Peter Sokolowski of Merriam-Webster tweeted this a little while ago: "Just had a conversation with a man who prefers prescriptive dictionaries. Descriptive ones, he says, make him 'nauseous.' Sigh."

Those of you familiar with prescriptivism will recognize at once the nauseous/nauseated distinction that some of us spent years vainly enforcing. This distinction is that nauseous means "causing nausea" (and did so in Latin) while nauseated means "experiencing nausea."

The problem is that nauseous has been used in American English to mean "experiencing nausea" since the late nineteenth century, frequently so since the 1940s.

After an extensive examination of nauseous/nauseated/nauseating, in both literal and figurative senses, Merriam-Webster's Dictionary of English Usage concludes: "At present, nauseous is most often used as a predicate adjective meaning "nauseated" literally; it has some figurative use as well. Usage writers decry these developments of the last 40 years, but they are now standard in general prose. The older sense of nauseous meaning "nauseating," both literal and figurative, seems to be in decline, replaced by nauseating. Nauseated is usually literal, but is less common that nauseous. Any handbook that tells you that nauseous cannot mean "nauseated" is out of touch with the contemporary language. In current use it seldom means anything else."

Garner's Modern American Usage, conceding that nauseous for nauseated is ubiquitous, comes reluctantly to a similar conclusion. It is "so common that to call it an error is to exaggerate. Even so, careful writers tend to be sickened by the slippage and to follow the traditional distinction in formal writing."

The American Heritage Dictionary's usage note on nauseous say that "the word presents a classic example of of a word whose traditional, 'correct' usage is being supplanted by a newer, 'incorrect' one. In other words, what was once considered an error is becoming standard practice."

There you have it; the distinction, much eroded, is not a rule but a personal aesthetic choice, one that it is increasingly difficult to maintain.

What interests me more about Mr. Sokolowski's interlocutor is his demonstration of the applicability of Muphry's Law. It has four components: (a) If you write anything criticizing editing or proofreading, there will be a fault of some kind in what you have written. (b) If an author thanks you in a book for your editing or proofreading, there will be mistakes in the book. (c) The stronger the sentiment expressed in (a) and (b), the greater the fault. (d) Any book devoted to editing or style will be internally inconsistent.

Like Mr. Sokolowski's interlocutor, any peever complaining about slack usage will almost inevitably violate some shibboleth himself. This is the more the case because there is no universal set of rules, no unquestioned authority on usage.

You are welcome to consult authorities, and you should make some effort to determine which ones are current and reliable, also noting where they disagree and which ones take note of empirical evidence. (Empirical evidence counts because the language is what its users make it.) Then you must make your own judgments, based on your own tastes, your own ear for the language, your own sense of how the writers whose work you respect are using the language. After that you adjust your usage to subject, occasion, and audience. This is the road, and there are no shortcuts.