In what way is courage, in this case, something like a man with an empty gun?Atticus tells the children on the last page of Part 1 that he wants...

When Atticus shoots the mad dog, he is in complete control of the situation. The dog has no chance against a marksman with a gun. Mrs. Dubose, however, is like a person fighting her battle with an unloaded gun. She has no chance of living a longer life, so she picks a slightly different battle that she can win: overcoming her addiction to morphine before she dies. Atticus points out that real courage is

"when you know you're licked before you begin but you begin anyway and you see it through no matter what."

In Atticus' view, it took no courage to kill a defenseless dog. However, Mrs. Dubose showed real courage by taking seeing through her battle to the end.