The received idea as prefabricated opinion
A received idea is a judgment a person repeats without having formed it, adopted because it is socially safe and ready to hand rather than because it was reasoned out. Its tell is that it comes attached to a topic like a reflex: mention the subject and the opinion arrives automatically, often phrased in the same words every time. Flaubert's entries render these as imperatives or stock reactions to show that the opinion does the thinking in place of the person.