1 The Lord has taught with very great fullness, that souls not only continue to exist, not by passing from body to body, but that they preserve the same form [in their separate state] as the body had to which they were adapted, and that they remember the deeds which they did in this state of existence, and from which they have now ceased—in that narrative which is recorded respecting the rich man and that Lazarus who found repose in the bosom of Abraham. In this account He states that Dives knew Lazarus after death, and Abraham in like manner, and that each one of these persons continued in his own proper position, and that [Dives] requested Lazarus to be sent to relieve him— [Lazarus], on whom he did not [formerly] bestow even the crumbs [which fell] from his table. [He tells us] also of the answer given by Abraham, who was acquainted not only with what respected himself, but Dives also, and who enjoined those who did not wish to come into that place of torment to believe Moses and the prophets, and to receive the preaching of Him who was to rise again from the dead. By these things, then, it is plainly declared that souls continue to exist that they do not pass from body to body, that they possess the form of a man, so that they may be recognised, and retain the memory of things in this world; moreover, that the gift of prophecy was possessed by Abraham, and that each class [of souls] receives a habitation such as it has deserved, even before the judgment.
2. But if any persons at this point maintain that those souls, which only began a little while ago to exist, cannot endure for any length of time; but that they must, on the one hand, either be unborn, in order that they may be immortal, or if they have had a beginning in the way of generation, that they should die with the body itself— let them learn that God alone, who is Lord of all, is without beginning and without end, being truly and for ever the same, and always remaining the same unchangeable Being. But all things which proceed from Him, whatsoever have been made, and are made, do indeed receive their own beginning of generation, and on this account are inferior to Him who formed them, inasmuch as they are not unbegotten. Nevertheless they endure, and extend their existence into a long series of ages in accordance with the will of God their Creator; so that He grants them that they should be thus formed at the beginning, and that they should so exist afterwards.
3. For as the heaven which is above us, the firmament, the sun, the moon, the rest of the stars, and all their grandeur, although they had no previous existence, were called into being, and continue throughout a long course of time according to the will of God, so also any one who thinks thus respecting souls and spirits, and, in fact, respecting all created things, will not by any means go far astray, inasmuch as all things that have been made had a beginning when they were formed, but endure as long as God wills that they should have an existence and continuance. The prophetic Spirit bears testimony to these opinions, when He declares, “For He spoke, and they were made; He commanded, and they were created: He has established them for ever, yea, forever and ever.” And again, He thus speaks respecting the salvation of man: “He asked life of You, and You gave him length of days for ever and ever;” indicating that it is the Father of all who imparts continuance for ever and ever on those who are saved. For life does not arise from us, nor from our own nature; but it is bestowed according to the grace of God. And therefore he who shall preserve the life bestowed upon him, and give thanks to Him who imparted it, shall receive also length of days for ever and ever. But he who shall reject it, and prove himself ungrateful to his Maker, inasmuch as he has been created, and has not recognised Him who bestowed [the gift upon him], deprives himself of [the privilege of] continuance for ever and ever. And, for this reason, the Lord declared to those who showed themselves ungrateful towards Him: “If you have not been faithful in that which is little, who will give you that which is great?” indicating that those who, in this brief temporal life, have shown themselves ungrateful to Him who bestowed it, shall justly not receive from Him length of days for ever and ever.
4. But as the animal body is certainly not itself the soul, yet has fellowship with the soul as long as God pleases; so the soul herself is not life, but partakes in that life bestowed upon her by God. Wherefore also the prophetic word declares of the first-formed man, “He became a living soul,” teaching us that by the participation of life the soul became alive; so that the soul, and the life which it possesses, must be understood as being separate existences. When God therefore bestows life and perpetual duration, it comes to pass that even souls which did not previously exist should henceforth endure [for ever], since God has both willed that they should exist, and should continue in existence. For the will of God ought to govern and rule in all things, while all other things give way to Him, are in subjection, and devoted to His service. Thus far, then, let me speak concerning the creation and the continued duration of the soul.
Source: Adversus haereses (New Advent)