Species

120 Species

the same common terms may, in once case, be the species which is predicated of an

individual, and, in another case the individual of which a species is predicated: e.g. the

individual, Cæsar, belongs to the species man; but man, again, may be said to belong

to the species animal, &c., as we contemplate higher and more comprehensive terms.

A species, in short, when predicated of individuals, stands in the same relation to them

as the genus to the species; and when predicated of other lower species, it is then, in

respect of these, a genus, while it is a species in respect of a higher genus. Such a term

is called a subaltern species or genus; while the highest term of all, of which nothing

can be predicated, is the “summum genus;” the lowest of all, which can be predicated

of nothing, the “infimæ species.” The difference which, together with the genus, makes

up the species, is termed the “specific difference.”^19

By the third edition in 1859, the discussion had been rewritten by Richard Owen
to include the biological meaning of Cuvier, but this is as succinct a summary of
the traditional conception as one will find. Moreover, we should note that it follows
Aristotle in rejecting binary diairesis in favor of multiple species per genus, each of
which carries its own special differentiae (“specific differences”).
However, this view was not necessarily the view held by the leading philosophers
of the day. Mill and Whewell, particularly, had tried to accommodate the current
facts of natural history into the notion of a classification.^20 In his 1843 System of
Logic,^21 Mill showed considerable knowledge of botanical classification conventions
and awareness of variation within species. The discussion in Book I, chapter VII,
especially §3–4, is well informed as to scholastic and biological conventions, and
attempts a reconciliation of the two, without much success.
In Book I, chapter VIII, §4, he discusses the Cuvierian use of the term “Man” as
the scientific definition, “Man is a mammiferous animal having two hands.” This
defines Man by giving “the place which the species ought to occupy in that particular
[scientific] classification.” He notes the Aristotelian use of per genus et differentiam,
which he seems not to challenge. It is significant not for its resolution of the topic, but
because we see here a philosopher taking pains to use as many biological examples
as possible, although we also see elements and minerals appearing in the exemplia
gratia. He defines species, at least in the sense used by naturalists, as “not, of course,
the class in the sense of each individual of the class, but the individuals collectively,
considered as an aggregate whole ...”^22
Mill clearly is treating the species of the naturalist in a different sense, a “pop-
ular acceptation,” more general and less logical than the sense of the logician.
Nevertheless, both he and Whewell treated species as “natural classes,” as Whewell
stated it,^23 and in his response to Darwin’s Origin, Whewell was dismissive of the
idea that these classes could change. Hull quotes him as saying that, in botany, “... a
natural class is neither more nor less than the observed steady association of certain
properties, structures, and analogies, in several species and genera.”^24 A Humean

(^19) Brande and Cauvin 1853, 1137.
(^20) Hull 2003.
(^21) Mill 1930.
(^22) Mill, op. cit., Book I, chapter VII, §3.
(^23) Hull 2003, 184f.
(^24) Whewell 1831, 392, quoted in Hull 2003, 185.