Full Idea
Some beliefs are just unreasonable in a strong sense. Think of the man who, for no special reason, expects unexamined emeralds to be grue.
Gist of Idea
To just expect unexamined emeralds to be grue would be totally unreasonable
Source
David Lewis (On the Plurality of Worlds [1986], 1.4)
Book Reference
Lewis,David: 'On the Plurality of Worlds' [Blackwell 2001], p.38
A Reaction
This is a nice converse way of seeing the point that 'grue' is such an totally artificial predicate. I still say that the most illuminating point is that grue is not a colour, so seeing a grue thing is no confirmation at all.