Transcript Biological Classification

Locke vs Modern Biological
Classification
PHIL 2130
Essences = our ideas
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Ordinary essences are merely sorts, our ordinary
names for things:
‘The ranking of Things into Species, which is nothing
but sorting them under several Titles, is done by us,
according to the Ideas we have of them’ (III, vi, 13);
Take an individual human for example:
There is nothing essential to an individual human
That cannot be altered: Color, Shape can change;
memory loss, loss of locomotion can all result e.g. from
illness.
What’s at stake in Naming in the
17th century?
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Same names for different things (III, vi, 8):
Locke cites example of Chemistry
Different names for the same things:
Example of Ice vs Water, liquid vs solid gold (III, vi, 13);
A big issue in 17th century natural history:
Many different names for the same organisms: birds,
plants (from 1,000 to 18,000 species between 1500
and 1700), animals.
Species not founded on essences
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We would need to know if Nature has
established regular ‘Models of all Things to be
produced’;
Nature always attains that Essence
Monsters (meaning?) are a distinct species
Real Essence is knowable, which it is not (III,
vi, 15-20)
Does propagation prove species?
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No
Example of Hybrids
Flowers (tulip at right)
Mules (mating of Donkey
and Mare; see III, vi, 23)
Locke’s Influence on Taxonomy
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Some claimed it was possible to create a system of
classification that would reflect natural order;
Locke = a founder of a skeptical tradition in biological
systematics (taxonomy) of the reality of taxonomical
divisions, e.g. of an alleged ‘natural’ system of
classification;
Also inspires programme of improving classification
schemes, not on the basis of a purported natural
classification, but rather on an orderly system of
nomenclature, such that one name stands for one
thing/group of things.
Why did Locke think Essences are
unknowable?
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His mechanistic philosophy, the ‘New Philosophy’ of
the 17th century;
Matter has a substance and ‘constitutes everything in
creation’ (Ayers 1981, 250).;
All matter is a continuum: ‘in all the corporeal World,
we see no Chasms, or Gaps…the descent is by easy
steps, and a continued series of Things, that in each
remove, differ very little one from the other’ (III, vi, 12);
‘no need to postulate other universal natures’ (Ayers
1981, 250).
Locke’s Idea of Matter
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There are just different configurations (shapes) of that
matter, so that gold differs from a tree not in substance
but in structure;
All matter is subject to laws of motion (same era as
Newton)
Some philosophers like Descartes asserted they knew
the structure of matter;
‘Locke believed that Boyle’s version of
corpuscularianism–solid particles clashing in the void—
was the best inadequate theory available and that the
unknown truth must be something like it’ (Ayers 1981,
250)
‘A certain Chinese encyclopædia’
Borges quoted by Foucault, The Order of Things:
‘…animals are divided into: (a) belonging to the Emperor,
(b) embalmed, (c) tame, (d) sucking pigs, (e) sirens, (f)
fabulous, (g) stray dogs, (h) included in the present
classification, (i) frenzied, (j) innumerable, (k) drawn
with a very fine camelhair brush, (l) et cetera, (m)
having just broken the water pitcher, (n) that from a
long way off look like “flies”. In the wonderment of this
taxonomy, the thing we apprehend…as the exotic
charm of another system of thought, is the limitation of
our own, the stark impossibility of thinking that’.
What is Borges’s/Foucault’s point?
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There are many possible classifications of things:
animals, library books, pens, etc.
They may differ culturally, as suggested by the
descriptive phrase—’a chinese encyclopædia’
May be based on very different criteria of
differentiation: are there any clear criteria of
differentiation in the quote?
Is modern biological classification based on the
species concept (Mayr) a special case?
Is it universally accepted and understood?
Essentialism/Typology
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Aristotelian definition: essence (man=rational
animal), definition, name (man)
explicitly informed biological classification up to
the nineteenth century when Darwin and
Mendel made their discoveries;
Hull (1992) argues Aristotelian definition still
informs some taxonomists’ species definitions
today.
Modern Typology
Three essentialist tenets of biological typology:
 -ontological assertion that forms exist;
 -methodological assertion that taxonomy
should discern the essences of species;
 -logical assertion concerning definition.
According to Hull (1992), these all add up to
typology still being basically an Aristotelian
exercise.
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Aristotelian definition
in modern terms
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Properties severally necessary
And jointly sufficient
‘For example, being a three-sided closed plane figure
is necessary and sufficient for a triangle.’
This was the only kind of species definition permitted
until recently by the international codes agreed by
taxonomists;
Yet, ‘seldom is a property of any taxonomic value
distributed both universally and exclusively among the
members of a taxon [a biological grouping]’.
Eighteenth-century Taxonomy
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Carolus Linnaeus of Sweden (1707-1778) reformed
taxonomy, providing
Binomial nomenclature (2-word Latin name), and
An artificial sexual system of classification (see next
slide) for plants, one of his major contributions;
Based on morphological and reproductive
characteristics:
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The number and position of stamens (male) and pistils
(female), the reproductive organs in flowers.
The goal for 18th c. naturalists, was a natural basis for
classification that was not achievable at the time.
Linnaean Plant Taxonomy
Biological species concept
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Darwin (evolution) and Mendel (genetics) formulated
their theories in the mid-nineteenth century
This led to the development of the modern biological
species concept described by Mayr:
Species consist of populations
Have ‘reality’ and
‘an internal genetic program’
‘The development of the biological concept of the
species is one of the earliest manifestations of the
emancipation of biology from an inappropriate
philosophy…’ (Mayr, 17).
Philosophical Holdovers
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But, argues Hull (1992), a static species concept is still
adhered to by many biologists;
Why?
Even some evolutionary taxonomists (called
‘classificationists’) prefer typology
Because taxonomists’ job is easier if they call certain
properties or characteristics ‘essential’ and treat them
as fixed in time and space;
Why easier? Evolutionary taxonomy entails making
the unit of evolution the unit of classification (HINT:
‘evolution’ refers to change over time)
How is this done, according to Mayr?
Biological Species Concept
Members of species = reproductive community
(Do you recall what Locke said about this? Example of
the mule; is Locke wrong?)
 An ecological unit, interacting as a unit w/ other
species in same environment, but protected from these
other units by ‘isolating mechanisms’;
 A genetic unit, comprising an intercommunicating gene
pool of coadapted genes;
 The evolutionary taxonomist seeks to assign
populations to the correct rank or category in the
taxonomic hierarchy, most difficult when populations
exchange genes.
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Taxonomic Hierarchy
Assignment of taxa
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Higher taxa (phylum, genus, etc.) are defined by
intrinsic characteristics (e.g bird = feathered vertebrate;
any feathered vertebrate fits class of birds)
Species are unique in the hierarchy: they are defined
by relational properties, i.e. interbreeding or lack of it;
See Mayr, p. 19 on species-specific bird songs as
indications of relation.
Is this a universally applicable/acceptable concept?
Summary Table of Species
Concepts
Essentialist
Forms/Ideas/
universals?
Cause of
Variation
Role of
Morphology
Nominalist
Biological
Yes
No
No or N/A
Why?
Imperfect
realization of
the idea
N/A
Adaptation to
Environment/
Nat. Selec.
Very
Important
N/A
Used w/
genetic info
Further reading:
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D.L. Hull, ‘The Effect of Essentialism on
Taxonomy: Two Thousand Years of Stasis’, in
M. Ereshefsky, ed.,The Units of Evolution
(1992), pp. 199-225 (book on reserve in Main
Library).