6 In speaking thus does he not most clearly follow the error of the heathen and foist upon the simple faith of Christians the ravings of philosophy? In the same book he writes: “it remains that God is invisible. But if He is by nature invisible, He must be so even to the Saviour.” And lower down: “no soul which has descended into a human body has borne upon it so true an impress of its previous character as Christ's soul of which He says: 'no man takes it from me, but I lay it down of myself.'” And in another place: “we must carefully consider whether souls, when they have won salvation and have attained to the blessed life, may not cease to be souls.
For as the Lord and Saviour came to seek and to save that which was lost that it might cease to be lost; so the lost soul which the Lord came to save, when saved, will cease to be a soul. We must ask ourselves whether, as the lost was not lost once and again will not be, the soul likewise may have been and again may be not a soul.” And after a good many remarks upon the soul he brings in the following, “νοῦς or” intelligence by falling becomes a soul; and by acquiring virtue this will become intelligence again.
This at least is a fair inference from the case of Esau who for his old sins is condemned to lead a lower life. And concerning the heavenly bodies we must make a similar acknowledgment. The soul of the sun— or whatever else you like to call it— does not date its existence from the creation of the world; it already existed before it entered its shining and glowing body. So also with the moon and stars. From antecedent causes they have been made subject to vanity not willingly but for future reward, and are forced to do not their own will but the creator's who has assigned to them their several spheres.
Source: Letters (New Advent)