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2

The Medieval Bridge

BOËTHIUS: THE NATURE OF THE SPECIES IN LOGIC

In his On division (De divisione, c. 505 ), Boëthius (480–524/6 ) discussed the
nature of classication by division. In an extended introduction to the topic, he sets
out inuentially the basis for the “classicatory logic” of the next 1500 years, and
as he wrote in Latin, this was almost as inuential in the development of western
thought as Augustine’s works were. Nearly all his examples are based on animal/
human and similar biological cases, but it should not be thought this is a biological
concept, any more than Aristotle’s.
He distinguishes division of genus into species from whole into part, and utter-
ances into “proper signication.” His version of the diairesis is not binary, however.
“Every division of a genus into its species has to be made into two or more parts, but
there cannot be innitely many or fewer than two parts.”^1 The matter of accidents
and essences applies here to utterances (that is, of the meanings of propositions) not
species, and he notes that while a genus is the whole of which a species is a part,
more universal utterances such as equivocation are not wholes in nature.^2

ISIDORE OF SEVILLE: METAMORPHOSES

Isidore (c. 560–636), was one of the rst of the encyclopediasts after Pliny. He

wrote an extensive summary of the state of knowledge in the seventh century, bas-

ing his accounts on prior writings and their supposed etymologies (hence the title

Etymologiae), and discussed human and animal species briey in the midst of dis-

cussions about centaurs and other mythological beasts. In a short section entitled

“Metamorphoses (De transformatis),” he writes

many creatures naturally undergo mutation and, when they decay, are transformed into

different species—for instance bees, out of the rotted esh of calves, or beetles from

horses, locusts from mules, scorpions from crabs.^3

However, he does not follow this up with anything more general, and it merely

follows in the classical tradition of monstrosities.

(^1) 877C [Kretzmann and Stump 1988, 14].
(^2) 878D–879A.
(^3) Isidore of Seville 2005, 246 [XI.iv.3].