Q: I wonder what your feelings are on the use of “that” instead of “who” to refer to people. It seems to me that even well-educated speakers now use sentences like “He’s the doctor THAT diagnosed my Lyme disease” instead of “He’s the doctor WHO diagnosed my Lyme disease.” Am I the only one who’s disturbed by this?
A: Despite what many people believe, a person can be either a “that” or a “who.” There’s no foundation for the widespread belief that the word “that” should refer only to things and “who” only to people.
There may be a politeness issue here, though. Some may think using “that” in place of “who” or “whom” demeans or objectifies a human being. Still, there’s no grammatical or usage reason for such a rule, even though many style books persist in spreading the misconception.
A Dictionary of Contemporary American Usage, by Bergen and Cornelia Evans, has a good entry on the history of the relative pronouns “that,” “who,” and “which.” Here’s an excerpt:
“That has been the standard relative pronoun for about eight hundred years and can be used in speaking of persons, animals, or things. Four hundred years ago, which became popular as a substitute for the relative that and was used for persons, animals, and things. Three hundred years ago, who also became popular as a relative. It was used in speaking of persons and animals but not of things. This left English with more relative pronouns than it has any use for. … Who may in time drive out that as a relative referring to persons, but it has not yet done so.”
You can undoubtedly find writers on grammar and usage who disagree with this conclusion, but I think it’s sound.