NEW YORK – Ignorance is the root of all evil, according to Plato, who also famously gave us a still-current definition of its opposite: knowledge. For Plato, knowledge is “justified true belief.” That definition is worthy of consideration as we reflect on the perils of ignorance in the twenty-first century.
Plato thought that three conditions must be met in order for us to “know” something: the notion in question must actually be true; we must believe it (because if we do not believe something that is true, we can hardly claim that we know it); and, most subtly, it must be justifiable – there must be reasons why we believe the notion to be true.
Consider something that we all think we know: the earth is (approximately) round. This is as true as astronomical facts get, particularly because we have sent artificial satellites into orbit and seen that our planet is indeed roundish. Most of us (except for a lunatic fringe of flat-earthers) also believe this to be the case.