fairly doubted whether there is really the smallest perceptible
advance in the natural duration of human life since first we have
had any authentic history of man. The prejudices of all ages have
indeed been directly contrary to this supposition, and though I
would not lay much stress upon these prejudices, they will in
some measure tend to prove that there has been no marked advance
in an opposite direction.

It may perhaps be said that the world is yet so young, so
completely in its infancy, that it ought not to be expected that
any difference should appear so soon.

If this be the case, there is at once an end of all human
science. The whole train of reasonings from effects to causes
will be destroyed. We may shut our eyes to the book of nature, as
it will no longer be of any use to read it. The wildest and most
improbable conjectures may be advanced with as much certainty as
the most just and sublime theories, founded on careful and
reiterated experiments. We may return again to the old mode of
philosophising and make facts bend to systems, instead of
establishing systems upon facts. The grand and consistent theory
of Newton will be placed upon the same footing as the wild and
eccentric hypotheses of Descartes. In short, if the laws of
nature are thus fickle and inconstant, if it can be affirmed and
be believed that they will change, when for ages and ages they
have appeared immutable, the human mind will no longer have any
incitements to inquiry, but must remain fixed in inactive torpor,
or amuse itself only in bewildering dreams and extravagant
fancies.