Gaudium et Spes (Pastoral Constitution on the Church in the Modern World #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 (Wis 1:13; 2:23-24; Rom. 5:21; 6:23; James 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 God0