This book has a beautifully spare and classic title, meant to remind us of Cicero’s De Amicitia, but it makes a thoroughly unclassical argument. Although Alexander Nehamas begins with Aristotle, who “remains at the foundation of every serious discussion of friendship,” he doesn’t end there. In fact, he writes with the aim of upending Aristotle, who argued that friendship either “is a certain virtue or is accompanied by virtue.” Nehamas teaches that “a good friend can draw me into shameless immorality” and that “even the vicious have friends.” Rather like the mild-mannered disseminator of Nietzsche (played by Jimmy Stewart) in Alfred Hitchcock’s Rope, the Carpenter Professor in the Humanities at Princeton University seeks to persuade a broad audience that genuine friendship can be the agency of spiraling crime and death. This is how a postmodern Athenian adds “complexity,” “ambiguity,” and “nuance” to those ancient Athenians who reasoned that the best friendship required knowledge of the good.

Nehamas doesn’t reject that tradition root and branch. For instance, when he says that “‘Instrumental friendship’—whether based on advantage, pleasure, or anything else—is a contradiction in terms,” he follows Aristotle. Real friendship requires that a friend be loved for himself. It’s just that Nehamas has a rather more expansive idea of what is loveable, along with a profoundly deracinated view of the self.

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For example, he treats the relationship of the title characters in the movie Thelma and Louise (1991) as paradigmatic of friendship. “Their friendship is a good,” he declares, “not despite the fact that it leads them to kill, rob, intimidate, and destroy but because of it. They don’t just do bad things; they become admirable on account of doing them—or, rather, on account of what these things reveal about them and their new take on the world and each other.” Unlike the teacher in Rope who recoils from his Leopold-and-Loeb acolytes once their murderous depravity is manifest, Nehamas seems not to flinch from the consequences of his aestheticizing approach, in which what counts is character understood not as virtue but as stylized, ever-fluid individuality. Especially telling is the moment when Nehamas rejects the erotic “metaphysics” of Plato (another classic writer on friendship): “this effort [to know and love another] has an end, though not when it reaches perfection—which for Plato was the Form of beauty itself—but only when the friendship is over.” “End” in the sense of “purpose” is jettisoned in favor of “end” as “termination.” The only possible end physics gives us is death. No wonder Nehamas celebrates the suicide pact of Thelma and Louise—they do, after all, die with distinctive panache, holding hands (as if in victory) and hurtling off the edge of the Grand Canyon in a 1966 Ford Thunderbird convertible.

Postmodern perversity can be made very attractive, especially when it comes in the shapely forms of Geena Davis, Susan Sarandon, and Brad Pitt. For viewers still imbued with Aristotle, however, the movie can deliver quite another lesson. We see the ingrained vices of the characters, especially cowardice and immoderation, dictate their initial bad choices. Almost immediately, the women are drawn into a vortex of alcohol-fueled anger-mismanagement. Time and again, the one whose judgment at that particular moment is worse (and who is invariably acting selfishly) prevails, and the two of them descend further into desperado-dom.

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Nehamas is certainly right to stress the transformative power of our intimate companions: “Whether for better or worse, what we become is very much our friends’ doing, and the less settled we are in ourselves, the greater their contribution and the more pervasive their influence.” Nehamas writes charmingly of his reunions with a circle of Greek friends, none of whom seems to inhabit the dark side. Choosing a friend is risky business, however, especially for the young. That is exactly why Aristotle and parents everywhere have counseled attention to virtues of character, and why they are often at pains to demonstrate that a supposed friend might not be a true friend. It’s rather remarkable that the standards set by what Aristotle calls “complete friendship” or “friendship most of all” even now generally inform the ordinary view of what is more loosely called friendship. (For confirmation, read a few weeks’ worth of “Ask Amy” columns.)

Because Nehamas takes friendship seriously, his treatment can be insightful. He recognizes the unsupported status of friendship within Christianity and philosophic modernity alike. Under both dispensations, the full amplitude of ancient areté (excellence or virtue) is compressed into a narrower range called “morality.” At the same time, the simplified rules of morality are broadened to apply universally, which is to say, indiscriminately. He offers a nice critique of such formalism:

Modern moral thought centered its attention on the impartial principles that govern our obligations to one another in the abstract, our duties and responsibilities to the world at large and, in so doing, turned away from the narrower, partial, and preferential relationships of which friendship was often the emblem.

Instead of the deep, secluded, refreshing mountain-pools of friendship, we have the level flood-plain of humanity (traversed by concepts such as individual rights, the general will, the categorical imperative, and charity toward all).

There are other rewarding sections too, like the paragraphs on the abbot Saint Aelred and English poet Edmund Spenser, or the chapter on friendship and the arts, where Nehamas examines attempts to depict friendship on canvas. He concludes that friendship cannot be captured visually, because (unlike other forms of love—think of all those Madonnas) “it has no sure signs,” no specific, immediately understood posture or performance. It is, instead, “a structure of the soul.” Astonishingly, the author admits that friendship, in this respect, is just like courage and “every other virtue”—an insight that should have prompted deeper attention to Aristotle’s claim that friendship either is a virtue or keeps friendly company with virtue. (Nehamas, by the way, never registers that Aristotle formulates the relation between friendship and virtue in two different ways.)

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Because friendship develops and reveals itself over time, painting can’t do it justice. Literature is more promising. Novels are good, but drama—able to combine the visual (for friendship is “an embodied relationship”) and temporal aspects—is “friendship’s ideal medium.” Maybe—but he doesn’t consider the greatest (and thoroughly Aristotelian) novel about friendship, Jane Austen’s Emma.

The dramatic work he analyzes at length is Yasmina Reza’s Art, a 1994 French play that hinges on a threesome of friends torn apart over an expensive painting one of them has purchased. The characters’ differing reactions to this work of high modernism (a white canvas cut diagonally by a few white lines) lead to all manner of insults, central among them the loss of a sense of humor. Once again, Nehamas manages to find Aristotle inadequate: “Your sense of humor may well be crucial to our friendship, although for Aristotle it is an accidental feature of your personality and could only lead to a pleasure-philia; the same is true of your taste in music, books, clothes, and who knows what else.” Although Nehamas sees and laments the modern contraction of virtue to morality, he fails to appreciate the richness and subtlety of the ancient alternative. He seems to have forgotten that “wittiness” appears on Aristotle’s short list of virtues, and that the philosopher reflects in the Nicomachean Ethics (Book IV, chapter 8) on the delicate balance of humor and tact that constitutes “the playfulness of a liberal person.”

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More significantly, Nehamas’s interpretation of Art, while psychologically astute, ignores a major issue: the extent to which a friendship is understandably (perhaps even rightly) riven by the emergence of a foundational divide, like that in the play over the value of the contested art. Can a postmodernist and a Platonist really be friends? It is a question that arises for the reader of On Friendship. In trying to separate “the good of friendship” from goodness, Nehamas and his heroines, Thelma and Louise, have a wrong conception of what friendship is, I fear. Although I enjoyed many parts of this book, my conclusion—unfriendly though it may sound—is that we would do better to stick with the old Greeks. This passage from Xenophon’s Memorabilia, in which Socrates comments on his circle of friends, testifies to the genuine alchemy of conversation-based friendship:

“Accordingly, Antiphon, just as another is pleased by a good horse or a dog or a bird, so I myself am even more pleased by good friends, and if I possess something good I teach it, and I introduce them to others from whom, I believe, they will receive some benefit with a view to virtue. And reading collectively with my friends, I go through the treasures of the wise men of old which they wrote and left behind in their books; and if we see something good, we pick it out; and we hold that it is a great gain if we become friends with one another.” When I heard these things [says Xenophon], I formed the opinion that [Socrates] himself was blessed and that he led those who heard him to gentlemanliness (nobility and goodness).