Who is the narrator, can she or he read minds, and, more importantly, can we trust her or him?
Third-Person Omniscient Narrator
In A Canticle for Leibowitz, the narrator has the ability to enter any character's perspective it chooses—and it does just that. One of the best examples of the narrator's third-person omniscient style comes at the end of Fiat Homo.
Up until this point, we've mostly been stuck inside of Francis's point of view. But then Francis takes a headshot like a noob. So suddenly, we're inside of the old wanderer's perspective.
Then we enter the perspective of the valley's predators. And finally, we enter no one's perspective in particular when the narrator notes:
Eventually it was the Year of Our Lord 3174.
There were rumors of war. (12.96-97)
When a narrator travels in and out of that many characters—not to mention species—and across a couple hundred years, you know it's definitely an omniscient narrator.
As for the third-person bit, this means the narrator is not directly involved in the story. He's an outsider looking in, telling us what the characters are doing and thinking without being a character himself. This is why the narrator tells the story like this:
He sniffed. No smoke or ozone to be detected. Finally, he opened his eyes. (24.101)
If the narrator were inside of the story, those sentences would be written in first-person: I sniffed. Finally, I opened my eyes. Badda-bing, badda-boom, third-person narrator.