I've seen affirm defined as "To say that something is true in a confident way." I've looked at various antonyms, and antonyms of synonyms of affirm and none seem appropriate. I'm wondering if there's a word that would be defined as, "To say that something is false in a confident way."
I also know that you can "affirm" a negative, but I'm looking to use affirm along with this other word similar to the way confirm/deny are used together.