Game of Thrones, Season 4

Tywin Lannister:
Your brother is dead. Do you know what that means? [Tommen hesitates in answering] I'm not trying to trick you.

Tommen Baratheon:
It means I'll become king.

Tywin Lannister:
Yes, you will become king. What kind of king do you think you will be?

Tommen Baratheon:
A good king?

Tywin Lannister:
I think so as well; you have the right temperament for it. But what makes a good king, hmm? What is a good king's single most important quality?

Cersei Lannister:
This is hardly the place or the time-!

Tommen Baratheon:
Holiness?

Tywin Lannister:
Baelor the Blessed was holy and pious. He built this sept. He also named a six year old boy High Septon because he thought the boy could work miracles. He ended up fasting himself into an early grave because food was of this world and this world was sinful.

Tommen Baratheon:
Justice?

Tywin Lannister:
A good king must be just. Orys the First was just; everyone applauded his reforms, nobles and commoners alike, but he wasn't just for long. He was murdered in his sleep after less than a year by his own brother. Was that truly just of him, to abandon his subjects to an evil that he was too gullible to recognize?

Tommen Baratheon:
No. What about strength?

Tywin Lannister:
Yes, strength. King Robert was strong; he won the rebellion and crushed the Targaryen dynasty. And he attended three Small Council meetings in seventeen years of ruling, and he spent his time whoring, hunting and drinking until the last two killed him. So, we have a man who starves himself to death, a man who lets his own brother murder him and a man who thinks winning and ruling are the same thing. What do they all lack?

Tommen Baratheon:
Wisdom?

Tywin Lannister:
Yes!

Tommen Baratheon:
Wisdom is what makes a good king.

Tywin Lannister:
Yes. But what is wisdom? A house with great wealth and fertile lands asks you for your protection against another house with a strong navy that could one day oppose you. How do you know which choice is wise and which is not? Any experience of treasuries and granaries? Or shipyards and soldiers?

Tommen Baratheon:
No.

Tywin Lannister:
Of course not. A wise king knows what he knows and what he doesn't. You're young. A wise young king listens to his councilors and heeds their advice until he comes of age. And the wisest kings continue to listen to them long afterwards. Your brother was not a wise king. Your brother was not a good king. If he had been, he'd probably still be alive.