Scientific Knowledge

Well, if we are going to be exact about this, then we need to be discussing the field of epistemology. In epistemology, "knowledge" is defined to be justifed true beliefs.A person has knowledge if
(1) she beliefs that something is true,
(2) she's justified in her belief; that is, she has good reasons to believe what she does, and
(3) the thing she believes is actually true.There is no requirement of certainty.On the other hand, this sort of begs the question about when we actually know whether the thing believed is true or not.So maybe philosophy isn't where the discussion should lie. Maybe the discussion is about the plain meaning of words in everyday English.And in everyday English (to echo Modulus) people rarely require absolute certainty to use the word "know." In fact, the first example that pops into my mind of someone requiring absolute certainty for the use of the word "know" is when creationists try to insert their creationist beliefs as "possibilities" to be inserted into the school curriculum by insisting that one cannot "know" with absolute certainty that the universe isn't only 6000 years old.And that is pretty much the only time I ever hear anyone insist on absolute certainty: when their own arguments for their position is so weak that they can only claim it as a valid possibility by shoehorning it into that tiny, one-in-a-million chance that their opponent is wrong.Me, I'm going to the grocery store tonight. It will be early evening on a week night, and there is neither a natural disaster or human-made state of emergency, so I know it will be open. I can't be 100% certain of this, of course, but I am so certain that I can't think of a single reasonable person who will contradict me and claim I don't know whether the store will be open.Again, that is the plain meaning of the English word, the way almost everyone uses it in everyday life.Unless one feels they need more precision and uses the epistemological definition; but that isn't going to help out the needs-certainty crowd.