Ordinary human dilemmas are tougher to solve than the most difficult problems of physics and mathematics\
As a boy, I was a rock hound, and I learned how to identify minerals with the Mohs hardness test, named after the mineralogist who invented it. You take a known specimen, like quartz, and scratch an unknown specimen with it. If the quartz scratches the mystery specimen, you know it’s softer than quartz. It could be calcite or pyrite. If the quartz can’t scratch the specimen, it might be beryl or corundum, which are harder than quartz. Along with factors like color and crystalline structure, the hardness test can help you specify your specimen.
I loved the straightforward objectivity of the Mohs test. Recently, I’ve been brooding over a hardness—call it cognitive hardness—that is much harder to evaluate. Over the course of our lives, we face an enormous variety of cognitively hard tasks. For the past year, for example, I’ve been studying quantum mechanics, which is notoriously difficult to grasp. But is learning quantum mechanics harder, objectively, than chatting to my girlfriend about #MeToo without irritating her? Or talking to my daughter about climate change without depressing her?