Labyrinths of Reason by William Poundstone Page B

prosaic hypotheses over a less prosaic truth (as in the French Academy’s dismissal of meteorites). There is, for instance, a lot of evidence for the existence of ghosts. Many thousands of people have reported seeing them, and not all of them are kooks; there are even some fuzzy photographs. There is no categorical explanation for the reports of ghosts (other than that ghosts exist). It is maintained that there is always a “logical explanation,” but this explanation is in one case a branch scratching against a window, in another a hallucination, in another mice in the attic, in still another a hoax. In yet other cases, none of these explanations can be offered, but still it is maintained that some cause not involving the paranormal exists.
    In sheer quantity, the evidence for ghosts is probably greater than that for the existence of will-o’-the-wisps, the strange lights seen over marshes. Yet science believes in will-o’-the-wisps and not in ghosts. Ultimately, more theories are refuted by the poor quality of their own evidence than by contrary evidence. There is usually something wrong with a theory that has lots of supporting “evidence,” all of it dubious. This seems to be the case with the theorythat there are ghosts. On the other hand, some of the time will-o’-the-wisps are visible for all to see.
    But in Goodman’s paradox, we are skeptical of one hypothesis (emeralds are grue) even though it has precisely the same supporting evidence as another (emeralds are green). The problem rests with the hypothesis, not the evidence.
    “All emeralds are grue” speaks of an entity, grueness, that we can do without. Invoking Ockam’s razor, we can say, “Hold it! We already have all the color words we need. It is pointless to add a term like ‘grue’ until you produce something that is grue (and not just green).”
    BUT
—once again—the Gruebleen speaker can throw these words right back in our faces. He has all the colors he needs, has no need for “green,” won’t have until he sees something that actually is green (not grue).
    Lively debate on the grue-bleen paradox continues. For the time being, most analyses concur that our preference for “green” rather than “grue” is based on simplicity. The difficulty is finding a way out of this vicious cycle whereby the Gruebleen speaker can parrot our every argument! Here is one way.
The Day of Judgment
    Ask yourself what will happen on the semantic day of judgment, January 1, 2000 A.D. There are four possibilities.
    1. Everyone might wake up and find that the sky is green and the grass is blue! We’ll realize that “green” was the misleading term and “grue” was right—
    Otherwise, the speakers of Gruebleen will have to accept the sameness of colors after the zero hour in one of three ways:
    2. Gruebleen speakers could wake up and be
surprised
to find that the (still blue) sky has “changed” from bleen to grue. This is what Goodman facetiously implied.
    3. Or Gruebleen speakers could go to bed the previous night
fully expecting
the “change.” It would be like resetting a watch for daylight saving time or travel across time zones. The Gruebleen speakers would realize that their color terms don’t jibe with the way the world works.
    4. Finally, the Gruebleen speakers might not recognize the “change” at all (through failure to understand the time clause in the definitions cf “grue” and “bleen”). For
how do Gruebleen-speaking parents teach their children the language?
    Many philosophers believe that no one could really learn the Gruebleen language as their first language. Sure, parents would point to the grass and say “grue,” point to the sky and say “bleen.” But there is more to grue and bleen than that. The perceptual change (you shouldn’t call it a color change, since grue and bleen are colors to those using those words) at midnight, December 31, 1999, has to be communicated at some point in the process of acquiring