Full Idea
There is extensive 'armchair knowledge' in which experience plays no strictly evidential role, but it may not fit the stereotype of the a priori, because the contribution of experience was more than enabling, such as armchair truths about our environment.
Gist of Idea
There are 'armchair' truths which are not a priori, because experience was involved
Source
Timothy Williamson (The Philosophy of Philosophy [2007], 5.5)
Book Reference
Williamson,Timothy: 'The Philosophy of Philosophy' [Blackwell 2007], p.169
A Reaction
Once this point is conceded we have no idea where to draw the line. Does 'if it is red it can't be green' derive from experience? I think it might.