What is the theme of The Horse and the Boy? plese give me to possible theme of it

I would say that one of the main themes is independence and indpendent thinking. Shasta, for example, spends much of the book learning to think for himself and "shedding his slave mentality", and learning how to both think and act for himself. On the other side of the coin, Bree also wants to be "free" but he has a different path to follow.