Recursion

Abstract

Among the first things for which children are berated when they are learning their mother tongue is any attempt at a circular definition. “A chair is a chair with...” “You can’t explain something by using the word you’re explaining!” they’re told firmly.

“Well, just then I was inventing a new way of getting over a gate—would you like to hear it?”

“Very much indeed,” said Alice politely.

“I’ll tell you how I came to think of it,” said the Knight. “You see,” I said to myself, “The only difficulty is with the feet: the head is high enough already. Now, first I put my head on top of the gate—then the head’s high enough—then I stand on my head—then the feet are high enough, you see—then I’m over, you see.”

Through the Looking Glass