When the children ask Miss Maudie about Boo Radley, she replies "His name's Arthur and he's alive," and calls it a “morbid question” (ch 5).
I know he's alive, Jean Louise, because I haven't seen him carried out yet." (ch 5)
The children trust Miss Maudie’s opinion because she never lies to them or talks down to them. She also does not gossip like Miss Stephanie Crawford. She tells the truth, and is respectful to them even though they are children. She extends this benevolence to Boo Radley. Unlike the other neighbors, she does not talk down on him. She calls him by his name and treats him politely.
"Arthur Radley just stays in the house, that's all," said Miss Maudie. "Wouldn't you stay in the house if you didn't want to come out?" (CH 5)
Her explanation for Boo’s unusual behavior when he was young is that “old Mr. Radley was a foot-washing Baptist” (ch 5) and Boo just could not take it anymore, and that is why he stabbed him with scissors. When they ask her if he is crazy, she replies “"If he's not he should be by now” and tells them they do not know what happens to people inside closed doors.
The children ponder Miss Maudie’s speech, and decide that they should send Boo Radley a note to make him come out. They have decided that he really is lonely, and he would do better to have help to come out, so that they can be his friend.