"[T]here is nothing so dangerous for any one who has something to hide as conversation! Speech, so a wise old Frenchman said to me once, is an invention of man’s to prevent him from thinking. It is also an infallible means of discovering that which he wishes to hide. A human being, Hastings, cannot resist the opportunity to reveal himself and express his personality, which conversation gives him. Every time he will give himself away."
The A.B.C. Murders, Agatha Christie