This note does not contain major spoilers for the book.

Far future people are too secure to be happy, or something. So they do stupid things like duel each other to give life meaning. I think that's what he's saying; "An armed society is a polite society", but I don't think the author is actually fond of the idea himself.

It does lead to one very amusing point when a character casually mentions that he's never killed a non-human animal before, and implies that it bothers him quite a bit. Killing a human of course is no big deal.

All these questions about the "purpose" of the universe and what we are "supposed" to do never computed as questions for me; specifically, I never thought somebody else got to decide those things for us. But apparently they bothered a lot of intellectuals of Heinlein's era.

This has one of those lovely artsy covers that a lot of the Signet Heinlein's have around this period. No credit for the artist that I can find.