Know. It has many meanings. Know some one (friends, spouse, room ate), know a poem or what a book says, there currant circumstance ("I know the heaters on, I feel it" "I know I missed the turn" "I know were out of coke"), the biblical sense (sex).

But I want to talk about "know" as in "I know this is true" "I know there a god" "I know there is no god" "I know ghosts are real" basically stating something as a absolute fact. In this sense, no, no body knows anything. No one can know, that would require all the information on the particular subject and no one has all the information on any subject.

At best opinions and beliefs would be based on the best available evidence and at worse based on faith. We don't know, we have opinions and beliefs but we can't know.

While there are still situations where the word "know" should be used it should not be used as a statement of absolute fact. Instead the words "believe", "opinion" and "think" should be used.