ALTHOUGH WILLIAM GASS has turned his masterly hand to essays frequently in the past decade as he has labored to complete his novel The Tunnel, his discursive prose always reminds us that he is an imaginative writer of the highest order. Indeed, among contemporary American writers of fiction, he is matched as a stylist only by a very select group that includes Eudora Welty, Stanley Elkin, W.M. Spackman and Guy Davenport.

Despite the fact that Gass is a trained philosopher, he never thinks in uprooted, ungrounded abstractions but rather always plants his thoughts firmly in a rough, gravelly matrix of circumstantiality. Thus he writes, in a phrase that both states and illustrates his point, that "ideas carry bombs in their suitcases." Or when he discusses the purely ceremonial nature of consumer culture, he says "we wipe ourselves with a symbol of softness, push an ad around our face; the scale rolls up a number which means 'overweight,' and the innersoles of our shoes say 'hush!'"

The reader of Gass' essays can never drift off into a trance of comfortable (because empty) generalities, each phrase melting into the next through the smoky dissolves of an exhausted rhetoric. No, in every paragraph Gass writes, the very specificity of his images requires the reader to conjure up a matching picture, to expend an erg of energy, the way a far- sighted diner must hold his menu at arm's length in order to order at all.

In this volume Gass has collected 12 essays, one of which is an homage to Emerson (whose sentences rush "from side to side, rebounding as though from rubber bumpers, hurrying out to edges, sounding alarms") and another to Ford Madox Ford's neglected historical romance The Fifth Queen ("the wrk is so intensely visual, so alternately light and dark, you might think the words were being laid on the page like Holbein's paint"). Gass' enthusiasm returns the reader to the original text. At least I reread Emerson, surprised to discover that his sort of gloomy stoicism had ever been offered to the American public as advice, of all things.

Gass' remaining 10 essays are more broadly philosophical. In one he analyzes all the possible connotations of the word and in an exercise reminiscent of his dazzling thematic rhapsody On Being Blue. A pair of essays takes up the related subjects "On Talking to Oneself" and "On Reading to Oneself."

In several of these pieces Gass reminds us that written words should be pleasing to the ear when spoken. "Above all," he says, "the written word must be so set down that it rises up immediately in its readers to the level of the ear, and becomes a vital presence in their consciousness.t asks, that is, to be performed; to be returned to the world of orality it came from; it asks to be said, to be sung." Certainly Gass' own prose -- from his mythic novel, Omensetter's Luck, with its extended bravura soliloquy for a sex-crazed man of God to the flat, terse poetry of his hallucinatory story, "The Pedersen Kid" -- has always invited song. In fact in "The Pedersen Kid" (included in the collection In the Heart of the Heart of the Country), the breath marks are even notated.

But Gass is not just concerned with word music. He recognizes the intellectual nature of words. Although Gass may not be a Platonist, he has been permanently compromised by the irresistible theory of the Forms, those abstract entities that Plato claimed were far denser with reality than any of their mere instances on earth, so that "Chair" must be considered infinitely superior to any actual thing we might sit on. Or as Gass puts it, we are astride mythical horses that "sink down in the direction of things and their disconnections, to pornograph among the passions" or we "rise as if winged toward meanings, ideas, regions of pure relation."

THIS TENSION between the grittiness of the particular and the ethereal dynamism of the general is exactly what animates the best fiction and poetry. Wallace Stevens wrote a late poem called "What We See is What We Think." Conversely, William Carlos Williams declared, "No ideas but in things." Yet both poets point to this busy traffic between the intellectual and the material that constitutes any work of imaginative literature that is more than a list of facts or the exposition of a thesis.

In one essay, "Representation and the War for Reality," Gass clarifies the subject by dividing the world into the Thick and the Thin. Thins are reductionists. "Thins firmly believe that explanations should be simpler and quite other than the things explained." They make good scientists and philosophers. By contrast, Thicks are more concerned "with amassing facts rather than discovering laws." They make good novelists and historians. But in practice (at least sound practice), these two extremes come together, since "without arrangement and connection" there is "no history" and "without rhetoric, without pattern, without coherence there is only the ordinary novel."

I don't mean to reduce this rich, energetic book to a single topic, no matter how fertile. Gass attacks Roland Barthes and champions Freud, Rilke, Beckett and Gertrude Stein (I wish he'd write an essay on Wallace Stevens, his perfect subject). He argues that "I love you" depends for its meaning on which organ of the body energizes the words -- or at least that is his interpretation of Plato. He flits with the idea proposed by Leibnitz that "we are wholly windowless with regard to one another," yet he offers the possibility that reading a novel permits us to enter an alien system, "to become a different monad for a moment." He reminds us that wisdom is never general but rather something "found by means of a vocalized internal investigation," a sort of sustained dialogue of the soul and self. In "The Soul Inside the Sentence" Gass ingeniously elaborates Freud's theories of wish-fulfillment and sublimation as the underpinnings of creativity, but surely any psychoanalytic theory of art that leaves out Freud's notion of the repetition compulsion (proposed in his 1920 essay Beyond The Pleasure Principle) can only be partial.

Gass consistently defends an elaborate literary style. Thus Ford Madox Ford did not "have to assume a severe, undecorated, screwed-down style, as if weakness were a show of strength, as if only the simple were sincere, or the plain ennobling." Americans sometimes fall into the trap of imagining that the national style is invariably chaste, business-like. But Gass -- like Emerson, Whitman, Melville -- belongs to the other American tradition of inspired rhetoric. Perhaps the two great sources of this rhetorical style were the King James Bible and Shakespeare. The decline of the Renaissance ornate style Gass traces to the rise of the bourgeoisie and the novel and laments in a sentence worthy of his models, one I cannot and will not follow:

"The paragraph is replaced by the sentence; the sentence is shortened like a dress; the dress is moreover designed to be as plain as a Mennonite's nightgown; and that majestic, endlessly elaborating language, subtle and continuously discriminating, that joyful, private, yet publicly appointed prose, that mouthmade music, once headlong, resonant, and roaring, is reduced to a mousy squeak by the rising noise of the novel."