Doubles and Duality (The Prestige) The Prestige
Everything in the film comes in pairs, and the pairs are never equal
The Prestige is built on doubles. Two magicians. Two diaries. Two timelines. Two women destroyed by the rivalry. Two versions of the same trick. Two men sharing one name. The doubling is not decorative -- it is the film's structural principle and its deepest theme. Every pair in the film conceals an asymmetry: the double never functions the same way as the original, and the act of doubling always costs something.
Brian Eggert of Deep Focus Review noted that Nolan "reinforces this throughout... framing Borden and Angier in identical shots in various scenes, suggesting that the two magicians have parallel obsessions, similar drives." (deepfocusreview)
Borden's twin is the film's original double, hidden in plain sight
The film's central deception is that Alfred Borden and Bernard Fallon are identical twins who have shared one life since childhood. One performs as the magician; the other works as the ingenieur, disguised behind prosthetics. They swap constantly, and neither lives a complete life.
The twin arrangement is the film's deepest expression of total commitment to craft. The cost is measured in the people around them. One twin loves Sarah; the other loves Olivia. Sarah senses the inconsistency: "You mean it today. Which makes it so much harder when you don't." Her inability to distinguish husband from impostor drives her to suicide. The twin arrangement is not a trick -- it is a way of life that destroys everyone it touches.
Chung Ling Soo is the thesis statement about doubling
The Chinese magician Chung Ling Soo appears early in the film as a parable about the cost of maintaining a double life. He is an old man who can barely walk -- except that his frailty is an act. He maintains a hunched, shuffling persona every moment in public so that no one will suspect the physical strength required for his fishbowl trick. Borden sees through it instantly and names the theme.
"Total devotion to his art. Utter self-sacrifice." — Borden (Christian Bale), The Prestige (2006)
The historical Chung Ling Soo was himself a double: an American named William Ellsworth Robinson who performed as a Chinese magician for his entire career, dying in character when a bullet catch went wrong in 1918. The film compresses this historical doubling into a single scene that encapsulates the Borden twins' arrangement.
Gerald Root is the double who cannot be controlled
Angier's first attempt at The Transported Man uses Gerald Root, a drunken actor, as his double. Root is a functional mirror of the Borden twin arrangement, but degraded. Where Borden's twins share identity willingly, Root is a hired replacement who resents his role. He demands recognition -- "Of course I can. I'm the Great Danton" -- and begins blackmailing Angier.
Root represents what happens when the double is not committed to the arrangement. Borden's twins succeed because both accept the sacrifice. Root fails because he does not, and Angier cannot tolerate a system where someone else gets the applause. The New Transported Man falls apart not because the trick does not work, but because the double has leverage.
Tesla's machine creates the double that costs the most
The duplication machine produces perfect copies. Unlike Borden's twin arrangement (which pre-exists the rivalry) or the Root arrangement (which is negotiated), the machine creates doubles that are instantaneous, identical, and disposable. One version appears in the balcony; the other drowns in a tank. The machine resolves the problem of the unreliable double by making the double expendable.
The philosophical question the machine raises -- whether the drowning man is the "original" or the "copy" -- is the same question the twin arrangement poses in different terms. Borden's twins cannot determine which of them tied the knot that killed Julia. Angier cannot determine which of him will drown each night. Both forms of doubling dissolve the concept of a stable, singular self.
The two diaries are unreliable doubles of each other
The film's narrative structure is itself a doubling: Angier reads Borden's diary in Colorado; Borden reads Angier's diary in prison. Each diary lies to its reader. Borden's diary contains the trap -- "TESLA" is the cipher keyword, not the method. Angier's diary omits the machine's true nature. The diaries are doubles of the truth, each distorted by the writer's agenda.
The film doubles back on its own audience
Nolan's structural argument is that the film does to its audience what the magicians do to theirs. The audience watches two hours of a magic trick without detecting the switch -- just as Borden's audiences watch The Transported Man without seeing the twin. Michael Caine articulated this directly.
"What is unique about The Prestige is you have no idea there is another magician called Christopher Nolan who is the writer-director, who is working behind you. The whole movie you're seeing is a two-hour trick." — Michael Caine, Twitter/NolanAnalyst (2006)