This quote referencing Ben David (John Jones) summarizes much of the info.
Ben David
Porson (Richard Porson 1759 – 1808), in his ”Letters to Travis", p. 155, gives the following quotation:” Abbot Joachim (1135-1202) compared the final clauses of the seventh and eighth verses, whence he inferred, that the same expression ought to be interpreted in the same manner. Since, therefore, he said, nothing more than unity of testimony and consent can be meant by ”tres unum sunt” [Three are one] in the eighth verse, nothing more than unity of testimony and consent is meant in the seventh. This opinion the Lateran Council (AD 1215) and Thomas Aquinas (1225-1274) confuted [Joachim's interpretation], by cutting out the clause in the eighth verse.
This mangling even remained in the Complutensian Polyglot. It is a fascinating history.
Demonstrating the propensity of the Latins to play fast and loose with scripture to suit their own purposes.
The change to 1 John 5:8 shows that the importance of the "earthly witnesses" was diminishing rapidly. Rather the papacy was the witness on earth, the representative of the heavenly trinity, of God the Father, "God the Word" and "God the Holy Spirit".
BTW, nowhere else in John's writings, or in any other, are God the Father and [God the] Word juxtaposed. This is why you can know the Comma is definitely FAKE. "God the Word" was a post-NT invention of the ECFs. You can tell that the Comma intended "God the Word" (and "God the Holy Spirit") even if it doesn't say it explicitly, just because "the three are one."
Poor Abbot Joachim. Little did he know that he was living amidst the papacy of antichrist.
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The 4th Lateran Council took place during the crusade against the Albigenses.
"Raphael Lemkin, who coined the word "genocide" in the
20th century,
[193] referred to the Albigensian Crusade as "one of the most conclusive
cases of genocide in
religious history".
[3] Mark Gregory Pegg writes that "The Albigensian Crusade ushered genocide into the West
by linking divine salvation to mass murder, by making slaughter as loving an act as His sacrifice on the cross." (wiki)
en.wikipedia.org
The 4th Lateran Council had this to say about heretics "We excommunicate and anathematize every heresy raising itself up against this holy, orthodox and catholic faith which we have expounded above. We condemn all heretics, whatever names they may go under .....
If however a temporal lord, required and instructed by the church, neglects to cleanse his territory of this heretical filth, he shall be bound with the bond of excommunication by the metropolitan and other bishops of the province. If he refuses to give satisfaction within a year, this shall be reported to the supreme pontiff so that he may then declare his vassals absolved from their fealty to him and make the land available for occupation by Catholics so that these may, after they have expelled the heretics, possess it unopposed and preserve it in the purity of the faith -- saving the right of the suzerain provided that he makes no difficulty in the matter and puts no impediment in the way. The same law is to be observed no less as regards those who do not have a suzerain."