Charles-Louis de Secondat, Baron de La Brède et de Montesquieu (1689-1755), a leading figure in the French Enlightenment, began his career studying and then practicing law. With the acquisition of his fortune through marriage and inheritance, he settled into the life of a man of letters. He wrote novels, essays (on taste and history among other large subjects), and two books that rendered him famous. “Persian Letters” (1721), a satire on the absurdities of contemporary French society as seen by a visiting Persian, made him a figure of great réclame in his own day; and his “The Spirit of the Laws” (1748), on the influence of forms of government and of climate on nations, remains a central work of political philosophy in ours.

Between those two books, Montesquieu published “Considerations on the Causes of the Greatness of the Romans and Their Decline” (1734), a lesser-known work but one deserving the highest acclaim. In it Montesquieu combines the insights of the historian with those of the political philosopher, set out in brilliant aphoristic style. “At the birth of societies,” he writes early in this book, “the leaders of republics create the institutions; thereafter, it is the institutions that create the leaders of republics.” Everything Montesquieu wrote was against the background of his pervasive and persuasive views of human nature: “For the occasions which produce great changes are different but, since men have had the same passions at all times, the causes are always the same.” Notable among those passions are pride, greed and the love of glory.

To grasp the quality of Montesquieu’s “Considerations,” one has to imagine the 3,000-odd pages of Edward Gibbon’s “History of the Decline and Fall of the Roman Empire” condensed to a mere 220 pages and without losing much. Not that the views of the two men are everywhere congruent, but both are proficient in understanding the great sweep of events while simultaneously discerning the role of character in the play of history. Their art consists in balancing the effect of each upon the other.

Of the letters of Cicero, that last Roman republican, Montesquieu writes: “we can see the dejection and despair of the foremost men of the republic at this sudden revolution [the monarchical-minded triumvirate of Caesar, Pompey and Crassus] depriving them of their honors and even their occupations.” He finds Cicero’s “genius was superb, but his soul was common.” Comparing him to Cato, he notes: “Cicero always thought of himself first, Cato always forgot about himself. The latter wanted to save the republic for its own sake, the former in order to boast of it.”