Everything that has existed, lingers in the Eternity.

No, my friend, I am not drunk. I have just been to the dentist, and need not return for another six months! Is it not the most beautiful thought? --Poirot

... nothing is so boring as devotion.

It is ridiculous to set a detective story in New York City. New York City is itself a detective story.

... the belief in a superstratum of human beings ... is the most evil of all beliefs. For when you say, 'I am not as other men' -- you have lost the two most valuable qualities we have ever tried to attain: -- humility and brotherhood.

Ah, but life is like that! It does not permit you to arrange and order it as you will. It will not permit you to escape emotion, to live by the intellect and by reason! You cannot say, 'I will feel so much and no more.' Life, Mr. Welman, whatever else it is, is not reasonable. [Hercule Poirot]

Never worry about what you say to a man. They're so conceited that they never believe you mean it if it's unflattering.