Nearly all of the people or creatures that Alice meets in Looking-glass World are adults, at least in some sense of the word. However, none of the adults that Alice meets are especially helpful. Instead, the adults seem caught up in pointless philosophical or logical arguments and silly rules, and in many cases, Alice seems more competent and mature than they are. Together, all of this implies that adults aren't nearly as competent as children might think they are, while Alice's brief stint as queen suggests that adulthood itself isn't all it's cracked up to be.
The Red Queen first introduces Alice to the fact that in Looking-glass World, things don't function in the way that Alice expects them to. This is Alice's first clue that the adult world isn't going to live up to her expectations, good or bad, and that part of reaching adulthood is having these expectations about the world dashed. Alice's interactions with the White Queen have much the same effect. When Alice runs into the disheveled queen in the woods, the White Queen matter-of-factly explains that she can remember in both directions—that is, she can remember the future and the past—and to demonstrate, the queen screams before pricking her finger and then expresses sadness that a man is being punished for a crime he hasn't committed yet. However, when Alice questions the ethics of this and asks what will happen if the man doesn't commit the crime he's currently being punished for, the White Queen brushes her off. Through her reaction, the White Queen suggests that the adult world she represents is impenetrable and unknowable to a child like Alice—even though Alice obviously has valuable insights about it.
In other cases, Alice—the only actual child in Looking-glass World—appears far more adult than any of her "adult" companions, suggesting that in important ways, children are actually more observant, polite, and competent than the adults around them. Both the White King and the Red King, for example, are ineffective kings. While the Red King spends the entire novel asleep, the White King fails to follow through and send all his horses and men to rescue Humpty Dumpty. The White Queen, meanwhile, spends the novel in complete disarray and is unable to keep track of her shawl—a fairly childish problem to have—while the White Knight cannot ride for more than a few yards without unceremoniously tumbling off of his horse. Instead, it falls to Alice to help these adults when she can. She retrieves and pins the White Queen's shawl back on and helps the White Knight back onto his horse—and at one point pulls him out of a ditch, which he fell into face-first.
As queen—which, for Alice, is a symbolic version of adulthood—Alice discovers even more evidence that suggests that adults aren't all as competent or as powerful as she might think, or might dream of one day being herself. To begin with, having the crown may make Alice queen, but it doesn't offer her any enlightenment as to how one acts like a queen. Moving through Looking-glass World as a queen is just as disquieting and difficult as it was when Alice was a pawn: the other queens jointly arrange for Alice to throw a party, something which Alice has no knowledge of; Alice struggles to figure out how to get to the party in the first place; and finally, she finds herself unable to figure out the rules and correct behavior once she does finally make it to the party. With this, Carroll suggests that adulthood really isn't that noble of a goal: it's just as confusing as childhood is and it doesn't provide any real benefits aside from simply getting to call oneself an adult. Adulthood, per Through the Looking-Glass, is little different from childhood—the stakes may be higher and there are certainly privileges that come with being an adult in the eyes of society, but everyone is still just trying to figure out how to navigate the world.
Adulthood and the Adult World ThemeTracker
Adulthood and the Adult World Quotes in Through the Looking-Glass
"They're done up close, like a dahlia," said the Tiger-lily: "not tumbled about, like yours."
"But that's not your fault," the Rose added kindly. "You're beginning to fade, you know—and then one can't help one's petals getting a little untidy."
"Where do you come from?" said the Red Queen. "And where are you going? Look up, speak nicely, and don't twiddle your fingers all the time."
Alice attended to all of these directions, and explained, as well as she could, that she had lost her way.
"I don't know what you mean by your way," said the Queen: "all the ways about here belong to me—but why did you come out here at all?" she added in a kinder tone. "Curtsey while you're thinking what to say. It saves time."
"Seven years and six months!" Humpty Dumpty repeated thoughtfully. "An uncomfortable sort of age. Now if you'd asked my advice, I'd have said 'Leave off at seven'—but it's too late now."
"I never ask advice about growing," Alice said indignantly.
"Too proud?" the other enquired.
Alice felt even more indignant at this suggestion. "I mean," she said, "that one ca'n't help growing older."
"One ca'n't, perhaps," said Humpty Dumpty; "but two can. With proper assistance, you might have left off at seven."
"As to poetry, you know," said Humpty Dumpty, stretching out one of his great hands, "I can repeat poetry as well as other folk, if it comes to that—"
"Oh, it needn't come to that!" Alice hastily said, hoping to keep him from beginning.
"The piece I'm going to repeat," he went on without noticing her remark, "was written entirely for your amusement."
Alice felt that in that case she really ought to listen to it; so she sat down, and said "Thank you" rather sadly.
So she got up and walked about—rather stiffly just at first, as she was afraid that the crown might come off: but she comforted herself with the thought that there was nobody to see her, "and if I really am a Queen," she said as she sat down again, "I shall be able to manage it quite well in time."
Everything was happening so oddly that she didn't feel a bit surprised at finding the Red Queen and the White Queen sitting close to her, one on each side: she would have liked very much to ask them how they came there, but she feared it would not be quite civil.