Species

xxx Prologue

idealism were less essentialistic than the Received View indicated, a view in part
revised by Hull himself.^17 The Received View appears in fragmentary form through-
out a number of publications over the past seventy years, and we shall look at three
examples.
George Gaylord Simpson was perhaps the greatest of the paleontological evolu-
tionary theorists of the twentieth century. His inuential text Principles of Animal
Ta xonomy^18 included a chapter entitled “The development of modern taxonomy.”
According to Simpson, Scholastic logic, based on Aristotle, relied on the “essence”
of a “species,” which consists of its “genus” plus its “differentia,” which was a log-
ical relationship.^19 It was this that Linnaeus adopted,^20 and it has several serious
faults: one is that “properties” and “accidents” (Simpson’s scare quotation marks) are
excluded from the “essence” and therefore the definition (my emphasis) of the spe-
cies. Another is that this method produces a classication of characters not organ-
isms (his emphasis). From Linnaeus to Darwin there was an increasing emphasis on
empirical rather than a priori classication.
According to Simpson, there was a typological tradition stemming from Plato and
coming via Aristotle, Neo-Platonic, scholastic, and Thomist philosophy into biologi-
cal taxonomy. He writes:

The basic concept of typology is this: every natural group of organisms, hence every

natural taxon in classication, has an invariant, generalized or idealized pattern shared

by all members of the group. The pattern of the lower taxon is superimposed upon that

of the higher taxon to which it belongs, without essentially modifying the higher pat-

tern. ... Numerous different terms have been given to these idealized patterns, often

simply “type” but also “archetype,” “Bauplan” or “structural plan,” “Morphotypus” or

“morphotype,” “plan” and others.^21

In contrast, modern taxonomy relies on common descent,^22 statistical properties
of populations,^23 and biological relationships. Simpson took his historical informa-
tion on this subject from a paper by A. J. Cain.^24 Cain, following the interpretation
of Aristotle and the later logicians in H. W. B. Joseph’s inuential text,^25 had said
that Linnaeus based his conception of species on Aristotelian denition of essences,
on “a priori principles agreeable to the rules of logic.”^26 He later reversed this posi-
tion after retirement and time to properly read Linnaeus and Ray.^27 Nevertheless, his
earlier papers^28 became the foundation for the Received View.

(^17) Hull 1983.
(^18) Simpson 1951.
(^19) Simpson 1961, 36f.
(^20) Op. cit. 38.
(^21) Simpson 1961, 47.
(^22) Simpson 1961, 52–54.
(^23) Simpson 1961, 65.
(^24) Cain 1958; cf. Winsor 2001.
(^25) Joseph 1916.
(^26) Page 147, quoted by Winsor 2001, 249.
(^27) For example, in Cain 1993, Cain 1994, Cain 1995, Cain 1999.
(^28) Cain 1958, Cain 1959b, Cain 1959a.