Insights: Karl Barth's Reflections on the Life of Faith is a short book containing one-page insights on different topics selected from Karl Barth's writings by his assistant Eberhard Busch. One of the last insights in the book is called "Nothing Will Be Lost" wherein Barth discusses the final Judgment. Barth believed that there will be a future and final Judgment for the whole world, and this will happen suddenly and unexpectedly, and will be the culmination of world history. In this insight, Barth says he is most interested in his own experience of that final Judgment, not with the condemnation of others. Barth believed that we do not now see the world truly as it is, but at the final Judgment God will reveal world history to us and allow us to the world as God sees it. "For now we see in a mirror, dimly, but then we will see face to face. Now I know only in part; then I will know fully, even as I have been fully known" (1 Cor 13:12).
So then the final Judgment will allow all people to have a paradigm shift that was not possible before it, and this will cause all people understand God's providence in the world that was not previously accessible. At this point, Barth's hope for universalism emerges when he says that all people—include atheists—will see God's grace and mercy at work in the world: "As I live, says the Lord, every knee shall bow to me, and every tongue shall give praise to God" (Romans 14:11; cf. Philippians 2:10). Barth continues to explain that all people will likewise experience Eternal Punishment, which Barth says is the shame we will all have for not seeing the "light of the abundant wealth of God's grace". Barth ends with the hope for Universalism again, when he says that the final Judgment will reveal all the lost wonders of the world, including the most remote and hidden creatures in the natural world that was previously unknown. The result will be that nothing will be lost, and all of creation will be saved.
The final Judgment will be grand finale of the world, when everything is revealed to all. It's important to note that Barth did not believe that time would continue onward after the final Judgment, but the final Judgment would be the very last day of world history, and not the beginning of an afterlife.
NOTHING WILL BE LOST
For all of us must appear before the judgement seat of Christ - 2 Cor 5:10
I am much less interested in the punishment of this "outsider" than in the punishment that waits for me. And it consists certainly in the contrast that will become evident: on the one hand, the reality of salvation and of life, and, on the other, how little use we have made of them, and how shamefully small our gratitude has been. It is always healthiest for people to think first of all about themselves and from that standpoint to measure what it would mean if God's mercy is given to this whole ungrateful humanity and Christendom: the great nevertheless of God! For that will be judgment: the nevertheless of our gracious God. There we will be with our ocean of ingratitude, and God will say: I have loved you! And then we will be all ashamed. That will then really be eternal punishment, that we must be so ashamed, but it will be shame in the light of the abundant wealth of God's grace. That means that only then will our eyes—and those of atheists and everyone—be opened as to how much reason we have to be thankful. To see the mercy of God from eternity to eternity is more than we can take it in. I have not yet looked behind the curtain, but I can conceive of it in no other way than that everything and everyone that has ever been—including even theological history, which will perhaps be one of the darkest corners to be illuminated, and including the whole of natural history with all these sunken forests and all these little animals that once lived—all of that will be there. Nothing will be lost: nothing at all.
Karl Barth, Insights: Karl Barth's Reflections on the Life of Faith, p. 118 [Based on Eberhard Busch, Humane Theologie: Texte und Erläuterungen zur Theologie des alten Karl Barth (Zurich: EVZ Verlag, 1967), 31-33.]
Related: Atheism, eternal punishment, FInal Judgment, Insights, Insights: Karl Barth's Reflections on the Life of Faith, Karl Barth