Full Idea
When we acquire new evidence in perception, we do not first acquire unknown evidence and then somehow base knowledge on it later. Rather, acquiring new is evidence IS acquiring new knowledge.
Gist of Idea
We don't acquire evidence and then derive some knowledge, because evidence IS knowledge
Source
Timothy Williamson (Knowledge First (and reply) [2014], p.4)
Book Reference
'Contemporary Debates in Epistemology (2nd ed)', ed/tr. Steup/Turri/Sosa [Wiley Blackwell 2014], p.4
A Reaction
This makes his point much better than Idea 19526 does.
Related Ideas
Idea 19526 Surely I am acquainted with physical objects, not with appearances? [Williamson]
Idea 19536 Knowledge-first says your total evidence IS your knowledge [Williamson]