But is everything declared to be so by the Church, true?

[polonius]

A recent response to a post contained a very common belief among
Catholics:

"The CC has declared that ….."

Do you believe everything that the Catholic Church declares? Shall we look at some "infallible" teachings?

[MarysSon]

"The trouble with this history is that there are no historical facts to back it up. Distinctively Catholic beliefs—the papacy, priesthood, invocation of saints, sacraments, veneration of Mary, salvation by something besides “faith alone,� purgatory—were evident long before this supposed “paganization� took place. Another difficulty is that there are no historical records that imply an underground Fundamentalist church existed from the early fourth century to the Reformation. In those years there were many schisms and heresies, but present-day Fundamentalists cannot find among them their missing Fundamentalist church. There were no groups that believed in all, or even most, of the doctrines espoused by the Protestant Reformers (e.g. sola scriptura, salvation by “faith alone,� and an invisible church).''

Congratulations.
Looks like you finally did your homework.

You are correct - many of the pillars of Protestantism simply did NOT exist before the Protestant Revolt of the 16th century. Sola Scriptura, Sola Fide, Double Predestination, Eternal Security, Limited Atonement - these are ALL Protestant inventions that had NO place in the historic Christian faith prior to the 16th century.

[polonius]

MarysSon posted:

"The same if true for the Trinity. It wasn't officially defined until the Church was about 300 years old - but it was ALWAYS taught."

Question: When was the existence of a "Trinity" first taught?

In Scripture (Matt. 28:19).

RESPONSE: Perhaps I should rephrase my question. When was what we now have as Matt 28:19 added to the Gospel of Matthew.

[polonius]

Eusebius was present at the council of Nicea and was involved in the debates between Arias and the pagan view of Athanasius that became the trinity doctrine. If the manuscripts he had in front of him read “in the name of the Father, and of the Son and of the Holy Spirit,� he would never have quoted instead, “in my name.� So it appears that the earliest manuscripts read “in my name,� and the phrase was added.