For instance, Aeschylus represents men as originally living at hazard in sunless caves, and raised from that condition by Prometheus, who taught them the arts of life.

In Euripides we find a similar recognition of the ascent of mankind to a civilised state, from primitive barbarism, some god or other playing the part of Prometheus.

In such passages as these we have, it may be said, the idea that man has progressed; and it may fairly be suggested that belief in a natural progress lay, for Aeschylus as well as for Euripides, behind the poetical fiction of supernatural intervention.

But these recognitions of a progress were not incompatible with the widely-spread belief in an initial degeneration of the human race; nor did it usually appear as a rival doctrine.

The old legend of a "golden age" of simplicity, from which man had fallen away, was generally accepted as truth; and leading thinkers combined it with the doctrine of a gradual sequence of social and material improvements [Footnote: In the masterly survey of early Greek history which Thucydides prefixed to his work, he traces the social progress of the Greeks in historical times, and finds the key to it in the increase of wealth.] during the subsequent period of decline.