An interesting problem often presents itself when one employs an anarthrous nominal premodifier.
A what who which?
“Anarthrous nominal premodifier” is usage-ese for “false title,” one of a handful of other more user-friendly ways to describe a job title that is not a job title. A description of this concept that is, I think, better still is epithet (a versatile word meaning, in this case, “characterization”), and that’s the one I use here and elsewhere on this site.
An epithet — in which, for purposes of clarification or edification, a person’s name is preceded by a concise description of that person — is often derided as a coarse conceit of journalistic writing, but it appears quite often in books and other forms of publication as well, and it serves a useful purpose, eliminating the need to follow a person’s name with a more distracting (and often more extensive) parenthetical description.
Unfortunately, too many people form the epithet-name construction incorrectly, as in this sentence: “The essay was written by humanities professor, Paul A. Robinson.”
This is one of the most egregious mechanical errors a writer can make; few other such infelicities distinguish the amateur from the professional, and it is one of life’s mysteries how such an obvious error has come to be so persistent as well as pervasive. (The correct form, of course, is “The essay was written by humanities professor Paul A. Robinson.”)
The mistake probably stems from confusion with the nearly identical form in the more traditional sentences “The essay was written by a humanities professor, Paul A. Robinson” and “The essay was written by Paul A. Robinson, a humanities professor.” (These forms are preferable to those who find epithets antithetical to good writing.)
The distinction here is that in the corrected sentence, the phrase “humanities professor” is a restrictive appositive. (An appositive is a noun phrase that defines or modifies another noun phrase, and a restrictive appositive is one that applies to only one other noun phrase.) In this sentence, the only humanities professor the phrase can refer to is Paul A. Robinson.
The presence of the indefinite article in the other variations is the crucial indicator that they each include a nonrestrictive appositive, one that refers to any example of the appositive’s description; Paul A. Robinson is just one member of the class “humanities professor,” and the punctuation signals that fact.
The restrictive/nonrestrictive distinction in appositives should be observed when referring to inanimate objects as well. A common error is to insert punctuation between the appositives in “Have you read the book, The Bestseller?” If a generic reference to the book has already been made, this sentence is correct; the title is an elaboration. However, when used on first reference, this construction presumes that the sole example of the concept “book” is The Bestseller. Because The Bestseller is, in fact, only one example among countless others, the comma is omitted to indicate that “the book” and “The Bestseller” are identical.
The same principle applies to any form of composition (film, television program, and so on) or any other thing: “I went to the amusement park Funland.” (“I went to the amusement park, Funland,” in the absence of a previous reference, implies that only one amusement park exists. “I went to the world’s largest amusement park, Funland,” by contrast, is correct, because only one amusement park can be the world’s largest one.)
If you oppose appositive epithets, this post isn’t for you. But for the many writers who accept the construction as proper usage, I recommend that you use the proper usage properly.