Taking knowledge as a starting point › What Skepticism Must Establish

On Williamson's world-involving account, a successful perceiver and a deceived counterpart can have indistinguishable experiences while differing in what they know. Given that possibility and E = K, their bodies of evidence can differ. Nontransparency alone does not establish the possibility of such experiential duplicates. This challenges a skeptical argument that grants exactly the same evidence to both subjects. Williamson disputes that evidential starting point. The book's summary connects his criticism of skepticism to assumptions about access to evidence.

Suppose the successful worker knows that the report was accepted while the deceived worker knows only that an acceptance message appeared. On E = K, their bodies of evidence can differ. Describing the experiences as indistinguishable does not by itself erase that difference. A skeptic needs an argument for the stronger evidential equality, rather than obtaining it automatically from the experiential resemblance.

This response will not convince someone who insists that legitimate evidence must be internally recognizable. It also does not give the worker a magical test that rules out every forgery. Its purpose is to challenge one route to skepticism. A philosophical theory can distinguish knowing from deception without providing a decision procedure that a deceived person could reliably apply to discover which situation they occupy.