How pathetically scanty my self-knowledge is compared with, say, my knowledge of my room. There is no such thing as observation of the inner world, as there is of the outer world.
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.
He is a free and secure citizen of the world because he is on a chain that is long enough to allow him access to all parts of the earth, and yet not so long that he could be swept over the edge of it.