It must be remembered 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.