In fact, as Silvestro Centofonti observes in a lecture on the characteristics of Greek literature, the grand figure of the AEschylean Prometheus is a poetic personification of Thought, and of its mysterious fates in the sphere of life as a whole.  First, in its eternal existence, as a primitive and organic force in the system of the world; then in the order of human things, fettered by the bonds of civilization, and subject to the necessities, lusts, and evils which constantly, arise from the union of soul and matter in unsatisfied mortals.  Thought is itself the source of tormenting cares in this earthly slavery, yet the sense of power makes it invincible, firm in its purpose to endure all sufferings, to be superior to all events; assured of future freedom, and always on the way to achieve it by reverting to the grandeur of its innate perfection; finally attaining to this happy state, by shaking off all the enslaving bonds and anxious cares of the kingdom of Zeus, and by obtaining a perfect life through the inspirations of wisdom, when the revolutions of the heavens should fill the earth with divine power, and restore the happiness of primeval times.  It is evident that in this stupendous tragedy AEschylus is leading us to the truth in a threefold sense:  aesthetic, morally political, and cosmic.  The supreme idea which sums up the whole value of the composition is perhaps that of an inevitable reciprocity of action and reaction between mind and effective force, between the primitive providence of nature and the subsequent laws of art, both in the civilization of mankind and in the order and life of the universe.

In this way the evolution of the special myth was transformed into poetry by the interweaving, collection, and fusion with other myths, and in the minds of a higher order it was resolved into an allegory or symbol of the forces of nature, into providential laws or a moral conception.

This law of progressive transformation also occurs in the successive modifications of the special meaning of words, so far as they indicate not only the thing itself, but the image which gave rise to the primitive roots.  For a long while, those who heard the word were not only conscious of the object which it represented, but of its image, which thus became a source of aesthetic enjoyment to them.  As time went on, this image was no longer reproduced, and the bare indication remained, until the word gradually lost all material representation, and became an algebraical sign, which merely recalled the object in question to the mind.

When, for example, we now use the word (coltello), coulter, the instrument indicated by this phonetic sign immediately recurs to the mind and nothing else; the intelligence would see no impropriety in the use of some other sign if it were generally intelligible.  But in the times of primitive speech, the inventors of this rude instrument were conscious of the material image which gave rise to it, and they were likewise conscious of all the cognate images which diverged from the same root, and in this way a brief but vivid drama was presented to the imagination.