Read: Men at Arms
Being simple does not mean stupid.
That is the lesson taught by Men at Arms. And I believe Pratchett teaches it most excellently. Of course, the novel is instructive for so many more reasons. Yet I think this is the most important one.
It's good that I read all Discworld novels again (preferably on my train and plane trips). It may have taken me several years to see this important message: I just noticed that I have read the book before, in the German translation, more than a decade ago. And I did not get it back then. Let's blame it on the translation.