On what basis did the council teach the concept of

I'm not good at dis stuff but hoped i helped fam :)

The idea of purgatory has roots that date back into antiquity. A sort of proto-purgatory called the celestial Hades appears in the writings of Plato and Heraclides Ponticus and in many other pagan writers. This concept is distinguished from the Hades of the underworld described in the works of Homer and Hesiod. In contrast, the celestial Hades was understood as an intermediary place where souls spent an undetermined time after death before either moving on to a higher level of existence or being reincarnated back on earth. Its exact location varied from author to author. Heraclides of Pontus thought it was in the Milky Way; the Academicians, the Stoics, Cicero, Virgil, Plutarch, the Hermetical writings situated it between the Moon and the Earth or around the Moon; while Numenius and the Latin Neoplatonists thought it was located between the sphere of the fixed stars and the Earth.[1