"I was saying that this passion for specificity, for the hypnotic materiality of the world one is in, is all but at the heart of the task to which every American novelist has been enjoined since Herman Melville and his whale and Mark Twain and his river: to discover the most arresting, evocative verbal depiction for every last American thing. Without strong representation of the thing--animate or inanimate--without the crucial representation of what is real, there is nothing. Its concreteness, its unabashed focus on all the particulars, a fervor for the singular and a profound aversion to generalities, is fiction's lifeblood. It is from a scrupulous fidelity to the blizzard of specific data that is a personal life, it is from the force of its uncompromising particularity--from its physicalness--that the realistic novel, the insatiable realistic novel with its multitude of realities, derives its ruthless intimacy."
Here's an audio recording of the entire speech, a truly wonderful performance that includes extended comments on, and a reading from, Sabbath's Theater. The paragraph I've quoted begins at 7:15: