Most children's novels are concerned with the many changes their young protagonists go through, and this book is no different. Phillip, an 11-year-old American kid living in the Caribbean, goes through a whole lot of changes in The Cay. And thank goodness for that, because he starts out as a major pain in the butt.
From the very first chapter, Phillip is in a state of transformation. When we meet him, he's young, sheltered, and pretty immature. The war brings on the loss of his innocence, his blindness demands that he see the world in an entirely different way, and his friendship with the West Indian man Timothy prompts him to rethink his prejudiced ideas about race. Just as in life, all those changes Phillip goes through (even the really hard ones) result in a more mature and experienced character at the novel's conclusion.
The most important lesson Timothy teaches Phillip is that he can change himself for the better.
The Cay would be a stronger book if Timothy went through some transformations along with Phillip.