What reason was Milo given to enter dictionopolis?

Milo was given the reason, "Why not?"

He took a battered suitcase from the gatehouse and began to rummage busily through it, mumbling to himself, "No... no... no... this won't do... no... h-m-m-m... ah, this is fine," he cried triumphantly, holding up a small medallion on a chain. He dusted it off, and engraved on one side were the words "WHY NOT?"

"That's a good reason for almost anything—a bit used perhaps, but still quite serviceable." And with that he placed it around Milo's neck, pushed back the heavy iron gate, bowed low, and motioned them into the city.