to them to be no reason why the second chaos
should produce a world differing in the least respect from its
predecessor. The nth cycle would be indeed numerically distinct from
the first, but otherwise would be identical with it, and no man could
possibly discover the number of the cycle in which he was living. As no
end seems to have been assigned to the whole process, the course of
the world's history would contain an endless number of Trojan Wars, for
instance; an endless number of Platos would write an endless number
of Republics. Virgil uses this idea in his Fourth Eclogue, where he
meditates a return of the Golden Age:

Alter erit tum Tiphys, et altera quae uehat Argo
Delectos heroas; erunt etiam altera bella,
Atque iterum ad Troiam magnus mittetur Achilles.

The periodic theory might be held in forms in which this uncanny
doctrine of absolute identity was avoided; but at the best it meant an
endless monotonous iteration, which was singularly unlikely to stimulate
speculative interest in the future. 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. The day will come when time and human
diligence will clear