WHY ARE SOME
KINDS
HISTORICAL AND
OTHERS NOT?
LAURA FRANKLIN-HALL
NEW YORK UNIVERSITY
APRIL 2015
SCIENTIFIC
CLASSIFICATIONS
Niger-Congo languages
fundamental particles
granular materials
even-toed ungulates
genes
DIFFERENCES BETWEEN
CLASSIFICATIONS
• Fine-grained or coarse-grained
• Structural vs. functional
• Architectonic vs. simple
• Essentialist vs. non-essentialist
• Historical vs. synchronic
DIFFERENCES BETWEEN
CLASSIFICATIONS
• Fine-grained or coarse-grained
• Structural vs. functional
• Architectonic vs. simple
• Essentialist vs. non-essentialist
• Historical vs. synchronic
A full theory of
classification
would account
for all of these
differences
DIFFERENCES BETWEEN
CLASSIFICATIONS
• Fine-grained or coarse-grained
• Structural vs. functional
• Architectonic vs. simple
• Essentialist vs. non-essentialist
• Historical vs. synchronic
My focus:
to explore and
rationalize this
difference
PLAN
Step 1: Characterize synchronic vs. historical
Step 2: Ask why classifications are sometimes
historical and sometimes synchronic
Step 3: Use the Probability-Similarity Account
(PSA) to answer this question
Step 4: Rationalize and defend the PSA
Step 5: Consider implications for the minddependence of the natural kinds
1: SYNCHRONIC VS.
HISTORICAL
Synchronic
Classification
Historical
Classification
Key property is a
feature of the
classified individuals
grounded
synchronically
Key property is a
historical feature of
the individuals
classified – usually
descent via
reproduction
• Not exhaustive: there could be a ‘future classification’ where things are
grouped in terms of what they will bring about.
• Also, there are mixed cases: e.g., metamorphic rocks
1: SYNCHRONIC VS.
HISTORICAL
Synchronic
Classification
• Bacterial species by
nuclear DNA sequence
• Molecules by
constituent atoms plus
bonding
• Gaits by leg-lift patterns
Historical
Classification
• Metazoan species by
descent from a founding
population
• Words by sound /
meaning hybrid in a
language, with
languages individuated
by history
• Cultural items by origins
1: SYNCHRONIC VS.
HISTORICAL
Synchronic
Classification
• Bacterial species by
nuclear DNA sequence
• Molecules by
constituent atoms plus
bonding
• Gaits by leg-lift patterns
Historical
Classification
• Metazoan species by
descent from a founding
population
• Words by sound /
meaning hybrid in a
language, with
languages individuated
by history
• Cultural items by origins
1: SYNCHRONIC VS.
HISTORICAL
Caffeine
Synchronic
Classification
• Bacterial species by
nuclear DNA sequence
• Molecules by
constituent atoms plus
bonding
Formula: C8H10N4O2
IUPAC ID: 1,3,7-Trimethylpurine-2,6dione
• Gaits by leg-lift patterns
To count as caffeine, a substance
must just be made of such
molecules. It’s origin can be either
natural or artificial.
1: SYNCHRONIC VS.
HISTORICAL
The gallop
Synchronic
Classification
• Bacterial species by
nuclear DNA sequence
• Molecules by
constituent atoms plus
topology
A four-beat gait in which all
feet are briefly off the ground at
the same time
• Gaits by leg-lift patterns
For a motion to count as a
gallop, it doesn’t matter how
the animal learned the
process or anything else
about its ontogeny.
1: SYNCHRONIC VS.
HISTORICAL
Language Tree
Historical
Classification
• Metazoan species by
descent from a founding
population
Word
in a language
+ (defined by
origins)
‘False cognates are not instances
of the ‘same word’
i.e., ‘much’ and ‘mucho’
• Words by meaning/
sound hybrid in a
language, with
languages individuated
by history
• Cultural items by origins
1: SYNCHRONIC VS.
HISTORICAL
Holiday – The Day of the Dead
(Dia de Muertos)
Historical
Classification
• Metazoan species by
descent from a founding
population
•
•
•
•
Originated in southern Mexico, from a
Aztec rite.
Hybridized with All Souls Day.
Spread through Latin America where
the ‘same holiday’ is celebrated.
Similar in practice and belief to other
holidays found elsewhere (e.g., the
Ghost Festival in China); also involve
honoring ancestors.
• Words by meaning/
sound hybrid in a
language, with
languages individuated
by history
• Cultural items by origins
1: SYNCHRONIC VS.
HISTORICAL
Caveats
1) controversy about the ‘key property’ for some
classifications. I have tried to presume the
dominant view.
2) In biology, controversy about whether
classifications correspond to kinds or
individuals. I don’t think this difference makes a
difference and will put it aside.
2: THE EXPLANATORY
QUESTION
Why are some categories in use by scientists historical
and others synchronic?
(I say ‘in use by’ because there is some sense that both
historical and synchronic categories could be applied to
any science. The question is which kind of category
actually gets developed.)
Presuming, as many naturalistic philosophers do, that
the natural kinds correspond to the categories in use
by mature sciences, this question also permits us to
query why some natural kinds are historical and
others not.
2: THE EXPLANATORY
QUESTION
Why are some categories in use by scientists
historical and others synchronic?
Obvious reply
“Categories are historical in historical sciences and
synchronic otherwise”
No: all historical sciences that aim to account for causal
change will require synchronic categories as well
Biology, Linguistics and Anthropology all have synchronic
categories alongside their historical ones.
3: THE PROBABILITYSIMILARITY ACCOUNT
My proposal: for any domain of individuals,
scientific classifications of those individuals will
be historical whenever
The Probability of the Independent
Emergence of Similar things (PIES) is very
small
They are synchronic whenever
PIES is not very small
3: THE PROBABILITYSIMILARITY ACCOUNT
The Probability of the Independent
Emergence of Similar things (PIES)
3: THE PROBABILITYSIMILARITY ACCOUNT
The Probability of the Independent
Emergence of Similar things (PIES)
3: THE PROBABILITYSIMILARITY ACCOUNT
The Probability of the Independent
Emergence of Similar things (PIES)
3: THE PROBABILITYSIMILARITY ACCOUNT
The Probability of the Independent
Emergence of Similar things (PIES)
time
3: THE PROBABILITYSIMILARITY ACCOUNT
The Probability of the Independent
Emergence of Similar things (PIES)
time
3: THE PROBABILITYSIMILARITY ACCOUNT
The Probability of the Independent
Emergence of Similar things (PIES)
Case 1:
not independent
single event
time
3: THE PROBABILITYSIMILARITY ACCOUNT
The Probability of the Independent
Emergence of Similar things (PIES)
event 1
Case 2:
independent
event 2
time
3: THE PROBABILITYSIMILARITY ACCOUNT
The Probability of the Independent
Emergence of Similar things (PIES)
event 1
Case 2:
independent
event 2
time
N.B.: These
cartoons paper
over many issues,
some of which will
be addressed
shortly…
3: THE PROBABILITYSIMILARITY ACCOUNT
The Probability of the Independent
Emergence of Similar things (PIES)
PIES is high when
CASE 2 is likely 
Synchronic kinds
event 1
Case 2:
independent
PIES is low when
CASE 2 is unlikely 
Historical Kinds
We often judge
probabilities based on
frequencies, but they
can come apart.
event 2
time
3: THE PROBABILITYSIMILARITY ACCOUNT
Illustration: atoms
Probability that similar individual atoms (e.g.,
elements) comes about in independent
origination events is high. Thus, their kinds (the
elements) are synchronic.
Evidence: frequencies track probabilities and
many atoms of any elements have had separate
originations; some in one supernova, others in
another, others via radioactive decay.
3: THE PROBABILITYSIMILARITY ACCOUNT
Illustration: atoms
Probability that similar individual atoms (e.g.,
elements) comes about in independent
origination events is high. Thus, their kinds (the
elements) are synchronic.
Explanation: unlike with solar systems: small
variations in initial conditions for the generation
of an atom can still yield identical atoms; this
traces ultimately to the quantum nature of our
universe (see Ghirardi 2007)
3: THE PROBABILITYSIMILARITY ACCOUNT
Illustration: organisms
Probability that similar individual organisms (e.g.,
species) comes about independently is low.
Thus, organisms are divided into historical kinds:
the species.
Evidence: frequencies track probabilities and
famously there are no instances of strong
convergence between organisms with different
origins.
3: THE PROBABILITYSIMILARITY ACCOUNT
Illustration: organisms
Probability that similar individual organisms (e.g.,
species) comes about independently is low.
Thus, organisms are divided into historical kinds:
the species.
Explanation: Many small and undirected
modifications are required to result in any given
form. That these would be identical modifications
in two lines is highly unlikely.
3: THE PROBABILITYSIMILARITY ACCOUNT
The Probability of the Independent
Emergence of Similar things (PIES)
3: THE PROBABILITYSIMILARITY ACCOUNT
The Probability of the Independent
Emergence of Similar things (PIES)
REACTION:
SOUNDS PLAUSIBLE,
BUT WHAT
DETERMINES THESE
PROBABILIIES?
3: THE PROBABILITYSIMILARITY ACCOUNT
The Probability of the Independent
Emergence of Similar things (PIES)
MY ANSWER:
REACTION:
SOUNDS PLAUSIBLE,
BUT WHAT
DETERMINES THESE
PROBABILIIES?
A COMBINATION OF THE CAUSAL
FEATURES OF SYSTEMS AND
FEATURES OF US:
1) OUR ‘GAZE’,
2) OUR NOTION OF
INDEPENCENCE,
3) OUR STANDARDS FOR
SIMILARITIES
4: DEFENDING THE
ACCOUNT
Two-part defense of the PIES standard:
1) Saves the phenomena: looks at different
scientific examples, and see whether PIES
tracks classification-type
1) Rationalize the principle: argue that it makes
sense for practice to respect it
4: DEFENDING THE
ACCOUNT
Two-part defense of the PIES standard:
1) Saves the phenomena: looks at different
scientific examples, and see whether PIES
tracks classification-type
4: DEFENDING THE
ACCOUNT
The case of biology
1. Eukaryotic Species
2. Bacterial Species
3. Plant Species
4. Kinds in Astrobiology
5. Kinds for Convergence-Lovers
6. Lamarckian Species
Saving the
Phenomena
4: DEFENDING THE
ACCOUNT
1. Eukaryotic Species
CLASSIFICATION TYPE: HISTORICAL
The species of an organism
is most often taken to be a
function of its history
(phylogenetic species
concept)
An organism’s synchronic
properties are not relevant to
questions of its species
membership
Saving the
Phenomena
4: DEFENDING THE
ACCOUNT
Saving the
Phenomena
1. Eukaryotic Species
CLASSIFICATION TYPE: HISTORICAL
The species of an organism
is most often taken to be a
function of its history
(phylogenetic species
concept)
Mom!
An organism’s synchronic
properties are not relevant to
questions of its species
membership
‘swamp pig’
not a pig
‘’snail’-born-of-pig’
is a pig
4: DEFENDING THE
ACCOUNT
Saving the
Phenomena
1. Eukaryotic Species
EXPLANATION
PIES Analysis: The probability of the evolution of
any very complex package of traits, such as are
found among pigs, is extreme low. (cf ‘Dollo’s law’)
 historical kinds
4: DEFENDING THE
ACCOUNT
Saving the
Phenomena
2. Bacterial Species
CLASSIFICATION TYPE: SYNCHRONIC
The ‘official definition’ of bacterial
species depends on similarity
between genomes*.
An organism’s history is not strictly
relevant to species membership.
*70% DNA molecule cross-hybridization, which occurs with
approximates 95% nucleotide identity
Bacterial ‘tree’
4: DEFENDING THE
ACCOUNT
Saving the
Phenomena
2. Bacterial Species
CLASSIFICATION TYPE: SYNCHRONIC
The ‘official definition’ of bacterial
species depends on similarity
between genomes*.
Bacterial ‘tree’
staph
An organism’s history is not strictly
relevant to species membership.
Mom!
swamp E. coli and E.coli-borne-of-staph are E. coli
4: DEFENDING THE
ACCOUNT
2. Bacterial Species
Top:
transduction
Bottom:
conjugation
Saving the
Phenomena
EXPLANATION
Speciation via non-reproductive gene
transfer (aka Lateral Gene Transfer or
LGT).
This makes it comparatively easy to
get the same set of traits in separate
lineages
4: DEFENDING THE
ACCOUNT
2. Bacterial Species
Top:
transduction
Bottom:
conjugation
Saving the
Phenomena
EXPLANATION
Speciation via non-reproductive gene
transfer (aka Lateral Gene Transfer or
LGT).
This makes it comparatively easy to
get the same set of traits in separate
lineages
PIES Analysis: The probability of the repeated
independent emergence of a particular package of
traits, such as are found among E. coli, is not
extremely low  synchronic kinds
4: DEFENDING THE
ACCOUNT
3. Plant Species
CLASSIFICATION TYPE: SYNCHRONIC
Recurrent speciation in some
plant species; botanists
studying these species consider
products to be single species
with multiple origins.
“The same species can actually
form multiple times”
“Recurrent speciation […] is the
rule, not the exception”
Saving the
Phenomena
4: DEFENDING THE
ACCOUNT
Saving the
Phenomena
3. Plant Species
EXPLANATION
Hybridization
PIES Analysis: Hybrid
speciation increases
likelihood of similar entities
with ‘independent’ origins
 Synchronic kinds
T. dubius, T. pratensis, and T. porrifolius were introduced from Europe into
Eastern Washington/Idaho in the early 1900s. Two polyploid hybids, T.
miscellus and T. mirus, came about many times when ranges overlapped.
4: DEFENDING THE
ACCOUNT
4. Astrobiological Groupings (‘species’?)
CLASSIFICATION TYPE: SYNCHRONIC
Astrobiologists—unlike most others who think about
the life sciences—sometimes talk of a ‘periodic
table of organisms’.
They don’t know just what the bins in this table will
be due to the n=1 problem (i.e., our only examples
of living things are from earth)
But they imagine that being in a bin is grounded
synchronically, not via history.
Saving the
Phenomena
4: DEFENDING THE
ACCOUNT
Saving the
Phenomena
4. Astrobiological Groupings (‘species’?)
EXPLANATION
Focus on such an enormous sample
space, in concert with low standards
of similarity
PIES Analysis: Broad
sample space makes
similar organisms with
independent origins less
unlikely  synchronic
kinds
4: DEFENDING THE
ACCOUNT
5. Categories among the convergence-obsessed
CLASSIFICATION TYPE: SYNCHRONIC
Heterodox biologists
(Conway Morris and
McGhee) have also tried to
design ‘a periodic table of
life’.
Membership in a bin depends
on synchronic properties, not
history.
Saving the
Phenomena
4: DEFENDING THE
ACCOUNT
Saving the
Phenomena
5. Categories among the convergence-obsessed
EXPLANATION
These scientists believe that strong
convergence is likely (e.g., similar forms will
evolve via very different lineages). They also
have in mind comparatively weak standards
for similarity.
PIES Analysis: Peculiar
causal theory + weak
standard for similarity
makes PIES high 
synchronic kinds
4: DEFENDING THE
ACCOUNT
6. Lamarckian ‘Species’
Saving the
Phenomena
4: DEFENDING THE
ACCOUNT
DARWIN’S VIEW:
LIFE’S TREE
time
6. Lamarckian ‘Species’
Saving the
Phenomena
Chapter
4, On the
Origin of
Species
Saving the
Phenomena
4: DEFENDING THE
ACCOUNT
6. Lamarckian ‘Species’
LAMARCK’S VIEW:
LIFE’S REEDS
time
present
These are separatelyoriginating ‘reed-like’
lineages
Saving the
Phenomena
4: DEFENDING THE
ACCOUNT
6. Lamarckian ‘Species’
LAMARCK’S VIEW:
LIFE’S REEDS
present
time
CLASSIFICATION TYPE: SYNCHRONIC
These are separatelyoriginating ‘reed-like’
lineages
Similar individuals can have
independent origins. When L
talks about ‘species’ he is using
a synchronic conception. He
has a false view of origins, but
he is still following the PIES
principle.
Saving the
Phenomena
4: DEFENDING THE
ACCOUNT
The case of biology - RECAP
1. Eukaryotic Species
HISTORICAL
2. Prokaryotic Species
SYNCHRONIC
3. Plant Species
SYNCHRONIC
4. Kinds in Astrobiology
SYNCHRONIC
5. Kinds for convergence-lovers
SYNCHRONIC
6. Lamarckian Species
SYNCHRONIC
Saving the
Phenomena
4: DEFENDING THE
ACCOUNT
The Probability of the Independent
Emergence of Similar things (PIES)
MY ANSWER:
REACTION:
SOUNDS PLAUSIBLE,
BUT WHAT
DETERMINES THESE
PROBABILIIES?
A COMBINATION OF THE CAUSAL
FEATURES OF SYSTEMS AND
FEATURES OF US:
1) OUR ‘GAZE’,
2) OUR NOTION OF
INDEPENCENCE,
3) OUR STANDARDS FOR
SIMILARITIES
4: DEFENDING THE
ACCOUNT
1. CAUSAL FACTS (C)
2. GAZE (G)
3. SIMILARITY STANDARDS (S)
4. INDEPENDENCE
CONDITIONS (I)
Saving the
Phenomena
Saving the
Phenomena
4: DEFENDING THE
ACCOUNT
The case of biology - RECAP
DIAGNOSIS
1. Eukaryotic Species
none
2. Prokaryotic Species
causal dif, demanding notion of I
3. Plant Species
causal dif, demanding notion of I
4. Kinds in Astrobiology
weak S, wide gaze
5. Kinds for convergence-lovers causal dif, weak S
6. Lamarckian Species
causal dif
4: DEFENDING THE
ACCOUNT
The case of linguistics
1. Most words
2. Sounds
3. ‘Huh?’
Saving the
Phenomena
4: DEFENDING THE
ACCOUNT
1. Most words
much (13th c.) ←< southern Middle
English muchel (where “u” is actually
front
[y]; 12th c.) < Old English miċel ‘big’
< Proto-Germanic *mikilaz (cf.
Gothic mikils) < Proto-IndoEuropean *meǵ- (cf. Greek mégas
and Latin
magnus, both ‘big’, and Hittite mēk
‘much’)12
Spanish mucho < *muito (cf.
Portuguese muito and the Spanish
adverb muy,
which was truncated in unstressed
position in rapid speech) < Latin
multum ‘much’ < *mol-to-; the root is
PIE *mel-, which appears also in
Latin melior ‘better’ (> Spanish
mejor)
Saving the
Phenomena
Groupings of utterances into words has
historical component
Illustration: ‘false cognates’ are not
considered to be instances of the same
word, even though they can (in the
extreme) be signs that both share sound
and meaning.
Explanation: arbitrariness of connection
between sign and signifier makes
sound-meaning combinations with
independent origins unlikely
4: DEFENDING THE
ACCOUNT
2. Sounds
Saving the
Phenomena
Individual sounds are not classified in
a way that depends on history
Most sounds have ‘multiple origins’ in
different language systems
Saving the
Phenomena
4: DEFENDING THE
ACCOUNT
The case of linguistics
3. ‘Huh?’
The exception proves the rule: the word
‘huh’ does have independent origins,
and is not considered a ‘false cognate’
but instead a ‘universal word’.
Why? Strong
‘selection pressures’
on this utterance
made similarity in the
face of ‘independent
origins’ likely.
4: DEFENDING THE
ACCOUNT
Two-part defense of the PIES standard:
1) Saves the phenomena: looks at different
scientific examples, and see whether PIES
tracks classification-type
1) Rationalize the principle: argue that it
makes sense for practice to respect it
STRATEGY: point to two scientific goals accomplished
by using historical categories when PIES <<
4: DEFENDING THE
ACCOUNT
Rationalizing the
Principle
Use of Categories: Strong Generalizations
e.g., Pandas eat bamboo, electrons have mass of
9.109 x 10-31
When PIES << the strongest possible
generalizations will use historical categories
When PIES ~<< (non-disjunctive) historical
categories will not be as strong
4: DEFENDING THE
ACCOUNT
Rationalizing the
Principle
Use of Categories: Explanatoriness
Generalization Strength only explains why
historical categories are coequal with
synchronic ones with PIES << not why they
would be preferred.
Explanatoriness goes further. Historical
categories include information that accounts for
similarities common to a kind: that is, that these
instances have a common origin.
Note: explanatoriness also accounts of which synchronic features are considered
‘key’, as in an explanatory approach to Lockean essences
PLAN
Step 1: Characterize synchronic vs. historical
Step 2: Ask why classifications are sometimes
historical and sometimes synchronic
Step 3: Use the Probability-Similarity Account
(PSA) to answer this question
Step 4: Rationalize and defend the PSA
Step 5: Consider implications for the minddependence of the natural kinds
5: MINDDEPENDENCE?
Mind-dependence or ‘reality’ or natural kinds
on PIES picture?
5: MINDDEPENDENCE?
Mind-dependence or ‘reality’ or natural kinds
on PIES picture?
Because PIES depends both on the causal
systems and features of us (gaze,
similarities standards, standard for
independence), facts about whether kinds
are historical will not be strongly mindindependent. This speaks against a certain
kind of realism.
5: MINDDEPENDENCE?
Mind-dependence or ‘reality’ or natural kinds
Note: focus here on the ‘reality’ of their
on PIES picture?
status as historical or synchronic
Two ways it is consistent with ‘realism’
(properly understood)
1. Promiscuous realism
2. Categorical Bottlenecks
5: MINDDEPENDENCE?
Mind-dependence or ‘reality’ or natural kinds
on PIES picture?
1. Promiscuous realism
Deny the premise, floated above, that grouping corresponding
to the classifications of science are the natural kinds. Permit
the natural kinds to be promiscuous, to outrun the
classifications of science.
Contextual features that determine what kind of classification
we out to use then determine simply which kinds to focus on /
find relevant, and the subjectivity of PIES will not undermine
the kinds mind-independence.
5: MINDDEPENDENCE?
Mind-dependence or ‘reality’ or natural kinds
on PIES picture?
2.
Categorical Bottlenecks
See Franklin-Hall, L (2015) “Natural Kinds as Categorical Bottlenecks” Phil Studies
5: MINDDEPENDENCE?
Mind-dependence or ‘reality’ or natural kinds
on PIES picture?
2.
Categorical Bottlenecks
Epistemic agent space
x
x
x
x
Categorization Space
x
x
x
x
See Franklin-Hall, L (2015) “Natural Kinds as Categorical Bottlenecks” Phil Studies
5: MINDDEPENDENCE?
Mind-dependence or ‘reality’ or natural kinds
on PIES picture?
2.
Categorical Bottlenecks
Epistemic agent space
x
x x
x
x
x
Categorization Space
x
x
See Franklin-Hall, L (2015) “Natural Kinds as Categorical Bottlenecks” Phil Studies
5: MINDDEPENDENCE?
Mind-dependence or ‘reality’ or natural kinds
on PIES picture?
2.
Categorical Bottlenecks
Epistemic agent space
x
Eukaryotic species,
elements, and
molecules have the
‘bottleneck’ structure
– more ‘real’
x x
x
x
x
Kinds of
plants,
bacteria, etc.
do not
Categorization Space
x
x
See Franklin-Hall, L (2015) “Natural Kinds as Categorical Bottlenecks” Phil Studies
FINAL
(COUNTER?)
EXAMPLE
Higgs Boson
PIES <<
But a synchronic
rather than historical
kind
Why? Holism in
classificatory
principles
THANKS!