Linguistic theory (also known as the 'new riddle of induction') concerning the concept of confirmation or prediction, developed by the American philosopher Nelson Goodman (1906-1998).
According to Goodman, it is possible to define a vocabulary in such a way that, given a choice between two possibilities, it is as likely that the possibility which runs counter to previous experience will be chosen as will the more predictable one.
To illustrate this apparent breakdown in reasoning, Goodman devised a new predicate (which he called 'grue'); given a choice between two separate provable statements that all emeralds were green and all emeralds were blue, he argued instead that all emeralds were in fact 'grue'.
Also see: induction, INDUCTIVE PRINCIPLE
N Goodman, Fact, Fiction and Forecast (1954, revised 1965)