"...the college of Sir Isaac Newton, renowned inventor of the milled-edge coin and the catflap!"
"The what?" said Richard.
"The catflap! A device of the utmost cunning, perspicuity and invention. It is a door within a door, you see, a..."
"Yes," said Richard, "there was also the small matter of gravity."
"Gravity," said Dirk with a slightly dismissive shrug, "yes, there was that as well, I suppose. Though that, of course, was merely a discovery. It was there to be discovered." He took a penny out of his pocket and tossed it casually onto the pebbles that ran alongside the paved pathway.
"You see?" he said. "They even keep it on at weekends. Someone was bound to notice sooner or later. But the catflap... ah, there is a very different matter. Invention, pure creative invention."
"I would have thought it was quite obvious. Anyone could have thought of it."
"Ah," said Dirk, "it is a rare mind indeed that can render the hitherto nonexistent blindingly obvious."
Douglas Adams, Dirk Gently's Holistic Detective Agency