Why does Atticus think Mr. Tate is claiming that Bob Ewell fell on his knife in Harper Lee's To Kill a Mockingbird?
Atticus begins fretting about Jem. He thinks that Jem stabbed Bob Ewell. He is already thinking about an upcoming court case with a self defense plea. Heck Tate tells Atticus that Jem did not stab Bob Ewell with a knife. Atticus misunderstands Heck Tate. He thinks the man is trying to spare his son a trial. He tells Heck that he does not want to deny the truth. Atticus does not want to cover up his son stabbing and killing a man.
Heck tells Atticus that Bob Ewell fell on his own knife. He killed himself. Atticus insists that he does not want what Jem did covered up. Heck protests again and even offers proof. Atticus tells Heck that he needs to be truthful in all ways. He cannot protect his son. He says that he "can't live one way in town and another way in [his] home" (To Kill a Mockingbird, Chapter 30).
Insistent, Heck shows Atticus proof. He pulls out the knife. He acts out what had happened. Finally, Heck shouts at Atticus. He tells him that he is not trying to protect Jem. Instead, he is trying to protect Boo.