They're talking about things of which they don't have the slightest understanding, anyway. It's only because of their stupidity that they're able to be so sure of themselves.
I can't decide if this movie is so spectacularly, breathtakingly dumb as to induce stupidity in anyone who watches, or so brutally brilliant that it disarms all reason. What's the difference?
I certainly must,' said she. 'This sensation of listlessness, weariness, stupidity, this disinclination to sit down and employ myself, this feeling of everything's being dull and insipid about the house! I must be in love; I should be the oddest creature in the world if I were not.