You should employ your little grey cells.

I often wonder why the whole world is so prone to generalise. Generalisations are seldom if ever true and are usually utterly inaccurate.

Sometimes I feel sure he is as mad as a hatter and then, just as he is at his maddest, I find there is a method in his madness.

Ideas are like everything else. They've got to be marketed.

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

lawyers never go to law, do they? They know better.

Youth is a failing only too easily outgrown.