There is a very general philosophical question which asks how, on the basis of what human beings get through the senses, they can ever have good reason to accept the beliefs, hypothesis, and theories they hold about the world. What is in question are the credentials or the degree of well-foundedness of what is taken to be a fully-formed conception of the world and our place in it, as embodied in everything we believe. To show how (or which of) those beliefs amount to knowledge, or to beliefs we have good reason to hold, would be to explain, philosophically, how knowledge of the world is possible. If there are no such questions, our best reasons are inadequate, scepticism is the right answer, we do not know what we think we know.
[This passage (1999, 139) by Stroud is culled from The philosophy of Donald Davidson, edited
by Lewis Hahn. One would wish that Neil deGrasse Tyson and Bill Nye had
read this. Before they made their pronouncements about philosophy.]