In the novel To Kill A Mockingbird, what is Atticus's temperament?

Atticus is very calm, even mellow.  His children think it
is because he is old, but it has more to do with his attitude toward people.  He
believes that everyone should be treated with respect.  What makes him unusual is that
this idea extends to children, poor people, outcasts and people of all
races.

Atticus tries to raise his children to be good
people.  He treats them with "exaggerated courtesy" and more like adults than children. 
This is likely due to his attitudes toward people in general, and the fact that he
raised them without a mother.  He chose Calpurnia to be not just a cook and housekeeper,
but rather his partner in raising his children.

Atticus is
never mean or loud.  He threatens constantly to beat Scout and Jem, but it is revealed
that he has never laid a hand on either of them.  He tells Jack that he has gotten away
with threats instead, but based on Jem’s attitude it is clear that his children are more
afraid of losing his respect and letting him down.

Atticus
is soft-spoken, but when he talks everyone listens.  His manner at trial is polite and
shrewd, but also unnervingly calm.  When he is polite and gentle to Mayella, she assumes
he is making fun of her.  He treats the jury just as respectfully, and they return that
respect by taking longer than usual to convict Tom.