Grue....

Perusing a philosophical books catalog, I came across a title and book description so obscure that I had no choice but to look it up:

"Grue!: The New Riddle of Induction

This book contains 15 essays on grue, all by eminent philosophers, as well as an annotated bibliography summarizing everything ever written on grue.
"This is a monumental document in the history of twentieth-century philosophy."

Obviously, I couldn't just let that lie. What's "grue"? How could it be so important? Was I suffering from aphasia or had the philosophical community gone funny on me?

My Webster's Encyclopedic Unabridged Dictionary was no help, defining grue as a Scottish term for shudder.....

Apparently grue is a color..... green, until it turns blue. This is an illustration of the problem of inductive reasoning, as most powerfully laid out by David Hume (18c) who argued that inductive reasoning (generalization from particulars) cannot be logically proven effective except by invoking inductive reasoning with past examples of effective inductive reasoning. This is a very sound circular argument, and as such, unconvincing. "grue" was devised as an example of this problem in 1966, and apparently the cleverness of it caught the philosophical world by storm: how can you tell, the problem goes, whether the grass is green or simply green-for-now (aka grue)?

The scary part is that, now that I know this, it'll probably end up in my lectures somehow.