In a comment on my treatment of universalism and Romans 10, Dave said the following:
Also, what about the spirits that Christ preached to who were disobedient in the time of Noah? They were to be judged according to the flesh, but live according to the spirit.(I Peter 3:18-20a and 4:6).
I don't think either I Peter passage teaches universalism. As I started to explain why in a comment, I decided I might as well make it a post, so here it is.
I Peter 3:18-20a:
For Christ also suffered once for sins, the righteous for the unrighteous, that he might bring us to God, being put to death in the flesh but made alive in the spirit, in which he went and proclaimed to the spirits in prison, because they formerly did not obey, when God's patience waited in the days of Noah, while the ark was being prepared, in which a few, that is, eight persons, were brought safely through water. (I Peter 3:18-20, ESV)
This passage is neither clear nor undisputed. The main reason it shouldn't ever be used to justify universalism is because it shouldn't be used to justify any doctrine. Too many possible interpretations have been defended by godly, careful thinkers who know their Bible very well and are out to seek what the epistle genuinely teaches. Martin Luther confessed that he had no idea what Peter meant in this passage, and it's always good for us to recognize our ignorance when it comes to hard passages. It's always good never to make a major doctrine out of something that isn't clearly taught in multiple places. If universalism is meant here, it's not clear, so this passage should not be a major component of any argument for universalism.
I'm not going to discuss a couple famous interpretations, but I'm mentioning them just to show how diverse people's conclusions have been on this passage. Augustine considered this passage to be about Christ's preaching through Noah to people before the flood. In our time, the likes of D.A. Carson and Wayne Grudem support such an interpretation. John Calvin took the reference to be about Christ's preaching to those who had believed while alive with what information they had but had died before Christ and who were now given the whole gospel. The fact that such major thinkers could support these interpretations means they must be considered, even if most scholars think those are fairly unlikely interpretations. Since these aren't the majority view nor what universalists think, I'm not going to say any more about them.
The view currently in most favor among I Peter commentators of all stripes is that the spirits Christ preached to were the fallen angels of Genesis 6 (whose identity as fallen angels is itself even more disputed, but considering the interpretations of the beginning of Genesis 6 would be enough for its own post; if I'd had a blog when I studied that issue a few years ago, I would have written exactly such a post). This interpretation takes the message preached to be one of victory and judgment, not salvation.
[Side note: given that the message to angels can be one of victory and judgment, it seems strange to me that no one has considered the possibility that he preached such a message to human spirits, because that also seems as possible as some of the other options. Then showing that it's a preaching to dead humans wouldn't even be enough to establish the conclusion universalists seek to derive from this passage. There would have to be an additional argument that the preaching is a message of salvation. Interestingly, universalists would have Augustine, Carson, and Grudem on their side for this issue (but not for the thesis that the preaching must take place after the people die).]
This last option (the preaching to angels, not my extra possibility that I haven't seen anyone defend) is the majority view, for a number of reasons. First, almost all instances of the word translated "spirits" refer to angels and not dead human beings.
Second, the word translated "prison" is never used anywhere else for a place of punishment of humans after death, while many other terms existed so as not to require a quirky use of another word here. This term is used in Revelation for Satan's 1000-year confinement, and you can find talk of evil angels in prison in plenty of intertestamental and first century apocalyptic literature, especially in the books of Enoch. Given that similar passages in II Peter and Jude clearly allude to Enoch's accounts of those, it's fairly likely that I Peter here also does, and therefore the preaching is likely to be to those same spirits in prison.
Third, the idea of repentance after death does, at least on the surface, seem at odds with statements throughout the book that emphasize righteous behavior here and now that will lead to either judgment or salvation. Eternal life in I Peter seems to be tied to persevering in the faith in this life, as it is in Paul, John, Hebrews, and other places.
So it doesn't at all seem to me that I Peter 3:18ff. could establish universalism. There are too many other possibilities for what it could be referring to, and the one that seems most accepted by scholars, with good argument behind that acceptance, does not support universalism at all.
I Peter 4:1-6
Since therefore Christ suffered in the flesh, arm yourselves with the same way of thinking, for whoever has suffered in the flesh has ceased from sin, so as to live for the rest of the time in the flesh no longer for human passions but for the will of God. The time that is past suffices for doing what the Gentiles want to do, living in sensuality, passions, drunkenness, orgies, drinking parties, and lawless idolatry. With respect to this they are surprised when you do not join them in the same flood of debauchery, and they malign you; but they will give account to him who is ready to judge the living and the dead. For this is why the gospel was preached even to those who are dead, that though judged in the flesh the way people are, they might live in the spirit the way God does. (I Peter 4:1-6, ESV)
I Peter 4:6 almost certainly refers the preaching to those who have now heard the gospel (through that preaching) and have since died. I think the context makes that clear. The probable flow is as follows. Evildoers will give account to the one who will judge all. The reason the gospel was preached to people who have now died was to give them an opportunity to repent before it was too late. Those who did are now living in the spirit (rather than being dead in the spirit) the way God is living in the spirit.
Almost all the major contemporary commentators (I'm fairly sure John Elliott, Paul Achtemeier, J. Ramsey Michaels, Peter Davids, Thomas Schreiner, Wayne Grudem, and I. Howard Marshall all think this) consider this to be the most likely meaning of this verse. The point is to make it clear that dying isn't just the end. There's a point to preaching the gospel to people who will die. The death of the righteous isn't punishment, and our temporary sufferings and trials are just that, temporary. We have eternal life to look forward to. This thus fits with the primary theme of I Peter.
Again there are alternative interpretations. Augustine thought this was a preaching to the spiritually dead, though I think the context rules this out, and the word for "dead" is almost never used this way without contextual hints that it's being so used.
The universalist interpretation takes the preaching to be toward those who have died, and the preaching takes place after they have died. I see no argument for this that doesn't depends on intepretating I Pet 3:18ff. in the universalist way, which I've already at least shed some doubt on, and some of those considerations apply here as well, e.g. the overall argument of the epistle that what we do here is what counts in eternity, which is why the call to persevere now is grounded in statements about eternal life or judgment after death.
As with the previous passage, even a preaching to the dead doesn't require a preaching to all the dead (which is required for the universalist interpretation). It might be limited to those who never got to hear the gospel in life. It might be limited to those before Christ came. It might be limited to genuine believers before Christ came, who will all believe once they hear the full gospel.
Other considerations count against all of those possibilities anyway. The passage never says Christ preached. It just says the gospel was preached. That's not an objection to the view, but a likely explanation for not having a subject is that the subject is simply a variable that doesn't require an explicit subject, given all the people who have preached the gospel to those who are now dead. There's no such explanation why there's no subject if the preacher is Christ.
There are also other passages that count pretty strongly against the possibility of repentance after death, most notably the parable of Lazarus in Luke 16, the announcement that death is final and then judgment takes place in Hebrews 9:27, and then what seems to me to be a clear distinction in Jesus' own teaching between those whose suffering will be eternal and those whose life will be eternally with God (e.g. Matthew 25:31-46). I know Keith DeRose has tried to deal with such passages, but I don't think his interpretation of them is the most likely.
At best, the universalist interpretation of these two passages is unclear and thus shouldn't be used to rest any case on. I've tried to explain why I think an even stronger claim can be made against such interpretations, that they are a good deal less likely than more standard interpretations. Therefore, I don't think these passages do much toward making a case for universalism.