Church Declarations on Death

Sixteenth Council of Carthage 418

(501) 222
1. This has been decided by all the bishops … gathered together in the holy Synod of Carthage:  Whoever says that Adam, the first man, was made mortal in the sense that he was to die a bodily death whether he sinned or not, which means that to quit the body would not be a punishment for sin but a necessity of nature, anathema sit.

Council of Orange 435-442

The Indiculus,

2nd Council of Orange, 529

1. If anyone says that through the offence of  Adam’s sin the whole man, body and soul, was not changed for the worse, but believes that only the body was subjected to corruption while the freedom of the soul remained unharmed, he is misled by the error of Pelagius and goes against Scripture which says: “the soul that sins shall die” (Ezek 18:20).

2. If anyone maintains that the fall harmed Adam alone and not his descendants, or declares that only bodily death which is the punishment of sin, but not sin itself which is the death of the soul was passed on to the whole human race by one man, he ascribes injustice to God and contradicts the words of the apostle: “Sin came into the world through one man and death through sin and so death spread to all people because all humans sinned” (Rom 5:12)

Gaudium et Spes (Church in the Modern World, Vatican II, 1965)
18. It is in the face of death that the riddle a human existence grows most acute. Not only is man tormented by pain and by the advancing deterioration of his body, but even more so by a dread of perpetual extinction. He rightly follows the intuition of his heart when he abhors and repudiates the utter ruin and total disappearance of his own person. He rebels against death because he bears in himself an eternal seed which cannot be reduced to sheer matter. All the endeavors of technology, though useful in the extreme, cannot calm his anxiety; for prolongation of biological life is unable to satisfy that desire for higher life which is inescapably lodged in his breast.

Although the mystery of death utterly beggars the imagination, the Church has been taught by divine revelation and firmly teaches that man has been created by God for a blissful purpose beyond the reach of earthly misery. In addition, that bodily death from which man would have been immune had he not sinned (14, Cf. Wis. 1:13; 2:23-24; Rom. 5:21; 6:23; Jas. 1:15.) will be vanquished, according to the Christian faith, when man who was ruined by his own doing is restored to wholeness by an almighty and merciful Saviour. For God has called man and still calls him so that with his entire being he might be joined to Him in an endless sharing of a divine life beyond all corruption. Christ won this victory when He rose to life, for by His death He freed man from death. Hence to every thoughtful man a solidly established faith provides the answer to his anxiety about what the future holds for him. At the same time faith gives him the power to be united in Christ with his loved ones who have already been snatched away by death; faith arouses the hope that they have found true life with God.

Wis. 1:13 because God did not make death, and he does not delight in the death of the living.
Wis. 2:23-24; for God created us for incorruption, and made us in the image of his own eternity,  24 but through the devil's envy death entered the world, and those who belong to his company experience it.
Rom. 5:21; that, just as sin exercised dominion in death, so grace might also exercise dominion through justification leading to eternal life through Jesus Christ our Lord.
Rom. 6:23; For the wages of sin is death, but the free gift of God is eternal life in Christ Jesus our Lord.
Jas. 1:15 then, when that desire has conceived, it gives birth to sin, and that sin, when it is fully grown, gives birth to death.

Note also the interesting review that J. RATZINGER offers on the reference to Wis 1:13 and to 2:23-24 in Gaudium et Spes, art. 18, n. 14 (H. VORGRIMLER, ed., Commentary on the Documents of Vatican II, vol. 5; "Pastoral Constitution on the Church in the Modern World", Part I, Chapter I, J. RATZINGER, trans. W.J. O'HARA, Freiburg: 1969).  After elucidating the ambiguity of death as a natural phenomenon and as an experience of dread, using the categories of existential philosophy, RATZINGER critiques the formulation adopted in the constitution as being somewhat unintelligible to contemporary thought.
"On the basis of this phenomenon of absurdity, shown above all in dread, as well as on that of the difference between authentic and inauthentic life, it would have been possible to make clearer the meaning of the statement which appears rather disconnected in the latter half of the article, to the effect that man would have been immune from bodily death if he had not sinned.  This thesis in its classical dogmatic form is scarcely intelligible to present-day thought, but could be made so by means of an existential analysis of the constitutive features of human life which established a distinction between death as a natural phenomenon and death as seen in the personal categories proper to human life (p. 141). H. VORGRIMLER, ed., Commentary on the Documents of Vatican II, vol. 5; "Pastoral Constitution on the Church in the Modern World", Part I, Chapter I, J. RATZINGER, trans. W.J. O'HARA, Freiburg: 1969).

The Universal Catholic Catechism

376 By the radiance of this grace all dimensions of man's life were confirmed. As long as he remained in the divine intimacy, man would not have to suffer or die.[252] The inner harmony of the human person, the harmony between man and woman,[253] and finally the harmony between the first couple and all creation, comprised the state called "original justice".

385 God is infinitely good and all his works are good. Yet no one can escape the experience of suffering or the evils in nature which seem to be linked to the limitations proper to creatures: and above all to the question of moral evil. Where does evil come from? "I sought whence evil comes and there was no solution", said St. Augustine,[257] and his own painful quest would only be resolved by his conversion to the living God. For "the mystery of lawlessness" is clarified only in the light of the "mystery of our religion".[258] The revelation of divine love in Christ manifested at the same time the extent of evil and the superabundance of grace.[259] We must therefore approach the question of the origin of evil by fixing the eyes of our faith on him who alone is its conqueror.[260]

418 As a result of original sin, human nature is weakened in its powers, subject to ignorance, suffering and the domination of death, and inclined to sin (this inclination is called "concupiscence").