The art of Alexandria is full of such devices; that of Pergamon is more vigorous and dramatic; but in both alike we find the influence of a learned study of mythology, full of quaint and far-fetched allusions and symbols.

The culmination of this learned mythology is to be seen in the great altar of Pergamon, on which the gods who are in combat with the giants include not only all figures, appropriate and inappropriate, from the Hellenic pantheon, but many other deities whose right of admission to that pantheon is more than doubtful.

The figures of the gods no longer correspond to the belief in any real divinities, but are either mere artistic types, repeated again and again in accordance with convention, or else they are regarded as symbols representing different aspects of divine power.
Symbolism of this kind is a common symptom of the decay of religious faith.

The more thoughtful or educated classes, who follow the speculations of philosophers as to the nature of the deity, find it possible to reconcile these speculations with the forms of popular religion by accepting the forms in a symbolic sense.

The common people, on the other hand, finding the old forms inadequate to satisfy their religious aspirations, import new and strange divinities, whose cult is often mixed with magic or mystic rites.