4.
For we must take into account a phenomenon
often noted but never
explained: a sort of respiratory
rhythm in history, a psychological
balancing-wheel,
which creates kinships between one epoch and another,
separated by long intervals. According to 
E 
. d'Ors, a
classical era is
followed by a baroque era; in the cos-
mological imagination, a Parmenidean era is followed
by a
Heraclitean era. Intellectual rigor gives way to
an insurgence of
instinctive forces. There are whole-
some but
harsh disciplines (like Aristotelianism) which
are obstacles to such
revolts; then the day comes when
the barrier collapses. It was maintained
by timidity;
all of a sudden fear has disappeared, and the attractive
but disturbing doctrines regain their sway and release
an enormous internal
flood of images. These move-
ments are
difficult to explain, for social causation does
not help; neither do the
discoveries of new worlds or
of Greek manuscripts. But they must be
recognized
and taken into account.
We can indicate summarily some of these intellectual
rhythms. The triumph of
scholastic philosophy in the
thirteenth century inaugurated a Parmenidean
era in
cosmology. The Florentine Renaissance in the fifteenth
century
inaugurated a Heraclitean era which was
joined with the Neo-Platonism of
the first centuries;
the new spirit kept growing stronger making
possible
the infinite worlds of Bruno's cosmology and the dis-
coveries of Kepler and Galileo. The
seventeenth cen-
tury saw the opposition between
classical French
thought dominated by Descartes and British thought
dominated by the appeal of the infinite. Newton rec-
onciled temporarily the two tendencies by satisfying
both. But
the eighteenth century, in the main super-
ficially classical, marked a return to the Renaissance,
to a
taste for magic and the occult; Leibniz' philoso-
phy, whose influence was enormous, strengthened the
renewed need
for Plenitude, infinite Diversity, and
creative profusion. And the
nineteenth century, despite
the steady progress of pure science, was to
see, about
every twenty years, a return of this Leibnizian intel-
lectual outlook accompanied by the
flourishing growth
of the same dreams; for example, the plurality of in-
habited worlds offered itself to a plurality
of existing
beings in a continuous ascent towards an unattainable
Perfection.
The relations between imagination and astronomy
will be studied here from
two points of view: how
imagination favors or obstructs the efforts of true
sci-
entists; and how, among
nonspecialists, it takes posses-
sion of
discoveries, distorts them, and supplements
them in its own way. We shall give only some attention
to the
second point of view.
