I was reading Goodman's [Facts, fictions and forecasts] and was confused by the new riddle of induction. I don't really see what's new about it, it seems to me like a restatement of Hume's problem about justifying the principle of the uniformity of nature.
Consider Goodman's new riddle of induction that any observation before an arbitrary time t of an emerald being green confirms both statements:
-All emeralds are green
-All emeralds are grue (green before time t and blue after)
All attempts to discredit the riddle by pointing out the complexity of the definition of grue have failed because it's possible to construct the definition "green" from "grue" and "bleen" (blue before time t and green after).
An example of such a construction: green can be defined as grue before time t and bleen after.
I seem to be able to solve this problem by invoking the principle of the uniformity of nature. A definition like grue is not uniform with respect to past experiences, as there are no examples of objects possessing this 'grue' property. This problem is therefore again about justifying the uniformity of nature.
My question is: How is this new problem different from the old problem about the justification of the uniformity of nature?
To make this clearer, let's suppose that the uniformity of nature (UON) was justified:
I can now answer Goodman by saying that "Green" is a natural definition because my past experiences of seeing green things staying green allowed me to generalize that all thing green stay green which is reflected in my definition of the word "green"(green and will always be green). The definition "grue" is unnatural because it's not supported by past experiences and UON