Answer: The theme is persuading McBeth to kill, as a necessary act to become King and eventually hold power.
Step-by-step explanation:
- Context first: remember the character by itself is ambition personalized! For Lady McBeth, the simple idea of becoming a Queen, or reaching such a powerful position is a most, no matter the cost. For her, the way to reach power is leading her husband to become a King, so the next step is to convince him to even commit a murder, as a 'necessary' act.
- The extract mentioned above: it is the moment when she tries to corral him. Since he has a moral conflict for killing someone close to him, she takes that as cowardice, rather than as a simple conflict. Therefore, she openly asks him to do what it takes to become a King, even if she has to say it to his ears as much as necessary to reach the goal.