Q: President Obama said at a press conference last month that he and the South Korean leader “both agree” on the need to break the pattern of on-again, off-again talks with North Korea. I think using “both” here is not only redundant but also hyperbolic. Do any two people both disagree?
A: It’s true that the word “both” could often be omitted without changing the meaning of a sentence. But does that make it wrong? Not necessarily. There’s a fine line between an emphatic use and a redundancy.
As the Oxford English Dictionary says, “both adds emphasis to the sentence by suggesting a contrast with the statement as it would have been had one of the terms been omitted.”
The kind of sentence you mention illustrates a common use of “both.” It’s often used, according to the OED, in relation to two nouns or pronouns (or a noun and a pronoun) coupled by “and,” as in “both John and I came,” “both the king and the queen spoke,” “Mercury and Venus are both inferior planets,” and so on.
If you want to get technical about the relationship between “both” and the nouns or pronouns, the OED says “both” may be viewed here “as an adjective in attributive relation to the two substantives.”
Like you, many usage writers over the years have condemned the use of “both” with “agree,” since the verb has the idea of duality built in.
It’s true that “they both agree” or “the sisters both agree” or “Dad and I both agree” could do without “both,” since the verb implies “both.” But I would argue that there’s nothing grammatically wrong with constructions like these, and that the emphatic use of “both” is legitimate.
The phrase “both agree” is extremely common. The Internet has a couple of hundred thousand examples, and a quick search of the OED and other sources finds these citations:
1767, from Sir William Blackstone’s Commentaries on the Laws of England: “If they do not both agree within six months, the right of presentation shall lapse.”
1784, William Cowper: “As my two syllablemongers, Beattie and Blair, both agree that language was originally inspired ….”
1873, Matthew Arnold: “You and I both agree.”
1929, David O. Selznick: “I feel confident that you and Cooper will both agree that the re-editing has really been a tremendous game.”
Merriam-Webster’s Dictionary of English Usage asks “who has limited agree to an implication of duality that makes both redundant?”
“Not users of English, certainly,” M-W answers, adding, “In the end, after two centuries and more of comment, this molehill is still a molehill. It is a trivial matter and not worth worrying about.”
On the other hand, I would draw the line at “they both disagree.” Why? To be perfectly honest, “they both disagree” DOES seem out-and-out redundant (unless the two people are disagreeing with a third party). It simply does not sound like good idiomatic English.
But I know that it’s possible to both agree and disagree with my answer!