Lesedauer: 4 min
“One in the same” will generally be considered wrong. No dictionary recognizes it. You should avoid it and use the standard form of “one and the same.”
Apart from shoring up my prejudices (a function it performs I suspect for so many people) Twitter occasionally lobs a new (to me) eggcorn my way.
One it flung at me recently is “one in the same”.
It should be “one and the same”.
What does “one and the same” mean?
As the Collins Cobuild dictionary helpfully defines it, “When two or more people or things are thought to be separate and you say that they are one and the same, you mean that they are in fact one single person or thing.”
You use it mostly, but not exclusively, as the complement of to be, in the latter’s various forms, as these examples suggest.
Luckily, Nancy’s father and her attorney were one and the same person.
I’m willing to work for the party because its interests and my interests are one and the same.
I grew up equating sex with love, believing them to be one and the same.
As you can see, the phrase can either be used on its own or with a following noun (person, 1st e.g. above.)
The nouns people most often use with it, other than person, are time and thing, but, as the last two examples below show, you can use it with any noun appropriate to your meaning.
They [sc. beaver dams] are at one and the same time parts of beaver societies and parts of beaver nature.
…that is to say, that sexuality and gender are not one and the same thing, and their complex interaction not only varies from one society to the next but also within a given culture.
It is possible that different paradigms introduce different ways of classifying one and the same set of objects.
The imagination must carry me out of myself into the feelings of others by one and the same process by which I am thrown forward as it were into my future being.
Hazlitt, Essay on the Principle of Human Action, i, 1–2.
Who uses it? Why do people get it wrong?
It crops up most frequently in formal or technical prose in the areas of the Arts and Humanities and Religion and Law. That means it is not common in general writing or speech, which helps explain why people convert it to “one in the same”.
And the speech mechanism of that conversion is not far to seek: in speaking, the phrase will be pronounced “one ’n’ the same”, and people who have never come across it in writing will interpret that ‘n’ as ‘in’.
Does “one in the same” make any sense?
Merriam-Webster online suggests that it doesn’t and argues that it would have to refer to a Russian doll-type arrangement.
I’m not so sure.
At the back of my mind, for that use of “in” I hear an echo of religious, specifically Christian, specifically Trinitarian, usage, i.e. God the three in one, but perhaps that’s just me.
(Can someone hear things at the back of their mind? Only asking. Ed.)
On a more mundane level, it must, surely, be influenced by advertising phrases highlighting the benefits of a product, such as being a “2-in-1 laptop and tablet”.
Other than that, I can’t fathom what it means to people who use it. I’d have to ask them.
It has been argued that it makes sense if you think of one thing being inside a clone of itself. In the case of people, though, that explanation could suggest (auto)cannibalism. Eeek!
Surprisingly, though, it is used in the same sort of circles that use the correct form, judging by the examples in the eggcorn database, e.g. Any time you visit our service desks, you will have the agreeable impression that helping the library and staying young are one in the same.
(UC Berkeley, Annual Report of the Libraries, Fall 2001).
The Merriam-Webster usage note also cites examples from publications which one can’t help feeling ought to have editors who know better, e.g.
a politician whose public and private persona seem to be one in the same.
— Newsweek, 8 Sept. 2017
Where does “one and the same” come from?
It is a calque, or translation of the Latin unus et idem, meaning, erm, “one and the same”, recorded as being used by Cicero and Horace.1 Piquantly, its first citation in the OED is from a translation from Latin, possibly by Cranmer, of Edward Fox and others’ treatise about the legitimacy of Henry VIII’s marriage to his brother’s wife (Catherine of Aragon) titled The determinations of the moste famous and mooste excellent vniuersities of Italy and Fraunce, that it is so vnlefull [sic] for a man to marie his brothers wyfe, that the pope hath no power to dispence therewith.
One and the same selfe man may be bothe a preest and a maryed man.
The phrase occurs 451 times in the OED, which gives some indication of its embeddedness in English.
How often do people muck it up?
That depends on where you look. In a corpus of academic journals (as one might hope but not necessarily expect these days) the dunderhead version is vanishingly small, 7 vs. 1994 (i.e. less than 0.5 per cent). In a general corpus (OEC, 2014) the proportions change to 192 vs. 3,183 (i.e. 6 per cent). And in a more recent corpus, 750ish vs. 4,283 (i.e. 17.5 per cent).
A few people are even using it slightly differently, in comparisons to mean “exactly the same as”:
Fructose is the sugar that’s prevalent in fruits, and it’s one in the same as cane sugar, which is simply much more concentrated.
And then there’s the song by Selena Gomez and Demi Lovato (whoever they might be; I only found it by googling). They spell it correctly, but then others misspell it.
As M-W poignantly pleads “Please try to avoid misinterpreting this venerable phrase.”
1 From Horace’s Epistles we have …ego, utrum Nave ferar magna an parva, ferar unus et idem.
I, whether I be carried in a large or a small boat, shall be carried as one and the same man.
Which, as the motto of the Royal Navy’s training establishment HMS Collingwood is sexed up and, at one and the same time, dumbed down to ferar unus et idem, “I shall carry on regardless”. A noble and uplifting sentiment, somewhat undermined by the existence of the film Carry On Regardless.