indeed, the failure of any idea only contributes to the success of its descendants. Such is the

potential for what I call competitive monism: the elimination of monistic risk-laden claims

through discourse.32

I now begin in earnest to show competitive monism in action as I analyze the merits of

32 I am indebted to Hull’s theory of knowledge and Ereshefsky’s framework of eliminative pluralism. I believe,

however, that a more monistic and traditionally realistic bent is key for any competitive benefits to become fully

realized.

Augustine 20

three species concepts. By pitting them against each other, I hope to gesture at a way forward.

Such an analysis will establish a methodology for future dialog in philosophy along more

scientific terms – if there can be such a thing.

A) EVOLUTIONARY SPECIES CONCEPT

One can imagine that the diversity of life is but the tips and tributaries of the long lineage of the

tree of life. Indeed, retracing the paths through which organisms find their current forms offers

great insight into the categories themselves. For example, carrots are evolutionarily and

historically quite distinct from dogs, yet perhaps not as distantly as they are from as countless

bacteria and fungi. More technically, a species may be defined as both the fundamental unit of

evolution and the result of evolution acting on a lineage.33 Evolution always and only acts

through species, and it is this action by which the former changes and ultimately reconstitutes the

latter.

A great initial benefit of such a historically contingent approach is that it allows one to

sidestep much of the more hairy and quantitative discussion of systematic cladistics. It also

neglects to state much about the relative weight and importance of traits; often their presence or

lack thereof is enough of an indication to construct a conjectural Darwinian history.

Even such a cursory view resolves much of the problems and ambiguity inherent in the

biological species concept. Rather than being defined by sexually reproductive viability, species

here are defined by ancestry more generally. So plants, bacteria, and extinct organisms can still

be classified. (And mules, too.) Indeed, a species concept such as this is already invoked, either

implicitly or otherwise, in much scientific work. Although obvious, it is still worth stating

33 The definition is my own and is a simple proposal distinct but similar to the following concepts in Matson’s list:

2) Cladistic, 6) Evolutionary, and 9) Phylogenetic, which I have grouped together here and conceptually related.

Ibid.

Augustine 21

outright.

Yet difficulties arise regarding the categories themselves. One faces difficulty in

differentiating species from larger units such as genera and families. Indeed, cladistics in popular

categories such as Dinosauria and Hominidea are so rife with revisions on these higher level

relationships that the student is all but forced to focus their study to the physical characteristics

and their relationship to the singular species name. This, of course, points to a larger problem:

that such evolutionary histories are hopelessly dependent on a historical narrative supported by

scant or lacking physical evidence. All classification efforts face this limitation, but unique to the

evolutionary species concept is the strong insistence on the notion of a timeline or phylogeny.

Such a thing is ontologically unreal – a heuristic created after the fact – yet is often justly

inferred through physical evidence. Even so, the heuristic is a powerful mental model, indeed,

resting at the core of evolution.

B) ECOLOGICAL SPECIES CONCEPT

A species may be defined by the common role its members fulfil in an ecological niche.34 Dupré

proposes that the ecological units could fulfill a large degree of the proposed purpose of the

species unit.35 These ecological units could be that of predatory, prey, parasite, and scavenger,

etc., or they could refer more generally to the kinds of behaviors, diets, habitats, adaptions and

geographical distributions that guide evolution. Such a proposal is optimistic in its attempt to

sidestep the more thorny problems of classification in a traditional taxonomy by reference to the

environment an organism molds itself around. However, this kind of ecological classification

often fails to represent subgroups well, especially in terms of competition and convergent

34 The definition is my own and is distinct but similar to Matson’s concepts 4) Competition, 5) Ecological, and 7)

Isolation, which I have found conceptually related. Ibid. 35 Dupré, “On the Impossibility of a Monistic Account of Species,” 13.

Augustine 22

evolution. Similarities in morphological character and ecological role sometimes obscure

divergent evolutionary histories. The three species of freshwater-restricted river dolphins live in

three different rivers: the Ganges/Brahmaputra Rivers in India, the Yangtze of China, and the

Amazon of South America. These rivers do not connect and genetic analysis shows the three

species to be distinct evolutionarily.36 Their similarity is merely the result of optimization for

their environment through natural selection operating over evolutionary time.

Yet these are still three dolphins, and are common by that accord alone, with a

presumably common, saltwater-based ancestor that spread to each of the three rivers. Other

organisms can still converge morphologically and ecologically despite completely different

lineages. Consider the dolphin, again, but this time as an open-water, rather large predator

distinct in its long snout, prominent dorsal fin, barrel-shaped body, the necessity of continuous

swimming, wakeful or nonexistent sleep patterns, and an ambient temperature higher than the

surrounding water.37 Tuna and most ichthyosaurians share these characteristics on ecological and

morphological grounds, yet the three are distantly related in terms of evolutionary history.

Indeed, they all belong to different classes, sharing only Kingdom Animalia and Phylum

Chordata. (Taxonomically, they are similar only as vertebrates i.e. everything else represents a

taxonomic divergence.) Their similarity is not perfect, but one can infer a similar role in their

respective ecosystems as large, aquatic predators. And yet, the surface-level similarity between

these three disparate species is more evidence of convergent evolution than anything else.

The confusion between phylogeny and ecology can also be confused in the opposite

direction: a similar evolutionary history does not guarantee parity in ecological terms. Take the

36 William F Perrin, Bernd Würsig, and J.G.M Thewissen, eds., Encyclopedia of Marine Mammals (San Diego,

2002), https://catalog.lib.uchicago.edu/vufind/Record/4601286. 37 With the latter two inferred by the fossil record for ichthyosaurians.

Augustine 23

order Rodentia, for example. Rats and other rodents are a fairly homogenous group both

genetically and morphologically that have since globalized and dominated their new

environments. Ignoring for a moment different species of rats being grouped in the same niche,

one must consider that rats are ecologically flexible. Rats of the same species may fulfill

different niches. Out of a large group of morphologically identical rats, some may act as

scavengers, some as insectivores, and some as herbivores, some as opportunistic hunters, and

may all be classified as separate ecological species. This seems like an obvious problem the

ecological species concept would be hard pressed to resolve.

Simply put, such a proposal lacks specificity, which is one of the chief requirements that

biologists demand of their units of measurement. And the species is posited to be the

fundamental unit of classical, macro-evolutionary biology.38 While Dupré’s proposal implies that

ecological niches may delineate species from one another, niches offer little in the way of actual

discernment. Indeed one must wonder whether morphological similarity begets ecological

similarity, or vice versa. Surely the two are intertwined – the very concept of a niche implies

evolution by means of natural selection – yet I cannot help but sense that an organism’s

morphology has a certain ontological priority. That is, it is the organism’s morphology that

prompts it to take a certain role in its ecological environment, and only by dint of changes in that

morphology does its ecological role change. At best, environment seems to apply selective

pressure, which may in itself change, but a change which is only felt by the organism through its

morphology, anyway.

Indeed, an ecological species concept relies on recognition of the ecological niche by the

scientist. A niche is a much more invisible and amorphous category than that of a species. Much

38 With the fundamental unit of evolution on its small scale, more developmental side occupied by the ‘gene’,

however dubiously defined.

Augustine 24

of ecology is behavioral and observational (eating habits, mating patterns, territorial ranges), and

this is often difficult to observe in living wild species, let alone conjectures as to extinct

organisms. To shift the burden of classification away from the species itself and onto ecological

roles is to further confuse the discussion. If the weight of the argument against traditional species

concepts is their unnaturalness or unknowability, then ecological concepts of species hardly

resolve these worries.

C) HOMEOSTATIC PROPERTY CLUSTER (HPC) SPECIES CONCEPT

Boyd sidesteps the pluralist discussion through his proposal of species as defined by homeostatic

property clusters (HPC), rather than the necessary and sufficient conditions of traditional

definitions. In rather technical fashion, Boyd defines familial relationship between clusters

shared properties of members of a species.39 The contingency of this familial relationship is key

– there is nothing inherent or eternal about their appearance together. Rather, certain mechanisms

– accidental or otherwise – are responsible for the clustering of these properties together. Thus,

the family coheres together in a kind of temporary homeostasis, which we define as a species.

A species is nothing more than a slice of these clusters at a certain moment in time, a

contingent coherence before the processes of extinction and speciation begin anew after their

brief respite and drive previously stable populations apart. This crucial concept is recapitulated

well by Bird and Tobin

Homeostatic property clusters occur when mechanisms exist that cause the properties to

cluster by ensuring that deviations from the cluster have a low chance of persisting; the

presence of some of the properties in the cluster favours the presence of the others. A

homeostatic mechanism thereby achieves self-regulation, maintaining a stable range of

properties.40

39 Boyd, “Homeostasis, Species, and Higher Taxa,” 143. 40 Alexander Bird and Emma Tobin, “Natural Kinds,” in The Stanford Encyclopedia of Philosophy, ed. Edward N.

Augustine 25

The referenced homeostatic mechanism that causes the properties to cluster is natural selection.

The ensurance that deviations from the newly defined cluster have a low chance of persisting is

differential reproductive success. The presence of some of the properties in the cluster

correlating to the presence of others is an epistemological claim regarding the accumulative

nature of morphological change in evolution e.g. all apes are at the very least mammals and share

mammalian features. The process described is evolution, with species and their clusters of traits,

its product.

Importantly, resemblance between members of the same family need not be perfect.

Indeed, this case is more common than not, so its allowance in any species concept is crucial.

Through his Wittgensteinian technical definition, Boyd has carved theoretical space for groups

of traits to determine membership in a species, with no single trait being necessary or sufficient

to determine membership by itself.41 Indeed, contingency is a key feature of this definition “the

properties that determine the conditions for falling under t may vary over time (or space)...The

historicity of the individuation conditions for the property cluster is thus essential for the

naturalness of the kind”.42 Meaning that no single trait need be common among all species in the

taxonomy, and no single trait need qualify or disqualify organisms from inclusion in a given

species. This flexibility stems from the contingent nature of properties in an HPC concept. Any

traits examined for a given organism will necessarily be fitted to a level of specificity needed to

include all members of its own species and exclude similar species. This ‘fitting’ is intuitively

done science often (think about how quickly and easily you can distinguish two skulls, choosing

Zalta, Spring 2016, 2016, http://plato.stanford.edu/archives/spr2016/entries/natural-kinds/. See also Ereshefsky,

“Species as Homeostatic Property Cluster Kinds.” 41 “some but not all of the relevant underlying homeostatic mechanisms may be present.” Boyd, “Homeostasis,

Species, and Higher Taxa,” 143. 42 Ibid., 144. Historicity meaning something like ‘contextual nature’ of the conditions for inclusion in the cluster.

Augustine 26

different morphological traits from distinguishing between two leaves) but is difficult to

formalize without an HPC concept.

The presence of indeterminate cases – meaning, individuals which may not be easily

sorted into one species or another – does not invalidate the species itself. Rather, such

indeterminacy is merely evidence of a species in motion (as they nearly always are, excepting

stable outliers like turtles, crocodiles, and dragonflies) and as such does not invalidate the

category itself. Only with reference to the original species can one even observe any divergence.

And it is this motion through time that determines the evolutionarily historical character of

species as a concept.

Dupré objects that the widespread presence of flight capability, for example, in insects,

bats, and birds, does not clearly necessitate a nonphylogenetic classification system.43 Instead, it

may be enough to cite convergent evolution, ecological niches, or simple adaptation and leave it

at that. The repeated occurrence of powered flight fulfils an explanatory or mechanistic role

rather than directly taxonomic. In an HPC system, superficial similarities like wings would be

overshadowed by vast differences in, say, macroscopic body plans, bone structure, and

circulatory systems between insects, bats, and birds. In this way, a convergence on powered

flight would be treated taxonomically as a happy accident at the end of three winding paths,

avoiding Dupre’s objection of ahistoricicism. It seems to me that historical or evolutionary

characteristics can be one among many in the property cluster. While they are not strictly

necessary, there is little to disqualify them.

A large part of the original objections to essentialism stem from its association with

neoplatonic eidos, or non-physical, eternal ideas. However, the philosophical support behind a

43 Dupré, “On the Impossibility of a Monistic Account of Species,” 13.

Augustine 27

system like HPC shows that characteristics like the visual similarity of organisms and the fixity

of traits are somehow deeply important to the enterprise of speciation. HPC attempts to capture

these aspects (and perhaps ‘save’ the original merits of essentialism) and present them in a more

agreeable epistemological fashion. It is largely successful in allowing comparisons between

organisms with whatever degree of granularity a given situation requires.

Hull furthers a similar species concept, arguing that species can be considered as

"spatiotemporally localized entities connected in [and through] space and time."44 Similarly but

distinctly, Kitcher argues that species should be considered as historically connected sets of

individuals (as distinct from ahistorical essentialist definitions, supposedly).45 In this way,

Kitcher aims to consider, say, humans as similar to each other temporally and genetically, rather

than in any reference to structurally similar traits as pheneticism would have it. Kitcher would

then avoid the problem of classifying a shark (a fish) as similar or related to a dolphin (a

mammal), despite their physical similarities. Such a species concept can be called ‘historically

evolutionary’, sharing much with some standard evolutionary species concepts, or even a

historical form of cladism. The essential difference being that Kitcher’s concept is grounded in a

knowledge of evolutionary history. That is to say, a proposed species concept of the kind would

be laden not only with the theoretical implications of evolution but also particular narratives

invoked for given organisms and lineages. This is not necessarily a detriment. I believe, and I

think both Hull and Dupré would agree, that there is something deeply explanatory and

distinctive about the common form of an evolutionary narrative. I would offer a Darwinian

history of Kitcher's kind as a perfect example of theory laden-ness as itself constituting a form of

44 Hull, “On the Plurality of Species: Questioning the Party Line,” 31. 45 Philip Kitcher, “Species,” Philosophy of Science 51 (1984): 314.

Augustine 28

utility.46 It is often assumed that theory laden-ness suggests only bias in the negative sense, but

for well-established and often-tested theories like evolution, its reach and power are only

expanded.

Seemingly aware of the benefits and limitations of individual species concepts, Dupré

posits a hybrid theory. He notes that the recognition species concept of reproductive capability,47

taken together with knowledge of genomic inheritance and a general sense of historically

evolutionary heritage, produces an attractive notion of morphological similarity explained

through a theoretically historical mechanism.48 However, Dupré points out common problemsin

the many asexual species and cases of indeterminate breeding capability (i.e. hybridization and

other complicated methods of plant reproduction). Dupré explicitly objects to Hull’s (1989)

particular attempt to circumvent this problem through historical organism lineages, on the

grounds that it forfeits practical utility for theoretical appeal.49 Instead, Dupré’s position is such

that evolutionary history can be a general tool or even a characteristic of ‘good’ theories rather

than the sole factor of classification. I agree with this assessment, yet I am not convinced that

utility can be so cleanly separated from notions of theoretical significance, as evolution in

particular colors most every historical species concept.

In any case, these kinds of reoccurring philosophical commitments across all of the above

species concepts are indicative of a complex epistemological reality participated in by legions of

scientists and philosophers. Before broaching that weighty topic, however, I return to the matter

of the mule. Having now defined several replacements for the biological species concepts, I will

46 Philip Kitcher, “Darwin’s Achievement,” in In Mendel’s Mirror: Philosophical Reflections on Biology (Oxford ;

New York: Oxford University Press, 2003), 45–93. 47 Dupré refers to this as the ‘biological species concept’, although the difference is unclear. 48 Dupré, “On the Impossibility of a Monistic Account of Species,” 6. 49 Ibid., 7.

Augustine 29

attempt to resolve the problem of how to classify the mule with an original proposal.

THE MULE, NEWLY CLASSIFIED

I classify the mule as Equus augustus under a homeostatic property cluster species

concept weighted strongly due to morphological similarity, moderately due to evolutionary

history, and minimally due to genetic analysis and reproductive viability. One infers a strong

evolutionary similarity to its parents and its morphology certainly corroborates as much. Its

sterility is an interesting facet of its morphology but does little to disqualify it, as reproductive

viability is neither sufficient nor necessary to constitute membership in my proposed species

concept. As such, the mule is a member of its own unique species and should be described

accordingly.

DISCURSIVE COMPETITION

Having established the theoretical groundwork and resolved the matter of the mule, I begin the

second level of my argument, critical as it represents a shift in scope. Here I will examine

discourse about the species debate. Pluralists have their modes of discourse in the species debate,

and monists have theirs, and they clash by publishing papers. In this context, I will expose the

methods of pluralists as a flawed form of inquiry. Yet monism alone is no better. Rather,

discourse about the philosophy of biology needs to be structured in a more competitive way.

Ereshefsky,50 Hull,51 and Lakatos52 each argue that science takes place in a competitive

50 Marc Ereshefsky, “Eliminative Pluralism,” Philosophy of Science, 1992, 671–90. 51 David L Hull, “A Mechanism and Its Metaphysics: An Evolutionary Account of the Social and Conceptual

Development of Science,” Biology and Philosophy 3, no. 2 (1988): 123–55; ibid.; Paulo Abrantes and Charbel Niño

El-Hani, “Gould, Hull, and the Individuation of Scientific Theories,” Foundations of Science 14, no. 4 (November

2009): 295–313, doi:10.1007/s10699-009-9161-3; David L Hull, Science as a Process: An Evolutionary Account of

Augustine 30

community.

This stands against pluralists like Dupré who claim that the debate be resigned quickly

without much in the way of resolution.53 Dupré’s error is not merely his commitment to

pluralism, but rather, his reluctance to even posit a theory. Withdrawing from the species debate,

or conceding that the problem cannot be solved, offers no avenue forward. Make no mistake – I

have offered a potential solution to the species debate in the HPC concept, but hardly expect to

settle the matter. What’s far more important is the methodology I have here attempted to

exemplify: that I have critiqued and eliminated other species concepts, and taken a concrete

position of my own in an attempt to further the discourse.

On similar grounds, Hull offers a critique of the general notion of philosophical

pluralism, with the species concept as his case study.54 He outlines a problem that runs far deeper

in the philosophical enterprise:

How can consensus exist with respect to the ontological status of species if pluralism is

the party line among philosophers of science, especially philosophers of biology?

Everyone seems to feel obligated to espouse the position held by all thoughtful scholars –

a nuanced pluralism, as distinct from any crude, simplistic monism….A clear contrast

exists between more simplistic notions of monism and pluralism, but no one seems to

hold any of these simplistic alternatives. When pushed, most authors retreat to some

platitudinous middle ground.55

Indeed, Hull identifies thin lines between the intermediate forms of pluralism and monism. As

almost no one holds an extreme view, Hull concludes that most people hold a similar belief and

the Social and Conceptual Development of Science (Chicago: University of Chicago Press, 1988); Hull, “On the

Plurality of Species: Questioning the Party Line.” 52 Imre Lakatos, “History of Science and Its Rational Reconstructions,” PSA: Proceedings of the Biennial Meeting

of the Philosophy of Science Association 1970 (1970): 91–136; Imre Lakatos, Paul Feyerabend, and Matteo

Motterlini, For and against Method: Including Lakatos’s Lectures on Scientific Method and the Lakatos-

Feyerabend Correspondence (Chicago: University of Chicago Press, 1999). 53 Dupré, “On the Impossibility of a Monistic Account of Species,” 18. 54 I must again acknowledge the work of the late David L. Hull, which led me to many positions in this paper. 55 Hull, “On the Plurality of Species: Questioning the Party Line,” 24.

Augustine 31

try to explain it in different ways. If this claim is true, then there is a real danger of losing useful

or necessary distinctions to the desire for academic correctness and a fashionable theory.

Unlike natural processes, the philosophy of science exists in a social realm, where

important traits are subject to arbitrary extinction. As Gould and Lewontin argue, "Human

cultural practices can be orthogenetic and drive towards extinction in ways that Darwinian

processes, based on genetic selection, cannot."56 There is then a real danger that philosophers of

biology will unwittingly destroy any useful notion of a species concept or natural kind, or merely

avoid stating anything of substance, which is nearly the same thing.

Hull takes issue with a pluralist like Harry Collins who argues that sociologists must,

"treat the social world as real, and as something about which we can have sound data, whereas

we should treat the natural world as something problematic – a social construct rather than

something real."57 Here Hull furthers the bulk of his argument: a paradox at the core of the

pluralistic position, “With respect to science – so pluralists claim – serious, respectable

alternative positions always exist for every issue, but when one steps back to view philosophy of

science, one and only one position is acceptable: pluralism.”58 Any pluralist’s advocacy within

science only serves to cement their philosophical monism – a commitment to scientific pluralism

– as the very thing they had just characterized as close-minded.

A natural product of this problematization is that self-proclaimed pluralists often have

their pet projects. For example, Hull identifies Sober and Wilson's 1998 Unto Others as

pluralistic on their survey of multiple accounts of selfless behavior, yet when it comes to

56 S. J. Gould and R. C. Lewontin, “The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the

Adaptionist Programme,” Proceedings of the Royal Society of London, Biological Sciences, 205, no. 1161 (1979):

584. 57 H. M. Collins, “What Is TRASP?: The Radical Programme as a Methodological Imperative,” Philosophy of the

Social Sciences 11, no. 2 (June 1, 1981): 215–24, doi:10.1177/004839318101100207. 58 Hull, “On the Plurality of Species: Questioning the Party Line,” 27.

Augustine 32

evolutionary inheritance, they are suddenly monistic and group selection becomes the only ‘real’

model.59 Even the most careful pluralists, of which Sober and Wilson are good examples, face

these kinds of reflexive problems. Indeed, such problems necessarily surface as a product of the

pluralistic position, weakening the very mode of argument.

I cannot emphasize enough that argument is to philosophy as experimentation is to

science; it is the process through which the community advances. One can build as careful of a

position as they want, but when it comes down to it discourse is what validates or discredits a

theory. Along these lines Gould and Lewontin pose a now famous caricature of discourse gone

awry in the philosophy of biology:

In natural history, all possible things happen sometimes; you generally do not support

your favoured phenomenon by declaring rivals impossible in theory. Rather, you

acknowledge the rival, but circumscribe its domain of action so narrowly that it cannot

have any importance in the affairs of nature. Then, you often congratulate yourself for

being such an undogmatic and ecumenical chap. We maintain that alternatives to

selection for best overall design have generally been relegated to unimportance by this

mode of argument.60

Either philosophers of science hold different positions on philosophy and science – a strange

position, to be sure – or pluralism is more restrictive philosophically than its proponents hoped it

would be freeing. Hull concludes that staunch pluralists paradoxically argue that one

philosophical position to be the only valid one.61 These pluralists act like philosophical monists.

They should, correspondingly, hold that there is one valid reading of evolution and one position

on the species problem, as well.

A true, honest pluralism can then only be meaningfully applied to those things which one

does not know or hold opinions on. However, it is essential to science that this not be the case.

59 Ibid. 27. 60 Gould and Lewontin, “The Spandrels of San Marco and the Panglossian Paradigm: A Critique of the Adaptionist

Programme,” 585. 61 Hull, “On the Plurality of Species: Questioning the Party Line,” 27.

Augustine 33

Science is a community activity that progresses based on its own internal forces of group

selection. Scientific theories and alternatives must be advanced with fervor if rigorous

methodological scrutiny is to be applied to them. Science would simply not advance if each

scientist conceded their position. No, scientists present a theory and support it with evidence and

argument. It is familiar, almost intuitive, that scientists have their projects, programs, and

positions that they try to assemble evidence for and defend. They are certainly biased, but that

bias is ironed out through the group dynamics. For the scientific gaze is not always disinterested,

and neither is the philosophical. Hull writes,

My remark about watching out for scientists when they do philosophy was intended to

emphasize that scientists do not always approach philosophy in a totally disinterested,

dispassionate way. They usually are engaged in a particular scientific research program

and turn to philosophy to aid them in this program. The preceding is not intended as a

criticism. I think that this is the way in which scientists should approach philosophy. If

they find a particular philosophical analysis appropriate to their own undertaking, that is

one mark in favor of that analysis. However, other scientists with other concerns might

disagree. Philosophers are not judges empowered to adjudicate scientific disputes. Nor

are they weapons to be used by one group of scientists against another. They are as much

a part of the process of rational inquiry as are scientists themselves.62

Philosophy is as much an inquisitive process as science is. The risk-laden nature of claims in

both fields are to the benefit of each. Agreement between philosophy and science occurs

sometimes, but not always. This is likely to happen in any community with a diversity of views.

In a community that searches for the way that nature works, however, it is inevitable, precisely

because disagreement is necessary to winnow potential theories into the truth.

Hull demarcates the practitioners’ methodological differences into their respective fields,

"Philosophers find pluralism extremely attractive in science, much more so than in philosophy.

Scientists in turn do not find pluralism all that attractive in their own area of expertise and

62 Hull, The Metaphysics of Evolution, 160.

Augustine 34

usually stay well clear of philosophy.”63 Such personal convictions are fundamental to the

practice of science. Indeed, some scientists hold onto outdated ideas long past the rest of the

community has adopted its replacement. However, like a sterile bee drone, these dissenters fulfill

an essential role in the community of science. That is, the correct replacement idea would not be

adopted without the contrast provided by proponents of the old false idea. Instead, it would stand

established as an empty truth, without argumentative backing. John Stuart Mill supports this

notion of argument as the process and test of truth in On Liberty:

Strange is it that men should admit the validity of the arguments for free discussion, but

object to their being ‘pushed to an extreme,’ not seeing that unless the reasons are good

for an extreme case, they are not good for any case. Strange that they should imagine that

they are not assuming infallibility when they acknowledge that there should be free

discussion on all subjects which can possibly be doubtful, but think that some particular

principle or doctrine should be forbidden to be questioned because it is so certain, that is,

because they are certain that it is certain.64

Because of science’s epistemological status as a community activity, it cannot progress if

individuals proclaim to be judge and jury of truth. No, science can only accumulate if individuals

delegate to the group’s consensus. Despite this emphasis on group thought, it is up to the

individual to posit and defend their own opinions, if they have good reason to hold it. If the

opinion is right, then the group will benefit from it being shared, and if it is wrong, the group

validates its established belief through, “the clearer perception and livelier impression of truth

produced by its collision with error.”65 Mill provides this latter tenant and warns against the

dangers of complacency and assumption that come with any kind of accepted party position

If we were never to act on our opinions, because those opinions may be wrong, we should

leave all our interests uncared for, and all our duties unperformed….There is the greatest

difference between presuming an opinion to be true because, with every opportunity for

contesting it, it has not been refuted, and assuming its truth for the purpose of not

63 Hull, “On the Plurality of Species: Questioning the Party Line,” 27. 64 John Stuart Mill, On Liberty, ed. Elizabeth Rapaport (Indianapolis: Hackett, 1978), 20. 65 Ibid., 16.

Augustine 35

permitting its refutation. Complete liberty of contradicting and disproving our opinion is

there very condition which justifies us in assuming its truth for purposes of action; and on

no other terms can a being with human faculties have any rational assurance of being

right.66

Science as a rational group activity thrives on the presence and denial of falsehoods as much as it

does on the repetition of truth. One cannot be certain of the truth if there are no serious

alternatives through which to test it. Despite whatever truth value an alternative proposal may

have, rigorous discussion always strengthens both the truth and the community. Such is the

apparent paradox of science as a community of stubborn individuals, yet it functions

swimmingly precisely because it resolves itself through good, repeated practice. Over time, the

community will be forced to repeatedly confront the correct stance. This process may be slow –

as was certainly the case for evolution – but if no arguments or evidence can disprove it as false

then it will be accepted as truth. Much like a fierce struggle for survival – it is the presence of

strong alternatives that is the very condition which allows this process of truth production to

occur.

All of this is extremely salient for Hull’s problematization of pluralism, which not only

fails to posit a contending view but, through its agnosticism, furthers the notion that there is no

answer. As long as pluralists continue to claim agnosticism, there will be no answer. Hull

believes that pluralism exists only so long as theorists claim agnosticism on a problem, or if there

is no clear frontrunner for a theoretical candidate. Once a view is established into the theoretical

canon, monism toward the (justly) established view tends to beat out pluralism. Only when there

is a threat of dogmatism is pluralism again warranted, albeit with some caveats. In this case,

pluralism belongs to those who reject the established view but can offer no alternative. The

moment that pluralists do have something meaningful to offer, they become monistic in regard to

66 Ibid., 18. Emphasis added.

Augustine 36

their anti-dogmatic proposal. Thus, science’s long-term accumulation of knowledge bounces

between agnosticism and answers, pluralism and monism, orthodoxy and revolution, all tending

toward progress. Philosophy need proceed in a similar fashion, instead of viewing monism as a

fashion out of season.

Constantly, however, the practice of science only applies when there is a concrete

problem to be solved. I would argue that science is unconcerned with issues that are unknowable

– those belong to the realm of philosophy. As such, scientists tend to be either monists or

completely agnostic about a given philosophical issue, while philosophers tend to want to keep

all roads open until they have a reason to close some routes down. Once an issue is solved,

philosophers simply tend to move on to uncharted waters! Thus, a perpetual situation forms, one

in which scientists work within conceptual orthodoxy, while philosophers find themselves

against an ever-increasing number of problems. One wonders if they will ever fully chart the

map of impossible questions, or if knowing the answer to this question is, itself, impossible.

THEORETICAL SIGNIFICANCE

In the abstract, this kind of competition through risk-laden discourse produces knowledge

by disqualifying untrue positions. What does this discourse look like in action? To this one can

look at the discourse surrounding any number of issues, although one must be careful to limit

themselves to claims rather than simply recapitulating pluralistic positions.

Along these lines, Hull raises a problem of ‘theoretical significance’ that grounds many

debates around the species concept. Hull classifies and ranks various species concepts with

regard to universality, applicability, and especially theoretical significance – three characteristics

Augustine 37

he identifies as primary identifiers of good scientific theories in general.67 He recapitulates

'universality' as a trade-off between generality and coverage in application. That is, while

grouping organisms based on outward appearance can be applied to all organisms, it provides

little insight and would often be forced to separate organisms that we consider to be in the same

species (for example: male and female, breeds of dogs, races of humans, eye color mutations, or

sterile worker bees are all examples of dissimilar organisms that we may consider to belong to

the same species). Conversely, a recognition species concept, defined as being able to produce

fertile offspring, only applies to sexually reproducing organisms.68 Hull notes that this group is

rare enough to be problematic to the idea of species as sexual reproduction.69 I too reject the

recognition species concept as the sole criterion for species, however, in sexual organisms in

which it can be applied it is not only useful, but hints at the evolutionary relationship that I

believe rests at the core of the species concept. 'Applicability' is the ease of classification,

varying from visual similarity (very easy but weak) to evolutionarily historical claims (quite

strong but very difficult). Importantly, historical claims can only be confirmed in hindsight,

assuming a relatively static or at least historically consistent idea of species through time.

Theoretical significance largely boils down to prior epistemological commitments or a

devotion to philosophical pluralism/monism, often exchanged for a sense of neutrality.

Importantly, some species concepts differ in the theoretical treatment of the historically

differentiated species, that is, a species as a snapshot of history and location or as a lineage that

transcends those spatiotemporal barriers. Hull writes, "The most easily applied [species]

concepts tend to be those with the least theoretical commitment, whereas those concepts that

67 Ibid., 38. 68 The difference between the recognition concept and the biological species concept is unclear. See footnote 47. 69 Ibid., 41.

Augustine 38

produce theoretically significant species tend to be the most difficult to apply."70 Thus, Hull

explains that concepts such as 'evolution', 'selection', or 'species' are so general that they have an

extremely widespread use but also create widespread disagreement about their theoretical

meaning.

Dupré agrees with Hull that, “there can be no classification wholly innocent of theoretical

contamination,” yet he uses this same reasoning as a call to pluralism.71 Hull may respond that

such cases of theoretical contamination would persist in either case. Theoretical predisposition

limits objectivity in science and obscures theorist’s positions in favor of notions of ‘schools’ or

‘camps’, complicating the debate.

Mayden evaluates a host of species concept candidates under similar terms, but is much

more restrictive in his ideal concept.72 Hull recapitulates Mayden’s ideal as one in which

a species concept must be theoretically significant and include sexual, asexual and hybrid

species; it must be a non-relational lineage concept that treats species as individuals

rather than as classes; and it must place no constraints on necessary attributes that a

species must possess in order to be validated.73

Mayden does so to separate out operationality from Hull's umbrella concept of 'theoretical

significance'. In doing so, a species concept can be very theoretically significant but have little

operational value and still rank highly.

This surprising conclusion is a product of Mayden's belief that a 'primary' species concept

need not explain everything right away; 'secondary' or derivative theories can fill that void later.

Thus, Mayden posits that a species concept should be like the umbrella concept of 'evolution':

theoretically strong and endlessly applicable, but without immediate operational utility or

70 Ibid., 42. 71 Dupré, “On the Impossibility of a Monistic Account of Species,” 5. 72 Richard Mayden, “A Hierarchy of Species Concepts: The Denouement in the Saga of the Species Problem,” in

Species: New Interdisciplinary Essays, ed. Robert A. Wilson (Cambridge, Mass: MIT Press, 1999). 73 Hull, “On the Plurality of Species: Questioning the Party Line,” 42.

Augustine 39

functionality. Mayden then concludes his survey with the historically evolutionary species

concept scoring the highest as both highly useful and significant. Hull, surprisingly, remains

agnostic on the current candidates, at least in regard to his proposed criteria of theory laden-ness,

universality, and applicability.

It seems to me that Mayden passes the buck on these practical issues to others – those

who will search for mechanisms and applications of an established, conceptually strong idea of

speciation. While Mayden's support for such a complex, rich, and fertile theory makes sense,

Hull notes that his acceptance then limits his views of species as lineages with particular

historical existence. Whether such commitments have a significant impact will remain to be

seen, but it illustrates Hull's point quite well – that all theoretical preconceptions, often of what a

concept should look like, have their trade-offs.

Indeed, Hull characterizes all philosophical discussions of science as having theoretical

implications, "The problem with pheneticism is that it comes into conflict with [Kitcher's]

philosophical monism of the moment – namely, that no such things as theory-free observations,

let alone concepts exist. Hence, any way to define the species category in a theoretically neutral

way is impossible."74 It seems that, despite their best intentions, a true pluralism is impossible (if

not harmful, as I have argued).

Only forms of monism remain as viable options, with those that encourage competition

chief among them. Philosophical debate should adopt the commonplace scientific characteristic

of natural selection – the survival of the fittest – and apply it to its own method of inquiry. It can

do this through a rigorous, competitive monism. I posit that a wide valence of monistic views is

the only proper method through which philosophy, like science, can filter fact from hypothesis.

74 Ibid., 43.

Augustine 40

CONCLUSION: KNOWLEDGE EVOLVES

[T]he evolutionary analogy is sufficiently fundamental to too many currently

popular analyses of science to ignore.

—David Hull75

The competition and improvement of ideas, as I have described in Part II, draws direct reference

to evolution as an analogy. Natural selection is a powerful conceptual metaphor that applies also

in the philosophical world.

A living species illustrate a close parallel between a real, living species (so obvious in the

natural world) and a theory as a species: both function as the units that compete, change, and

improve over time, unfolding in increasing complexity through a process of natural selection. I

propose notions of ‘intellectual selection’ and ‘scientific evolution’, philosophical concepts

separate from but built upon the actual species debate. The theory I propose, however, applies

more generally, with knowledge and its formation relevant throughout the sciences.

My argument can be recapitulated in reverse: knowledge evolves through the competition

of ideas, acting as species do in the natural environment. In the philosophy of biology, ideas

called species concepts are competing. Philosophy can only pursue a valid definition of species if

it adopts a competitively monistic methodology. In this schema, species concepts are winnowed

and improved by a mechanism of intellectual selection through risk-laden discourse. In this way,

competitive monism mirrors natural selection.

Ideas compete in their own intellectual ecosystem. Both categorical claims about species

(the first level) and epistemological claims about the philosophy of biology (the second level)

function as the subject of a separate, more abstracted level of inquiry. On this third level, ideas

75 Hull, The Metaphysics of Evolution, 262.

Augustine 41

and intellectual movements function as organisms competing in a harsh environment. Here, ideas

shift from the products of scientific inquiry to the base units on which philosophy operates. Ideas

become the units of selection, in an environment of critical inquiry. Just as experiment and

observation are the raw material that science processes into knowledge, knowledge is the raw

material that philosophy works on through intellectual selection. Scientific and historical texts,

complete in themselves for a different process, become the primary sources for another, yet

incomplete form of inquiry: philosophy as the continual refinement of knowledge through

discourse.

We must imagine an intellectual ecosystem, surrounded by an encouraging discursive

atmosphere, with ideas competing as the units of selection. Such a conceptual move is rather

simple epistemologically,

Genes, chromosomes, gametes, and organisms are clearly particulars. They are also

prime examples of entities that function in selection processes (Lewontin, 1970). It

follows, then, that if other entities, such as colonies and populations, can be selected in

the same sense as genes, chromosomes, and organisms, then they too must be

particular.76

Ideas function as individual and units of selection, too. Ideas may occasionally be lost or

suppressed, but most stick around long enough to compete against other ideas. The best tend to

rise to the top of the pile. Importantly, ideas have no corporeal form or conception of ownership.

They can be stolen, a reason that prompts Hull to hypothesize as to why “explicit

acknowledgement is so important in science” as a community. 77 Discursive rules and etiquette

have developed to protect philosophical discourse, too. Yet, stolen ideas contribute their fitness

gains to the community in the same way that genuine ideas do.78 Moreover, ideas participate in a

76 Ibid., 160. 77 Ibid., 262. 78 Ibid. Hull hints at a potential objection in which scholars would become more secretive as intellectual theft

Augustine 42

competition to retain their place in the intellectual ecosystem: otherwise known as ‘knowledge’.

In precisely the same way that species become better attuned to their environments,

knowledge, taken as a cumulative entity containing all ideas yet to be disproven, increases in

fitness over time. Better than the natural world, however, the intellectual sphere is durable. The

written word persists beyond the death of any individual. The products of experience are costly

and at constant threat of elimination. In the intellectual ecosystem, any gains in fitness that

knowledge experiences are permanent and cumulative – in a way that biological species are not.

In biology, organisms fight through constant and costly death to pass on their small gains in

fitness. Each generation must learn things anew, and often without help from others. Worse, the

benefits of natural selection are constantly hampered the same process. Injury can threaten, death

can delay, and extinction can completely erased progress.

Despite the fact of death, it is trivial to claim that species improve over time. The rapid

lifecycles of bacteria, birds, and mammals bestow their offspring with gains in fitness that allows

them to outcompete their parents. Even stable species, a limiting case of evolutionary stasis,

suggest a kind of improvement. Turtles have remained stable morphologically for millions of

years, with each and every generation validating the evolutionary success of their form. The

continued existence of a species is a constant reaffirmation of their fitness in regard to their

environment.

If one agrees that species improve in fitness despite the possibility of death, then one is

must also admit that ideas evolve even more vigorously without it. Ideas benefit from the same

became more common, which would have deleterious effects on the community and its refinement of knowledge.

To my mind, hints of this secrecy can be found in the master/apprentice relationship of late scholastic/early modern

science.

Augustine 43

competitive procedures of natural selection without any of the setbacks of natural death. In the

world of ideas, the benefits of selection are never erased or overwritten, only amassed. Humanity

has created technologies of the mind to retain knowledge beyond death. Without the

accumulation of knowledge, humans would be but animals. The act of copying further refines

knowledge for the next generation. In this idealized world, pluralism and monism fall away and

are replaced by a constant refreshing and reaffirmation. Together, discourse’s dual processes of

retention and refinement accelerate the progression of intellectual evolution a thousandfold.

Because ideas persist after death, knowledge doesn’t just evolve – it is perfected.

Ideas are born, either from others or by chance, and those unfit quickly fade away. From

risk-laden discourse a more refined product – knowledge – directly follows. And from this

nascent knowledge, people, so diverse and independent, naturally assort and reassert themselves

into disciplines organized to accelerate knowledge-formation. There is a constant progression in

this process, as one idea bears countless others, as social instincts drive every person to

scrutinize all to the benefit of each, and as technology extends memory beyond the frail limits of

the body; and as science, philosophy, and all the varied efforts of the human mind have carried

on, from so humble a beginning ideas so great and persevering have been, and are being,

evolved.

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