that no thinker had any means of knowing how near to the end of his
cycle the present hour might be. The most influential school of the
later Greek age, the Stoics, adopted the theory of cycles, and the
natural psychological effect of the theory is vividly reflected in
Marcus Aurelius, who frequently dwells on it in his Meditations.
"The rational soul," he says, "wanders round the whole world and
through the encompassing void, and gazes into infinite time, and
considers the periodic destructions and rebirths of the universe,
and reflects that our posterity will see nothing new, and that our
ancestors saw nothing greater than we have seen. A man of forty
years, possessing the most moderate intelligence, may be said to
have seen all that is past and all that is to come; so uniform is
the world." [Footnote: xi. I. The cyclical theory was curiously
revived in the nineteenth; century by Nietzsche, and it is
interesting to note his avowal that it took him a long time to
overcome the feeling of pessimism which the doctrine inspired.]

3.

And yet one Stoic philosopher saw clearly, and declared
emphatically, that increases in knowledge must be expected in the
future.

"There are many peoples to-day," Seneca wrote, "who are ignorant of
the cause of eclipses of the moon, and it has only recently been
demonstrated among ourselves. The day will come when time and human
diligence will clear up problems which are now obscure. We divide
the few years of our lives unequally between study and vice, and it
will therefore be the work of many generations to explain such
phenomena as comets. One day our posterity will marvel at our