The Chaldaean Oracles belong to the “Underworld of Platonism”. They reflect some important philosophical elements in Imperial-age Platonism, while setting them within a framework dominated by a religious and ritual approach, and marked by soteriological concerns. The universe of the CO presents a tripartite structure (with three kosmoi: the “empyrean” and intelligible cosmos, the “ethereal” cosmos of the stars, and the “material” one in which the sublunary world is located). The soul, which has a divine and intelligible origin, has descended into the earthly realm through the sphere of the stars. Many oracles urge the soul to flee the corporeal and material dimension, and to return to the divine sphere from which it has originated. From a metaphysical perspective, the Chaldaean system presents itself as an ontogonic monism, whereby a Supreme Being generates the whole of reality through a series of intermediate realities. Moreover, the CO share Numenius’ and Alcinous’ distinction between a supreme intellect and a cosmic one, entrusted with ordering the sensible world.