New riddle of induction: Difference between revisions

For some arbitrary future time ''t'', say January 1, {{#expr:{{#time:Y}} + 10}}, <!-- The expression gives the current year plus ten, for a date guaranteed to be in the future no matter when this page is retrieved. --> for all green things observed prior to ''t'', such as emeralds[[emerald]]s and well-watered [[grass]], both the predicates ''green'' and ''grue'' apply. Likewise for all blue things observed prior to ''t'', such as bluebirds[[bluebird]]s or [[blue flowersflower]]s, both the predicates ''blue'' and ''bleen'' apply. On January 2, {{#expr:{{#time:Y}} + 10}}, however, emeralds and well-watered grass are ''bleen'' and bluebirds or blue flowers are ''grue''. The predicates ''grue'' and ''bleen'' are not the kinds of predicates used in everyday life or in science, but they apply in just the same way as the predicates ''green'' and ''blue'' up until some future time ''t''. From the perspective of observers before time ''t'' it is indeterminate which predicates are future projectible (''green'' and ''blue'' or ''grue'' and ''bleen'').