Madness seems to be the first idea that comes to mind, but there is more to that, I guess. It's curved, bumped and interlaced path that the brain is set to follow. Some of us just make better shortcuts or maybe have a better lighting system and appear to make so called rational choices easier. Whereas other directors concentrate on action or at least causal relationships to show why the iii has done this or that, Herzog makes a different choice. Namely, his camera swirls around the hero, we observe him in a close-up for most of the time.
Action is reduced to minimum.
We observe faces, feelings expressed and those intentionally muted. All in close view. I claim that Herzog's movies, and Aguirre in particular, require active, though also hypnotic or stoned participation in the performance. Have you happened to notice that if the dialogues had been deleted from the movie, probably we wouldn't have seen the difference. What matters is monologue, monologue and monologue only.