Meister Eckhart once preached, "If thou wilt be without sin, prate not about God." Keeping that in mind...
Someone asked me recently for my thoughts on why God would create someone whom He knows will go to an eternal punishment.
My first thought is that the mystery of why God would create someone He knows will go to an eternal punishment is bound up in the mystery of why God would create anyone at all. You can't truly solve the former without solving the latter, and mysteries aren't things you truly solve.
With that note of caution sounded, the short answer to the question has to be that God wants to create someone He knows will go to an eternal punishment. That sounds awful, doesn't it? Why would God want to do that?
The idea that works best for me, today, is that God wants to create someone who will be damned because God wants that person to share in the divine life of the Trinity
forever, and the person can't share in that life unless he's created.
The key here is that God wants me to share eternal life with Him. He wants me-as-He-created-me. He doesn't want me-as-I-would-be-if-I-couldn't-be-damned. Or rather, me-as-I-would-be-if-I-couldn't-be-damned is not me-as-God-created-me. Those terms describe two different people -- people belonging to two different species, in fact.
Now, I don't know what's so hot about me-as-God-created-me that He would want to spend eternity with me. I have the impression, though, that He wants to spend eternity with creatures who freely choose to spend eternity with Him, which clearly means He has to create creatures who can freely choose to spend eternity with Him. And if they can do that, then they have to be able to freely choose not to spend eternity with Him.
Could God create only those people whom He knows will freely choose to spend eternity with Him? Maybe, but by not creating those who would have freely chosen
otherwise, He would be failing to love them, and that's impossible for God.
I'd be surprised if any of this actually helps anyone troubled by the question. I wouldn't be surprised if it causes people to be troubled by the question who didn't used to be. But it's the best response I have right now in the face of this deep mystery of love, freedom, and justice.