What clues does Lee give the reader about how Atticus feels? What do Atticus comments tell the reader about his beliefs?

Initially Atticus thinks Jem killed Ewell. Atticus cannot fathom somebody attacking children. Atticus looks for the best in people and thinks even Bob Ewell was not capable of such a heinous act,

Atticus shook his head. “I can’t conceive of a man who’d"...

In the end Atticus discovers he underestimated the power of ignorance and hate,

“I thought he got it all out of him the day he threatened me. Even if he hadn’t, I thought he’d come after me.”