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.
What about the justification of that belief? How would you answer if someone asked you why you believe that the earth is round?
The obvious place to begin would be to point to the aforementioned satellite images, but then our skeptical interlocutor could reasonably ask if you know how those images were obtained. Unless you are an expert on space engineering and imaging software, you may have some trouble at that point.
Of course, you could fall back on more traditional reasons to believe in a round earth, like the fact that our planet projects a round-looking shadow on the moon during eclipses. Naturally, you would have to be in a position to explain – if challenged – what an eclipse is and how you know that. You see where this could easily go: if we push far enough, most of us do not actually know, in the Platonic sense, much of anything. In other words, we are far more ignorant than we realize. Read the rest on Project Syndicate.