The fear of the unknown in Macbeth.

Part of the unknown is the supernatural. Elizabethans were spellbound by witches and the dark arts. Shakespeare knew this and fashions the witches front and center in the play. In terms of character, Macbeth was perpetually paranoid of the unknown. He used the witches knowing Banquo's warning that the witches "Win us with honest trifles, to betray 's. In deepest consequence." Macbeth is obsessed about knowing his future. Even though the spirits tell him "none of woman born shall harm Macbeth", he still resolves to murder Macduff and his family just to make sure.