the investigating spirit; who thought for themselves and supplied
more or less rational explanations of observed phenomena. Could
we eliminate the work of some score or so of classical observers
and thinkers, the classical epoch would seem as much a dark age
as does the epoch that succeeded it.

But immediately we are met with the question: Why do no great
original investigators appear during all these later centuries?
We have already offered a part explanation in the fact that the
borders of civilization, where racial mingling naturally took
place, were peopled with semi-barbarians. But we must not forget
that in the centres of civilization all along there were many men
of powerful intellect. Indeed, it would violate the principle of
historical continuity to suppose that there was any sudden change
in the level of mentality of the Roman world at the close of the
classical period. We must assume, then, that the direction in
which the great minds turned was for some reason changed. Newton
is said to have alleged that he made his discoveries by
"intending" his mind in a certain direction continuously. It is
probable that the same explanation may be given of almost every
great scientific discovery. Anaxagoras could not have thought out
the theory of the moon's phases; Aristarchus could not have found
out the true mechanism of the solar system; Eratosthenes could
not have developed his plan for measuring the earth, had not each
of these investigators "intended" his mind persistently towards
the problems in question.

Nor can we doubt that men lived in every generation of the dark
age who were capable of creative thought in the field of science,
bad they chosen similarly to "intend" their minds in the right