Did the early Church Fathers have a complete agreement on how to interpret 1 Peter 3:18-20? Did the early Church Fathers have a complete agreement on how to interpret 1 Peter 3:18-20 or did they also have some differences in the way they interpreted these words by Peter? I specifically mean the words highlighted in the verses below:


  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. (1 Peter 3:18-20 ESV)



Who are the spirits?
What is the prison?
What exactly did Jesus proclaim to them?
The most detailed analysis of various different views in the early Church concerning this verse is to be found in a letter by Saint Augustine to a Bishop called Evodius that wrote a letter to him asking for his opinion.(Saint Augustine, Letter 164, A.D. 414)

I will summarize the letter which illustrates both the different opinions at the time as well as Augustine's reasonable conclusion.

First Augustine admits this is a difficult passage, he then mentions the problems he has with various views other's propose.  First he can't see the logic of those who claim Christ went to hell to preach to just the souls who died in the flood:


  If the Lord when He died preached in hell to spirits in prison, why were those who continued unbelieving while the ark was a preparing the only ones counted worthy of this favour, namely, the Lord’s descending into hell? For in the ages between the time of Noah and the passion of Christ, there died many thousands of so many nations whom He might have found in hell. (Saint Augustine, Letter 164, A.D. 414)


Next he disagrees in the possibility that the Bishop suggested who originally asked the question, that maybe Jesus descended into hell preaching and potentially delivering every unbelieving soul from Adam to Christ. He disagrees because Augustine thinks it is presumptuous to decide who these souls could be and that maybe it's not referring to any soul.


  But who these were it is presumptuous for us to define. For if we say that all who were found there were then delivered without exception, who will not rejoice if we can prove this? ...These things being so, if the Saviour delivered all from that place, and, to quote the terms of the question in your letter, “emptied hell, so that now from that time forward the last judgment was to be expected,” the following things occasion not unreasonable perplexity on this subject, and are wont to present themselves to me in the meantime when I think on it. First, by what authoritative statements can this opinion be confirmed? For the words of Scripture, that “the pains of hell were loosed” by the death of Christ, do not establish this, seeing that this statement may be understood as referring to Himself, and meaning that he so far loosed (that is, made ineffectual) the pains of hell that He Himself was not held by them, especially since it is added that it was “impossible for Him to be holden of them.”  (Saint Augustine, Letter 164, A.D. 414)


He then makes a surprising and curious admission that "although the authority of the canonical Scriptures cannot be brought forward as speaking expressly in its support" it was the tradition that Augustine also supports that Adam was in hell and was a soul delivered by Christ when he descended into hell. Then he reject other opinions of the day that also included "Seth, Noah and his house, Abraham, Isaac, Jacob, and the other patriarchs" in this release from hell, because he believes they were not in hell but in Abraham's bosom which was similar to paradise and not part of hell.

Augustine (in contrast to his believe that Christ did descend into hell and saved Adam) now argues against the idea that this verse actually speaks of saving anybody from hell. He hinges his idea that as 1 Peter 4:6 says "For for this cause was the gospel preached also to them that are dead, that they might be judged according to men in the flesh, but live according to God in the Spirit."actually i plies Christ only preached to those 'in the flesh' but those in hell had no flesh. 


  For how can they be judged in the flesh, which if they be in hell they no longer have, and which if they have been loosed from the pains of hell they have not yet resumed?   (Saint Augustine, Letter 164, A.D. 414)


He also dismissed the idea that maybe those who rose from the graves when Christ was on the cross is being referred to.

Augustine then dismisses those who feel it unfair if Christ did not descend into hell to preach to those before the gospel was manifest because it was not clearly preached before. He argues that if that is the case then it is also unfair today for those who die before hearing the gospel, with no real difference.

Finally Augustine presents his own view, which answers your questions.

The spirits in prison are just symbols of rejectors of God in the past, applied in the present time. God has always preached the gospel in the past through Christ and those who died in the flood had rejected the gospel.


  Consider, however, I pray you, whether all that the Apostle Peter says concerning spirits shut up in prison, who were unbelieving in the days of Noah, may not after all have been written without any reference to hell, but rather to those times the typical character of which he has transferred to the present time....But to the men of Noah’s time the gospel was preached in vain, because they believed not when God’s long suffering waited for them during the many years in which the ark was being built (for the building of the ark was itself in a certain sense a preaching of mercy); even as now men similar to them are unbelieving, who, to use the same figure, are shut up in the darkness of ignorance as in a prison, beholding in vain the Church which is being built up throughout the world, while judgment is impending, as the flood was by which at that time all the unbelieving perished....For although he had not yet come in the flesh, as He came when afterwards He “showed Himself upon earth, and conversed with men,”﻿ nevertheless he certainly came often to this earth, from the beginning of the human race, whether to rebuke the wicked, as Cain, and before that, Adam and his wife, when they sinned, or to comfort the good, or to admonish both, so that some should to their salvation believe, others should to their condemnation refuse to believe,—coming then not in the flesh but in the spirit, speaking by suitable manifestations of Himself to such persons and in such manner as seemed good to Him. As to this expression, “He came in the spirit,” surely He, as the Son of God, is a Spirit in the essence of His Deity, for that is not corporeal; but what is at any time done by the Son without the Holy Spirit, or without the Father, seeing that all the works of the Trinity are inseparable? (Saint Augustine, Letter 164, A.D. 414)


So Augustine would answer this way.


Who are the spirits? (Those who rejected the gospel of Christ when being preached  to by Christ in the days of Noah)
What is the prison?(There ignorance when in the flesh in the days of Noah, am not sure why he did not think the present tense of those in hell but I guess as he was arguing against preaching to those in hell, Augustine also imagines the prison not to be hell either)
What exactly did Jesus proclaim to them?(The gospel was preached by Noah for the Promise of the Messiah in the Old Testament was the gospel in a more obscure form.)


However it must be said that not all the Fathers agreed with Augustine, for example, though only a brief mention, it seems clear that St Athanasius thought Jesus after he died literally preached to the souls in hell.


  This Body it was that was laid in a grave, when the Word had left it, yet was not parted from it, to preach, as Peter says, also to the spirits in prison﻿. (Athanasius, Letter to Epictetus 5h