Linguists and English-usage types have long engaged in a back-and-forth regarding the extent to which it’s appropriate for English usage to be subject to “rules.” On one side are descriptivists; on the other, prescriptivists. Here’s how journalist Robin Lane Greene described the tussle in a recent New York Times debate with Bryan Garner:
Welcome to another round of the Language Wars. By now we know the battle lines: As a “descriptivist,” I try to describe language as it is used. As a “prescriptivist,” you focus on how language should be used. If we were from the two extremes, I would open fire by saying that you preach stodgy nonrules that most people don’t obey, and that people like you don’t understand that language must grow and change. You would then call me a permissivist who ignores the fact that people can use language incompetently or well, and that people want to write and speak well.
For more of this sort of thing, see this New Yorker piece by Joan Acocella, analyses of that piece on Language Log (here and here), and Steven Pinker’s letter to the New Yorker in response to Acocella’s piece (here).
For anyone trying to be clear without being pedantic, it’s easy enough to occupy the middle ground between the two warring camps. For purposes of my expository prose, that’s what I do.
Otherwise, I’m spared having to navigate between descriptivism and prescriptivism, because for purposes of contract language, I’m a raging prescriptivist. I’m a nun patrolling the classroom, ready to rap knuckles with a ruler.
That’s because contract language regulates conduct, with money at stake. As a result, contract prose is subjected to greater stresses than are other kinds of writing. Compared with slipshod narrative prose, confusion or lack of clarity in contract language is far more likely to have unfortunate consequences. It follows you need to keep a tight rein on contract language. That’s why, for example, the account in the third edition of MSCD of “the part versus the whole” ambiguity—featuring and and or—is more comprehensive than any account in the literature on linguistics.
If you think that the clarity and consistency achieved by following guidelines unduly cramps your style, then go ahead and indulge in a descriptivist approach—treat contract drafting as a craft. But that comes at a steep price, namely the time and money wasted in dealing with glitchy contract language, not to mention the risk of confusion leading to dispute.
But given the limited and stylized nature of contract language, my prescriptivism is mostly different from the sort aimed at general writing. You won’t find in guides to English usage anything about categories of contract language, use of defined terms, and other distinctive features of contract language.