Editing Problem of induction (section)

===Nelson Goodman's new riddle of induction===
{{main|New riddle of induction}}
[[Nelson Goodman]]'s ''[[Fact, Fiction, and Forecast]]'' (1955) presented a different description of the problem of induction in the chapter entitled "The New Riddle of Induction". Goodman proposed the new [[predicate (mathematical logic)|predicate]] "[[Grue and Bleen|grue]]". Something is grue if and only if it has been (or will be, according to a scientific, general hypothesis<ref>Goodman, Nelson. ''Fact, Fiction, and Forecast'' (4th edition). Harvard University Press, 1983, p. 74, "will each confirm the general hypothesis that all emeralds are grue"</ref><ref>[http://math.mit.edu/~tchow/grue.html Goodman’s original definition of grue]</ref>) observed to be green before a certain time ''t'', and blue if observed after that time. The "new" problem of induction is, since all emeralds we have ever seen are both green and grue, why do we suppose that after time ''t'' we will find green but not grue emeralds? The problem here raised is that two different inductions will be true and false under the same conditions. In other words:

* Given the observations of a lot of green emeralds, someone using a common language will inductively infer that all emeralds are green (therefore, he will believe that any emerald he will ever find will be green, even after time ''t'').
* Given the same set of observations of green emeralds, someone using the predicate "grue" will inductively infer that all emeralds, which will be observed after ''t'', will be blue, despite the fact that he observed only green emeralds so far.

One could argue, using [[Occam's razor]], that greenness is more likely than grueness because the concept of grueness is more complex than that of greenness. Goodman, however, points out that the predicate "grue" only appears more complex than the predicate "green" because we have defined grue in terms of blue and green. If we had always been brought up to think in terms of "grue" and "bleen" (where bleen is blue before time ''t'', and green thereafter), we would intuitively consider "green" to be a crazy and complicated predicate. Goodman believed that which scientific hypotheses we favour depend on which predicates are "entrenched" in our language.{{or|date=November 2024}}

[[Willard Van Orman Quine]] offers a practical solution to this problem<ref>{{cite book |editor=Nicholas Rescher |editor-link=Nicholas Rescher |title=Essays in Honor of Carl G. Hempel| publisher=D. Reidel |location=Dordrecht |author=Willard Van Orman Quine |contribution=Natural Kinds |year=1970 |pages=41–56 |contribution-url=http://fitelson.org/confirmation/quine_nk.pdf|display-editors=etal|title-link=Carl G. Hempel}} Reprinted in: Quine (1969), ''Ontological Relativity and Other Essays'', Ch. 5.</ref> by making the [[metaphysics|metaphysical]] claim that only predicates that identify a "[[natural kind]]" (i.e. a real property of real things) can be legitimately used in a scientific hypothesis. [[Roy Bhaskar|R. Bhaskar]] also offers a practical solution to the problem. He argues that the problem of induction only arises if we deny the possibility of a reason for the predicate, located in the enduring nature of something.<ref>{{Cite book|title=A Realist Theory of Science|url=https://archive.org/details/realisttheorysci00bhas|url-access=limited|last=Bhaskar|first=Roy|publisher=Routledge|year=2008|isbn=978-0-415-45494-0|location=New York|pages=[https://archive.org/details/realisttheorysci00bhas/page/n247 215]–228}}</ref> For example, we know that all emeralds are green, not because we have only ever seen green emeralds, but because the chemical make-up of emeralds insists that they must be green. If we were to change that structure, they would not be green. For instance, emeralds are a kind of green [[beryl]], made green by trace amounts of chromium and sometimes vanadium. Without these trace elements, the gems would be colourless.