When we believe in the God who loves us, who in Jesus became man for us, it is once a profession and a certainty of eternal life. And when we profess our belief in eternal life, it is a profession of faith in the living God. Because there is a God, we , whom he calls and sees, know that we shall not fall into a vacuum. For that reason, belief in eternal life becomes a very practical testimonial, not just a theory about something that will come to pass at an unspecified date in the future. That is why it was timely and proper for the Sacred Congregation for the Doctrine of the Faith to remind us, and all Christendom, once again of this profession of belief in the incarnate God who loved us even unto death. It was right and necessary to remind us that the measure of human life is what we call eternity, that heaven and hell, and Purgatory actually exists, and that human beings have souls that do not die with their bodies, but are bearers of the good news of God’s love and of the Resurrection. Such a testimonial is practical [i.e., not merely theoretical] because the whole measure of our lives is determined from this standpoint, because this means that we must live for what is lasting…Faith has as its goal- and that is the goal of all the love that exists between the Christ and us- that there be an interchange of life, that Christ’s life and ours be intertwined, that our lives be inscribed in his and his in ours, that that promise be fulfilled that Saint Teresa of Avila heard addressed to her by the Lord: “Do not be troubled; my concerns are yours and yours are mine!” We should live in such a way that this interchanged of lives becomes a reality, that his concerns truly do become ours and ours become his, and that Christ’s life and ours are inseparbale and therefore true.
From: Christlicher Glaube und Europa, pp. 139-40