practically won. The issue of the controversy must be decided not by
rhetoric but by physics. And Fontenelle offers what he regards as a
formal Cartesian proof of the permanence of natural forces.

If the Ancients had better intellects than ours, the brains of that
age must have been better arranged, formed of firmer or more
delicate fibres, fuller of "animal spirits." But if such a
difference existed, Nature must have been more vigorous; and in that
case the trees must have profited by that superior vigour and have
been larger and finer. The truth is that Nature has in her hands a
certain paste which is always the same, which she is ever turning
over and over again in a thousand ways, and of which she forms men,
animals, and plants. She has not formed Homer, Demosthenes, and
Plato of a finer or better kneaded clay than our poets, orators, and
philosophers. Do not object that minds are not material. They are
connected by a material bond with the brain, and it is the quality
of this material bond that determines intellectual differences.

But although natural processes do not change from age to age, they
differ in their effects in different climates. "It is certain that
as a result of the reciprocal dependence which exists between all
parts of the material world, differences of climate, which so
clearly affect the life of plants, must also produce some effect on
human brains." May it not be said then that, in consequence of
climatic conditions, ancient Greece and Rome produced men of mental
qualities different from those which could be produced in France?
Oranges grow easily in Italy; it is more difficult to cultivate them
in France. Fontenelle replies that art and cultivation exert a much
greater influence on human brains than on the soil; ideas can be
transported more easily from one country to another than plants; and