I've posted on the interplay between those two concepts on a variety of occasions. Universalism is a well-meaning, good-hearted theological yearning. It rises from the faith of those who know that God is love, and from that love the idea that any might be eternally damnificated seems anathema.
The conceptual problem with hell, particularly coupled with divine omniscience and omnipotence, is clear. It seems to infer a God who's a monster, who fashions creatures for the sole purpose of adding crispy-bits to some giant cosmic deep fat fryer.
Christians who are attempting to be orthodox and universalist, though, have the immense struggle before them of 1) asserting that God loves all beings and 2) asserting that God is neither zealous or just.
Universalism, in its simplest form, seems to imply that there's no variance in the character of the divine relationship with us no matter what we do. God is Love, whether we are Pope Francis or Pol Pot, whether we love and cherish others or we beat and humiliate and torture them.
On the one hand, that's true. On the other, it doesn't adequately grasp the terrible justice of God's Love. Fully knowing and participating in the other, sharing in the truth of their lives completely? No hellfire could burn the unjust and the cruel as painfully.
And there's always the whole "salvation through Jesus Christ" thing, which for Christians is a nontrivial thing. Did Jesus matter? Why? And if Jesus does not matter, what is the impetus for following him, particularly if it changes nothing at all? I can be a saint or a selfish, smug, libertine bastard. The God of universalism does not care. There is only love, and it's all the same in the end.
Most significantly, for those of us in my denomination, there was traditionally the challenge that came when the right-wing noticed you'd gone all mushy and UU-ish in your faith. Charges of apostasy and heresy can fly, and have flown, as fulminating folks fret ferociously about the decline of the faith. That happens less so now, as there's been a right-wing exodus, but it's still there.
So straight up statements of universalism are...difficult.
This whole thing strikes me as funny, because...well...what I believe is so much more heretical than mere universalism.
One advantage of being a functional nobody, I suppose. I pastor a sweet, gracious, small church. I go to few meetings and have no public face other than this wee blog and my sparsely-selling books. Ah well. It keeps me from being yet another thing for John Piper to anguish about, I suppose.
That heresy...and it is heresy, in the truest sense of the world...revolves around my understanding of creation. Along with a growing number of scientists, I hold that creation is not one linear time and space, but an infinite multiverse.
In our multiversal creation, I believe that God not only can save anyone, God does, actually and materially.
Does the Creator of All Things know what it would be like if every being lived fully in accordance with the Divine Intent? Absolutely. To say God does not...that God cannot...is an offense to both Divine Sovereignty and God's imagination. God both knows that, and makes it real. Is there any meaningful difference between the knowledge of God and existence itself? No, or God's knowledge of the true good would be no more real than our human dreamings.
On the other hand, I know that this creation is not that perfect realm. I know it because I, myself, am not that good. I am not, in my full self, conformed to the best possible self I could be. Here, I'm not talking "best self" in the sense of the health and wealth hucksters, the Osteens and the Oprahs.
I'm talking about being the self that lives fully governed by the grace and compassion of Jesus of Nazareth.
Though that is my metric, my goal, and my purpose, I am not that person. I do not serve Jesus as I could. I make choices, struggle though I might, that take me away from being that person. I know, just as surely, that the church is not perfect. It is a corpus mixtum, threads of gold woven amongst the mess of human community. And God help us, one look at our mess of a world lets us know that it is far, far from the best possible reality.
At every moment, the possibility of being that person...or of being a redeemed people...exists. It is fully known, fully in God's presence, as real as I am as I write this. As, at the same time, is every possible way we might fall.
We are both saved and damned, with uncountable gradations and in a fractal infinity of iterations.
Universalism seems, well, too small. A quaint echo of the modern era, with its linear thinking and pre-established narrative.
The divine work is so much more than that.