The answer is:
The ghosts create haunting memories of his father and create a desire to seek revenge.
In Act 1, Scene 5 from Shakespeare's "Hamlet," the protagonist is faced with an external stimuli like his father's ghost, who tells him to seek revenge. As a consequence, his brain is in a state of confusion and indecisiveness. On the one hand, his internal stimuli wishes to avenge his father's unfair death and becomes obsessed with it. However, he is a distinguished, gentlemanly prince who has never thought of killing anyone because he is simply not a murderer.