As you yourself have said, what other explanation can there be?' Poirot stared straight ahead of him. 'That is what I ask myself,' he said. 'That is what I never cease to ask myself.
Do you believe in the value of truth, my dear, or don’t you?” “Of course I believe in the truth,” said Rhoda, staring. “Yes, you say that, but perhaps you haven’t thought about it. The truth hurts sometimes – and destroys one’s illusions.” “I’d rather have it all the same.” said Rhoda. “So would I. But I don’t know that we’re wise.” Mrs. Oliver; Rhoda Dawes
If you confront anyone who has lied with the truth, he will usually admit it - often out of sheer surprise. It is only necessary to guess right to produce your effect.
Too much mercy... often resulted in further crimes which were fatal to innocent victims who need not have been victims if justice had been put first and mercy second.
I don't think necessity is the mother of invention. Invention, in my opinion, arises directly from idleness, possibly also from laziness - to save oneself trouble.