In the past few days, I keep seeing people misuse the phrase "that of" in the same kind of way, apparently for emphasis. Like this:
* My primary concern is that of earthquakes.
Where the speaker meant to say that their primary concern is earthquakes themselves; but that's not what "that of earthquakes" means.
Here's one possible way to test whether you've incorrectly put "that of" in a sentence that has the structure "My A is that of B":
- Replace "that of" with "the A of". (* "My primary concern is the concern of earthquakes.") Or replace "that of B" with "the same A as B's". (* "My primary concern is the same concern as earthquakes's.")
- If the sentence doesn't read smoothly, then you've probably misused "that of."
The problem with the above test is that there are some borderline-inappropriate uses that pass the test:
* My subject tonight is that of grammar.
* The company's core business is that of computer graphics.
In both cases, you could argue that the sentence is correct, and both cases sort of pass my above test: "My subject tonight is the subject of grammar"; "The company's core business is the business of computer graphics." But in both cases, the "that of" is redundant.
So here's another test, probably better: just cut "that of" from the sentence, and see if the sentence still makes sense; if it does, then you were probably misusing "that of."
I think there's a subject/object confusion at the heart of the misuse; in the standard use of "that of," the B in the phrase "that of B" is a person or organization that owns (or to which can be attributed) the thing named by A.
Here's an example of how to use "that of" correctly:
His premise was that of Newton: that matter and energy are distinct.
In other words, his premise was the same as Newton's premise.
I imagine this is yet another case where my prescriptivist side will have to learn to live with the new phrasing; I suspect it's becoming more widespread over time. But it bugs me.
Of course, for all I know, the usage I'm objecting to has been around longer than I have; I don't currently have any easy way to check on that. If any of you know, let me know.
(Wrote this back in March, but neglected to post it.)