Protestants, and even Roman Catholics (in Vatican II), other than this pope apparently, acknowledge an “invisible Church” which transcends all human organizations—the members of whom are only known, ultimately by God Himself.
Think about it, are all those whose names are on the Church roles really Christians? Are false Roman Catholics—who’ve been baptized but who really don’t believe in Jesus, or the creeds of the Church really Christians...even though outwardly they appear to believe? Of course we should treat professing Christians as Christians...but, only God really knows the heart. Therefore, even assuming Roman Catholic is the “only true Church” (which I do not), you have the visible Church (all who profess to be Catholics) and the invisible Church (the sincere, true Christians among the members of the visible Church). Persons in Heaven too—whose names and graves here on earth are long forgotten are also part of that “invisible Church.”
So it isn’t perfect doctrine or even the most right doctrine in a Church that defines it—rather faith and trust in Jesus—which makes a person a Christian, and part of the larger—trans-denominational, invisible Church.
As soon as any Roman Catholic calls someone a Christian who’s not a Roman Catholic....they are assuming this idea of an invisible Church.
As to the idea “There is, at most, only one doctrine that can be true” you are missing something. The gospel of Jesus and the purest true heavenly theology are certainly too glorious to be understood fully—in all their aspects. As St. Augustine taught, we apprehend God’s spiritual truths...we don’t comprehend them. In fact all of eternity for us will probably be spent finding new wonders of God’s grace...
My point is this, is that every body of believers in Jesus, that is a Church, is likely wrong about some things, and right about others....and while some Churches are surely more wrong than others—and some have a more pure doctrine than others—we all, as St. Paul said in 1 Cor. 13, “see through a glass darkly.”
If the Apostle who wrote 1/3 of the New Testament can say that—than surely we who’ve come since—including the Roman Church, should also admit—we all still see through a glass darkly. This isn’t giving into subjectivism—its only acknowledging human limits. Yes there are some errors that disqualify a Church as a Church (denying the truths, say in the Apostles or Nicene Creeds for example) but it is sheer institutional arrogance to claim “we are the only true church organization.”
Jesus accepts all who call upon His name and truly believe in Him.
“Catholics” do not determine what the Church teaches. That can only come from revelation, infallibly determined for all time. There should be no doubt that Roman Catholicism has always claimed to be the One True Faith (despite modernist obfuscation by liberal churchmen).
You seem to be saying that there is no true faith and that all religions are false to some degree. That is not the Catholic position.
“See through a glass darkly” means that we cannot appreciate the full glory of God, at least while still on earth. It does not mean that we should accept error. We must never be willing to do that.
For St. Paul says, “though we, or an angel from heaven, should preach unto you any gospel other than that which we preached unto you, let him be anathema. As we have said before, so say I now again, if any man preacheth unto you any gospel other than that which ye received, let him be anathema.”
Amen!