McCoy: Are you trying to kill me, Spock? Is that what you really want? Think. What are you feeling? Rage? Jealousy? Have you ever had those feelings before?
Spock: This is impossible. Impossible. I am a Vulcan.
McCoy: he Vulcan you knew won't exist for another 5,000 years. Think, man. What's happening on your planet right now, at this very moment?
Spock: My ancestors are barbarians, warlike barbarians. Who nearly killed themselves off with their own passions.
McCoy: Spock, you're reverting into your ancestors... 5,000 years before you were born!
Spock: I've lost myself. I do not know who I am.