The want for power corrupts
"I have no spur to prick the sides of my intent, but only vaulting ambition..."
- no legitimate reason to kill Duncan
- willing to kill a good man for power
- ambition = his wanting to be king
"There is none but he whose being I do fear: and under him my Genius is rebuked, as it is said Mark Antony's was by Caesar."
- speaking about Banquo
- fears his own best friend because he could steal his power
- plans to kill him
"Be bloody, bold and resolute; laugh to scorn the power of man, for none of woman born shall harm Macbeth."
- believes no one can kill him
- ...but is paranoid enough to kill Macduff's family
- plans to kill Macduff's wife, kids and servants in his castle