Msgr. Ronald Knox once observed: “To be present when two other people are arguing is, almost always, to be in a state of impotent fury at their joint incompetence.” I've sometimes been one of those “two other people,” and I've made my share of incompetent remarks.

But I've also been on the receiving end of comments that aren't so much incompetent as they are incomprehensible. These are the sort of comments that give the Catholic apologist pause as he scratches his head in wonderment: Did he really just say that? Such remarks offer an unexpected glimpse into the thinking of those opposed to the Catholic faith.

Conversing with an evangelical Protestant pastor about John 6 and the Eucharist, I was stunned to hear him say this of the belief that the Eucharist is the true body and blood of Jesus Christ: “That's crazy. That demands too much faith.” This from a godly man who believes that faith is the most important gift from God. So, I asked, does this mean that God is limited? He insisted it didn't, but wouldn't retract his statement.

I once exchanged several letters with the head of the local “Atheists and Freethinkers Society.” This atheist continually insisted that his thinking was rational and scientific, apparently to cover up the fact that his arguments were highly emotional and illogical. Amazingly, in his final letter to me, he wrote: “I never stated ‘there is no God.’ A supernatural being may exist. I would submit, however, that your God doesn't exist, since your concept of God is internally self-contradictory.” Since the entire exchange had been about the existence of God and he called himself an “atheist,” I was slightly confused and quite amused. I still am.

Talking with two Jehovah's Witnesses, I asked why anyone should believe the Watchtower Society, established more than 1,850 years after the founding of the Catholic Church. The defensive reply: “We trace our beliefs back to men such as John Huss and John Wycliffe.” When I pointed out that both Huss and Wycliffe believed in the Trinity — a doctrine they had vehemently attacked earlier in our conversation — they quickly changed the topic.

Then there are my exasperating conversations with hip, neo-Hindu types about the nature of truth. All of them insist, matter-of-factly, that “there is no truth.” For some reasons, those conversations went nowhere fast.

Tim LaHaye, creator of the Left Behind books, exchanged a few emails with me about some points of Church history. Responding to my statements about the inquisitions and the medieval era, he wrote: “You have bought into the spin that Catholic schools have put on history. Once you decide to accept that protective and often flawed view of history — what has happened to you is understandable.” When I pointed out that all of the data and information I relied on came from non-Christian sources, he did not respond.

Similarly, a fan of The Da Vinci Code wrote this in response to my criticisms of that novel: “[The Da Vinci Code] is the first book you have ever read on this subject not written by the church. You believe everything you are told. You are a blind religious fanatic.” Never mind that The Da Vinci Hoax, which I co-authored with Sandra Miesel, contains a selected bibliography with more than 100 titles — most of them of non-Christian. Or that Sandra has two graduate degrees from the University of Illinois, hardly a bastion of orthodox Catholicism.

Did they really say that? I'm still scratching my head.

Carl E. Olson writes from Eugene, Oregon. The Da Vinci Hoax is available from Ignatius Press (www.ignatius.com).