Mark Liberman exposes a new victim of the "Law of Prescriptive Retaliation" — the Murphy-esque principle that corrections of linguistic error are themselves inevitably prone to error. The law was independently discovered around 1999 by Jed Hartman, Erin McKean, and alt.usage.english contributor Skitt. But it looks like an earlier observer of prescriptivist pitfalls has them all beat by a mile: Ambrose Bierce, in his slender, unjustly neglected volume of 1909, Write it Right: A Little Blacklist of Literary Faults.
Unlike the venerable Mr. Strunk and other early 20th-century contemporaries in the verbal hygiene racket, Bierce was acutely aware of the need for humility in any critique of English usage:
In neither taste nor precision is any man's practice a court of last appeal, for writers all, both great and small, are habitual sinners against the light; and their accuser is cheerfully aware that his own work will supply (as in making this book it has supplied) many "awful examples" — his later work less abundantly, he hopes, than his earlier. He nevertheless believes that this does not disqualify him for showing by other instances than his own how not to write. The infallible teacher is still in the forest primeval, throwing seeds to the white blackbirds.
Thanks to Jason Streed of the Finches' Wings blog for unearthing this quote. Streed further explains Bierce's allusion to "white blackbirds":
Posted by Benjamin Zimmer at November 12, 2005 11:45 AM
I was curious as to what "white blackbirds" could be referring to. Googling turned up its usage in various proverbs as a figure of improbability — "There'll be white blackbirds before an unwilling woman ties the knot" — as well as this a bit from the fascinating Aberdeen Bestiary: "In the regions of Achaia, according to Isidore, there are white blackbirds. A white blackbird represents purity of will. But by Achaia we understand the industrious sister. There are two sisters, Rachel and Leah, namely the active and the contemplative life. Leah we take to be the industrious one. The active life teaches us to devote ourselves to works of charity, to teach men who lack discernment, to have the purity of chastity, to work with our own hands. This is Achaia, the active life. In Achaia, therefore, like the white blackbirds, live those who live chastely the active life."