Lactantius — Divine Institutes 7.8
There is therefore one highest good: immortality, for the taking of which we were both shaped from the beginning and born. Toward this we tend; this human nature looks to; toward this virtue carries us forward. Because we have grasped this good, it remains that we also speak about immortality itself. Plato's arguments, though they contribute much to the matter, still have too little firmness for proving and filling out the truth, because he had neither completed the account of the whole great mystery and gathered it into one nor grasped the highest good. For although he held the truth about the soul's immortality, he nevertheless did not discuss it as the highest good. We therefore can choose the truth by surer signs, who gather it not by doubtful suspicion but have learned it by divine tradition.
But Plato argued thus: that whatever senses through itself and is always moved is immortal; for what has no beginning of motion will also have no end, because it cannot be deserted by itself. That argument would also give eternity to mute animals, unless he had distinguished them by the addition of wisdom. He therefore added, to escape this sharing, that it cannot be that the human mind is not immortal, whose wondrous skill in finding and speed in thinking and ease in perceiving and learning and memory of past things and foresight of future things and knowledge of countless arts and matters — which the other living beings lack — appears divine and heavenly, because the origin of a mind that takes in so much and holds so much is found nowhere on earth, since it has nothing mixed from earthly concretion: but it is necessary that what is heavy and dissoluble in the human be resolved into earth, but what is thin and subtle is indeed indivisible and, freed from the dwelling of the body as from a prison, flies to heaven and to its own nature. These are roughly Plato's points gathered briefly, which are explained at length and richly in him. In the same opinion earlier was also Pythagoras and his teacher Pherecydes, whom Cicero reports was first to dispute about the eternity of souls. All of whom, though they excelled in eloquence, nevertheless in this contest at least had no less authority who argued against this opinion — first Dicaearchus, then Democritus, finally Epicurus — so much so that the very matter they fought over among themselves was called into doubt. Finally Tullius, having set out all their opinions on immortality and death, pronounced that he did not know what is true. Of these opinions, he says, which is true, some god will have seen. And again elsewhere: since each of those opinions had most learned authors and what is certain cannot be divined —. But we have no need of divination, to whom divinity itself has opened the truth.
Latin
Unum est igitur summum bonum inmortalitas, ad quam capiendam et formati a principio et nati sumus. ad hanc tendimus, hanc spectat humana natura, ad hanc nos prouehit uirtus: quod bonum quia deprehendimus, superest ut etiam de ipsa inmortalitate dicamus. Platonis argumenta quamuis ad rem multum conferant, tamen parum habent firmitatis ad probandam et inplendam ueritatem, quoniam nec rationem totius mysterii magni consummauerat in unumque collegerat nec summum bonum conprehenderat. nam licet uerum de animae inmortalitate sentiret, tamen non ita de illa tamquam de summo bono disserebat. nos igitur certioribus signis eligere possumus ueritatem, qui eam non ancipiti suspicione colligimus, sed diuina traditione cognouimus.
Plato autem sic argumentatus est: immortale esse quicquid per se ipsum et sentit et semper mouetur; quod enim principium motus non habet, nec finem habiturum, quia deseri a semet ipso non potest. quod argumentum etiam mutis animalibus aeternitatem daret, nisi adiectione sapientiae discreuisset. addidit ergo, ut effugeret hanc communitatem, fieri non posse quin sit inmortalis animus humanus, cuius miranda sollertia inueniendi et celeritas cogitandi et facilitas percipiendi atque discendi et memoria praeteritorum et prouidentia futurorum et artium rerumque innumerabilium scientia, qua ceterae careant animantes, diuina et caelestis appareat, quia et origo animi, qui tanta capiat, tanta contineat, nulla reperiatur in terra, siquidem ex concretione terrena nihil habeat admixtum: sed necesse esse in terram resolui quod est in homine ponderosum et dissolubile, quod autem tenue atque suptile, id uero esse indiuiduum ac domicilio corporis uelut carcere liberatum ad caelum et ad naturam suam peruolare. haec fere Platonis collecta breuiter, quae aput ipsum late copioseque explicantur. in eadem sententia fuit etiam Pythagoras antea eiusque praeceptor Pherecydes, quem Cicero tradidit primum de aeternitate animarum disputauisse. qui omnes licet eloquentia excellerent, tamen in hac dumtaxat contentione non minus auctoritatis habuerunt qui contra hanc sententiam disserebant, Dicaearchus primo, deinde Democritus, postremo Epicurus, adeo ut res ipsa de qua inter se pugnabant in dubium uocaretur. denique Tullius expositis horum omnium de inmortalitate ac morte sententiis nescire se quid sit uerum pronuntiauit. harum inquit sententiarum quae uera sit, deus aliqui uiderit. et rursus alibi quoniam utraque inquit earum sententiarum doctissimos habuit auctores nec quid certi sit diuinari potest —. uerum nobis diuinatione opus non est, quibus ueritatem diuinitas ipsa patefecit.