Douglas Adams Quote
If on the other hand he went to pay his respects to The Door and it wasn't there... what then? The answer, of course, was very simple. He had a whole board of circuits for dealing with exactly this problem, in fact this was the very heart of his function. He would continue to believe in it whatever the facts turned out to be, what else was the meaning of Belief? The Door would still be there, even if the Door was not.
Dirk Gently's Holistic Detective Agency (ed. Simon and Schuster, 2014) - ISBN: 9781476782997