“Many a good argument is ruined by some fool who knows what he is talking about.”

“I wasn't fooled. He was avoiding looking at me. "There's nothing to talk about."
"I knew you'd say that. Actually, it was a toss-up between that and 'I don't know what you're talking about.'"
Dimitri sighed.”

“A fool boasts about what little he knows. A wise man keeps quiet about what he knows and is safe.”

“Purely mathematical symbols have no meaning by themselves; it is the privilege of pure mathematicians, to quote Bertrand Russell, not to know what they are talking about. …It is the physicist, and not the mathematician, who must know what he is talking about.”

“He was a fool,” said Willow calmly to Klein. “There are many who refuse their responsibilities. Fooling themselves they search for a ‘higher ideal’. He was a fool.”
“What are responsibilities?” said Klein laconically. “He knows. Responsibility, my dear, is another word for self-interest. For survival.”

“When a man who is drinking neat gin starts talking about his mother he is past all argument.”

“As with many people, Charles, who could not talk, wrote with fullness. He set down his loneliness and his perplexities, and he put on paper many things he did not know about himself.”

“A loser doesn’t know what he’ll do if he loses but talks about what he’ll do if he wins and a winner doesn’t talk about what he’ll do if he wins but knows what he’ll do if he loses.”

“I’m just a propagandist and a propagandist doesn’t have to know what he is talking about, just so he talks about it most convincingly.”

“You know what is good about these Dixie Chicks burnings or bashings? It's a wonderful, wonderful way for really stupid people to hook up. They meet, they throw some things on the fire, they talk about Vin Diesel, they tell stories about who their favorite Fox anchor is, they exchange phone numbers and in some cases has led to marriages.”