Identity is how the character sees himself throughout the book and how others see him. Identity is tied to Appearance and Society Class. An example of identity is: a character considering themselves the "wild" one, just like Ponyboy considers himself a "Greaser". ... Sunsets are a part of Ponyboy's identity.
It is shown that the animals have human-like intelligence, and as a result chose to leave their home, but I'm not sure if there is enough evidence to prove any theme.
