"Any sensible ruler would have killed off Leonard, and Lord Vetinari was extremely sensible and often wondered why he had not done so. He'd decided that it was because, imprisoned in the priceless, inquiring amber of Leonard's massive mind, underneath that bright investigative genius was a kind of willful innocence that might in lesser men be called stupidity. It was the seat and soul of that force which, down the millennia, had caused mankind to stick its fingers in the electric light socket of the Universe and play with the switch to see what happened - and then be very surprised when it did."