You'll have such proof as exists. You are the only one responsible for your own wants. - Isaac Asimov

Well, besides, I've arranged with the computer that anyone who doesn't look and sound like one of us will be killed if he — or she — tries to board the ship. I've taken the liberty of explaining that to the Port Commander. I told him very politely that I would love to turn off that particular facility out of deference to the reputation that the Sayshell City Spaceport holds for absolute integrity and security — throughout the Galaxy, I said — but the ship is a new model and I didn't know how to turn it off.
"He didn't believe that, surely."
"Of course not! But he had to pretend he did, as otherwise he would have had no choice but to be insulted. And since there would be nothing he could do about that, being insulted would only lead to humiliation. And since he didn't want that, the simplest path to follow was to believe what I said."
"And that's another example of how people are?"
"Yes. You'll get used to this."

Earth's population was still rising. Some day, with all that the Cities could do, the available calories per person would simply fall below basic subsistence level.

Hardin groaned in spirit. The Board seemed to suffer violently from Encyclopedia on the brain. He said icily: 'Has it ever occurred to this Board that it is barely possible that Terminus may have interests other than the Encyclopedia?' Pirenne replied: 'I do not conceive, Hardin, that the Foundation can have any interest other than the Encyclopedia.' 'I didn't say the Foundation; I said Terminus.