This American expression has always puzzled me. I'm not sure if you are aware, but in the rest of the English-speaking world, the phrase is "I couldn't care less". In both cases, the term is used when the speaker wants to convey that he doesn't care at all about the subject in question. The American version appears to be functionally illiterate, because its grammatical meaning is the exact opposite of the intended meaning. "I could care less" means that you care more than you might about something. I.e. you care somewhat about Y, but it's possible you could care even less than you do. I.e. Y is not of trivial importance to you, you do care about it more than the minimum. By contrast, "I couldn't care less" means that it is literally impossible for you to care less about the subject. You therefore care nothing at all about Y, as it is simply not possible to care any less about it. Y is therefore of trivial importance to you. In other words, the American version of the expression makes no sense whatsoever. Not only is it wrong, but it's almost the opposite of what people who use it think it means. It's like saying "I can take it or leave it" when you mean "I absolutely must have it", or "I am really interested in baseball" when you have no interest in baseball whatsoever. Can someone explain how this version came about? Are people who use it aware that it is a totally incorrect usage of language? If not, why not? If so, why do they keep using it?