[actualdc1]

In my experience (as a student of philosophy at a strong university program), Stanford Encyclopedia of Philosophy is the go-to reference resource for such articles. Here's their version:

http://plato.stanford.edu/entries/skepticism-content-externa...

[hyperpape]

I think it's a slightly better article in this case. But neither one is really suitable HN. They both presuppose too much background, I think.