Dumas regularly describes characters through allusions to other literary characters. This motif first appears in Chapter 1, when he introduces d'Artagnan by alluding to Don Quixote:
A young man…Let us sketch a rapid portrait of him. Imagine Don Quixote at eighteen, a Don Quixote without chain mail or thigh pieces, wearing a woolen doublet whose original blue had been transformed into an elusive shade between purple and azure.
Don Quixote is the titular character of Miguel de Cervantes's 17th-century book about a man who reads too many romances and convinces himself that he is a knight. Before even revealing d'Artagnan's name, Dumas asks readers to imagine this deluded literary "knight." The comparison allows Dumas to convey a lot about d'Artagnan all at once. He fits the literary archetype (especially popular in the 19th century) of a sheltered young man who is obsessed with adventure and believes he knows something about the world because he has read a lot about it. Dumas is establishing his novel as comedic as well as dramatic and adventurous. He invites readers to laugh at d'Artagnan as many of them have likely laughed at Don Quixote. He is also joking at the expense of his readers and himself: the only reason this allusion works to establish d'Artagnan as a comedic figure is because Don Quixote is a familiar figure. Dumas and his readers, too, might spend too much time reading for their own good.
This is far from the only time Dumas resorts to a literary allusion to describe a character. In Chapter 32, after Porthos's deeply disappointing dinner at the Coquenard house, Dumas compares Madame Coquenard to a character in a Molière play:
Madame Coquenard sighed once again. Since Molière had not yet written The Miser, she was an earlier version of Harpagon.
Molière was a hugely popular French playwright whose comedies are some of the most famous works of satire in French. He wrote The Miser in the 1660s, some 40 years after the action of Dumas's book takes place. Harpagon (whose name refers jokingly to a grappling hook) is the miser of the play's title. He is an old man who gets himself and his children into a series of outrageous situations due to his obsession with "hooking" other families' wealth. Dumas compares Madame Coquenard to "an earlier version of Harpagon" to underscore the comical trouble Porthos encounters getting her to relinquish any wealth. Again, he assumes that his readers are familiar with the most popular books and media of the day. This allusion not only helps him characterize Madame Coquenard as a certain type of literary figure, but it also once again establishes the book's self-consciousness as a literary work.
In Chapter 4, d'Artagnan tries to befriend Aramis by returning the handkerchief the musketeer has dropped, but this turns out to be a mistake. As the other musketeers make fun of Aramis for having Madame de Bois-Tracy's handkerchief, one of them alludes to the biblical story of King Solomon:
“If you swear on your honor and I swear on mine, one of us will obviously be lying. Let’s do something better than that, Montaran: let’s each take half.”
“Of the handkerchief?”
“Yes.”
“Good idea!” exclaimed one of the other guards. “Solomon’s judgment! Aramis, you’re a wise man.”
In the Bible, two women appear before King Solomon, both claiming that they are the mother to the same baby. Rather than make a judgment based on the women's testimony, Solomon proposes cutting the baby in two so that each woman will get half. Solomon does not intend to follow through on this proposal. Instead, he trusts that whichever woman says she will give up the baby to protect it must be the true mother.
The musketeer who refers to "Solomon's judgment" is remarking on Aramis's cleverness. Aramis and another musketeer have accused one another of having an affair with Madame de Bois-Tracy, whose husband they each consider a friend. They have been arguing over who should take the handkerchief to give back to Monsieur de Bois-Tracy with news that his wife has been having an affair with the other man. As the one who has proposed cutting the handkerchief in half, Aramis has suggested that the handkerchief is insignificant to him as a token of a mistress's love, just like the baby is ultimately insignificant to the woman who would allow it to be cut in half.
This exchange is both tense and comical. The handkerchief itself may be an allusion to Shakespeare's tragedy Othello, in which the villainous Iago plants Desdemona's handkerchief in another man's chambers as part of his dastardly plot to frame her for cheating on Othello. The handkerchief in Shakespeare's play helps bring about a horrible, violent end for Othello, Desdemona, and other characters. Readers familiar with the play (as most of Dumas's readers likely were) would recognize the handkerchief as a symbol of infidelity that might have dire consequences. If Aramis is discovered to be having an affair with another man's wife, he could face those consequences. At the same time, the fact that the appearance of the handkerchief mostly results in banter suggests that among the right company, it is merely a social gaffe to let others see evidence of an affair. It is quite possible that both of these men are having affairs with other men's wives, but they are expected to keep it quiet.
In Chapter 8, d'Artagnan sits in his room and thinks in awe about his new friendship with Athos, Porthos and Aramis. As he thinks of what they could achieve together (ideally in exchange for some good money), he conjures to mind a simile that alludes to a law of physics:
He racked his brain in search of a purpose to which that fourfold force could be applied. He had no doubt that, like Archimedes’ lever, it could lift the world if it was properly used.
Archimedes's law of the lever is the notion that a lever can be balanced with different weights on each side if those weights are placed nearer or farther from the fulcrum, or center of gravity. For example, on a see-saw (a kind of lever), a lighter-weight child and a heavier child can balance one another if the heavier child sits closer to the center. Even though there is less weight on one side, sitting at the end of the see-saw gives the smaller child more leverage. Leverage and weight combine, producing enough cumulative force on that side of the lever to keep it balanced. Archimedes did not discover levers, but he was the first person we know of to describe this effect. He famously claimed that if he had enough space for leverage, he could move the entire world with his foot.
D'Artagnan compares the "fourfold force" of the musketeers to Archimedes's lever. They have currently been brought low by a lack of funds, but he feels confident that if they found the right use for their combined power, they too could "lift the world." As if in answer to his wishes, Monsieur Bonacieux knocks on his door and asks for help tracking down his wife, who has been kidnapped. This plea leads to some challenges for d'Artagnan and his friends, but ultimately it does launch them into their next adventure and its rewards.
In Chapter 25, d'Artagnan sees Monsieur Bonacieux, and one look at his face tells him that the man is responsible for his own wife's kidnapping. Dumas alludes to the pseudoscience of physiognomy as he uses a metaphor to describe how d'Artagnan arrives at his conclusion:
He noticed the sickly, yellowish pallor caused by an infiltration of bile in the blood; that might not be significant, but he also noticed something cunning and treacherous in the wrinkles of his face. A criminal does not laugh in the same way as an honest man, a hypocrite does not shed the same tears as a man of good faith. Duplicity is a mask, and no matter how well made that mask may be, it can always be distinguished from the face with a little attention.
According to this passage, "duplicity is a mask" that people wear plainly on their faces. D'Artagnan can supposedly deduce from the wrinkles on Monsieur Bonacieux's face that he has betrayed someone. He can tell from his complexion that there has been "an infiltration of bile in the blood" that, combined with other signs, indicates that the man is up to something. In the 19th century, people believed in physiognomy, a pseudoscience that claimed it was possible to identify biological differences between good people and bad people, "criminals" and law-abiding citizens. The shape and look of someone's face, physiognomists argued, could tell you what kind of person they were. When Dumas writes that, "A criminal does not laugh in the same way as an honest man, a hypocrite does not shed the same tears as a man of faith," he is not only being poetic but also alluding to this flawed belief system.
While it sounds ridiculous today to say that someone's wrinkles can indicate whether or not they have betrayed someone they love, there are still many holdovers of physiognomy in today's discourse around crime. Physiognomy's popularity coincided with the popularization of crime fiction in the later 19th century. Swashbuckling novels such as The Three Musketeers fed into that genre, and the way crime writers described "criminals" and detectives using physiognomy as a reference point still informs the way we think about these categories of people. Later, popular television shows like Criminal Minds continued to reproduce certain images of what a "criminal" looks like, and those ideas in turn have seeped into legislation, law enforcement, and the justice system.
Dumas regularly describes characters through allusions to other literary characters. This motif first appears in Chapter 1, when he introduces d'Artagnan by alluding to Don Quixote:
A young man…Let us sketch a rapid portrait of him. Imagine Don Quixote at eighteen, a Don Quixote without chain mail or thigh pieces, wearing a woolen doublet whose original blue had been transformed into an elusive shade between purple and azure.
Don Quixote is the titular character of Miguel de Cervantes's 17th-century book about a man who reads too many romances and convinces himself that he is a knight. Before even revealing d'Artagnan's name, Dumas asks readers to imagine this deluded literary "knight." The comparison allows Dumas to convey a lot about d'Artagnan all at once. He fits the literary archetype (especially popular in the 19th century) of a sheltered young man who is obsessed with adventure and believes he knows something about the world because he has read a lot about it. Dumas is establishing his novel as comedic as well as dramatic and adventurous. He invites readers to laugh at d'Artagnan as many of them have likely laughed at Don Quixote. He is also joking at the expense of his readers and himself: the only reason this allusion works to establish d'Artagnan as a comedic figure is because Don Quixote is a familiar figure. Dumas and his readers, too, might spend too much time reading for their own good.
This is far from the only time Dumas resorts to a literary allusion to describe a character. In Chapter 32, after Porthos's deeply disappointing dinner at the Coquenard house, Dumas compares Madame Coquenard to a character in a Molière play:
Madame Coquenard sighed once again. Since Molière had not yet written The Miser, she was an earlier version of Harpagon.
Molière was a hugely popular French playwright whose comedies are some of the most famous works of satire in French. He wrote The Miser in the 1660s, some 40 years after the action of Dumas's book takes place. Harpagon (whose name refers jokingly to a grappling hook) is the miser of the play's title. He is an old man who gets himself and his children into a series of outrageous situations due to his obsession with "hooking" other families' wealth. Dumas compares Madame Coquenard to "an earlier version of Harpagon" to underscore the comical trouble Porthos encounters getting her to relinquish any wealth. Again, he assumes that his readers are familiar with the most popular books and media of the day. This allusion not only helps him characterize Madame Coquenard as a certain type of literary figure, but it also once again establishes the book's self-consciousness as a literary work.