When you want to say that someone doesn't know anything about a particular thing, do you say they don't know jack about it, or that they know jack about it?

I've seen it used both ways. Which is correct?

marked as duplicate by user240918, FumbleFingers, Nigel J, jimm101, Skooba Feb 14 '18 at 20:06

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.


That this and similar slang expressions set up the apparent paradox of x = not x has a particular fascination for linguists. The logic, however, is easy to grasp.

If jack is a quantity of absolutely no value, i. e. zero, then the difference between

He knows zero.


He doesn't know zero.

is basically zero.

Both expressions are "correct" in the descriptive sense that native speakers use both.

Not the answer you're looking for? Browse other questions tagged or ask your own question.