, and any one
supposition is then just as good as another. If a person were to tell
me that men would ultimately have eyes and hands behind them as well as
before them, I should admit the usefulness of the addition, but should
give as a reason for my disbelief of it, that I saw no indications
whatever in the past from which I could infer the smallest probability
of such a change. If this be not allowed a valid objection, all
conjectures are alike, and all equally philosophical. I own it appears
to me that in the train of our present observations, there are no more
genuine indications that man will become immortal upon earth than that
he will have four eyes and four hands, or that trees will grow
horizontally instead of perpendicularly.

It will be said, perhaps, that many discoveries have already taken
place in the world that were totally unforeseen and unexpected. This I
grant to be true; but if a person had predicted these discoveries
without being guided by any analogies or indications from past facts,
he would deserve the name of seer or prophet, but not of philosopher.
The wonder that some of our modern discoveries would excite in the
savage inhabitants of Europe in the times of Theseus and Achilles,
proves but little. Persons almost entirely unacquainted with the powers
of a machine cannot be expected to guess at its effects. I am far from
saying, that we are at present by any means fully acquainted with the
powers of the human mind; but we certainly know more of this instrument
than was known four thousand years ago; and therefore, though not to be
called competent judges, we are certainly much better able than savages
to say what is, or is not, within its grasp. A watch would strike a
savage with as much surprise as a perpetual motion; yet one is to us a
most familiar piece of mechanism, and the other has constantly eluded
the efforts of the most acute intellects. In many instances we are now
able to perceive the causes, which prevent an unlimited improvement in
those inventions, which seemed to promise fairly for it at first. The
original improvers of telescopes would probably think, that as long as
the size of the specula and the length of the tubes could be increased,
the powers and advantages of the instrument would increase; but
experience has since taught us, that the smallness of the field, the
deficiency of light, and the circumstance of the atmosphere being
magnified, prevent the beneficial results that