Reflection/Reversal
The most apparent example of this theme is the looking-glass itself, which provides a reflection of the actual world for Alice to explore. Within the looking-glass, everything is backwards. Text is reversed: Alice reads the poem Jabberwocky backwards. Space/direction is inverted: Alice must walk away from where she wants to go in the garden in order to actually get there. Ideas are also inverted, which is plain in many of the conversations that Alice has with the characters encountered in the looking-glass world. Tweedledee and Tweedledum are mirror images of each other. The White Knight talks about putting a right foot into a left shoe. In the railway carriage, Alice is traveling in the wrong direction.
Satire
Carroll does not mean this tale to be serious. For one thing, an imaginative child who talks to cats is the protagonist, and it is she who leads the reader through the book. Additionally, there is no sense of consistency in the book; as soon as a rule for the looking-glass world is introduced, it is either abandoned or changed. Further, Carroll appears to be poking fun at adult intellectualism. All the characters who attempt logical debate either argue themselves into confusion or lose to a seven-year-old Alice.
Dreaming
Carroll sets his entire book in the context of a dream. Whose dream it is remains unclear, but Alice definitely acknowledges that she was having adventures in someone's dream, if not her own. What is so important about this is the fact that the absence of reality does not matter to the protagonist, and it clearly does not matter to the author. In fact, Carroll seems to believe that dreaming is the ideal, especially for young children, as suggested by the poem at the very end of the book. He goes as far as to suggest that there might not be any set reality at all, and that life is just the stuff of dreams.
This nonchalance about the issue of what is real and what is not is partly what makes Alice such a compelling protagonist. The precocious Alice takes everything in stride. In a way, her vast imagination allows Carroll to expose the reader to a multitude of fantasies. And because Alice never ultimately passes judgment to the point of denying these whimsies, the author is able to bring his reader into an intricate world entirely of his own invention.
Alienation
Alice is in fact alone through much of the story, though not as much literally as figuratively. She is the only one of her kind in the Looking-Glass world, so even though she is surrounded by creatures pretty much at all times, she has trouble relating to their foreign ways. She is also isolated from the rest of her family due to her imagination; there is a reference to the frustration she causes when she plays pretend. At many points in the story, the reader has the sense that Alice has no place to go to feel at home; she expresses her loneliness while in the Looking-Glass world, but she immediately rebounds and worries about ultimately having to end the game and return to her house.
Adulthood
Carroll's attitudes toward adulthood are not entirely clear in the book, though the book itself can be seen as a motif for the progression from childhood to adulthood, as represented by Alice's journey as a pawn to queenhood. She undergoes many experiences that can be seen as crucial for development, such as the discovery of identity that is demanded by the situation in the wood of forgetfulness. Many of the poems recited focus on the theme of passing youth. However, the incompetence and immaturity of those that may be considered adult characters in the book calls the idea of a progression into question. Alice often proves to be smarter, more thoughtful and more resourceful than the "adults" she encounters in the looking glass.
Moral Choice and Social Ettiquette
There are many cases in Through the Looking Glass in which the question of control and intentionality come into play. Looming over the entire novel is the question of whether Alice's adventures were really just a figment of the Red King's dream. Additionally, it is unclear whether Alice has any choice about moving from the second to the eighth square, and there are a number of instances during which she seems to question her goal.
Carroll, as a Victorian era author, is concerned about the methodical, logical examination of behavior. Within almost every conversation Alice has with the characters in the Looking-Glass world is at least one critique of their social norms. But these are not serious critiques, for it has been established by the author that everyone in this world lives backwards, and as Alice has observed, many aspects of living backwards seem impossible. Inevitably, though, this often nonsensical evaluation of rules might indeed be a comment on the burdensome obligations of adulthood and the moral/social responsibilities that accompany it.