Final answer:
Brutus suggests that Mark Antony is harmless without Caesar's leadership, indicating that without Caesar's guidance, Antony's power is greatly diminished.
Step-by-step explanation:
In the lines 181-183 from Shakespeare's Julius Caesar, Brutus suggests that 'Mark Antony is harmless without Caesar's leadership' by comparing Antony to Caesar's severed arm, powerless without Caesar's head, which signifies control and direction. Antony, who was indeed close to Caesar and a shrewd general in his own right, was seen by Brutus as a non-threat once Caesar, the ultimate source of authority and power, was gone. It's important to note that while Brutus dismisses Antony's threat in these lines, the later events in the play reveal that Antony was far from harmless, playing a pivotal role in the aftermath of Caesar's assassination.