When I said that "an exception to a rule cannot 'prove' it (at least not in the modern sense), it can only DISprove it, a former colleague of mine at SUNY Oswego and a very good friend scoffed at me and said that it certainly could. I replied that an exception can only show that the "rule" is not a rule. He refused to be logical, although he was a Professor of English. But the use of the word "proves" in the old slogan does not mean that the rule has been proven in the modern sense, but in the archaic sense of "tests":
The Book of Literary Terms: The Genres of Fiction, Drama, Nonfiction, Literary Criticism, and Scholarship, by Lewis Turco, Hanover: University Press of New England (www.UPNE.com), 1999. ISBN 0874519543, cloth; ISBN 0-874519-55-1, paper. A companion volume to The Book of Dialogue and The Book of Forms. A Choice “Outstanding academic title” for 2000.