Full Idea
Philosophers tend to associate illusions with skepticism. But since illusions are signs of modular construction, they are actually reason for scientific hope. Illusions have been very useful in helping us to understand vision.
Gist of Idea
Illusions are not a reason for skepticism, but a source of interesting scientific information
Source
Roy Sorensen (Vagueness and Contradiction [2001], 1.4)
Book Reference
Sorensen,Roy: 'Vagueness and Contradiction' [OUP 2004], p.38
A Reaction
This is a nice reversal of the usual view. If I see double, it reveals to me that my eyes are not aligned properly. Anyone led to scepticism by illusions should pay more attention to themselves, and less to the reality they hope to know directly.