Proofs & Theories is a long-awaited first gathering of essays by one of this country's most brilliant poets. Like her poems, the prose of Ms. Gluck, who won the Pulitzer Prize for poetry in 1993 for The Wild Iris, is compressed, fastidious, fierce, alert, and absolutely unconsoled. The force of her thought is apparent everywhere in her writing and whether she is contemplating - skeptically - the critical currency of ideas like "courage" and "sincerity, " T. S. Eliot's reduced reputation as a poet of impersonality, the loyalties of the objectivist George Oppen, or the ferocity in the headlong art of Sylvia Plath, there is something exhilarating about her seriousness, spare, austere, mind-clearing, and adamantly alive. She shares her skepticism with a whole temper of post-modern critical thought. But post-modernism, on the whole, has stood aside from what artists have thought was at stake in their art in order to dissect it. Ms. Gluck is also quite expert - wry sometimes, darkly funny even - at dissection but in these essays one never doubts what is at stake: an art as truthful, adamant, and unflinching as the intelligence that she brings to her own. Proofs & Theories is not a casual collection. It is the testament of a major poet.