The Dewey Decimal System, invented in 1876 by Melvil Dewey, sought to categorize books by organizing all knowledge into 10 broad classes, with each class further broken down into 10 divisions and each division into 10 sections. For finding a specific title there is nothing like it, its supporters say, particularly since it is used all over the world. Though many college libraries use the Library of Congress system, for more than a century Dewey has been a mainstay in American public libraries, about 95 percent of which continue to rely on it.

The system does have its flaws, though, being limited in what it can do with subjects like cooking and travel, for instance, both of which happen to be popular at bookstores.

Further, noted Barbara Kwasnik, a professor at the School of Information Studies at Syracuse University, Dewey had a strong classification bias when it was created. There was an emphasis on topics like Christianity and American history, for example, and not enough on Eastern religions and on history outside of the American experience.

But Joan S. Mitchell, editor in chief of the Dewey Decimal Classification, the cooperative that administers the system, pointed out that Dewey had been revised 22 times to address such biases, most recently in 2004.

Ms. Mitchell also said she could not recall an earlier instance of an American public library’s totally abandoning Dewey or the Library of Congress system since she became editor of Dewey in 1993. Of Mr. Courtright, she said gently: “Perhaps he knows his library’s clientele and he’s meeting their needs. Libraries are always experimenting to meet the needs of its patrons.”

Her assessment, though, understates his goals. Throughout the recent annual convention of the American Library Association, in Washington, Mr. Courtright and 16 of his employees paraded around wearing and distributing eye-catching badges that bore the word “Dewey” encircled in red with a slash across the middle.

Though Mr. Courtright’s assault on Dewey was not an official topic at the convention this year — the association requires at least a year’s notice for such a designation — his intent is to have it discussed formally next year.

Does he think his approach could signal the death of Dewey in libraries across the nation?

“I think it could be,” Mr. Courtright said. “And it probably should be.”