are, we owe this knowledge to those who
before us traveled the uncharted seas. If we have inherited a great
commerce and dominion of science, it is because their argosies had
been on the ocean and their camels on the desert. _Discipulus est
prioris posterior dies;_ man cannot know all at once; knowledge must
be built up by laborious generations. In all times, as in our own,
the advance of knowledge is very largely by elimination and
negation; we ascertain what is not true, and we weed it out. To
perceive and respect the limits of the knowable, we must have sought
to transgress them. We can build our bridge over the chasm of
ignorance with stored material in which the thirteenth century was
poor indeed; we can fix our bearings where then was no foundation;
yet man may be well engaged when he knows not the ends of his work;
and the schoolmen in digging for treasure cultivated the field of
knowledge, even for Galileo and Harvey, for Newton and Darwin. Their
many errors came not of indolence, for they were passionate workers;
not of hatred of light, for they were eager for the light; not of
fickleness, for they wrought with unparalleled devotion; nor indeed
of ignorance of particular things, {307} for they knew many things.
They erred because they did not know, and they could not know the
conditions of the problems which, as they emerged from the cauldron
of war and from the wreck of letters and science, they were
nevertheless bound to attack, if civil societies worthy of the name
were to be constructed."

We are very prone to think that the interests of the men of the Middle
Ages were very different to our own, and that they had not the
slightest inkling of what were to be the interests of the future
centuries. Ordinarily students of science, for instance, would be sure
to think that electricity and magnetism, interest in which is supposed
to be a thing of comparatively recent years, or at most of the last
two centuries, would not be mentioned at all in the thirteenth
century. Such an idea is not only absolutely false to the history of
science as we know it, but is utterly unjust to the powers of
observation of men who have always noted, and almost necessarily tried
to investigate, the phenomena which are now grouped under these
sciences. Perhaps no better idea of the intense interest of this first
century of university life in natural phenomena can be obtained, than
will be g