St.C: "Since the whole sentence hinges on the word useful, Webster's Dictionary has had a part to play."
So you are contending that everything Jesus said about the role of the Holy Spirit -- (dwelling in his apostles and in individual Christians reading what they wrote, ie: Scripture) -- can be nullified by one word?
That it all depends upon what the meaning of "is" is -- I mean, what the meaning of "useful" is?
Paul, in one of his letters to Timothy, admonishes him to remind the individuals that make up the church to rightly apply the Word of Truth, and not to strive about words." [2Tim.2:14-15]
Now with that in mind, let's address your hangup about the meaning of a word:
Some versions of the Bible translate the Greek word "ophelimos" as "useful". ("use, usefulness, & utility" have a shared meaning element: "capacity for serving an end or purpose").
However, the Greek word "ophelimos" more accurately means "profitable": "yielding advantageous / beneficial returns or results". "Profit": "a valuable return: GAIN"
Paul also writes in 2 Tim.3:16: "ALL graphe [Scripture] is theopneustos [God-breathed] and is ophelimos [profitable] for ....". Hold fast the pattern of sound words which you have heard from me ... and keep by the Holy Spirit who dwells in us that good thing [the gospel] which was [past tense]committed to you. [2 Tim.1:13-14]
And of course in 1 Cor.14:37, (The New Testament) Paul says, ".... the things I am writing to you are a command from the Lord." ["Thus sayeth the Lord". "God's Words". "Scripture". "theopneustos (God-breathed)".
And Peter classifies "..all of his [Paul's] epistles" with "the other Scriptures". [2 Pet.3:16].
And in 1 Tim.5:18, Paul quotes Jesus' words in Luke 10:7, and calls them, "Scripture".
And in John 14:26 and 16:13, Jesus promised that the Holy Spirit would bring all that he had said to the disciples' remembrance and would guide them into all truth.
Jesus, himself, promised that they would be able to remember and record without error, ALL that Jesus had said. [The definition of "theopneustos God-breathed)"].
Find other references to Jesus' promise in 2Pet.3:2; 1Cor.2:13; 1Thess.4:15; Rev.22:18-19, etc.
St.C: "Since the RCC doesn't seem to feel it needs to twist the meanings of words, my confidence in their interpretation is greater than those who would inject arbitrary definitions. Or does the Holy Spirit or "the mind of Christ" have trouble with the written word."
:D
St.C: "John 14:26 would appear to contradict sola scriptura, but I'm sure you have an explanation."
Jesus' promise to his apostles that he would send them the Holy Spirit to remind them of "everything I have said to you", is a guarantee that what they wrote is "theopneustos" [God-breathed]. Because of the promise Jesus made to the 12 apostles, they are the ONLY authorized agents of Christ. No writing after the death of the 12 can be canonical. Only the 12 can attest to the truth of a writing about Christ. When all the eyewitnesses had died, the canon of revelation about Christ ceased.
In A.D. 367 the Thirty-ninth Paschal Letter of Athanasius contained an exact list of the twenty-seven New Testament books we have today. This was the list of books accepted by the churches in the eastern part of the Mediterranean world. Thirty years later, in A.D. 397, the Council of Carthage, representing the churches in the western part of the Mediterranean world, agreed with the eastern churches on the same list. These are the earliest final lists of our canon of Scripture.
No. I am simply stating that what you say (not Jesus), is nullified. No matter what synonyms you want to employ for the word useful,( profitable, advantageous,having beneficial results) it can never have the meaning you give it; useful can never mean personal interpretation as infallible authority.
Furthermore, I am shocked that you would imply that Jesus said individual Christians reading what the apostles wrote would have the Holy Spirit dwelling within them. There is absolutely no mention of Jesus telling anyone to write anything, let alone what the result of reading it would be.
Paul in one of his letters to Timothy, admonishes him to remind the individuals that make up the church to rightly apply the Word of Truth and not to strive about words. 2 Tim 2;14-15
Look, I'm not the one digging up Greek translations, just applying the term "useful" as it is meant in its simplest, most universally understood meaning. A hammer is useful in building a house. However, you will require much more to attain your goal. Frankly, IMHO, Paul's admonition to Timothy applies to you.