Before we rebuke these writers for their intellectual cowardice, we ought to acknowledge the genuine difficulty of the task they shirk. The literary world is tiny. The subgroup represented by novelists is even tinier. If you’re an author who regularly reviews other authors, the chances of running into a person whose novel you have criticized are fairly high. (All the higher, if you happen to live in New York City or some other center of ambition.) It may not be the worst thing in the world to find yourself side by side at a cocktail party with the angry man whose work you described as mediocre in last Sunday’s paper, but the threat of such encounters is not a great spur to critical honesty.

Membership in any small, somewhat beleaguered professional community engenders not just social anxiety but also collegial loyalty and empathy. A novelist can avoid literary functions, but not his fellow feeling for other novelists. Once you know the hard labor it takes to complete even a lousy novel — once you’ve experienced the sting and misery of your own bad reviews — it’s only natural to feel some hesitation about inflicting pain on a colleague.

If nonfiction writers are, by and large, less squeamish about criticizing one another’s work, this is not, one suspects, because they are a bolder or less compassionate bunch, but rather because the criticism of nonfiction tends to be a more impersonal business than that of assessing novels. The critic of nonfiction contests matters of fact, of interpretation, of ideological stance. The critic of fiction, by contrast, has only aesthetic criteria to work with. You may respectfully take issue with another writer’s analysis of the Weimar Republic without impugning his skill and dignity as a historian. But when you argue that a novelist’s characters are implausible or that his sentences are inelegant, there’s no disguising the rebuke to his artistry.

Given these powerful deterrents to candor, why urge novelists to write criticism at all? Certainly not because the world needs more “hatchet jobs” or literary “feuds.” (The fact that literary argument is so often spoken of in these debased terms can only act as a further disincentive for the review-shy novelist.) No, the real reason for encouraging novelists to overcome their critical inhibitions is that their contributions help maintain the rigor and vitality of the public conversation about books. Practical experience in an art form is not an essential qualification for writing about that art form. (As Samuel Johnson pointed out, “you may scold a carpenter who has made you a bad table, though you cannot make a table.”) Yet an artist’s perspective is clearly useful to the critical debate. (The thoughts of a master carpenter on what went wrong with your wonky table will always be of some interest.)

From the novelist’s point of view, participation in what Gore Vidal used to call “book chat” is not just a public service, but an act of self-interest. Whenever a novelist wades into the critical fray, he is not only helping to explain and maintain literary standards, but also, in some important sense, defending the value of his vocation.