Curious things, habits. People themselves never knew they had them. [Witness for the Prosecution, also published in The Hound of Death and Other Stories.]

You don't realize what fine fighting material there is in age. ... You show me any one who's lived to over seventy and you show me a fighter - some one who's got the will to live.

There are questions that you don't ask because you're afraid of the answers to them.

It is a curious thought, but it is only when you see people looking ridiculous that you realize just how much you love them.

Until one looks back on one's own past one fails to realise what an extraordinary view of the world a child has.

Poirot said placidly, “One does not, you know, employ merely the muscles. I do not need to bend and measure the footprints and pick up the cigarette ends and examine the bent blades of grass. It is enough for me to sit back in my chair and think. It is this – ” he tapped his egg-shaped head – “this, that functions!

The human mind prefers to be spoon-fed with the thoughts of others, but deprived of such nourishment it will, reluctantly, begin to think for itself - and such thinking, remember, is original thinking and may have valuable results.