Imagine someone knocks on your door and proceeds to say: “You need to rearrange your furniture. And paint this house a new color. Oh, and renovate the master bedroom.”

What little detail would he be overlooking? That he isn’t an interior decorator and has poor taste in colors? No, of course not — he’s ignoring the fact he doesn’t own the house!

Years ago, shortly after my wife and I entered the Catholic Church, there was a knock on our door. It was two Jehovah’s Witnesses, a husband and wife, eager to tell me about the Watchtower Society. The wife was especially anxious to explain how belief in the Trinity was unbiblical, a creation of the Catholic Church at the Council of Nicaea. Soon she was referencing this and that passage of Scripture, suggesting we examine “the original Greek” together.

She wanted, as it were, to rearrange furniture and argue over paint colors. As a former fundamentalist who had, by God’s grace, journeyed into the Catholic Church, I was tempted to jump into an argument about verse, passage and book. But I took a different approach, asking, “Why are you using a Catholic book to attack the Catholic Church?” In other words, I wanted to talk about ownership!

That surprised them. What did I mean? In short, I explained the following: They accepted, apparently without pause, the divine authority of the New Testament. Why? By what reasoning or evidence did they ascribe authority to those 27 books? I noted that although they denounced the Council of Nicaea for supposedly “creating” the Trinity through papist hook and Catholic crook, they somehow missed how the same papacy, bishops and Church later recognized and defined the New Testament canon. How could they — members of an organization founded in the 1880s — condemn with such confidence the authoritative pronouncements of the ancient Church while referring to a collection of books that was defined, compiled and defended by the same Church?

Their response was both defensive and desperate. “We trace our roots back through men like John Hus and John Wycliffe!” I noted that however much those two men deviated from Catholic teaching, neither one ever denounced the Church’s belief in the Trinity. My guests departed shortly thereafter.

A few years later, there was another knock on my door. This time it was three Mormon missionaries. After the usual pleasantries, I said: “There is just one question I’m hoping you can answer. When was the ‘great apostasy,’ and how did it come about?”

“Well,” said the apparent leader, “surely you agree there has been spiritual darkness in the world since the time of Adam —”

“Yeah,” I agreed. “Sure. And?”

“— and that man has constantly fallen away from God and has sinned and —”

“Yes, of course. But when was the ‘great apostasy’? In the 300s? The medieval era? Some other time?”

He took a stab at an answer: “It happened right after Jesus’ death.”

But how is it, I asked, that Jesus, having promised Peter that the gates of hell would not prevail against the Church, and having sent the disciples out to make disciples of all nations, would let everyone fall into apostasy? After all, there is plenty of historical evidence of early Christians martyred for their faith in Jesus Christ.

“Who?” one asked. “Give an example.” I told him about Ignatius of Antioch, martyred around A.D. 110, who was likely a disciple of the apostle John. To which he replied, with obvious impatience: “Well, clearly you aren’t going to change your mind. You’re set in what you believe.” He then added, defensively, “I know by the testimony of the Holy Spirit that Joseph Smith was a true prophet.”

Since then, I’ve had similar discussions with Mormon missionaries. Each time, they express a solid belief in the fact of a “great apostasy,” yet are unable to provide much in the way of details. Each time, they are consternated by my lack of faith in their lack of knowledge. One urged me, “If you read this booklet” — titled “The Restoration of the Gospel of Jesus Christ” — “and pray to know that Joseph Smith was a prophet, you’ll recognize the truth.”

Sorry. Just because you knock on my door doesn’t mean you own the house; so step away from the furniture.

Carl E. Olson is the editor of Ignatius Insight (www.ignatiusinsight.com) and writes from Eugene, Ore.