It seems wrong to call desire a theme of Dangerous Liaisons; it would probably be make more sense to call it a driving force, or maybe, the only possible explanation for why anyone would act that way. Desire is not only the motivating force in Dangerous Liaisons, it is itself the most desired commodity. In a society where people live in such luxury that they can want for nothing, the very act of wanting something makes that commodity become valuable.
War, or at least a minor altercation in Corsica, is in the background of Dangerous Liaisons. War is also in the foreground, since battle is the metaphor constantly used by Merteuil and Valmont to describe their amorous exploits.
Religion is another metaphor used to describe love, employed in particular by Valmont. To gain some ground on the Présidente de Tourvel, he writes to her in terms to which she will be forced by her convictions to respond. These are religious terms: for example, Valmont accuses his Présidente of refusing to listen to his prayers, of punishing him unfairly for his misdeeds, and of averting her eyes from him like some unfortunate person one has no intention of assisting. This could be called parody, but Valmont is not mocking, or even imitating, Tourvel's writing style. Rather, he is anticipating her reading style, and how much what she reads will reflect on her. Thus, he invents situations in which she could be responsible for his unhappiness, even though he was the one who started the whole affair. She can only believe what he says if she is sure that it pertains to her. What better way to convince a devout woman, Valmont reasons, than to convince her that she is the one who has done wrong. As the novel progresses, "faith," for the Présidente de Tourvel, has progressively more to do with the duty she owes Valmont than the duty she owes her god.
Education comes in many colors, but in Dangerous Liaisons, "receiving an education" usually refers to a loss of innocence, as opposed to learning the periodic table. It is unclear whether the Marquise de Merteuil's frequent referral to the seduction of Cécile as the girl's education is entirely an unkind joke. The Vicomte de Valmont participates in this unusual view of education aswell. In Letter One Hundred and Ten, he describes Cécile's recent anatomy lessons in bed with him, in which he has taught her "a sort of debauchee's catechism" ("une espèce de catéchisme à débauche") to help her remember the names of all the important parts. Indeed, Merteuil seems to have a place in her company all picked out for Cécile, once the girl has undergone a few tests and trials (Letter One Hundred and Six):
I had some thought of making a kind of assistant in intrigue out of her, of employing her, as it were, for subordinate roles, but I see that the material is lacking.
(J'avais eu quelque envie d'en faire au moins une intrigante subalterne, et de la prendre pour jouer les seconds sous moi: mais je vois qu'il n'y a pas d'étoffe...)
The education to which the Marquise refers is clearly an education for the stage. In Merteuil's opinion, a woman is made and not born, and she is a character she herself creates. The right material is absolutely essential for the creation of a proper character; without it, a woman cannot control her own fate or her own person. The debauching aspect of this enterprise is, therefore, a necessary precaution.
Valmont describes, in Letter Seventy-six, his arrival on the scene at Madame de Rosemonde's estate as operatic: "In fact I dropped from the clouds, like a god in an opera who comes down to unravel the plot" ("En effet, je tombai des nues, comme une Divinité d'Opéra qui vient faire un dénouement"). Opera held an important place in daily life in the 18th century. Here, the opera is present beneath the form of a metaphor. Stagings of operas in the 18th century frequently used mechanized devices to introduce characters at the conclusion of the piece. Ingenuity and artifice were often simultaneously present in the opera, just as they are present in the complex stagings and correspondences of the society depicted in Dangerous Liaisons.
There are two different ways in which the theme of class is brought up in Dangerous Liaisons. Class can only be discussed when there is a difference in class. For example, Merteuil never feels compelled to mention to Valmont how interesting it is that he is an aristocrat. As a result, class is discussed in relation to the servant class and in relation to the bourgeoisie. Servants know everything that goes on in the house where they serve, and yet this knowledge seldom seems to work to their advantage. The Marquise de Merteuil, for example, secured the loyalty of her maidservant, Victoire, by arranging for her to be sent to jail and then rescuing her. If Victoire ever does something to annoy the Marquise, she will very quickly find herself in the slammer again. The aristocracy's mission to make dependency a one-way street, since it has all the power and the lower classes depend on it, seems to be failing when it comes to the middle class. This is on account of a new kind money, which is not attached to land or to inheritance, and which can be used to purchase those privileges which were previously due by default to the aristocracy. For example, the courtesan Emilie is almost purchased by a bourgeois man before Valmont comes a-courting. Luckily, Valmont's old-fashioned aristo-sleaze continues to take precedence over cold, hard cash.
After she is jilted by Valmont, the Présidente de Tourvel is in correspondence with Madame de Rosemonde, whose rheumatism often prevents her from writing her own letters. Madame de Rosemonde writes (Letter One hundred and Twenty-six) that, ill as she is, she herself will serve as Tourvel's doctor ("Médecin") during this period of grief over love. It is interesting that Rosemonde does not offer herself up as confessor or comforter. The suggestion that love is a sickness proves so convincing that soon Tourvel will indeed die of love for Valmont. What Valmont sought to describe as a kind of religious devotion or sacrifice, Madame de Rosemonde wishes Tourvel to view as an indisposition. In fact, Valmont himself claimed to be indisposed when the Présidente refused to see him or accept his love. Illness is also the final punishment of the Marquise de Merteuil. As certain witty members of society remark, sickness reveals the true ugliness of the Marquise's soul.
Dangerous Liaisons contains no symbol more important than the letter. However, the novel cannot really be said to contain letters, since it is entirely composed of them. Instead, it makes more sense to say that the symbolism of the letter is vital to the way in which the plot works. The action in the novel depends on two characteristics of letters: that they say something, and that they can be read.
We should be forewarned that this is a little bit obvious: the key to the lock on Cécile's door symbolizes access to her person. By convincing her to give up the key to her room, Valmont convinces Cécile to surrender herself to him.