Atticus proves to be strong willed when he stands up to a group of hostile (and drunk) men at the courthouse in chapter 15. The men ask him to step aside so they can capture Tom. Atticus simply replies, "You can turn around and go home again, Walter, Heck Tate's around here somewhere." He is unwilling to move, even though he is surrounded by an angry mob of men. He explains his own sense of justice by not moving. He would rather the courts decide than to have a group of angry men decide Tom's fate. He only wants justice--which is the reason he took the case from the beginning.
Atticus proves to be intelligent in most every scene. He uses an adult's vocabulary when talking with his children. He does this to teach them. He reads with Scout every night, as well, to help improve her skills. He shows his intelligence most when he gives his closing statement to the jury in chapter 20. He points out that "all men are created equal" and he mentions Mayella's inappropriate actions towards Tom to make his point. And by using his manners as he questions people on the stand, he shows kindness. Mr. Gilmer never holds back how he feels about Tom by calling him "boy" and sneering at him. However, Atticus is kind and polite to all on the stand, even when they don't really deserve it.