Looking back we can see how indirectly we know the environment in
which nevertheless we live. We can see that the news of it comes to us
now fast, now slowly; but that whatever we believe to be a true
picture, we treat as if it were the environment itself. It is harder
to remember that about the beliefs upon which we are now acting, but
in respect to other peoples and other ages we flatter ourselves that
it is easy to see when they were in deadly earnest about ludicrous
pictures of the world. We insist, because of our superior hindsight,
that the world as they needed to know it, and the world as they did
know it, were often two quite contradictory things. We can see, too,
that while they governed and fought, traded and reformed in the world
as they imagined it to be, they produced results, or failed to produce
any, in the world as it was. They started for the Indies and found
America. They diagnosed evil and hanged old women. They thought they
could grow rich by always selling and never buying. A caliph, obeying
what he conceived to be the Will of Allah, burned the library at
Alexandria.

Writing about the year 389, St. Ambrose stated the case for the
prisoner in Plato's cave who resolutely declines to turn his head. "To
discuss the nature and position of the earth does not help us in our
hope of the life to come. It is enough to know what Scripture states.
'That He hung up the earth upon nothing' (Job xxvi. 7). Why then argue
whether He hung it up in air or upon the water, and raise a
controversy as to how the thin air could sustain the earth; or why, if
upon the waters, the earth does not go crashing down to the bottom?...
Not because the earth is in the middle, as if suspended on even
balance, but because the majesty of God constrains it by the law of
His will, does it endure stable upon the unstable and the void."
[Footnote: Hexaemeron, i. cap 6, quoted in _The Mediæval Mind_,