The New Riddle of Induction

Suppose we say that something is 'grue' if it is either green and first observed before January 1st, 2000 or blue and first observed on or after January 1st 2000. All emeralds so far observed are grue: why do we not, therefore, infer that all emeralds are grue?


The primary source is Goodman 1954, chapter III.

Note that 'grue' is sometimes also defined as "green before 2000, blue afterwards", that the definition given above is the original one, and that some solutions to the problem only work with the second definition, not the original one.

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Copyright David Chart 1997