It is now 500 years since Niccolò Machiavelli produced the most famous book on politics ever written. On Dec. 10, 1513, he wrote a letter to a friend describing a day in his life and remarking by the way that he had composed a "little work," one of his "whimsies," on principalities. This was "The Prince," a short book for the busy executive so shocking that it wasn't published until 1532, after Machiavelli's death. It was coupled with the "Discourses on Livy" (1531), a much longer book for those readers with more time to observe and reflect. These are his major works, the ones that he said contain everything he knew.
In them he openly denounced both Christianity and the church: the "ambitious idleness" that Christianity imposed on Christians by demeaning worldly honor and also the "dishonesty" of priests, who govern by invoking the fear of God but "do not [themselves] fear the punishment that they do not see and do not believe." He attacked morality by declaring it unaffordable: A good man will "come to ruin" among so many others who aren't good. And he redirected politics by asserting that a prince must "learn to be able not to be good." Yet he also said, still more shockingly, that he believed that his advice to do evil "would bring common benefit to everyone."
The general response to this blast from its first appearance was to make Machiavelli's name into an epithet of scheming evil. Since the 19th century, however, almost all Machiavelli scholars have made excuses for him, blaming the corruption of his time or his "context" rather than him. The question is how well this attempt to rescue Machiavelli from condemnation serves either our understanding or his reputation.
The late Corrado Vivanti, editor of the standard edition of Machiavelli's works, helps to answer this question with this sensible and useful book. First published in 2008 in Italian and now appearing in translation to mark the quincentenary of "The Prince," it is a scholar's book, addressing a general audience but with a view to the choir of fellow academics. With the benign calm appropriate to messages from the grave, Vivanti delivers some hurtful blows, as when he declares the widespread republican interpretation of Machiavelli, holding that republics can avoid the faults of princes, to be a "somewhat forced reading." Jacob Burckhardt, the 19th-century Swiss historian who invented the term "Renaissance," is reproved for his fancy aesthetic slant on Machiavelli's "art of the state."
Vivanti devotes the first half of his book to events in Machiavelli's life, for Machiavelli himself had spoken of his knowledge from "long experience with modern things," as well as his "continuous reading" of the ancients. One experience was watching the popular preacher Savonarola being hanged and burned in Florence for heresy in 1498, but Vivanti doesn't explain why Machiavelli could have praised him in the "Discourses" for his "learning, prudence, and virtue of spirit."
The second half then briefly analyzes each of Machiavelli's writings, most of them done after he left office as secretary of the Florentine republic in 1512. Vivanti calls "The Prince" "typically humanist" because it mixes together ancient and modern examples. To do this today would be considered ahistorical. But since the practice was typical in Machiavelli's time, the author says, it is "cloaked in history." In this way, Vivanti uses history to cloak the Machiavellian call for republics to adopt "well-used cruelties"—and not be upset about it. Other humanists recommended no such thing. But then Machiavelli never hesitated to arouse "the indignation of God-fearing souls."
Machiavelli's political experience was by no means glorious, certainly not as notable as that of the several figures that he disparages in "The Prince"—to say nothing of Cesare Borgia, the bastard son of Pope Alexander VI, whose example he cites as the best teacher. Yet Machiavelli's "The Prince" is as momentous as it is famous. His writings, even the minor ones, show the greatness for which he is being remembered this year. How then can the greatness of his writings be interpreted in the light of his deeds, which are mediocre at best and overall a failure? For as secretary he tried and failed to secure a vigorous citizen militia so that Florence wouldn't have to depend on mercenaries. Machiavelli in other words failed to live up to his own signature motto—its depth explored in his writings—of relying on "one's own arms."
The error of trying to explain a great thinker through his "sources," as scholars like to say, whether in other writings or in the events of his time, consists in trying to explain greatness by means of non-greatness, which is to explain it away. Vivanti is aware of the problem. Quoting another historian, he says that "from the mind of Machiavelli flows the modern world of the state." In his preface, he sets forth the greatness of Machiavelli, not as a figure of his time, the Renaissance, but as a founder of modernity.
For this grand role, the mind of Machiavelli must have been capable of acting on its own, informed but not dictated by the events of the time. Machiavelli had much to say on this issue himself. The prince, he said, must act "according to the times," but in such a way as to change those times. To be successful a prince must be a new prince, one who doesn't accept the status quo. Even an established prince must take account of his rivals and enemies and not wait for them to displace him but move ahead of them "proactively," as we would say, virtuously, as he said. The new prince must strive to set the trend and make everyone else depend on him, so that he doesn't merely follow the trend.
Is this piece of Machiavelli's mind beginning to feel familiar to our modern eye and ear? Here, in the constant need for novelty and acquisition—our freedom in combat with our necessity—we have the germ of our modern politics, our business, our intellectuals, our arts, our morals.
Mr. Mansfield is a professor of government at Harvard University.
A version of this article appeared June 24, 2013, on page A17 in the U.S. edition of The Wall Street Journal, with the headline: Birth of the Modern.