I think it'd be interesting to quote 2 Peter 3:9 to Calvinists
The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance.Simply taking this at what it plainly says, either the Calvinist understanding of The Sovereignty of God (that nothing happens He doesn't want to happen) is false, or Universalism is true (in which case other aspects of Calvinism are not true).
The Calvanist rationalization would probably be that that verse only means the Elect. But the context doesn't support that, this is eschatological, Peter is talking about ungodly unbelieving men all through this chapter.
But the Sovereignty of God is the Calvansit's strongest argument, after Biblically refuting all five points and Biblically proving Free Will in a debate with one, they just resort to shouting "how dare you insinuate God doesn't always gets His way". Before I was willing to consider Unversalisim a valid option I had a response to that Calvansit argument I had posted on this blog. But I didn't really cite Bible verses there, I just made a logical argument.
Does Universalism deny free will as much as Calvanism does? Depends how you look at it, many would say you can choose to reject God, it's just the consequence of that won't be endless punishment but rather separation from God (being not allowed into New Jerusalem). But some popular Universalist proof texts imply Jesus is drawing all men to Him, not just saving them from damnation., mainly John 12:32. But the stronger Universlaism proof text of that chapter is verse 47, 32 is easier for anti-Unisersalists to interpret differently without denying the plain reading.
The easiest Point of Calvanism to refute is Limited Atonement, they have no verses in support of it and we have countless verses showing Jesus shed Blood covered All Sin even of unbelievers. But the one thing Calvanists fall back on is the logical argument of, "how can that be the case if some (even most in the opinions of many Evangelicals) of those people are damned anyway?" The standard Arminian view is He paid the penalty for your Sin regardless, but if you don't accept Him it will have to be paid twice.
That's enough talking about Calvanism for now.
Back before I was willing to entertain Universalism there was nothing in my Theology that wasn't Conservative. It was only on political and social issues I'm a Liberal SJW Libertarian.
There are Universalists with a wide variety of views on other issues. Many Unversalists are full on Progressive Christians with theological views I can't accept. Some incorporating a Preterist argument for how to deal with the "gnashing of teeth" and Outer Darkness references in Matthew, making it about what happened to Israel in 70 AD. Long before I changed my perspective on Universalism I had already shown that the Outer Darkness is outside New Jerusalem in the New Heavens and New Earth.
I feel the Unviersalism I'm now pretty convinced of is dependent on a Futurist and Premillenial Eschatology. It's only taking Revelation 21-22 literally not figuratively that I feel it can be shown our Eternal Destiny isn't as simple as some people are damned and some are saved. As well as with Chapter 20 for showing that the contemporary after life (whatever it looks like) is NOT our Eternal Destiny.
Lots of Universalists also default to what I criticized on this blog often when I was just arguing for standard Eternal Security, appealing to the authority of the Early Church Fathers. While many would object to the claim that Universalism was believed by as many of them as proponents claim, certainly no Pre-Nicean father besides Tertulian contradicted it, and same with most Post-Nicean fathers till Augustine of Hippo.
None of those previous posts of mine insists they were wrong on everything, my ultimate point is they should be irrelevant one way or the other. Universalism supporting statements have been cited from both among the ones I've been the most sympathetic to (like Ireneaus and his pupil Hippolytus) and most suspicious of (like Clement of Alexandria and his pupil Origen).
It does concern me that the Universalists who most lean on the Early Church Fathers for Universalist arguments are also sometimes the most inclined to combine that with other views I don't like, like Denying a Bodily Resurrection, or denying Substitutionary Atonement. Like in this Book you can read online for free.
Now an argument from Early Church History used against Universalism tends to be attempts to associate it with the Gnostics. Certainly not all Gnositics believed it as Augustine being all for Eternal Damnation shows. Universlaism supporters have made a point out of that none of the many books written by Early Church Fathers against the Gnostics cite Universalism as a reason they are heretics.
What's most interesting to me isn't how many Early Fathers might have been Universalists, but who is the first to clearly not be.
Tertulian was also the first Church Father to write in Latin, which is why he is important to the argument that Eternal Damnation has it's origins in flawed translations of the Scriptures into Latin. But Jerome to whom the Vulgate is attributed (I suspect the Vulgate as it is now has been changed by Catholic editors a lot from what Jerome originally did) has also been cited as supporting Universalism (in quotes I talked about before). And Jerome has also been quoted as labeling Tertulian not a true Church Father.
Tertulian is also popular with the Jesus Words Only people I've talked about before because in Against Marcion he was incredibly hostile to Paul, denying his status as an Apostle.
What I find interesting in that correlation is that Paul uses Aionion in a way that clearly contradicts it meaning Eternal. In Romans 16:25, but the KJV doesn't render it Eternal here like it does other times. "which was kept secret since the world began" there is no Greek word for began here, only Aionon's root Aion being sometimes translated "world" supports using that word here. He's saying it was kept secret Aionios, but in verse 26 it is clear this secret is made known now.
Paul also wrote many of the strongest Universlaist proof texts. Most listed here are from Paul. And I would add to those another from Romans 11 "All Israel shall be Saved" a verse loved by Dispensationalists. But taken fully literally it means every Israelite, even Ciaphas and Ananias and Judas Iscariot and Dathan and Korah. Nothing there supports saying only all Israel alive at that time, I believe this eschatological Salvation of Israel is tied to the resurrection of the dead in Ezekiel 37.
Universlaism can be argued for Independent of Paul, but so can Faith Alone and Eternal Security yet that doesn't stop the Jesus Words Only people from thinking rejecting Paul is enough to destroy those doctrines.
Tertulian of course also held views I agree with. He alone among the Early Church Fathers supported the half brothers of Jesus being born of Mary. And he did seem to believe in Eternal Security for those who Believed in Jesus in this life. He said that only the Marytrs go directly to God's presence when they die (where they're seen in Fifth Seal n Revelation 6) the rest of the believers go to Hades/Sheol like the unbelievers but a different compartment, Abraham's Bosom. A subject which could be worthy of it's own post.
I just want to say one more thing on the Aionion debate. When Josephus described the Pharrisees as believing in eternal punishment he used the terms eirgmos aidios (eternal imprisonment) and timorion adialeipton (endless torment) not aionion kolasin (age-long chastisement) which Jesus used.
You know the concept that forgiveness is for your own sake not the person you're forgiving? Well The Bible applies that to God himself. Isaiah 43:25.
I, even I, am he that blotteth out thy transgressions for mine own sake, and will not remember thy sins.When you understand that concept, Universalisim makes even more sense, it shows He will not be forgiving only those who ask forgiveness.