Idiom-Magic﹕需要是發明之母 Necessity Is The Mother Of Invention

【明報專訊】People don't invent things that are not essential (必需的) or useful: they invent (發明) them because they are necessary (必要的). That's the idea behind this saying. "I had trouble seeing in the dark so I invented the light bulb (電燈泡). As always, necessity is the mother of invention," the firefly (螢火蟲) said.