Earlier quoted context omitted.
That certainly borrows from Socrates: " I know one thing: that I know nothing. "
It's an idea that recurs throughout history. We've got Socrates and Shakespeare already mentioned in the thread, to which I'll add: W B Yeats: "The best lack all conviction, and the worst / Are full of passionate intensity." Bertrand Russell: "The fundamental cause of the trouble is that in the modern world the stupid are cocksure while the intelligent are full of doubt." Charles Darwin: "Ignorance more frequently be…
I always read this quote by Yeats as a lamentation about the status of the world, similar to your Russel quote that's a bit more explicit. But the Socrates quote is clearly not in this vein...
It never occurred to me before that Yeats might be more in line with Socrates than with Russell. You can read him as praising the best for their lack of conviction and condemning the worst for their passion. I like that reading much better. (Of course, I've never read the source, just heard it quoted.)