General approach

Translation philosophy in brief
Reasonable consistency of terminology is of course important in a complex text like L’Esprit des lois, but it is not the only consideration. There are in Montesquieu many passages constructed on rather strict parallels, very often further reinforced by parallel syntax: in such instances, it is obviously important to adhere to that intention – even when it seems quite rigid – as much as possible. On the other hand, attempts to apply one English word, and only one, throughout for a given French word inevitably force the translator to distort or frankly mistake the meaning in particular instances. I am striving for a reasonable compromise which will doubtless seem undesirable to some. I would nevertheless appreciate their help in avoiding misperceptions or outright errors. The idea that one can preserve the purity of Montesquieu’s meaning by sticking to the same English word at all times seems to me linguistically misguided, and can induce what might be called category mistakes. Does Montesquieu mean the “same” thing every time he uses a multifunction word (like, say, mœurs)? Of course not; it is an illusion to thing that any word in one language can occupy the same identical semantic space as some word in another.

Some remarks on the tentative vocabulary choices.
The most obvious change I am proposing is in the title, where for a number of reasons it seems to me that the singular Spirit of Law may be a better reflection of Montesquieu’s overall meaning than its traditional rendition. For an initial discussion of this and some of the other problems identified, I refer the reader to my article “On the Nugent translation of L’Esprit des lois”, History of Political Thought, vol. XXXIX, no. 1 (2018), p. 83-106.

I am also breaking in other ways with the traditional translations, even sometimes with respect to terms that appear frequently in Montesquieu’s argument. One of these is to find a replacement for the term “spring” (for ressort) which has been resorted to by all translators so far. The major objection to “spring” is simply that, while Montesquieu does in a few instances use ressort in a mechanical sense (especially in the 1757 Avertissement), the English word spring (unlike the French ressort, has no recognized metaphorical value that can “naturalize” its application, in particular, to the dynamics of the various types of government. (Dictionnaire de Trévoux: “Ressort se dit figurément en choses spirituelles et morales, et signifie cause, moyen”.) The use of ressort by Montesquieu does not constitute a neologism, but it does in English when Nugent translates it as “spring”. After considering such things as “muscle”, which ultimately seems too organic for this specific context, I have experimented with “impetus”,  “incentive”, “energy”. And it is clear from many passages that principe is in any case a synonym for ressort; so it is not as if one had to maintain some term rigidly – particularly “spring” – as the systematic equivalent of ressort.

Peuple is a complicated and ambiguous term in French because it can mean either the body of the people (< populus in Latin), in which case it can also take the plural; or commoners (plebs) as opposed to upper classes; or again it can have a general meaning like the English “people”. Populaire, as in gouvernement populaire, is closely linked to that meaning. “People” is ambiguous also in English, but not in analogous ways. Its first meaning is very close to the first French one, but the second refers to the aggregate of citizens and is obligatorily a plural. To use “people” very many times in succession in the singular begins to sound odd. Like previous translators, I have usually in such passages shifted (fairly seamlessly, I hope) into the plural, despite some slippage of meaning that seems to me unavoidable. The second French definition, also much used by Montesquieu, refers to those who are not noble or rich, and is often best rendered by “commoners” or “common people”. And of course other words such as gens and on also are sometimes best translated as “people”.

Pouvoir and puissance have similar and overlapping usage; sometimes, but by no means always, Montesquieu keeps them separate, as if by opposition, and at other times he seems to substitute them indiscriminately (XI, 6). I have generally rendered pouvoir as “power” and puissance as “authority”. There are also, of course, occurrences of autorité that seem to call for “authority”.

Probably everyone who has taught this work has some examples of passages that were badly handled. If we can pool some of this information, perhaps some improvements can be made.