"Besides knowing a lot that is everyday and trite, I myself think that we know a lot
that is interesting and esoteric and controversial. We know a lot about things unseen:
tiny particles and pervasive fields, not to mention one another's underwear. Sometimes
we even know what an author meant by his writings. But on these questions, let us agree
to disagree peacefully with the champions of 'post-knowledgeism'. The most trite and
ordinary parts of our knowledge will be problem enough.

For no sooner do we engage in epistemology - the systematic philosophical examination
of knowledge - than we meet a compelling argument that we know next to nothing. The
sceptical argument is nothing new or fancy. It is just this: it seems as if knowledge must
be by definition infallible. If you claim that S knows that P, and yet you grant that S cannot
eliminate a certain possibility in which not-P, it certainly seems as if you have
granted that S does not after all know that P. To speak of fallible knowledge, of knowledge
despite uneliminated possibilities of error, just sounds contradictory.

Blind Freddy can see where this will lead. Let your paranoid fantasies rip - CIA
plots, hallucinogens in the tap water, conspiracies to deceive, old Nick himself - and
soon you find that uneliminated possibilities of error are everywhere. Those possibilities
of error are far-fetched, of course, but possibilities all the same. They bite into even our
most everyday knowledge. We never have infallible knowledge."

Excerpt from Elusive Knowledge
by David Lewis