Captain James T. Kirk: [talking about Kirk's "negative" side-duplicate] I have to take him back... inside myself. I can't survive without him. I don't want to take him back. He's like an animal, a thoughtless, brutal animal, yet it's me... me. Lt. Cmdr. Leonard 'Bones' McCoy, M.D.: Jim... you're no different than anyone else. We all have our darker side. We need it! It's half of what we are. It's not ugly. It's human. Captain James T. Kirk: Human. Lt. Cmdr. Leonard 'Bones' McCoy, M.D.: Yes, human. A lot of what he is makes you the man you are. God forbid I should have to agree with Spock, but he was right. Without the negative side, you wouldn't be the captain - you couldn't be, and you know it. Your strength of command lies mostly in him. Captain James T. Kirk: What do I have? Lt. Cmdr. Leonard 'Bones' McCoy, M.D.: You have the goodness. Captain James T. Kirk: Not enough. I have a ship to command. Lt. Cmdr. Leonard 'Bones' McCoy, M.D.: The intelligence, the logic. It appears your half has most of that, and perhaps that's where man's essential courage comes from. For you see, he was afraid, and you weren't.
Yes, human. A lot of what he is makes you the man you are. God forbid I should have to agree with Spock, but he was right. Without the negative side, you wouldn't be the captain - you couldn't be, and you know it. Your strength of command lies mostly in him.