Usage
Q. I have a question about usage rather than style, but probably relevant to this site nonetheless. In your fifteenth edition, paragraph 6.92, in the first example sentence, you use “can” in the clause “can he have been out of his mind?” Several sources, including Michael Swan’s Practical English Usage, state that ‘could’ is used to talk about past possibility. Is using ‘can’ a mistake?
A. According to Fowler’s, in the past tense, “could . . . is more or less obligatory” (3rd edition, s.v. “can”). When I read the example you cite, it sounds vaguely as if it might be idiomatically natural to some. It sounds old-fashioned, and I really expected Fowler’s to at least have something to say about it. On a hunch, I searched Dickens’s Hard Times. Here’s a little paragraph of dialogue that exhibits the same usage:
“Mrs. Bounderby,” said Harthouse, perfectly hearing this understrain as it went on; “your brother’s face is quite familiar to me. Can I have seen him abroad? Or at some public school, perhaps?”
Mr. James Harthouse is an attorney and presumably well spoken. The phrase is of course perfectly intelligible even today, and on its own terms, not wrong. It expresses a present-tense concern (“can” [it be true]) about something in the past. But it does perhaps seem mannered to a modern American ear.
