atmosphere, limited in its range so that it would be
impossible to breathe beyond a certain distance from the planet. He
knew nothing about the intense cold that would make life impossible
just a little way above the surface.

The world in which our forefathers lived until modern times was just
this magic, Jack-and-the-Beanstalk world, a world without any
impossibilities in it, without any improbabilities in it. All this
thought of the true and the untrue, the possible and the impossible,
the probable and the improbable, is the result of the fact that man has
grown up, has left his childhood behind him, has begun to think, has
begun to study, has begun to search for reality, to find out the nature
of the world in which he lives, the forces with which he must deal, to
understand the universe at least in some narrow range, measured by his
so-far experience.

The world, then, until modern times has believed too readily, has
accepted things too easily. Let us note, for example, what have been
called by way of pre-eminence the Ages of Faith, the Middle Ages, the
age, say, from the seventh or eighth century until the thirteenth or
fourteenth. What was characteristic of those ages? Were they grand,
noble? They were ages of ignorance, of superstition, of cruelty, of
immorality, of poverty, of tyranny, of degradation. Almost everything
existed that men would no longer bear to-day; and hardly any of the
grand things that characterize modern civilization had then been heard
of.

Where did this modern civilization of ours begin? Did it ever occur to
you that it began when men began to doubt? It began, we say, with the
Renaissance. What was the Renaissance? The Renaissance was the birth of
doubt, the birth of question, the demand on the part of men, who began
to wake up and think, for evidence. It was the beginning of the
scientific age, the birth of the scientific spirit which has renovated,
re- created, uplifted the world. Men began to think, to look about
them, and to prove all things. And instead of holding fast all things,
as they had been doing in the past, they began to hold fast only the
things which they found by experience, and after testing and trial, to
be good.

Here began, then, the civilization of the world; and all that is finest
and highest in industry, in education, in discovery, in the whole
external civilization of the world, came in with the coming of this
spirit that questions and that asks for proof.