In Paris, the Persians express themselves on a wide variety of subjects, from governmental institutions to salon caricatures. The difference of temperament of the two friends is notable, Usbek being more experienced and asking many questions, Rica less implicated and more free, and more attracted by Parisian life. Although this takes place in the declining years of the aged king, much of what he has accomplished is still admired in a Paris where the Invalides is being completed and cafés and theatre proliferate. We observe the function of parliaments, tribunals, religious bodies (Capuchins, Jesuits, etc.), public places and their publics (the Tuileries, the Palais Royal), state foundations (the hospital of the Quinze-Vingts  for the blind, the Invalides for those wounded in war). They describe a thriving culture, where even the presence of two Persians quickly becomes a popular phenomenon, thanks to the proliferation of prints (letter 28 ). The café – where debates take place (letter 34 ) – has become established as a public institution, as were already the theatre and opera. There are still people foolish enough to search at their own expense for the philosopher's stone; the newsmonger and the periodical press are beginning to play a role in everyday life. Everything from institutions (the university, the Academy, Sciences, the Bull Unigenitus) via groups (fashion, dandies, coquettes) to individuals (the opera singer, the old warrior, the rake, and so forth) comes to the eye of the reader.
Usbek for his part is troubled by religious contrasts. Though it never occurs to him to cease being a Muslim, and while he still wonders at some aspects of Christianity (the Trinity, communion), he writes to austere authorities to inquire, for example, why some foods are considered to be unclean (letters 15–17 [16–18]). He also assimilates the two religions and even all religions with respect to their social utility.
Certain sequences of letters by a single author develop more fully a particular subject, such as letters 11–14 from Usbek to Mirza on the Troglodytes, letters 109–118 (113–122) from Usbek to Rhedi on demography, letters 128–132 (134–138) from Rica on his visit to the library at Saint-Victor. They sketch analyses that will later be developed in L’Esprit des lois for many subjects such as the types of powers, the influence of climate and the critique of colonization.