In the Last Discourse, St. John records this prayer of Jesus:
Now glorify me, Father, with you, with the glory that I had with you before the world began. I revealed your name to those whom you gave me out of the world...
I pray for them. I do not pray for the world but for the ones you have given me, because they are yours, and everything of mine is yours and everything of yours is mine, and I have been glorified in them.
The words I've italicized are challenging. They challenge the universalistic spirit of our times -- which, I suspect, is largely a matter of evangelical sloth; it sure saves me a lot of trouble if everyone is saved.
At the same time, they pose a challenge of humility for those who want to profess an orthodox understanding of predestination. If I take it upon myself to determine who belongs to God and who belongs to the world, I run the risk of finding out too late that I am one who belongs to the world.
Let me add this suggestion: The world can be found within the heart of each person for whom Jesus prays,. It's there in the form of sin, attachment to sin, and even not-altogether-sinful attachment to anything that is not God. In praying for His disciples, Jesus does not pray for them as they currently are; rather, He prays for them as they belong to the Father -- which is to say, as they are perfect.
Today's sinner is the same person as the Last Day's resurrected saint. But all of today's sinner is not resurrected -- or, equivalently, the sin that makes the Last Day's saint less than he should be today is not included in his resurrection.
The prayer of Jesus is heard and answered; neither for His own sake, nor for His Father's -- nor, for that matter, for His disciples' sake -- would Jesus pray for that hard, unredeemable part of our hearts that belongs to, even constitutes a part of, the world.