Story. Plot. Imagination.
The movie is dreadfully slow. Much of the dialog just meanders about and doesn't advance the story (apparently a lot of it was improvised by the actors, and it sounds it). Tony, our main character--- the stranger played variously by Johnny Depp, Jude Law, Colin Farrel, and mostly by the late Heath Ledger--- is a mystery on his first appearance and a mystery at the end. (Honestly, how often do I have to say it--- tell us what your character wants!) Terry Gilliam provides plenty of dots, but doesn't bother to connect them in a meaningful way. Part of the inconsistencies of character may not be his fault--- I mean, Tony is played by four actors--- but if I were in charge (of this movie, if not the world) that would make me want to work all the harder to make the character's arc clear.
At the end of the movie, I couldn't tell whether Tony was a con man, a good guy trapped by bad men and/or his own ambitions, a victim, or a player. I didn't know whether he was a genuine amnesiac or a fake one. Gilliam provides evidence for all of these, but never decides between one or the other.
I've liked some Gilliam films more than others, but even my least favorites had moments of wonderful imagination and beauty. This film is no exception, although there's a lot of flat, uninteresting action between the gorgeous fantasy bits. Much of the camera work is simply dull, and much of the action is busy to the point of incoherence.
For instance, a large number of the dramatic scenes between people consist entirely of two-shots--- shots from a medium distance showing both people. There is a surprising lack of closeups. (My god! I thought. This is filmed like a low-budget European movie from the Sixties!)
A closeup lets you into the actor's mind--- you can see from his expression how the line is meant to be understood, or whether he's lying, or confused, or trying to fast-talk his way through a situation. If you can't quite make out the face, all that nuance is lost.
And Gilliam makes it even worse, because during Lily Cole's big dramatic scene, he not only films it in medium shot but has the actress's face covered by her hair! You can't see anything but waving arms and flying red hair. WTF?
So all this leads up to Walter's Theory of Gilliam. Which is that Gilliam is infatuated with Story, and with Image, but disdains Plot.
Story, for the purpose of this discussion, is what actually happens during the course of the film/play/novel. Plot, however, is how the Story is revealed to the Viewer/Reader, each element of the Story arranged so as to enthrall and delight the audience.
Gilliam clearly adores Story. His films are full of references to classic Stories, be they the story of Percival, or Agamemnon and Clytemaestra, or stories about deals or dealings with the Devil. Baron Munchausen, which is my favorite Gilliam movie, is about a storyteller.
And Gilliam loves nothing more than Image. Give him an opportunity to sock the viewer in the eye with a giant phantasmagoric fruit salad of surprise, majesty, and delight, and he'll take it.
He's the great exponent of the unfettered imagination. All his films, in the end, are about the collision between Imagination and Reality. Usually Reality intrudes in an unpleasant way at the end of the film--- Brazil comes to mind--- but Imagination can triumph here and there, as in Time Bandits and Munchausen.
And in any case, Gilliam's sympathies are entirely with Imagination.
But Gilliam hates Plot. I'm not sure why. All those Stories that he loves--- Percival and Agamemnon and deal-with-the-Devil--- all have Plots. But Gilliam can't really be bothered to figure out what his stories and ideas and images actually mean.
Maybe he thinks he knows. But he's sure as hell not telling me.
I suspect he feels that the discipline of plotting would stand in the way of the unfettered imagination. (What--- cage all those fabulous, free, delirious Images within the iron bars of Meaning! How ordinary! How bourgeois! How unSpecial it would make me!)
And he's probably right--- at least some of those Images and Ideas would be tempered or altered. But the ones that remained would have a good deal more sock.
But then, I'm Mr. Plot. I like arcs and plot points and reveals. (Arcs! You want my characters to have arcs! Next you'll want them to follow that stupid Hero's Journey!)
((No, Mr. Gilliam, anything but that! I'm as bored with the Hero's Journey as anyone, trust me!))
What an arc means is that the character changes. And if he changes, he's just more interesting. The absolutely flat arc of Raoul Duke in Fear and Loathing in Las Vegas made the movie unwatchable. I couldn't stand being penned up with him for two hours, and neither could anyone else!
Now it has to be said that many characters do have arcs in Doctor Parnassus, including Doctor Parnassus himself and his daughter Valentina. Even the Devil has an arc, and the Devil never has an arc. They're all much more interesting than Tony.
I have a feeling that Gilliam started with the idea of a traveling show carrying a magic mirror around, and the magic mirror gave him an opportunity for all sorts of fantastic imagery, and that everything else was kind of an afterthought. Tony entered, hanging by the neck below Blackfriars Bridge, because Gilliam needed someone for the audience to first experience the Imaginarium alongside of. But other than fulfilling that basic need--- that an of being able to put a Bankable Star like Heath Ledger in the film--- Gilliam wasn't that interested in the character.
Now, it may be that I'm completely wrong here. All the answers may in fact be in the script, and if I read the shooting script I may be able to understand the plot a lot better, along with the characters' arcs . It could be that Tony's arc is buried somewhere in his scenes, which are so full of shouting, crashing objects, wild images, and frantic action, that I completely missed it. In which case, Mr. Gilliam, that's still your fault.
And now, here's the one real SPOILER, so if you plan to see the movie you should stop now.
Tony is first encountered hanging beneath Blackfriar's Bridge with mystic runes painted on his forehead. We're led to understand that he hanged himself in remorse for his shady business dealings. But he's later shown to have swallowed a pipe that allowed him to breathe while a noose was around his neck. Why did he hang himself AND CHEAT? I mean, what was the point?
It may be that Tony was hanged by the Russian Maffya types he was in business with, in which case his efforts to cheat death were well taken. But the Russians didn't seem surprised when they saw him alive later in the movie.
And the mystic runes? Mr Nick gives half an explanation, but never mind.