Full Idea
Arguments for the absolute unknowability or non-existence of an external object only works by assuming that another external object, an individual, is known completely in so far as that individual expresses a judgement about an external object.
Gist of Idea
Arguments that objects are unknowable or non-existent assume the knower's existence
Source
Stephen S. Colvin (The Common-Sense View of Reality [1902], p.145)
Book Reference
-: 'Philosophical Review' [-], p.145
A Reaction
Anti-realism is a decay that eats into everything. You can't doubt all the externals without doubting all the internals as well.