Q: Every time I say, "I could care less," my husband stops me and says, "It's 'I couldn't care less.'" But everyone I know says it the same way I do. Which is correct?—Anonymous
A: For years, my grandma beat "I couldn't care less" into my head just as often as she made me eat my dinner vegetables. And just like broccoli, her grammar correction always left a bad taste in my mouth. But was she right?
When taken literally, the two phrases have opposite meanings. "I couldn't care less" means that it's impossible for me to care any less about the subject at hand than I already do. If I say, "I couldn't care less about hockey," I mean that on a scale of one to 10—with 10 suggesting that I'm the most enthusiastic hockey fan this side of Canada, and one meaning I don't give a flip about the sport—I'm a one. I don't care about hockey at all.
On the other hand, "I could care less" literally means "I care more than I might seem to." If you could care less, you're saying that you care some, which is the opposite of not caring at all.
Now, some folks will argue that "could care less" is intended to be sarcastic and therefore shouldn't be taken literally. But it's hard to convey that in print, so it just looks like unpolished writing.
Stick with "I couldn't care less."
No matter what type of writing you do, mastering the fundamentals of grammar and mechanics is an important first step to having a successful writing career.