It seems that you are changing the argument.
An “understanding of essential doctrines" is quite different from "an understanding of what these essential doctrines are.”
Very different, indeed.
This has been the disagreement all along. I have always maintained that we can know what is essential in scripture. I have not changed the arguement.
To draw the distinction above shows a lack of understanding on your part. When I understand a verse or verses in context; I also understand if it is essential. I understand Acts 1:5 and I know that Acts 1:5 is essential for the christian. As I read on in scripture this is confirmed many times.
The completeness of the essentials in scripture becomes confused without the Church but not to the point of being rejected by the Church as non-christian unless they deny certain essentials like Mormons or JW’s.
To be sure: a Protestant can come to a correct understanding of essential doctrine in Scripture.
When a Protestant says, “There is one God”, that is correct.
When a Protestant says, “Jesus is Divine”, that is correct.
When a Protestant says, “The Eucharist is the Body and Blood, Soul and Divinity of Christ”, that is correct.
NOW! When a Protestant says, “The Bible says that “A” an essential doctrine”, I will have to ask him, “Where does the Bible say that?” and he will have to give some obfuscations, and some ambiguous responses, but he will NOT be able to state, “Bible Verse Z says that Belief A is an essential doctrine.”
One needs the CHURCH to proclaim this to be an essential.
All Protestants can understand Psalm 44:2 but that doesn’t mean it’s an essential because they “understand” it.
I never said that every understood verse in scripture means that it is essential to be considered a non-catholic christian.
I said an essential verse can be known/understood as essential.
Without the Church though an essential can be missed or misapplied. While they have known essentials enough to be declared a separated christian, they missed or misapplied others that would make them Catholic.
It seems to me you are mixing two arguements. It seems to me that you are trying to counter the sola scriptura position by denying that they can know an essential doctrine as essential solely from scripture. The sola scriptura arguement does not belong here.
I deny the sola scriptura position, that is that scripture is the sole authority. However, I still maintain that anyone can know what is an essential doctrine from that scripture or group of scriptures alone but they run the risk of misapplying it without the authority of the Church.
By understanding the verse “In the beginning was the Word, and the Word was with God, and the Word was God.” in the context of the entire new testament comes the understanding that this is essential.
By understanding the verse “you must believe that God is and that He is the rewarder of those that diligently seek Him” we have the understanding that this is an essential.
By understanding the verses that relate to the Apostles Creed, we have the understanding of what is essential to be a christian.
Sola Scriptura says that scripture is the sole authority, it shows a human weakness in not understanding that Jesus taught the Apostles and they in turn passed on that teaching and that Jesus’ authority was passed down to the Apostles and they in turn passed down that authority and that in scripture and in the early church (Tradition)Peter and then his successors were given a primary position.
A person can indeed know, that is understand, essential doctrine from Scripture alone but outside of the Church they cannot know it completely and they are subject to incorrect application. That is why there are various divisions in protestanism.