V
1. Crises of the Chain of Being: The Controversies
over the Notion of Species.
We have said that for Kant
the empirical use of ideas such as that of
continuity
and of the plenitude of forms (plenum
formarum) was
illegitimate and could only make for
contradictions and
controversies. His conclusion seems to be, and
indeed
is, in part, a commentary on the eighteenth-century
discussions
of continuity and plenitude in the biological
world.
At first the new instruments of scientific research do
not seem to
contradict the idea of a Scale of Creatures.
Indeed, the already widespread
use of the microscope
makes it possible to observe the world of the
infinitely
small; and in 1739 the discovery of Trembley's Hydra
is hailed as the discovery of the missing link between
the vegetable and animal worlds. Even the skeptical
“Pyrrhonism” of men of science, or their awareness
of
the limitations of experimental research, echoes
Leibniz' vision of a
universal “plenum” of which we
have a partial vision
only. No, it is rather the debate
over the notion of biological species
that challenges
the foundations of the Chain of Being, and in
particular
the principle of plenitude. In order to salvage this
principle it was necessary to attribute only a conven-
tional, not real, value to biological classifications:
sub-
division into species would in fact
have created in
nature a too nicely spaced series, letting precisely
those
imperceptible gradations escape which assure conti-
nuity and plenitude in the natural world.
The conventionality of species is affirmed in Buffon's
Discours sur la manière d'étudier et de
traiter l'Histoire
naturelle, which prefaces the first volume
of his Histoire
naturelle (1748). The methods
or “systems” of classifi-
cation are, to be sure, indispensable but artificial: as
against
the nuances of natural reality we have an arbi-
trarily articulated series. The error of all classification
rests on the inability to grasp the processes of nature,
which are always
realized by degrees, by imperceptible
nuances, thus escaping all division.
In short, only indi-
viduals exist in
reality; genera or species do not.
But Buffon wholly reversed his position in the course
of his research,
prompted by the now general recogni-
tion of
species as a genetic entity. In fact, in Volume
XIII of the same work
(1765) he affirms that the only
true beings in nature are species and not individuals.
Robinet, a firm advocate of the principle of pleni-
tude, was quite clear about the dangers inherent in
classifications: if we accept the separation of nature
into orders of this
kind, the Chain of Being is fatally
broken (
De la nature [1766], IV, 4-5).
Doubtless the
introduction of the idea of species as a genetic entity
contributed decisively to this crisis of the principle of
plenitude: since
two individuals are said to belong to
the same species if they are capable
of producing a
fertile offspring and of transmitting to it their own
hereditary characteristics, it is hard to imagine a
“full”
concatenation among the diverse species.
Actually, in
the second half of the eighteenth century, the notion
of
species is already established and operative in the
biological sciences.
The controversies—accelerated by
the always growing body of
empirical data, and par-
ticularly by the
data of the new science of paleon-
tology—had to do rather with the fixity or nonfixity
of
the species (taken now as established entities).
2. Crisis of the Chain of Being: Permanence and
Becoming in Nature.
In a world hierarchically ar-
ranged,
such as the one described by the great meta-
phor of a Chain or scale of beings, orders of creatures
had to be
considered fixed ab aeterno with their essen-
tial and thus unalterable
characteristics. In the third
decade of the century Réaumur wrote:
“The author
of nature wanted our earth to be populated with
a
prodigious number of species of animals, and has given
the earth
those species fit for it to possess....” And
again:
“One must start from the principle that the
species of insects
are—no less than those of animals—
invariable in
form” (Mémoires pour servir à
l'histoire
des insectes [1734-42], II, XL-XLI). The
physician
Antonio Vallisnieri (1661-1730) affirmed on anatomical
grounds that it was impossible for carnivorous habits
to be acquired: it is
no accident (only to regret it
afterward) that God, immutable and
omnipotent,
wanted herbivores to be so different from carnivores:
such
difference is but another proof of the unalterable
structure of that great
theater that is nature (Opere
fisico-mediche,
I, 315A). In general all adaptation phe-
nomena should be interpreted not as chance environ-
mental mutations but as providentially
preordained
laws (ibid., I, 137B). The fixity of species is also basic
to Linnaeus' Philosophia botanica (1751).
Faith in the permanence of nature (required by the
idea of the Chain of
Being) and the affirmation that
there is evolution in nature are clearly
contradictory:
mediating between them was a theory of the preexis-
tence of seeds—already
diffuse, beginning from the last
decades of the seventeenth
century—according to
which every living thing would exist
already formed
in all its parts in the seed, and all seeds, created
ab
initio, would simply be transmitted
and developed in
reproduction. With such a doctrine—adopted by
Fon-
tenelle and Leibniz among
others—one could conceive
of the history of nature as
explication and development
of all those possibilities already foreseen
ab aeterno as
essential parts of the
world's structure.
This transformist view afforded a reconciliation of
the idea of plenitude
with that of the perfectibility
of nature. And in this sense it is used,
for example,
by Robinet in his De la nature
(1761-68). In a word,
natural development, if seen as development of matu-
ration of preexisting seeds, adds nothing
really new to
creation but simply explicates its original
productivity.
Nature is continuously working itself out, and the
principle of plenitude is manifest in this temporal
process.
Yet just this transformism was bound to challenge,
explicitly or implicitly,
the notion of the fixity of spe-
cies and thus
precipitate a crisis in the hierarchical
image of the cosmos. But for that
matter numerous
and grave objections to the fixity of species were
being
raised by the necessity to give some plausible account
of
hereditary and adaptation phenomena, which re-
quire the intervention of variation and of environ-
mental determination. Remarkable how Maupertuis
in
his Essai de cosmologie (1750), precisely
by reflecting
upon adaptation phenomena and the natural selection
that
implies, was led to draw the same conclusion that
Kant was to draw some
years later, in regard to the
illegitimacy of the empirical use of the
principles of
plenitude, of homogeneity, and of continuity. Only
those
species that have certain adaptable relations
(rapports
de convenance) with nature may survive.
One would say that chance has produced an incalculable
multitude of
individuals; a small number happened to be
so constructed that the
parts of each creature were capable
of satisfying its needs; in
another number, infinitely larger,
there was neither adaptability
nor order; such species have
all perished... and the species that
we see today are the
tiniest part of all a blind destiny has
produced
(Essai, in
Oeuvres [1756], I, 11-12).
The continuity of the natural world can never be, then,
an empirical
statement: uniformity is (as we may say)
a spiritual exigency and has no
exact counterpart in
experience: Continuity pleases our mind, but does
it
please Nature? (Elle plaît à notre
esprit, mais plaît-elle
à la
Nature?—ibid., 51). The Chain of Being, thanks
to
which we may imagine a universe so constituted
that the beings that fill it
can only be the perfectly
juxtaposed parts of the whole, was perhaps broken
up
by some telluric cataclysm; however that may be, it
cannot now be
reconstructed on the basis of observa-
tion.
And it is for this reason that Maupertuis, in the
third part of his Essai, presents it as pure conjecture.
But even more telling than Maupertuis' Essai of the
new philosophy of nature is his Système de la
nature
(first ed., in Latin, 1751), wherein we witness the
disso-
lution of that bond between
natural forms and divine
creativity which had, from the Timaeus on, formed the
basis of the Chain of Being. To suppose
that all indi-
viduals were made by the divine will on one and the
same day
of creation, says Maupertuis, means to have
recourse to a miraculous rather
than physical explana-
tion. The laws at
work in nature, which are the only
object of science, operate to conserve
and also to
transform natural forms (French edition [1756], sec-
tions XI-XLIX).
The importance of this new conception of the rela-
tions between God and nature is certainly the decisive
element
in the dissolution of the Chain of Being. As
Roger has observed ([1963],
pp. 486-87), Maupertuis,
rejecting the preexistence of seeds, the notion of
God
as “maker,” and the fixity of forms, was led to
study
the life of natural forms in time, introducing duration
into
biological sciences as an essential element. This
general temporalization
of nature is a particular exam-
ple of what
Lovejoy has called ([1936], p. 242) the
“temporalizing” of the Chain of Being. According to
the traditional conception, the Scale of Creatures was
static and the
temporal process brought no enrichment.
In the new
“temporalized” version the plenum
for-
marum was conceived
instead “not as the inventory
but as the program of nature,
which is being carried
out gradually and exceedingly slowly in cosmic
history”
(ibid., p. 244).
