[Footnote: It may be observed that Augustine (De Civ.

Dei, x.
14) compares the teaching (recta eruditio) of the people of God, in the gradual process of history, to the education of an individual.
Prudentius has a similar comparison for a different purpose (c.
Symmachum, ii.

315 sqq.): Tardis semper processibus aucta Crescit vita hominis et longo proficit usu.

Sic aevi mortalis habet se mobilis ordo, Sic variat natura vices, infantia repit, etc.
Floras (Epitome, ad init.) had already divided Roman history into four periods corresponding to infancy, adolescence, manhood, and old age.] They must seek for some new synthesis to replace it.
Another feature of the medieval theory, pertinent to our inquiry, was an idea which Christianity took over from Greek and Roman thinkers.

In the later period of Greek history, which began with the conquests of Alexander the Great, there had emerged the conception of the whole inhabited world as a unity and totality, the idea of the whole human race as one.