Lady Macbeth fears that her husband, Macbeth, lacks the ruthlessness and ambition required to seize the crown. Specifically, she fears that he wont have the courage to act purposefully and doubts that he will pursue the kind of ruthless action needed to facilitate his ascension to the throne. Lady Macbeth believes that manhood is defined by murder and implies that Macbeth is less than a man whenever he shows signs of faltering. She thinks very lowly of her husband and actually fears that he would not have what it takes to kill a person or two to receive the throne.