Nietzschean Philosophy
The entire plot of Rope revolves around Brandon and Phillip's misapprehension of the philosophy of Friedrich Nietzsche. The Nietzschean concept of the ubermensch comes up in his book Thus Spoke Zarathustra, and is an outline for a hypothetical ideal society, in which the world's superior citizens are able to transcend simple morality and control the world as they please. The various references to Nietzsche’s concept of the ubermensch become a thematic center in the film. Brandon and Phillip justify their murder of David on the grounds of their intellectual superiority. Cadell is an influential proponent of Nietzsche, and he openly talks about his admiration for Nietzsche's thoughts on murder at the dinner party, before he realizes that Phillip and Brandon have actually committed a murder. When he does finally realize that the men have acted on what is for him simply an abstract concept, Cadell is horrified and he disavows his interest in the concept completely.
Broad Daylight (Dark vs. Light)
When Phillip and Brandon commit the murder, it is the middle of the day in New York City. At first we see the sunny city itself, and then the drawn curtains of Brandon's apartment. The closed shades signal something nefarious is happening inside, and indeed it is: a man is being strangled. After they kill David, Brandon urges Phillip to open the curtains, which he does hesitantly, as Brandon says, “No one ever feels safe in the dark, no one who’s ever a child that is." They must commit their deed in the dark, but Brandon rather unusually insists that the darkness is frightening. Throughout dinner, the sun sinks in the sky and it gets darker and darker, as the mystery unfolds. Then later, when Cadell comes back to the apartment after the party, suspicious that something terrible has happened, he says of David's disappearance, "Yes, it must’ve been in broad daylight when it happened." They are not even talking about murder, but Cadell's statement makes the intoxicated Phillip upset, and he wants to know what Cadell thinks must have happened in broad daylight. Indeed, it was the murder of David Kentley. The theme of darkness is pervasive throughout, and most of the characters are figuratively "in the dark" for the duration of the film.
The "Perfect Murder"
Connecting to the Nietzschean ideal of the ubermensch is Brandon's fixation on committing the "perfect murder," one in which the superior man kills the inferior man without consequence. He is obsessed with the perfection of the murder, and after they kill David he says to Phillip, "Well, the Davids of the world merely occupy space, which is why he was the perfect victim for the perfect murder.” David is the perfect victim precisely because he is, in Brandon's estimation, average, and thus inferior to Brandon.
Brandon's desire to commit the perfect murder is of a piece with his desire to do everything perfectly. He wants to be the perfect host of the perfect party, and his charm and competence as a leader are immense. However, the lengths to which he will go to feel as though he is perfect are murderous and violent.
Art
After they kill David, Brandon says to Phillip, "You know I’d never do anything unless I did it perfectly. I’ve always wished for more artistic talent. Well, murder can be an art too.” Here again we see that David always wants to do things perfectly, and we learn more about why. He longs to have artistic talent, but has none. In lieu of an artistic outlet, he has resorted to the artful murder, one which goes off without a hitch, and in which all the component parts add up to the perfect deception. In Brandon's mind, murder is a creative act, rather than a destructive one, and in this way it is akin to an artistic practice.
Phillip contrasts with Brandon in that he actually has artistic talent, and is set to play the piano at Town Hall soon. A deeply sensitive and feeling soul, Phillip can hardly handle the aftermath of the murder, and drinks excessively and commits social faux pas throughout the night. The one pastime that anchors him is music, and sitting at the piano. When Cadell questions him about his lying about wringing chickens' necks, Phillip simply plays a piece on the piano. Then later, when Cadell has fired the gun out the window, summoning the police, Phillip sits at the piano and plays as the movie ends.
The "Real Real Me"
When Kenneth and Janet have a conversation at the party, orchestrated by Brandon, Janet confides in Kenneth that David was hugely helpful to her after Kenneth broke up with her, and gave her a shoulder to cry on. Janet tells him that in public she is often prone to social insecurity, but that with David she can really "relax." Explaining further, she blushes as she tells Kenneth that David lets her feel all "the real real me" stuff. Presumably, she means that David lets her feel like she can be herself, in contrast to the rest of the world that wants her to be something she is not. The question of pretenses and social performance is a broader theme of the movie as well. Indeed the dinner party itself requires a great deal of performance and adherence to etiquette from all of the characters in the film. There are several moments in which that etiquette and pretension bursts and people start acting like themselves, but for the most part, everyone adheres to a certain code of manners, which requires that no one quite access the "real real me."
Homosexuality
This is a difficult theme to characterize, as there were strict codes that prevented a more explicit depiction of homosexuality at the time, but the film's two murderers, Brandon and Phillip, are implied to be homosexual. Mr. Cadell also was supposedly meant to be homosexual, although there are no explicit indicators of this being the case. Even the people who worked on the film knew about the connotations, but referred to homosexuality as "it" throughout filming. At the time, several American cities banned the film because of the implication of queer love. The screenwriter, Arthur Laurents, was openly gay, and Farley Granger and John Dall, the two actors portraying Brandon and Phillip, both engaged in same sex relationships in their real life. Indeed, the very story on which the film is based is the real life murderers Leopold and Loeb, gay lovers who killed a younger man. The most explicitly homosexual the film gets—and even this is not explicit at all—is the moment in which Brandon describes his feeling of exhilaration at having killed David, and his description sounds almost post-coital. While it is shrouded in suggestion and never explicitly named, homosexual desire is alluded to throughout the film.
Playing God
Brandon's belief that he is superior to his companions lies not only in the fact that he feels entitled to murder David Kentley, but also that he wants to completely control and orchestrate the evening. He believes so firmly in his powers of deception that he keeps the rope that they used to kill David, eventually tying up a bundle of books with it to give to Mr. Kentley. He also wants to sow the seeds of affection and love between Kenneth and Janet, now that David is dead.
When Cadell discusses Nietzsche's argument about the privilege to murder, Mr. Kentley becomes rattled, and insists that it is presumptuous and dangerous for a person to think that they have the authority to decide if someone deserves to live or die. Later, when he discovers that they have killed David, Cadell echoes Mr. Kentley's thoughts, saying, "By what right did you decide that that boy in there was inferior and could be killed? Did you think you were God, Brandon?" Brandon exhibits extreme hubris in thinking that he can control the world around him.
