What you may have noticed with several of the Grammar 101 and Idiomatica posts here on the blog is that many errors stem from the same central issue. People are used to hearing certain words or phrases spoken in casual conversation, but they might not write them nearly as often. Then, thanks to the wonderful convenience of automatic spell check, the error fails to get marked as a mistake. And this is the case today with “one and the same.”
This is precisely the same phenomenon that led me to thinking that minus well was correct. It’s the same reason why so many people think that the common idiom is to nip it in the butt rather than in the bud. You hear these turns of phrase not infrequently, but they rarely show up in writing and you’d barely ever write them yourself.
The idiomatic expression “one and the same” means that two (or more) items or things are practically identical. They are one. They are the same. The use of the word “one” here is similar to the Three Musketeers exclaiming, “One for all, and all for one.” It’s the same “one” as in the Pledge of Allegiance when you declare that we are “one Nation under God, indivisible.” We are all the same.
Here are a few more examples:
- As it turns out, petty con man Roger Kint and criminal mastermind Keyser Söze are one and the same.
- A compact SUV and a minivan are basically one and the same for driving the kids around town.
- Did you know that Pearle Vision and LensCrafters are actually one and the same, owned by the same company?
Using the first example there from The Usual Suspects, we can roughly reword that to say that Roger Kint and Keyser Soze are one. Roger Kint and Keyser Soze are the same. The redundant nature of the expression, where both “one” and “same” effectively hold the same meaning (identical), reinforces the similarity between the two things or people being discussed. This is for emphasis.
From what I can gather, “one and the same” originated some time in the mid-1800s and persists as a popular turn of phrase to this day. So even though “one in the same” is almost phonetically identical to the standard, correct spelling of the expression, they most certainly are not one and the same.