IN EACH academic domain, there are trendsetters. With the ability to capture the thoughts of a group of intellectuals and the authority to convince, this thinking-man's gentry can produce a book which liberates a community of critics. In this tradition, Mary McCarthy's Ideas and the Novel has prompted a ferocious critical attack on modern action.

Disparaging every attempt in the last fifty years to write a serious novel, a novel of ideas, the attacks come strong and steady. Some are self-serving, such as Gore Vidal's assertion that to rejuvenate fiction a writer must be witty and satiric. Others are malevolent such as Alfred Kazin's attempts to embarass the writer of the '80s with accusations of simplicity and incompetence. But these attacks are misguided. Fiction lives a healthy and vigorous life. Pummeled by the film industry, mass marketing and now McCarthy's vision of violation and out-dated expectation, the novel prospers.

McCarthy's collection of Northcliffe Lectures from University College in London, can be read in two ways. One is as pure literary criticism, as a reinterpretation of Stendhal and Balzac. She writes with assurance and insight of the 19th century novel, of George Eliot's "homely English novel," of the literary use of Napoleon as the personification of genius, of Les Miserables and Jean Valjean's conscience as a dialogue. Her writing is spirited but there are grounds for disagreement, such as her contention that the fiction of Conrad "went so far in' the direction of brevity and concentration that they were closer to the tale than the novel." A rather curious assertion in the light of Nostromo's 400 pages and Lord Jim's 300.

But McCarthy's musings serve a larger purpose, make a grander statement, or rather, indictment. She means to set the modern novel apart from and beneath its predecessors because today "Ideas are held not to belong in the novel; in the art of ficiton we have progressed beyond such simplicities," she writes sarcastically. And the writer McCarthy takes the critic McCarthy to heart. "I cannot philosophize in a novel in the good old way," she mourns. "Ideas are still today felt to be unsightly in the novel."

WHAT ARE these "Ideas" that she feels are strangely missing from the modern novel? We read hoping that she will give specifics. But she never does, nor does she even define what an "idea" is. She uses the term in any number of ways throughout the book. An idea is variously an unfinished thought, a theme, a motif, a model, a goal, an inclination, a theory. An idea seems to be anything that passes through the human brain, a feeling, a desire. If a protagonist is a representation of a particular character type he is "an idea."

It is disappointing to see an author write a book called Ideas and the Novel when the best she can manage to explain her theme is: "The nature of an idea, surely, is to be abstract i.e. the polar opposite of the concrete" or "a universal which we can ophosister according to our own taste and antiquarian knowledge."

Unable to define terms, McCarthy is unable to clarify her complaint about today's novel. Given that failure, her indictment rings empty. Nevertheless, she is sure the modern novel lacks serious purpose. Without evidence, she convicts a villain. Her book becomes a diatribe against Henry James who, she believes, singlehandedly created a new and inferior brand of fiction, "the pure novel." "When you think of James in the light of his predecessors," she writes, "you are suddenly conscious of what is not there: battles, riots, tempests, sunrises, the sewers of Paris, crime hunger, the plague, the scaffold, the clergy..." And most of all, she is convinced, ideas are gone. This is unconvincing in light of James' The Bostonians, a book packed with ideas.

BUT WITH THIS attack, we can begin to guess what McCarthy pines for. She wants a novel that addresses moral issues, that takes a political position, that is didactic and "serious." Are such novels extinct as McCarthy implies? Moral novels that take ideas seriously are, to the contrary, very strong, in Nadine Gordimer's Burger's Daughter, for example. Political novels still concern contemporary writers, especially feminists such as in Mary Gordon's Final Payments. McCarthy's arguments are not only vague but inaccurate.

Her interest in fiction overflows into the valid but unoriginal point that the film has taken the novel's place at the center of our culture. This returns her to her theme: "the moving picture...cannot be an idea spreader...A film cannot have a spokesman or chorus character to point the moral." Regardless of the film's "victory" over the novel, this contention would be difficult to maintain; film history, from Triumph of the Will to Norma Rac, proves her wrong.

McCarthy's indictment has given critics the confidence to claim that fiction has become a moral basket case. With persiflage and pronouncement, but without sound argument or distinction, McCarthy has written an uninteresting and inaccurate book, and has embellished a trend that does not deserve to be followed.