The major theme of Paradise Lost is DISOBEDIENCE TO GOD'S COMMANDS.
Paradise lost is an epic poem that talked about Adam and Eve and how they lost their God given paradise as a result of yielding to the devil's temptation. The devil decided to defile the man, who is newly created by God as a revenge on God for sending him and other fallen angels out of heaven and he went ahead and made Adam and Eve to sin against God.
What happened?! ¯\_(ツ)_/¯
Ivan does not say anything because he cannot speak.
After Rainsford comes to Zaroff's door, Ivan answers with a gun pointed at Rainsford. Rainsford tries to talk to Ivan, but he does not respond. When Zaroff comes to meet them he explains that even though Ivan is incredibly strong, he is "deaf and dumb" which means he is unable to hear or speak.
