The phrase ‘all and only’ is concise and expresses a precise logical meaning, but it is too compressed for most people to understood it.
I first came across the set phrase ‘all and only’ at the age of 25 when I began working in continental Europe. One of my new colleagues often drafted letters containing this phrase. He typically did this in formal letters for audit clients to sign as confirmation that they had given the audit team all necessary information.
In drafting these ‘letters of representation’, the aim was to make them:
- specific enough that people would realise what kind of information they need to give; but
- concise enough that the signatories would give the letter their full attention.
The letters my colleague drafted were full of sentences like (1). I don’t remember the exact contents or sentences, but (1) gives their flavour.
(1) The company’s accounting records capture all and only its legitimate transactions.
At the time, I found these sentences difficult to understand. As I said, I had never come across the phrase ‘all and only’ before. So, my colleague explained their meaning to me. Sentence (1) makes 2 separate assertions:
- the company’s accounting records capture all its legitimate transactions.
- the only things the company’s accounting records capture are its legitimate transactions.
Using ‘all and only to combine these 2 assertions certainly keeps the writing concise. In my colleague’s view, the resulting text is also clear.
Do writers use this phrase and do readers understand it?
My colleague assured me that the phrase ‘all and only’ was in routine use. I suspect this was true in his previous job with the African office of an international audit firm, where the dominant office culture was American.
I have the impression that ‘all and only’ may be more widely understood in North America than in the UK. In fact, I can’t remember ever seeing it in writing in the UK, except in texts written by professional logicians or professional philosophers.
Writing and editing tip
The phrase ‘all and only’ is concise. I certainly agree with keeping texts as concise as they can be do while still doing the job they need to do. In fact, writing is generally easier to understand if it is concise.
In addition, the phrase ‘all and only’ expresses a precise logical meaning—or, rather, 2 meanings. But in my view, that phrase is much too compressed to be readily understood by people who have had no exposure to philosophy or technical logic.
So, if you find yourself tempted use this phrase, you would do better to replace it with 2 separate statements, rather than wrapping them into a single composite statement.
In this respect, ‘all and only is very like ‘if, and only if’. Both phrases are logically impeccable. But, because they are so condensed, normal people (in fact, almost all people) do not readily understand them. I wrote about ‘if, and only if’ here https://languagemiscellany.com/2022/01/if-and-only-if/