gards 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 as a consequence of commerce and mutual
influence, peoples do not retain the original mental peculiarities due
to climate. This may not be true of the extreme climates in the torrid
and glacial zones, but in the temperate zone we may discount entirely
climatic influence. The climates of Greece and Italy and that of France
are too similar to cause any sensible difference between the Greeks or
Latins and the French.

Saint Sorlin and Perrault had argued directly from the permanence of
vigour in lions or trees to the permanence of vigour in man. If trees
are the same as ever, brains must also be the same. But what about the
minor premiss? Who knows that trees are precisely the same? It is an
indemonstrable assumption that oaks