“A great many men are mad, and no one knows it. They do not know it themselves”

“Can one build an honest house on dishonest foundation? I do not know. But I do know that I want to try. (Edward Ferrier)”

“One knows so little. When one knows more it is too late.”

“Do you know my friend that each one of us is a dark mystery, a maze of conflicting passions and desire and aptitudes?”

“At my time of life, one knows that the worst is usually true.”

“You do think you know about everything," said her husband. I do," said Tuppence.”

“You tell your lies and you think nobody knows. But there are two people who know. Yes- two people. One is le bon Dieu - and the other is Hercule Poirot”