I think the best response to skepticism comes from Wittgenstein's later philosophy. Wittgenstein said that in real use words have different meanings according t

I think the best response to skepticism comes from Wittgenstein's later philosophy. Wittgenstein said that in real use words have different meanings according to the language game and sort of activity people are involved in. So for instance the word "scale" has a different meaning when talking about maps as opposed to music. He goes on say that many senseless philosophical problems arise because the wrong meaning of a word is being used. In the case of skepticism, the problem is that a meaning of the "know" from logic is being applied inappropriately to the realm of object perception, where a different meaning is the correct one. And let me add that skeptics themselves use the normal meaning all the time, except when they get their minds in a very strange mentality for their particular style of philosophy, and pretend to believe the word has a very different meaning. Now skeptics might counter that their meaning of the term "know" is better for philosophical purposes than the ordinary one. But in fact their meaning gets you nowhere in terms of dealing with basic philosophical issues in area such as metaphysics and ethics, whereas with the ordinary one you can.