Species

The Medieval Bridge 39

It was the habit of Aristotle and the philosophers to classify objects into positive and

negative groups and to begin their discussions with the positive. Since it is our purpose

to give special attention to raptorials, we shall rst consider the nonrapacious (or nega-

tive) varieties; afterward we shall consider at length raptorial birds.

Since this is in fact opposed to Aristotle’s method of classication, inasmuch as it

allows for privative groups, this paragraph is perhaps more based upon the medieval

understanding of logic from Boëthius than directly upon Aristotle’s own works, and

may be considered spurious. Possibly the distinction had not become popularly rec-

ognized (among educated non-scholars).

Later in that chapter he promises a treatise on the “genera into which raptores

[sic] are divided, and the species in each genus,” which was never produced. But he

does note that “the same genera and species are given different names by diverse

authors. Sometimes the same bird may have a variety of synonyms; and the same

name applied to diverse birds so dissimilar that one cannot establish the true identity

of a species simply by its name.” He therefore notes, in complete anticipation of later

taxonomic problems, that

a description of the essential characters of individual birds [i.e., of a species] is more

difcult to furnish, whether they resemble or are different from another in the shape of

the limbs, the movements they make, the way they feed, the care of their young, their

mode of ight, and their style of defense. Let it, however, be remembered that, in gen-

eral, their bodily conditions and their other peculiarities are due to denite causes.^33

This is an amazing statement for the thirteenth century. Not only does he allow

that species must vary in their traits, but that they are caused to vary. He goes on to

say that different localities will have different genera and species, or a location may

be the only habitat of species not found elsewhere. He even says that a genus might

be found in many localities but with “a different color, or varying in other respects.”

It is not entirely exaggeration when Stresemann says of him that no direct observer

among ornithologists until Konrad Lorenz in 1933 surpassed him in “variety of

experience and acuteness of interpretation.”^34

The way he refers to species is so clearly in line with modern usage that he might

be considered to have been the rst to give a truly biological account. This is in part

due to the fact that he had practical concerns—breeding birds. When discussing bird

reproduction, he notes

Nature in her endeavor to preserve the race by the continuous multiplication of indi-

viduals has decreed that every species of the animal kingdom, whether it progresses

by the use of wings or walks on the ground, shall take pleasure in sexual union so that

they may seek instinctively to bring about such enjoyment.^35

(^33) Wood and Fyfe 1943, 10.
(^34) Stresemann 1975, 11.
(^35) Chapter 13-E [Wood and Fyfe 1943, 49].