It would be safe to say that the central theme is survival and adaptation to sudden change. Many have argued that this is an allegory to the transition from childhood to young adulthood, or from young adulthood to adulthood, which are transitions into complex, and complicated situations to which we have to adapt.
When Alice moves into Wonderland, things are difficult for her. More than just enjoy herself and have fun in the freedoms of being alone, Alice actually went through a series of quasi traumatic event, rare and odd changes, met very strange character, saw things she had never experienced before, and in some occasions she wished she could be back home.
Those are feelings very similar to those of people who are entering a new stage in their lives: Meeting strangers, having to problem solve alone, changes in our bodies, experimenting with things we have never tried, being chased or chasing something not knowing what it is. Those are subtopics that chain into the main idea of surviving change and facing the challenges of change.
Hope this helps!
Alice in Wonderland is such a rich work that it is difficult to land on one main theme but at the heart of the story lies the question of identity. Who are any of us? Who is Alice? Almost as soon as she enters the rabbit hole, Alice's sense of self is under constant assault, symbolized by how her physical body changes in ways outside of her control. While obeying orders (trying to fit in to her new world) she is constantly growing too small or too big for whatever task is at hand. She admits to the Caterpillar in chapter five that she is undergoing a crisis about her identity. When he asks her who she is, she responds:
'I—I hardly know, sir, just at present—at least I know who I was when I got up this morning, but I think I must have been changed several times since then.'
'What do you mean by that?' said the Caterpillar sternly. 'Explain yourself!'
'I can't explain myself, I'm afraid, sir' said Alice, 'because I'm not myself, you see.'
'I don't see,' said the Caterpillar.
'I'm afraid I can't put it more clearly,' Alice replied very politely, 'for I can't understand it myself to begin with; and being so many different sizes in a day is very confusing.'
This confusion about identity becomes central to this book. The Duchess's baby turns into a pig, the Cheshire cat into a smile, and the Queen and her court into a pack of cards. The outer world is often less than helpful in Alice's search for herself: she gets nowhere but more lost as she lets its craziness determine who she is. It is when she looks inward, holds her ground, and is not afraid that she awakes from her dream:
'Hold your tongue!' said the Queen, turning purple.
'I won't!' said Alice.
'Off with her head!' the Queen shouted at the top of her voice. Nobody moved.
'Who cares for you?' said Alice, (she had grown to her full size by this time.) 'You're nothing but a pack of cards!'
At this the whole pack rose up into the air, and came flying down upon her: she gave a little scream, half of fright and half of anger, and tried to beat them off, and found herself lying on the bank, with her head in the lap of her sister, who was gently brushing away some dead leaves that had fluttered down from the trees upon her face.
Define yourself, Carroll might advise, for the world around you is too cracked to do it for you.
Alice in Wonderland is a timeless story that is relevant in many cultures, having been translated in 40 languages. Through most of its history, Lewis Carroll's Alice in Wonderland has been described as a "coming of age" story about a young girl trying to figure out who she really is. These universal themes have allowed Alice to remain popular for many years and in many cultures.
The themes of identity, Alice figuring out who she is, and coming of age are so similar as to be one theme. Struggling to figure out who you are is an accepted part of late childhood and the teenage years for most people. As Alice travels through Wonderland, she is constantly bombarded by personal changes that challenge her perception of herself, not unlike the changes that children go through during the late childhood to teenage years.
The main theme of Alice in Wonderland can therefore be described as one of growing up and finding one's identity.