The Soul Immortal and Mortal

Etenim, fratres, anima immortalis perhibetur, et est immortalis secundum quemdam modum suum: quia est quaedam vita, quae potest praesentia sua carnem vivificare. Per animam quippe caro vivit. Haec vita mori non potest: et ideo anima immortalis est. Quare ergo dixi, Secundum suum modum? Audite quare. Quoniam est quaedam immortalitas vera, immortalitas quae est omnimodo incommutabilitas: de qua dicit Apostolus loquens de Deo, Qui solus habet immortalitatem, et lucem habitat inaccessibilem; quem nemo hominum vidit, sed nec videre potest: cui est honor et gloria in saecula saeculorum. Amen. Si ergo Deus solus habet immortalitatem, certe anima mortalis est. Ecce quare dixi immortalem esse animam secundum modum summ. Nam potest et mori. Intelligat caritas vestra, et nulla quaestio remanebit. Audeo dicere, anima potest mori, potest occidi. Certe immortalis est. Ecce audeo dicere, et immortalis est, et potest occidi: et ideo dixi quoniam est quaedam immortalitas, hoc est, omnimoda incommutabilitas, quam solus Deus habet, de quo dictum est, 'Qui solus habet immortalitatem.' Nam si anima non potest occidi, quomodo dixit ipse Dominus cum terreret nos, 'Eum timete, qui potestatem habet et corpus et animam occidere in gehenna?' Adhuc confirmavi, non solvi quaestionem. Probavi quia potest anima occidi. Contradici Evangelio non potest, nisi ab anima impia. Ecce mihi occurrit et hic, et venit in mentem quod dicam. Contradici non potest vitae, nisi ab anima mortua. Evangelium vita est, impietas et infidelitas mors animae est. Ecce potest mori et immortalis est. Quomodo moritur? Non ut non sit via, sed amittendo vitam. Etenim anima et vita est alciui rei, et habet etiam ipsa vitam suam. Ordinem attende creaturarum. Vita corporis anima est: vita animae Deus est. Sicut adest vita corpori, id est, anima, ne moriatur corpus: sic debet adesse vita animae, hoc est, Deus, ne moriatur anima. Sanctus Augustinus Hipponensis, Sermones ad Populum, Sermones De Scripturis Veteris et Novi Testamenti, Sermo LXV, Caput III-IV Source: Migne PL 38.428

Indeed, brothers, the soul is immortal, but it is immortal according to a certain manner, since it is a certain life which by its presence is able to give life to the flesh. Certainly the flesh lives by the soul. This life is not able to die and thus the soul is immortal. Why then did I say that it was immortal according to a certain manner? Hear why. Because there is a certain true immortality, an immortality which is unchangeable, according to which the Apostle says concerning God: 'He who alone has immortality and dwells in light inaccessible, whom no man has seen, nor is he able to see, to whom is honour and glory forever. Amen.' 1 If then God alone has immortality, certainly the soul is mortal. Thus see why I said that the soul was immortal in a certain manner. For it is able to die. Let your charity understand and no question shall remain. I venture to say, the soul can die, it can be killed. Yet it is immortal. Behold I dare to say it is immortal and that it can be killed, and therefore I have said that it has a certain immortality, that is, not at all that changeless one which God alone has, concerning which it has been said, 'He who alone has immortality.' For if the soul is not able to be killed, how then did the Lord say, when he admonished us, 'Fear him who has the power to destroy both the body and soul in hell.'? 2 Yet I have pressed not answered the question. I have asserted that the soul is able to be killed. The Gospel cannot not be contradicted unless by an impious soul. Behold, it occurs to me here, and it comes to my mind that I say: Life is not able to contradicted but by a dead soul. The Gospel is life, impiety and faithlessness is the death of the soul. Behold, the soul can die and it is immortal. How does it die? There is no way but by the loss of life. Indeed the soul is the life of something else, and it has its own life. Attend to the order of created things. The life of the body is the soul, the life of the soul is God. As life comes to the body, that is, by the soul, lest it perish, so God should be with the soul, lest the soul die. Saint Augustine of Hippo, Sermons on the Old and New Testament, from Sermon 65, Chap 3-4 1 Tim 6.16  2 Mt 10.28