Species

Species and the Birth of Modern Science 99

... but not content with this, they are unable to banish the thought that behind these

varieties there is but one genus, nay, that there might even be a common principle for

the earth and the salts.^230

Parsimony is due to the need for the understanding to reduce multiplicities into

unities. This is exactly what the scholastics would have sought. But he then continues:

The logical principle of genera, which postulates identity, is balanced by another prin-

ciple, namely that of species, which calls for manifoldness and diversity in things, not-

withstanding their agreement as coming under the same genus, and which prescribes

to the understanding that it attend to the diversity no less than to the identity.^231

Observation of things must discriminate, he says, as much as the “faculty of wit”

must nd the appropriate universal. This differs from the scholastic account, and in

some ways is more like Cusa’s contraction in species. Here, observation allows us to

group diversity of species under general predicates, he says, for if

... there were no lower concepts, there could not be higher concepts. Now the under-

standing can have knowledge only through concepts, and therefore, however far it car-

ries the process of division, never through mere intuition, but always again through

lower concepts. The knowledge of appearances in their complete determination, which

is possible only through the understanding, demands an endless progress in the speci-

cation of our concepts, and an advance to yet other remaining differences, from which

we have made an abstraction in the concept of the species, and still more so in that of

the genus.^232

Kant has it both ways after all: we abstract our more general categories from

empirical observation, and understanding divides categories logically so that reason

can deal with them.^233 But species border each other; there is a logical continuum

admitting of no transition from one to another per saltum, but only through all the

smaller degrees of difference between them.^234

This he calls the logical law of the continuum specierum, a version of the tran-
scendental law of lex continui in natura, which is Leibniz’s law of continuity. While
this applies to the realm of possible concepts, though, Kant rejects it in nature:

For in the rst place, the species in nature are actually divided, and must therefore con-

stitute a quantum discretum. ... And further, in the second place, we could not make

any determinate empirical use of this law, since it instructs us only in quite general

terms that we are to seek for grades of afnity, and yields no criterion whatsoever as to

how far, and in what manner, we are to prosecute the search for them.^235

(^230) Op. cit. B680f.
(^231) Op. cit. B682.
(^232) Op. cit. B684.
(^233) Op. cit. B695f.
(^234) Op. cit. B687.
(^235) Op. cit. B689.