How many times have you heard someone say I could care less? For every time you’ve heard it, have you wondered why the person saying it COULD care less about something he seemingly doesn’t care about at all?
The correct saying is I couldn’t care less–which, considering the context within which it’s always said, makes more sense.
I could care less if you’re breaking up with me means that you’re admitting that you do care about being tossed aside like yesterday’s newspaper. And while we all probably do care when that happens to us, we usually don’t want the other person to know, so we say I couldn’t care less (not I COULD care less), meaning, Here’s your hat; what’s your hurry?
I could care less means that you actually could care less than you do, which means that you do, in fact, care. I couldn’t care less means that you could not care any less than you do.
That’s the correct usage—in case you care.