One argument the Catholic Church uses to defend its authority is that in 1 Timothy 3:15, we read that the Church is the pillar of truth. Any argument against Catholicism can be covered by this defence. The Bible says it's an abomination to talk to the dead? Nope, the Catholic Church says you can pray to the Saints, and the Church is the pillar of truth, so it can't mean that. The Bible says Christ is the head of the Church? Nope, the Catholic Church says it's Peter's successor, and the Church is the pillar of truth. The Bible says salvation is by grace through faith, not of works? Nuh uh! The Catholic Church says works are heavily involved, and the Church is the pillar of truth.
Setting aside the tragic twisting of what it means that the Church is the pillar and ground of truth, the defence itself assumes that when Paul said the Church is the pillar and ground of truth, he necessarily meant the Catholic Church. But there's no evidence that he did. In fact, almost everything the Bible says militates against the idea that Catholicism even existed in the first century. Even Catholic attempts to twist it to make it say otherwise (such as the very pillar of truth argument we are discussing) are usually circular; they assume Catholic authority to interpret the Bible in the first place!
Interestingly, whereas Catholics are desperate to read "Catholic" in front of every occurrence of the word "Church" in the Bible, there is an instance in their own sources in which they are not always so willing to interpret the word "Church" as referring exclusively to the Catholic Church. Recently, the Catholic belief that there is "no salvation outside the Church" has been questioned, with the term "separated brethren" now being used to refer to Christians who may be saved, but are not part of the Catholic Church. Now, if 1 Timothy 3:15 must refer to the Catholic Church, why must the phrase "no salvation outside the Church" not refer to the Catholic Church also?
There are two other problems with this. The first is that it places the Church ahead of Christ. The truth is, there is no salvation outside of Christ. The Church was never crucified for our sins. I am not saved by confessing with my mouth "the Church is the Lord", or believing in my heart that God raised her from the dead. Rather, it is my faith in Christ's death and resurrection that makes me a part of His Church. This is why some Catholics (not all) are willing to go as far as to say that I am saved, or at the very least can be, despite my anti-Catholic stance. They simply say I will spend a fair bit of time in purgatory.
Which is the second problem with this interpretation. It is no secret that while there is salvation outside the Catholic Church, there is no salvation outside of Christ. One passage that demonstrates this irrefutably is found in John 6, which just happens to be a favorite passage for Catholics to snip up into snowflakes. In verse 53, Jesus says "Most assuredly, I say to you, unless you eat the flesh of the Son of Man and drink His blood, you have no life in you."
Catholics interpret this passage very literally. Whereas Jesus says multiple other things which are obviously not literal (you must be born again, I am the door, I knock and you must answer, I am the true vine etc.), Catholics insist that in John 6, Jesus literally meant we must eat His flesh and blood. Verse 53 shows that whatever Jesus is speaking of, salvation is impossible without it. You either "eat His flesh" and "drink His blood" and are saved, or you have no life in you. This is, therefore, a Heaven or Hell issue. Make the wrong call here and you are damned.
Now, in this passage, Jesus was spiritually describing (v63) the fact that we must come to Him and believe (v35). This makes sense. If you come to Jesus and believe, the Bible repeatedly affirms that you are saved (e.g. John 3:16; Acts 16:31; Romans 10:9; Hebrews 10:39 etc.), whereas those who do not believe are doomed (e.g. Mark 16:16; John 3:18 etc.) But Catholics insist that Jesus isn't speaking spiritually, but literally. And so when Jesus says if you do not consume His flesh and blood, you have no life in you, "no salvation outside the Church" makes perfect sense. If I have no life in me without literally eating the flesh and blood of Jesus, which is an almost uniquely Catholic doctrine, how could I possibly be saved without the Catholic Church? I might not even be able to be saved inside the Catholic Church, because there are various reasons I could be denied access to the Eucharist.
But it gets far worse for the Catholic. One time, the Pope was given the unenviable task of answering one of life's toughest questions: "Where is my dead atheist father?" It is never an easy question to answer. I remember panicking when I was asked the same question by a young woman, and my only answer was "I don't know how to answer that question". To this day, I still do not know a sensitive way to deliver such a painful truth: those who die in unbelief are condemned. To tell a child that truth so soon after he has lost his father is not a position I ever want to find myself in.
Nevertheless, it is a position the Pope found himself in. In my cowardice, I merely refused to answer the question. I refuse to lie and give a wrong answer, but to give the right answer is too painful, both to give and to hear, and may even harden the one who hears it against the Gospel. I regret the answer I gave, and pray that the Lord will bring some good out of it. But the Pope did not even take my cowardly approach. His response was "God surely was proud of your father, because it is easier as a believer to baptize your children than to baptize them when you are not a believer. Surely this pleased God very much." He then followed it up with "talk to your dad; pray to your dad."
So, not only does the phrase "no salvation outside the Church" no longer apply exclusively to the Catholic Church, but it may not even apply at all, according to "His Holiness", Pope Francis. You can be saved if you're "Protestant", but you can even be saved if you're an atheist!
But the truth is, as I showed above, there is no salvation outside of Christ. Those who die in unbelief are condemned. They are not in Heaven, and certainly can't be prayed to. This means that Pope Francis is preaching a false Gospel. Concerning this type of behaviour, Paul says "But even if we, or an angel from heaven, preach any other gospel to you than what we have preached to you, let him be anathema." Thus, barring repentance, the Pope is anathema according to Paul (as are all Popes throughout history, Francis just being the latest in a long line of such false prophets). I'm supposed to believe such a false prophet is the head of a Church that is the pillar and ground of truth?
So you see that Catholics are indescribably inconsistent when they say that because 1 Timothy 3:15 says the Church is the pillar and ground of truth, therefore Catholicism is true. It's a bad interpretation, it's a circular interpretation, it's a contradictory interpretation, and it causes large numbers of problems which, when followed down the road we have just followed, demonstrates that the Catholic Church preaches a false gospel, and thus cannot possibly be the Church that is the "pillar and ground of truth".