Q. In section 6.23 of the 16th edition, the following example is used to illustrate an appositive with a comma: “Ursula’s son, Clifford, had been a student of Norman Maclean’s.” I know that the usage displayed in the last three words of the sentence has become mainstream, but surely it has not become correct?
A. The double genitive (or double possessive) has long been correct. Even the old Fowler’s Modern English Usage included it among the “sturdy indefensibles”: that is, constructions that may be illogical and ungrammatical, but are idiomatic nonetheless. Fowler quotes its use in the opening lines of Shakespeare’s Antony and Cleopatra: “Nay but this dotage of our general’s o’erflows the measure.” (You can find this in Fowler’s under “of,” section 7: “Some freaks of idiom.”) Burchfield’s Fowler’s (s.v. “double possessive”) points out that the construction can serve a useful purpose, allowing us to distinguish between, say, “a picture of the king’s” and “a picture of the king.”