Full Idea
Observing green emeralds can confirm 'all emeralds are green' or 'all emeralds are grue', where 'grue' is an arbitrary predicate meaning 'green until t and then blue'. Thus predictions are arbitrary, depending on how the property is described.
Gist of Idea
Observing lots of green x can confirm 'all x are green' or 'all x are grue', where 'grue' is arbitrary
Source
report of Thomas Mautner (Penguin Dictionary of Philosophy [1996], p.225) by PG - Db (ideas)
Book Reference
Mautner,Thomas: 'Dictionary of Philosophy' [Penguin 1997], p.225
A Reaction
This increasingly strikes me as the sort of sceptical nonsense that is concocted by philosophers who are enthralled to language instead of reality. It does draw attention to an expectation of stability in induction, both in language and in nature.