How does Avi use imagery in Crispin: The Cross of Lead?

Examples of Imagery:

"Bear - in the short time I had known him - was a thousandfold more a faithful father to me."

"I was unfettered, alive to an earth I hardly knew but was eager to explore. What's more, I knew that feeling to be my newfound soul, a soul that lived in freedom. And my name - I knew with all my heart - was Crispin."