From reader AH:
I know I'm a little slow, but during the State of the Union, President Obama said something along the lines of the following (I'm not 100% certain that the noun was "soldier" and I don't remember the verb, but those aren't the relevant parts): "every soldier respects each other."
As soon as he'd said it, my dad and I exchanged a look of disconcertedness — Barack Obama shamelessly putting forth such a blatantly ungrammatical statement? However, when I analyzed it a moment later, I came to the conclusion that the structure "every X Ys each other" is equivalent to the structure "every X Ys each other X," which is correct, and that the more usual structure "all the Xs Y each other" is equivalent to the structure "all the Xs Y each other X," which to me seems at best ambiguous. If my reasoning is incorrect, where did I go wrong? And if my reasoning is correct, what accounts for the little jolt my dad and I (and probably other listeners) experienced as a reaction to Obama's sentence — and what accounts for the fact that we wouldn't even have noticed if he'd said "all the soldiers respect each other"?
They know that this generation’s success is only possible because past generations felt a responsibility to each other, and to the future of their country, and they know our way of life will only endure if we feel that same sense of shared responsibility.
More than that, the mission only succeeded because every member of that unit trusted each other — because you can’t charge up those stairs, into darkness and danger, unless you know that there’s somebody behind you, watching your back.
This nation is great because we get each other’s backs.
So what about "every member of that unit trusted each other"? Is it "a blatantly ungrammatical statement", as AH and her dad first thought? Or is it OK, as she later decided?
I believe that there are several different issues here. First, there's the idea that each other must be restricted to two, with one another used for more than two. The entry on "each other, one another" in the M-W Dictionary of English Usage refutes this:
Bardeen 1883 indicates that the use of each other for one another is legitimate, though carped at by some critics [...]. Actually the prescriptive rule is that each other is to be restricted to two and one another to more than two goes back even further [...]. Goold Brown 1851 cites the rule with approbation, and quote it from an even earlier grammarian [...]. Sundby et al. 1991 have found it in a 1785 grammar by a George N. Ussher. But Goold Brown also notes that "misapplication of the foregoing reciprocal terms are very frequent in books" and goes on to cite Samuel Johnson and Noah Webster in error. He further notes that "it is strange that phrases so very common should not be rightly understood." It is perhaps easier now that it was in 1851 to see why: evidence in the OED shows that the restriction has never existed in practice; the interchangeability of each other and one another had been established centuries before Ussher or somebody even earlier thought up the rule.
Fowler 1926 notes that some writers follow the rule but goes on to state that "the differentiation is neither of present utility nor based on historical usage [...]". Even Fowler's high reputation among usage commentators has not convinced those to whom the rule is dear; many still prescribe it. A few examples may illustrate the rule's baselessness:
Sixteen ministers who meet weekly at each other's houses — Samuel Johnson, Life of Swift
Most whom live remote from each other — Noah Webster, Essays
Two negatives in English destroy one another — Lowth 1763
It is a bad thing that men should hate each other; but it is far worse that they should contract the habit of cutting one another's throats without hatred — T.B. Macaulay
We conclude that the rule restricting each other to two and one another to more than two was cut out of the whole cloth. There is no sin in its violation. It is, however, easy and painless to observe if you so wish.
But I don't think that the imaginary "restricted to two" rule is what was bothering AH and her father, since the other two examples of each other in the SOTU, which didn't evoke any reaction, also had greater-than-two antecedents.
And I agree with AH in not trusting her attempt to settle the matter by thinking through the compositional logic of the construction from first principles. The entry in the OED explains why a fully compositional account of each other (in terms of the separate meanings of each and other) is misguided. Given that each other has been a lexicalized compound for many centuries, we can't expect to predict its usage from its etymological decomposition:
Originally this was a phrase construed as in 4 ['each to each'], each being the subject, and other (inflected in Old English óðerne, óðres, óðrum, etc.) being governed in acc., genit., or dat. by a verb, prep., or n. This use still occurs arch. or poet. (each to other, etc.). The words have however long become a compound (cf. Dutch elkander), so that we can say to each other, of each other, etc.
But the phrase "every member of that unit trusted each other" has another possible flaw, not engaged by MWDEU's examples. Every member is grammatically singular, and may seem to focus semantically on the members one at a time, which would lead to an absurd enumeration: "Member 1 trusted each other, and member 2 trusted each other, and …"
This seems to be the factor that took AH and her father aback — and when I think of it that way, it seems odd to me as well.
Since we can't apply logic to the question until we figure out what the semantic analysis of each other really is, we have no choice but to look at usage. What does Norma Loquendi have to say? Well, there are a large number of classical examples of the form "everybody VERBed each other" or "everyone VERBed each other". Thus Emily Bronte, Wuthering Heights, 1847:
I thought, though everybody hated and despised each other, they could not avoid loving me.
"Playfulness in High Life", Punch 1857:
A Lovely Creature had just been warbling, "Drink to me only with thine Eyes." There was a pause. Everybody stared unmeaningly at each other. There was not a sound, save the splash of the gold fish that, with unwearied fins, were carrying on their swimming-matches round the large glass bowl, when Lord Edgar Swann (the lineal descendant of the united houses of Swann and Edgar) leant forward, and said lovingly to his partner, "I wonder, by the bye, what kind of tipple it is that the Eye does drink?" "Why, Champagne d'Aï, to be sure!", exclaimed the every-ready Agnes, and, tapping his fingers playfully with her fan, she split the coffee over his legs.
The lucubrations of Isaac Bickerstaff, Esquire (The Tatler No. 95), 1711:
I sate with them till it was very late, sometimes in merry, sometimes in serious, Discourse, with this particular Pleasure, which gives the only true Relish to all Conversation, a Sense that every one of us like each other.
Phoebe Allen, Thanksgiving Tabernacle, 1888:
Altogether, she was very glad when the last hymn had been sung, and everyone had finished telling each other what a happy evening it had been, and how gratifying it was to feel themselves all so saintly in this world and so safe in the next, and it was with real relief that Jane found herself once more in the van.
And similarly, phrases like "Every NOUN VERBED each other" have a long and apparently respectable history:
Andrew Henderson, The life of John Earl of Stair, 1748:
Every Officer, and every Soldier, vied with each other in distinguishing himself under the Eye of his August Commander; but none more than the deceas'd Lord: For, being made Colonel of the Royal North British Dragoons, upon the 9th March 1702, he endeavoured to raise the Reputation of that Regisment; and, being sent to support a Battery, he stood at the Head of his Regiment, for several Hours, while the Troops were falling on each Hand of him, without the least Alternation of Countenance, or the last Desire to draw off, notwithstanding a furious Cannonade from that Quarter of the Town.
Charles Rollin, The Roman History, from the foundation of Rome to the battle of Actium. Translated from the French, 1711:
Every thing resembled each other in these two wars: the extraordinary efforts and preparations employed in them; the splendor of arms; the terrible ceremonies used for rendering the gods propitious, and initiating in some measure the soldiers by an oath of ancient form; and lastly the levies made universally throughout the whole extent of Smanium under that form, which devoted to Jupiter, and loaded with curses, all such among the youth, as should not present themselves for the service on the general's order, or should retire from it without his permission.
James Elmes, A general and bibliographical dictionary of the fine arts, 1824:
In defining the styles which prevailed at this period of history, we should consider that the orders are not only Greek and Roman, but Phoenician, Hebrew, Egyptian, and Assyrian; therefore are founded upon the experience of all ages, promoted by the vast treasure of all the great monarchs, and skill of the greatest artists and geometricians, every one emulating each other: experiments in this kind being very expensive, and errors incorrigible, is the reason tha the principle of architecture should be founded more on the study of antiquity than a dependance [sic] on fancy.
"Two Years Lost", in The Argosy, volume 26, 1878:
Another thing; their tastes and pursuits were so dissimilar. These balls and kettledrums and insane gatherings, which made her life, he hated. The social, sober partes ad Candelford, where every lady knew each other, were quite different.
Margaret Winslow, "Easter Eggs: A Russian Story", in The Churchman, 1880:
Everywhere they met other parties, on foot in carts, bound in the same direction, and every group greeted each other with the prescribed words, "Christ is risen," or answered again, "He is risen indeed."
George Jacob Holyoake, "The History of the Rochdale Pioneers", in Cooperation, Volume 1, 1909:
The Store very early began to exercise educational functions. Besides supplying the members with provisions, the Store became a meeting place, where almost every member met each other every evening after working hours.
Journal of the Scientific Laboratories, Denison University, 1943:
It should be noted that every group overlaps each other; that every item is both a "cause" and "effect" of every other single item; that the numerical order does not imply any priority whether causal, etiological, or temporal …
John P. Wilson, "Reversing Cultures: The Wounded Teaching the Healers", in Voices of Trauma: Treating psychological trauma across cultures, 2007:
The ritual of the "Talking Circle" is a most powerful one. [...] Eventually, I returned to my "seat" on the log and the next person got up and repeated the process. In this way then, the "Talking Circle" meant that every person encountered each other at least twice.
So I conclude that "every member of that unit trusted each other", though not to everyone's taste, can't be considered ."a blatantly ungrammatical statement".
From a rhetorical point of view, it's obvious that the triple repetition of each other in this year's SOTU relates to the speech's theme of teamwork, associated with the military and also with traditional American values. The "every member of that unit trusted each other" phrase at the end of the speech echoes the speech's beginning:
These achievements are a testament to the courage, selflessness and teamwork of America’s Armed Forces. At a time when too many of our institutions have let us down, they exceed all expectations. They’re not consumed with personal ambition. They don’t obsess over their differences. They focus on the mission at hand. They work together.
Imagine what we could accomplish if we followed their example.
FWIW, the 2012 SOTU message is far from the only one to feature each other. Among the 209 previous SOTU messages, James Buchanan used each other six times in 1857; Andrew Jackson used it five times in 1833; James K. Polk in 1848 and William McKinley in 1899 used it four times; and there were eight other messages with three instances of "each other": John Quincy Adams in 1825 and 1826, Andrew Jackson in 1831, James Buchanan in 1860, Teddy Roosevelt in 1904 and 1906, Harry Truman in 1946, and Bill Clinton in 1995. There have been 19 SOTU messages with two instances of "each other", from James Monroe in 1820 to Bill Clinton in 1997; 50 SOTU messages with one instance of "each other"; and 128 with none.
Fans of Zipf's Law will be pleased to see that doesn't fail to apply here:
As far as I can tell, though, none of the previous SOTU uses are of the form "Every NOUN VERBed each other".