V. PROGRESSIONISM
A new version of evolutionism began to make its
appearance in the latter half of the eighteenth century.
This was the metaphysical doctrine of universal
progress, or progressionism. It resulted in large measure
from what Lovejoy has called “the temporalizing of
the Chain of Being” (Lovejoy [1936], Ch. ix). According
to a conception derived from Platonic and Neo-
Platonic philosophy, the universe is a completed hier-
archy or “chain” which extends from entities having
a minimal degree of being, through all possible forms,
to the ens perfectissimum. This conception underwent
a modification which made its first appearance in
Leibniz. The stages of the hierarchy were regarded as
coming into existence successively in time, starting
with the lowest; and the movement towards the higher
stages was regarded as unfinished and as continually
producing new and diverse forms. Thus the conception
of a static chain of being became that of a unilinear
process of ascent to greater perfection.
The details of progressionism were worked out in
many different ways. Thus, Jean Jacques Rousseau and
Lord James Barrett Monboddo limited the scope of the
doctrine to man's advance from a primitive to a civi
lized state. This formulation not only gave a new
impetus to the idea of social or cultural evolution, but
also contained the radical suggestion that man was
derived from apelike ancestors, such as the orangutans,
with whom he forms a single species. Yet neither
Rousseau nor Monboddo accepted transformism. The
development of man did not imply for them that any
species-barriers were passed in the rise from animality
to humanity.
Another formulation of progressionism centered
around the idea that a single, basic prototype had been
more and more fully actualized in the history of nature.
This idea was clearly stated by Robinet in his De la
nature (1761). “A stone, an oak, a horse, a monkey,
a man are graduated variations of the prototype which
began to form itself with the least possible number of
elements” in the remote past. The succession of varia-
tions has been “so many steps towards the being of
humanity.” Herder advanced a similar idea in his Ideen
zu einer Philosophie der Geschichte der Menschheit
(1784-91), although he gave more emphasis to the
standard form (Hauptform) which is diversified in the
animal kingdom and most perfectly exemplified in man.
These ideas represented a response of speculative
minds to the facts of vertebrate homologies discussed
by Buffon and Louis Jean Marie Daubenton. The con-
clusions of the new science of comparative anatomy
were translated into terms of a teleological scheme
according to which the production of man has been
aimed at from the start and has been achieved by a
gradual perfecting of one prototype that appears in
all living things.
Various metaphysical explanations of this perfecting
process were offered. Robinet posited a “creative
power” (puissance active) that increased in strength
through the ages and produced higher forms despite
the resistance of brute matter. Herder attributed the
perfecting to vaguely conceived “purposes” of Nature
which have been realized in a necessary historical
order. Exponents of Naturphilosophie, such F. W. J.
Schelling and L. O. Oken, for whom progressionism
had a strong appeal, had recourse to the belief that
a divine power is expressed in the succession of forms.
God is gradually revealing his nature in the history
of the cosmos, and man is the being in whom at last
divinity is fully manifested. These teleological expla-
nation-schemes, especially the ones advocated by the
German Naturphilosophen, embodied the notion of
successive creation or spontaneous generation of kinds,
and hence were not transformist. They were rather
explanations which were strongly tinged with Neo-
Platonism, and formulated by minds of a romantic
rather than a scientific cast. Yet the biological sciences
in the early nineteenth century were much influenced
by such romantic speculations (cf. Nordenskiöld [1929],
Ch. xiv).
The linking of progressionism and transformism was
mainly due to Erasmus Darwin and Lamarck. These
men accepted the idea of a broad historical advance
of living things from simple to complex. But they
rejected the idea of a successive creation of kinds in
favor of the view that later kinds had descended with
modifications from earlier ones. Both men held that
what had occurred at successive stages of this descent
is amenable to explanation in natural terms. Erasmus
Darwin's explanation was sketchy and quasi-poetic;
Lamarck's explanation was more detailed and quasi-
scientific. The general pattern was similar in the two
cases. It invoked the notion that living things, by virtue
of an internal vital power, respond to the changing
environment in such a way as to satisfy their wants
or needs. As a result of this process, somatic charac-
teristics are developed which meet those wants or
needs, and are passed on to successive generations of
offspring. Thus in the course of time the organisms
concerned undergo alterations of form and function.
The alterations, however, are not random, for they are
phases of the progressive advance of living things from
lower to higher types.
Although Erasmus Darwin and Lamarck helped to
pave the way for the work of Charles Darwin, their
evolutionism was very different from his. They were
eighteenth-century deists, for whom the history of the
cosmos is the actualizing of a divine plan established
at creation. Deism and evolutionism were readily
combined in the view that God had so designed the
universe that evolution is the means by which His plan
is executed without miraculous intervention. The his-
torical succession of forms obeys the laws ordained by
God in the beginning. A basic aim of Erasmus Darwin
in his Zoonomia (1794-96), of Lamarck in his Phi-
losophie zoologique (1809), and somewhat later, of
Robert Chambers in his popular Vestiges of the Natural
History of Creation (1844), was to advocate deistic
evolutionism. All these works did indeed invoke em-
pirical facts. But the facts were introduced not to
support specific biological hypotheses, as was the case
with Charles Darwin. They were introduced to support
a general philosophy of nature. Furthermore, little
reference was made to the problem of the origin of
species. Erasmus Darwin scarcely mentions species,
whereas Lamarck took the position that since only
individual organisms exist in nature, species are arbi-
trary groupings which men establish. Moreover, indi-
vidual organisms are parts of a continuous, changing
process, which is constantly creating life at the bottom
of the scale and raising it upwards to more perfect
forms of organization (cf. Gillispie, 1959).
In the early nineteenth century biological progres-
sionism came under attack. The anatomist and paleon-
tologist, Cuvier, denied that living things can be ar-
ranged in a unilinear sequence. He contended that
there are four fundamental groups of animals, so
different that they cannot be integrated into an
ascending taxonomic scheme or regarded as belonging
to one historical series in which a single basic prototype
was gradually perfected. The embryologist, Karl E. von
Baer, and the paleontologist, Louis Agassiz, supported
these contentions. Von Baer argued that the develop-
mental processes in the four groups bear no significant
embryological relationships to each other. Serious
doubt was thus cast not only on the idea that living
things had evolved in a unilinear way, but also on the
idea that they had evolved at all. For Cuvier, von Baer,
and Agassiz rejected the notion of the mutability of
species. They were anti-evolutionists as well as anti-
progressionists. This fact tended to obscure the logical
point that since biological evolutionism does not entail
progressionism, it is quite possible to subscribe to the
former without subscribing to the latter. Hence in
much nineteenth-century thought evolution was
mistakenly identified with progress, not only in biology
but also in other disciplines.
The work of Cuvier and von Baer helped to under-
mine the influence of the idea of a great chain or scale
of beings. As zoological evidence accumulated, it be-
came hard to accept the progressionists' view that
living things form a single, tidy, unilinear series.
Lamarck, who was widely familiar with the evidence,
admitted that such a series could only be formed by
abstracting characteristics common to animal groups.
By the time of Charles Darwin, another metaphor had
come to the fore, namely, that of “a great tree” whose
twigs, branches, boughs, etc., represent respectively
species, genera, families, etc., of living things, ramify-
ing in a complex, irregular way from a single trunk,
or from two main trunks at the base. This figure of
the tree of life became a new paradigm in evolutionary
biology, bringing with it a shift in thought which
allowed account to be taken of the facts pointed out
by Cuvier and von Baer without rejecting the trans-
mutation of species. The book that accomplished this
revolutionary shift in thought was Charles Darwin's
On the Origin of Species (1859).
