I would venture to say you need to do some study of the
Early Church Fathers along with some history. The above is linked, so you don’t think it is Rome’s propoganda, to the same documents on a protestant site. Ignore the commentary, whether you read them from the protestant side or the catholic side about the writings and place them in context to what they are set against in history.
The church recognizes only some of the “Old Catholics”, not all of them. You have breakaways from breakaways, that are invalid. Not that it matters to them. If you want to know the early christian beliefs and read history then yes, I do know their beliefs. Ignorance is not a good thing. Yes Christ did leave a strategic plan, it’s called the church. He promised to protect it til the end of time, He initiated sacraments and the clergy to administer. Good plan in my opinion. The apopstles bear out the plan.
Does the “Universal church” consist of Mormons, JW’s, Budhists, Hindus, Islam etc, protestants who believe in reincarnation (yes there is one down the street from me and claims to be christian)? Or are you going to place some limits now on the meaning?
If you are, who gave you the authority to do so? They may disagree.
I would start with the 7 letters of Ignatius (disciple of John the apostle), 1 Clement, Barnabas, Polycarp, Iranaeus, Justin Matyr and the Shepherd of Hermas. Then move onto Cyprian, Origen, Jerome, Anthanasius, Augustine and Cyril. There are lots more though.
The early church councils will be beneficial as well. If you wish to persue what the gnostics and heretics believed, to set the stage of the writings, I can provide links to their writings and beliefs as well.
Peace and God Bless
Nicene