All courage begins with moral strength in this novel. In order to do what is right, a person must first have the strength and honesty of vision to understand what distinguishes right from wrong.
Several forms of courage are explored in To Kill a Mockingbird, showing that it is both a physical and mental state which can manifest itself in multiple actions.
Boo Radley, Tom Robinson, Atticus Finch, Scout Finch, Jem Finch and Mrs. Dubose are all characters that demonstrate the quality of courage. They also make clear the notion that courage is not necessarily tied to risking physical danger, but is often better defined by a dedication to principles first and acceptance of the consequences second.
Atticus articulates this view of courage when he discusses Mrs. Dubose' efforts to free herself of a morphine addiction.
"It's when you know you're licked before you begin but you see it through no matter what..."
Courage, in this novel, is defined by dedication to a sense of what is right and to pursuing the "right thing" regardless of consequences.