[Jim Cullen, who teaches at the Ethical Culture Fieldston School in New York, is a book review editor at HNN. He is the author of The American Dream: A Short History of an Idea that Shaped a Nation (Oxford, 2003) among other books, and has embarked on a project with the working title of "Sensing History: Hollywood Actors as Historians." He blogs at American History Now.]

The title is wonderfully concise: Loyalty is indeed a vexing virtue. In this intriguing and elegantly written book, Wall Street Journal writer Eric Felten explores an idea which is difficult to reject in the abstract, but which is almost always proves devilish in the details. Using illustrations that that span Greek tragedies to the distasteful deeds of Tiger Woods, Felten wears his learning lightly and yet always instructively in this little gem of a book that is cleverly jacketed in true blue, with gold lettering and an icon of a dog.

Felten, who champions loyalty, focuses on two core problems with it. As we all understand, any positive virtue -- prudence, piety, or any other, cardinal or otherwise -- has its downsides. What is perhaps peculiar to loyalty is its capacity to enable other vices. The same solidarity among soldiers that wins wars also permits atrocities; the trust we place in princes engenders arrogance that leads to tyranny. Loyalty is an essential lubricant for the social contract, but it also permits the most slippery of conduct.

But what's really rough about loyalty, Felten says, is that even in those cases where it is most justified -- very often because it's justified -- loyalty inevitably leads to conflict. It's easy to fight for God and Country; all too often, it's God or Country. Who among us has not had to choose between friends? And who can say with any certainty that loyalty to a child trumps that of a spouse? Felten notes that a cast of characters ranging from King Agamemnon to Immanuel Kant have insisted that it's possible to square this circle. He's unconvinced, and he makes a compelling case that we shouldn't be, either.

After introductory chapters that lay out these philosophical dilemmas, Felton moves to a set of domains for loyalty: marriage, friendship, business, and politics/institutions. What's perhaps most intriguing about the book is that he increasingly moves beyond simply framing the dilemmas of loyalty and takes positions that are all the more arresting because of their nuanced, self-aware character. Felten understands the power of passion and the insistent waywardness of the human heart, which in effect has a mind of its own. But he favors the rush of endorphins that come at the end of the marathon of marriage to the euphoria of spring infatuation. He finds that in the world of commerce, loyalty doesn't make much sense, not only because it fails to describe the way consumers or businesses actually behave, but also because loyalty can too easily become euphemisms for dead weight or taking relationships for granted. In friendship and politics -- two realms Felten believes should remain separate -- loyalty almost always involves condoning behavior with which one disagrees. But he sides with Sir Walter Scott's encomium that "I like a highland friend who will stand by me not only when I am in the right, but when I am a little in the wrong."

Strictly speaking, loyalty has no ideological valence. But in early 21st century public discourse, it skews Right more than Left. One of the more reliable stratagems by which the Left has tried to dislodge the dominant libertarianism of contemporary politics is the embrace of "social justice," a term whose egalitarian overtones resist the individualist accents of a Reaganesque vernacular. But social justice has little room for loyalty. Its great strength is its rejection of privilege; its great weakness is its perceived bloodlessness.  Felten notes that cosmopolitan liberals all too often dismiss patriotism as a pernicious zero-sum ideology, while glibly maintaining that a critical stance toward one's country represents a higher form of loyalty. In many cases, that's surely true. Such people would surely cringe at Theodore Roosevelt's characteristically bombastic 1918 pronouncement that "The man who loves other countries as much as his own stands on a level with the man who loves other women as much as he loves his wife." But it may be no accident that marriage and patriotism have declined in tandem with a broader anti-institutional tendency in U.S. society in recent decades. And maybe that's been a good thing, at least in some respects. But people lacking strong loyalties of their own will always be vulnerable to the terrible loyalties of others.