analogy:

a similarity between like features of two things, on which a comparison may be based.

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"Classical" world (and the West):

Spengler posits that the West is currently where Classical culture was in the Hellenistic age, during the transition from the Hellenistic age to Rome.  To further this argument he then provide 9 analogies or counter-parts, which he uses to argue for correspondence between Classical and Western history.  It is this methodology, by analogy, that characterizes many of his judgments.

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