@article {Schaffer:January 2003:0031-8116:31,
	author = "Schaffer J.",
	title = "Perceptual Knowledge Derailed",
	journal = "Philosophical Studies",
	volume = "112",
	year = "January 2003",
	abstract = "<P>The <I>tracking theory</I> treats knowledge as counterfactual covariation of belief and truth through a sphere of possibilities. I argue that the tracking theory cannot respect perceptual knowledge, because perceptual belief covaries with truth through a discontinuous scatter of possibilities. Perceptual knowledge is subject to <I>inner derailing</I>: there is an inner hollow of perceptual incompetence through which the differences are too small to track. Perceptual knowledge is subject to <I>outer derailing</I>: there are outlying islands of perceptual competence that extend well past skeptical sinkholes.</P>",
	pages = "31-45(15)",
	url = "http://www.ingentaconnect.com/content/klu/phil/2003/00000112/00000001/05107445"
}