Perhaps it is another example of associating meaning at the level of sentences rather than the logical meaning of the words, as Chris describes. I for one always believed the word was “thing” when I was growing up, and never questioned the meaning until I came across the alternative!

Language is sometimes used in a somewhat more complex manner than just communicating logically constructed sets of words. Take, say, virtually all of idiomatic English.

I think it’s a bit like reading, in a strange way. When you look at a sentence on a page, you’re not actually looking at the individual letters and building the words and sentence meaning out of them as you go along. You’re recognising whole words and phrases in one eyeful, and building up meaning from those.

Similarly, with many iodiomatic usages, it’s a waste of time looking for ‘meaning’ at the level of the logical construction – you have to get used to seeing it at the level of the whole phrase: i.e. ‘that whole phrase means this’. Everyone *knows* (and this is the important thing) that “I could care less” means “I couldn’t care less” despite its illogical interior. It’s a black box, really.

You’re right about the ‘just’ thing, above, though. If it introduces ambiguity, then it’s just wrong. But then how long before we get used to hearing that first ‘just’ construction, and automatically start to impute the meaning of the second?

In language, as in any fluid system, ‘right’ and ‘wrong’ are just floating markers that drift by us as we live our lives.

Oh, and the usual explanation of the “I could care less” phrase I’ve heard is “it’s sarcastic”, but that’s just a bizarre and rather desperate misunderstanding of the mechanics of sarcasm as far as I can see.