Notes from a Language Purist

"I could care less." Incorrect and silly. If you could care less, than that means you do care to some degree, which is never what people mean when they say it.

"I couldn't care less." Correct. You care so little that you couldn't possibly care less than you already do.

e.g. - I couldn't care less what you feel is morally right, the Holy Spirit-guided, Christ-established authority of the Church says you are wrong.