Lumpers and splitters are opposing factions in any discipline that has to place individual examples into rigorously defined categories.
The lumper–splitter problem occurs when there is the desire to create
classifications and assign examples to them, for example schools of literature, biological taxa and so on. A "lumper" is an individual who takes a gestalt
view of a definition, and assigns examples broadly, assuming that
differences are not as important as signature similarities. A "splitter"
is an individual who takes precise definitions, and creates new
categories to classify samples that differ in key ways.
Origin of the terms
The earliest known use of these terms was by Charles Darwin, in a letter to J. D. Hooker in 1857: It is good to have hair-splitters & lumpers. They were introduced more widely by George G. Simpson in his 1945 work The Principles of Classification and a Classification of Mammals. As he put it:
... splitters make very small units – their critics say that if they can tell two animals apart, they place them in different genera ... and if they cannot tell them apart, they place them in different species. ... Lumpers make large units – their critics say that if a carnivore is neither a dog nor a bear, they call it a cat.
A later use can be found in the title of a 1969 paper "On lumpers and splitters ..." by the medical geneticist Victor McKusick.
Reference to lumpers and splitters in the humanities appeared in a debate in 1975 between J. H. Hexter and Christopher Hill, in the Times Literary Supplement. It followed from Hexter's detailed review of Hill's book Change and Continuity in Seventeenth Century England, in which Hill developed Max Weber's argument that the rise of capitalism was facilitated by Calvinist
Puritanism. Hexter objected to Hill's "mining" of sources to find
evidence that supported his theories. Hexter argued that Hill plucked
quotations from sources in a way that distorted their meaning. Hexter
explained this as a mental habit that he called "lumping". According to
him, "lumpers" rejected differences and chose to emphasize similarities.
Any evidence that did not fit their arguments was ignored as aberrant.
Splitters, by contrast, emphasised differences, and resisted simple
schemes. While lumpers consistently tried to create coherent patterns,
splitters preferred incoherent complexity.
Usage in various fields
Biology
The categorization and naming of a particular species should be regarded as a hypothesis about the evolutionary
relationships and distinguishability of that group of organisms. As
further information comes to hand, the hypothesis may be confirmed or
refuted. Sometimes, especially in the past when communication was more
difficult, taxonomists working in isolation have given two distinct
names to individual organisms
later identified as the same species. When two named species are agreed
to be of the same species, the older species name is almost always
retained dropping the newer species name honoring a convention known as
"priority of nomenclature". This form of lumping is technically called
synonymization. Dividing a taxon into multiple, often new, taxa is
called splitting. Taxonomists are often referred to as "lumpers" or
"splitters" by their colleagues, depending on their personal approach to
recognizing differences or commonalities between organisms.
History
In history, lumpers are those who tend to create broad definitions
that cover large periods of time and many disciplines, whereas splitters
want to assign names to tight groups of inter-relationships. Lumping
tends to create a more and more unwieldy definition, with members having
less and less mutually in common. This can lead to definitions which
are little more than conventionalities, or groups which join
fundamentally different examples. Splitting often leads to "distinctions without difference", ornate and fussy categories, and failure to see underlying similarities.
For example, in the arts, "Romantic" can refer specifically to a period of German poetry roughly from 1780–1810, but would exclude the later work of Goethe, among other writers. In music it can mean every composer from Hummel through Rachmaninoff, plus many that came after.
Software modelling
Software engineering often proceeds by building models (sometimes known as model-driven architecture).
A lumper is keen to generalize, and produces models with a small number
of broadly defined objects. A splitter is reluctant to generalize, and
produces models with a large number of narrowly defined objects.
Conversion between the two styles is not necessarily symmetrical. For
example, if error messages in two narrowly defined classes behave in the
same way, the classes can be easily combined. But if some messages in a
broad class behave differently, every object in the class must be
examined before the class can be split. This illustrates the principle
that "splits can be lumped more easily than lumps can be split".
Language classification
There is no agreement among historical linguists about what amount of evidence is needed for two languages to be safely classified in the same language family. For this reason, many language families have had lumper–splitter controversies, including Altaic, Pama–Nyungan, Nilo-Saharan, and most of the larger families of the Americas. At a completely different level, the splitting of a mutually intelligible dialect continuum
into different languages, or lumping them into one, is also an issue
that continually comes up, though the consensus in contemporary
linguistics is that there is no completely objective way to settle the
question.
Splitters regard the comparative method (meaning not comparison in general, but only reconstruction of a common ancestor or protolanguage) as the only valid proof of kinship, and consider genetic relatedness to be the question of interest. American linguists of recent decades tend to be splitters.
Lumpers are more willing to admit techniques like mass lexical comparison or lexicostatistics,
and mass typological comparison, and to tolerate the uncertainty of
whether relationships found by these methods are the result of linguistic divergence (descent from common ancestor) or language convergence (borrowing). Much long-range comparison work has been from Russian linguists like Vladislav Illich-Svitych and Sergei Starostin. In the US, Greenberg's and Ruhlen's work has been met with little acceptance from linguists. Earlier American linguists like Morris Swadesh and Edward Sapir also pursued large-scale classifications like Sapir's 1929 scheme for the Americas, accompanied by controversy similar to that today.
Liturgical studies
Paul F. Bradshaw suggests that the same principles of lumping and splitting apply to the study of early Christian liturgy.
Lumpers, who tend to predominate, try to find a single line of texts
from the apostolic age to the fourth century (and later). Splitters see
many parallel and overlapping strands which intermingle and flow apart
so that there is not a single coherent path in development of liturgical
texts. Liturgical texts must not be taken solely at face value; often
there are hidden agendas in texts.
The Hindu religion is essentially a lumper's concept, sometimes also known as Smartism. Hindu splitters, and individual adherents, often identify themselves as adherents of a religion such as Shaivism, Vaishnavism, or Shaktism according to which deity they believe to be the supreme creator of the universe.
Philosophy
Freeman Dyson in 2005
Physicist and philosophy writer Freeman Dyson
has suggested that "observers of the philosophical scene" can be
broadly, if over-simplistically, divided into splitters and lumpers,
roughly corresponding to materialists, who imagine the world as divided into atoms, and Platonists, who regard the world as made up of ideas.
