The conclusion of Spirit of the Laws (as with this exegesis) launches with the “single chapter” Book 27, “About the Origins of the Roman Laws on Inheritances.” Taking up this subject, in light of the discussion of the Salic Laws in Book 18 (and to follow again in Book 28) brings into the foreground a recounting of “local histories” in light of the developmental principles elaborated in the work. The two books, 27 and 28, frame the manner of the historical analysis. They are followed by an interrupting Book 29, whose subject is “Legislators.” Then follow two books on French history employing the same developmental principles rehearsed in Books 27 and 28.

It is a mistake, however, to read the “successions” as referring only to “inheritances.” Montesquieu means the term in both senses, which the plural especially signifies. Thus, Book 27 opens the discussion of constitutional succession in Rome and constitutional succession to Rome as much as it refers to the civil law. The point of the histories—the record of incremental choices/decisions and their constitutional bearings—is meant to inform potential legislators as to how deliberately to proceed in seeking or shaping a hybrid constitution, against the background of Rome's failure in this regard.

We take special note, therefore, of the broader theme of constitutional possibilities and the security of a decent constitution. That discussion, in turn, requires distinguishing Montesquieu's real-world constitutionalism from utopianism. Thus, the introduction of Book 29 at the center of these closing analyses serves the purpose of underscoring the distinction between philosophical founding (with its utopian bearings) and that founding whose aim is to secure the constitutional possibilities inherent in the natural inclinations of humans and to do so not in a theoretical context but with an eye to dynamic possibilities revealed in the course of the development of societies—of which, two are now relevant: Rome and France.

That prospect is conveyed by the enigmatic closing words of Book 31 and thus of Spirit of the Laws as a whole: “Italiam, Italiam … I finish this work on fiefs where most authors have begun.” Montesquieu left this ejaculation unexplained in the original text, and he added a note for the 1757 edition only upon having heard from David Hume that he (Hume) and many other persons were unable to divine its meaning. The added note referred to Vergil's Aeneid, 3.523.