When is a lie not a lie? When it’s fiction. But where does fiction end and falsehood begin?

“This book is a work of fiction. Names, characters, places and incidents are product of the author’s imagination or are used fictitiously. Any resemblance to actual events or locales or persons, living or dead, is entirely coincidental.”

This standard disclaimer appears in the front matter of Dan Brown’s Angels & Demons. In a paradoxical sense, the disclaimer is itself a sort of fiction. While certain “names” and “places” are certainly “used fictitiously,” any “resemblance” to actual “locales” of such settings in the book as St. Peter’s Square, the Pantheon and the Sistine Chapel is obviously far from “entirely coincidental.” The same could be said of references to Galileo and Copernicus and incidents from their lives. Everyone knows this, and no one pays much attention to such disclaimers.

“References to all works of art, tombs, tunnels and architecture in Rome are entirely factual (as are their exact locations). They can still be seen today. The brotherhood of the Illuminati is also factual.”

This author’s note, just a few pages from the disclaimer above, has attracted much more attention and is generally regarded as meaning more or less what it says, whether true or false.

Taking both the disclaimer and the author’s note at face value, the two flatly contradict one another — which means that, at face value, at least one must be false, though not that the other must be true. In fact, the author’s note is no more strictly true than the disclaimer, and it looks much more like a blatant falsehood.

Some of the book’s inaccuracies may be no more than mistakes, if glaring ones.

For instance, Angels & Demons depicts Santa Maria della Vittoria in Rome at Piazza Barberini, a half mile from its real location. More problematic is a key reference to a tile in St. Peter’s Square pointing “West,” supposedly a clue pointing the way ahead in a 400-year-old scavenger hunt — a tile that is actually one of a circle of 16 tiles aligned to the points of the compass pointing in every possible direction.

Even more damaging, in a way, is Brown’s account of the Passetto di Borgo, the hidden passageway between the Vatican and Castel Sant’Angelo. The passetto is an elevated passageway, but Brown describes it as an underground tunnel beneath the streets of Rome — not only in the novel, but on his own website, in a Q&A billed as an “interview,” purportedly explaining how he himself was inspired to write Angels & Demons: “I was beneath Vatican City touring a tunnel called il passetto — a concealed passageway used by the early popes to escape in event of enemy attack.”

Significantly, Brown follows this blunder by writing, “According to the scholar giving the tour, one of the Vatican’s most feared ancient enemies was a secret brotherhood known as the Illuminati — the ‘enlightened ones’ — a cult of early scientists who had vowed revenge against the Vatican for crimes against scientists like Galileo and Copernicus.”

This touches on the central premise of Angels & Demons, the meta-narrative around which the action of the novel is constructed: the picture of the Church and science at war with one another. Brown connects this supposedly historical theme to a supposedly biographical event in his own life, implying a credible, “scholarly” basis for it — and, likewise, the author’s note claims a “factual” basis for the book’s depiction of the Illuminati.

In fact, the whole premise is without any reality — much like Brown’s moment of subterranean “inspiration” and possibly the tour, the “scholar” and the history lesson he describes.

To speak of what is known, the historical Illuminati was a late 18th-century political secret society with no particular interest in science. Copernicus was never even at odds with Church officials, and while the authorities’ mishandling of Galileo is certainly a black mark on Church history, his fate — lifelong house arrest following a verdict of “vehemently suspect of heresy” — is not the sort of outrage that tends to inspire murderous vows of revenge centuries after the fact.

If the meta-narrative of the Church and science at war with one another is without reality, it is also not a mere “product of the author’s imagination.” Just as The Da Vinci Code’s reading of history is drawn from sources like Holy Blood, Holy Grail, Angels & Demons relies on an anti-Catholic distortion of history long familiar from sources like Charles Chiniquy’s 1886 polemic Fifty Years in the Church of Rome.

Do the filmmakers know or care where the line between truth and untruth lies? A couple of weeks ago, the film’s director Ron Howard lashed out at William Donohue of the Catholic League over Donohue’s booklet Angels & Demons: More Demonic Than Angelic, defending himself and his new film from charges of anti-Catholicism and insisting that the film was merely fiction.

“Mr. Donohue’s booklet accuses us of lying when our movie trailer says the Catholic Church ordered a brutal massacre to silence the Illuminati centuries ago,” Howard wrote in an April 21 Huffington Post piece. “It would be a lie if we had ever suggested our movie is anything other than a work of fiction.”

Yet in a video featurette on the film’s website, Howard says, “One of the things I found most engrossing while I was reading Angels & Demons was the Illuminati. The Illuminati was formed in the 1600s. They were artists and scientists like Galileo and Bernini whose progressive ideas were threatening to the Vatican. … The early Illuminati were persecuted by the Church; they were hunted down, even executed and driven underground.”

Later, Howard adds, “So much has been written about the Illuminati. Some believe; some don’t. … What do we really know about the Illuminati?” That certainly seems to qualify as at least “suggesting” that the events Howard refers to are (or at least could be) something other than fiction.

In the Huffington Post piece, Howard writes, “I guess Mr. Donohue and I do have one thing in common: We both like to create fictional tales, as he has done with his silly and mean-spirited work of propaganda.”

To borrow a quip from my friend and fellow critic Peter Chattaway, I guess that means Howard admits that “fictional tales” — like Angels & Demons — can be “silly and mean-spirited works of propaganda.”

Steven D. Greydanus is editor

and chief critic at DecentFilms.com.