and beeches in the days of Socrates
and Cicero were not slightly better trees than the oaks and beeches of
to-day. Fontenelle saw the weakness of this reasoning. He saw that it
was necessary to prove that the trees, no less than human brains, have
not degenerated. But his a priori proof is simply a statement of the
Cartesian principle of the stability of natural processes, which he put
in a thoroughly unscientific form. The stability of the laws of nature
is a necessary hypothesis, without which science would be impossible.
But here it was put to an illegitimate use. For it means that, given
precisely the same conditions, the same physical phenomena will occur.
Fontenelle therefore was bound to show that conditions had not altered
in such a way as to cause changes in the quality of nature's organic
productions. He did not do this. He did not take into consideration, for
instance, that climatic conditions may vary from age to age as well as
from country to country.

4.

Having established the natural equality of the Ancients and Moderns,
Fontenelle inferred that whatever differences exist are due to external
conditions--(1) time; (2) political institutions and the estate of
affairs in general.

The ancients were prior in time to us, therefore they were the authors
of the first inventions. For that, they cannot be regarded as our
superiors. If we had been in their place we should have been the
inventors, like them; if they were in ours, they would add to those
inventions, like us. There is no great mystery in that. We must impute
equal merit to the early thinkers who showed the way and to the later
thinkers who pursued it. If the ancient attempts to explain the universe
have been recently replaced by the discovery of a simple system (the
Cartesian), we must consider that the truth could only be reached by
the elimination of false routes, and in this way the numbers of the
Pythagoreans, the ideas of Plato, the qualities of Aristotle, all served
indirectly to advance knowledge. "We are under an obligation to the
ancients for having exhausted almost all the false theories that could
be formed." Enlightened both by their true views and by their errors, it
is not surprising that we should surpass them.

But all this applies only to scientific studies, like mathematics,
physics, and medicine, which depend partly on correct reasoning and
partly on experience. Methods of reasoning improve slowly, and the most
important advan