Do you really know something? Or are you simply familiar with it?
Familiar, as in you’ve encountered it before, perhaps many times prior; it can now trigger a memory or two or more. Maybe you have lived with it, been exposed to it like nitrogen in the air, had it like breakfast for dinner.
Spent your whole life for it. (Or, okay, let’s say five years for a PhD.)
But is that enough to conclude that you truly, fully, accurately know the thing?
What does it mean to know, anyway?