Individualism
Philip Marlowe gets some assistance from Vivian Rutledge, but for the most part he goes it alone. His individualistic approach makes Marlowe a perpetual outsider. He is a character always knocking on doors to gain entry into a world that views him with suspicion at best, and usually contempt. Marlowe's rejection of teamwork, however lonely it makes him, always serves him well, and he ends up getting an advantage on his opponents by having acted alone. Individualism and the "lone wolf" identity are archetypal to the film noir anti-hero. Relying only on himself, Philip Marlowe is the very epitome of the American ideal of the rugged individualist doing it all by himself, and serving justice.
Deception and Corruption
No one trusts anyone else in the film, and with good reason. Marlowe alone seems capable of telling the truth on a regular basis, but in his job that is not something that is always such a good idea. Oftentimes, he is pressed to tell a white lie to get what he needs and to get answers. He must play dirty, like the criminals he is trying to catch. Underneath nearly every wholesome facade lies a dirty secret. The wealthy Sternwood's daughter is a nymphomaniac who does drugs, poses for pornographic photographs, and kills a man who rejects her. Her appearance of innocence is itself the central deception driving the plot forward. The events and people that Marlowe encounters in his search for the truth are consistently untrustworthy, saying one thing and doing another. In the sordid world of crime, deception is the only way to get ahead. In the final scene, Marlowe too must resort to deceptive means in order to apprehend Eddie Mars, lying about his whereabouts and then leading Mars' own associates to kill him.
Getting There First
At the end of the film, before Eddie Mars arrives at Geiger's, Marlowe turns to Vivian and tells her that Eddie Mars has been one step ahead of him the whole time, but that finally, now that they're back at Geiger's when Mars doesn't expect them to be, they are ahead. Marlowe, for all his competence, swagger, and cool attitude, is fighting an uphill battle for much of the film. While he can sniff out a rat and easily tell when he's being lied to, Eddie Mars's network is so extensive and the corruption of the central conflict runs in so many different directions that Marlowe is unable to get the upper hand. Finally, at the end, he acquires it. After getting Eddie Mars to admit to his crimes, Marlowe says, "You walked in here without a gun. You were gonna sit there and agree to everything just like you're doing now. When I went out that door, things were gonna be different. That's what those boys are doing out there. But everything's changed now, Eddie, because I got here first." Marlowe's defeat of Mars comes from his ability to show up first, to figure out how to get an advantage, and to save the day.
Games and Gambling
Central to the theme of corruption is the gambling operation run by antagonist Eddie Mars. At this operation, people gamble their money away and scantily clad women sell cigarettes. Gambling stands in as representative of all the corruption that has touched the Sternwoods' lives. Vivian later tells Marlowe that she is an avid gambler. In fact, Vivian's gambling habit puts her in a vulnerable position, as it connects her to Eddie Mars, whom she initially hires to cover up Sean Regan's murder, but who takes advantage of her and blackmails her with the information.
In addition to having negative connotations and representing corruption and vice, a more metaphorical "gambling" and playful gamesmanship underscores the budding romance between Marlowe and Vivian. When Vivian visits him at his office and goes to call the police, he takes the receiver and pranks the police station by pretending that the police are the ones who called them. Vivian is charmed, and easily plays along with the prank. This game is a complex flirtation between the two well-matched wits. Later, when they get a drink together, they engage in an iconic dialogue about horse racing—a popular way to gamble—that works as an extended sexual double entendre. They liken their sexual attraction to one another to betting on a horse and seeing if it will win. Thus, their courtship is itself a kind of romantic, emotional, and undeniably sexual gamble.
Sex
Sex is a powerful force in The Big Sleep. At the start of the film, it is a corrupting influence, as we see represented in the character of Carmen Sternwood. She has a markedly overflowing libido, one which goes beyond the bounds of propriety and threatens her family's reputation. When she first meets Marlowe, she throws herself at him, to the extent that he tells her father, "She tried to sit in my lap while I was standing up." She seduces men left and right without discretion, bites her thumb provocatively, and poses for pornographic photographs. Carmen's sexuality is dangerous and pathological, and it is Sean Regan's sexual rejection that incites her to murder him.
Marlowe and Vivian also have very active libidos, but they are cloaked in suggestion and discretion, which distinguishes them from the pathologically randy Carmen. Marlowe can hardly interact with a woman without flirting and seducing her, and Vivian is also a rather erotically powerful character, but each exercise self-control and discrimination and do not let their sexual desires get in the way of the jobs they must do. Both Vivian and Marlowe have a well-developed relationship to their own eroticism. The difference between them and Carmen is that their desire is focused, where hers is compulsive and affirmation-seeking. Sex is everywhere in The Big Sleep, even if the filmmakers were forced to go along with conservative Hays code stipulations at the time.
The Dogged Pursuit of Truth
Marlowe is, above all, committed to the truth. This is what makes him such a good private detective. While even the District Attorney's office is willing to turn a blind eye to Eddie Mars's corruption, Marlowe is unwilling to compromise and put the case to rest, even when Geiger's killer has been determined, Vivian has discharged him, and his friend Bernie urged him to move on. Marlowe's investment in the case, and his interest in unveiling the truth, runs deeper than this, and others' discouragement only compels him to work harder to figure out the mystery. Marlowe's pursuit of truth extends beyond the desire for money, as shown when he acknowledges the shabbiness of his office to Vivian. Marlowe wants to be an honest man and to get corruption off the streets. His idealistic pursuit gives him a fierce momentum, an unflappable resolve to do what is right, even in the face of danger, intimidation, brute force, and corruption.
Social Hierarchy
Marlowe must navigate a confusing and morally ambiguous path that takes him from the elite upper echelons of California society to its lower reaches and all the places in between. Class is not dealt with directly, but the initial scandal of the Sternwood household stems from the fact that the youngest Sternwood daughter is caught up in a world of vice and corruption. Even though Carmen Sternwood is from a good family, she engages in less savory pastimes. Vivian too, in spite of being a wealthy girl, enjoys gambling and has an irreverent bluntness that does not quite fit her social class. Corruption, the film argues, makes no prejudices based on class or rank. All characters seem equally likely to succumb to the siren song of corruption. While many believe that social hierarchy separates the good from the bad, The Big Sleep reveals that this is simply not the case. The wealthier among us have ugly skeletons in their closet too, the film suggests—perhaps more of them. Eddie Mars is a business owner and a landlord, and does not carry a gun himself (his own wife doesn't believe he's caught up with gangsters), but he leads a crew of violent thugs. Even though he is detached from them by his class, he is no better, and is in fact the criminal mastermind behind the whole operation.
Philip Marlowe has a unique role in this hierarchy. His outsider status affords him a special distinction that allows him access to all levels of the social hierarchy. His outsider status also lends him a moral dignity. When Vivian visits Marlowe at his office, she comments on his markedly humble facilities, to which he responds, "You can't make much money at this trade, if you're honest." Here, Marlowe insinuates that his honesty holds him back financially, and that if he were more flexible morally, he might be a wealthier man. Thus, honesty and the truth are antithetical to wealth accumulation, by Marlowe's logic.