Free Labyrinths of Reason by William Poundstone

compatible with either of his fellow jewelers’.) The paradox can’t be swept away as meaningless. Come the turn of the century, at least one prediction will be wrong. 1
    The paradox can become as absurd as you wish. Let “grurple” mean green before a designated “zero hour” and purple thereafter. Let “emerow” mean something that is an emerald before the zero hour and a cow thereafter. Then the green emerald confirms “All emerows are grurple,” which is to say, the green emerald will be a purple cow in 2000 A.D. By suitable choice of terms and zero hour,
anything
confirms that it will be
anything
else at
any
later time.
Gerrymander Categories
    As with Hempel’s paradox, there is an obvious “resolution” that fails miserably. The problem sure seems to be that gimmicky word “grue.” “Grue” is inherently a more complicated word than “green”—look at its definition above! Grue is a “gerrymander” category, to borrow a term from politics. It has no natural significance;it was constructed by Goodman with the sole aim of creating a paradox. It makes irrelevant reference to a specific point in time.
    We do use some rather artificial categories in the real world. When a person in Chicago says it is 5 o’clock, he is actually saying that it is 5 o’clock in the region west of 82.5 degrees west longitude and east of 97.5 degrees west longitude, except as these boundaries are amended by local observances of Central Standard Time. It’s 6 o’clock in the Eastern time zone, 4 o’clock in Mountain Time, and assorted other times at other places in the world. It’s every hour—someplace—all the time. This definition sounds at least as cockeyed as that of “grue.” It makes reference to geographic location, which is irrelevant to what time it is.
    How much more sensible it would be to use Greenwich Mean Time all over the world. When it was 5:30 P.M . in São Paulo, it would also be 5:30 P.M . in Tokyo, Lagos, Winnipeg, and everywhere else. We might then regard the current method of stating time a patchwork out of a logic paradox.
    And is “green” any less arbitrary? As logician W. V. O. Quine has pointed out, the concept of color is, to a physicist’s way of looking at things, arbitrary. Light comes in a continuum of wavelengths, and there is no special distinction to those wavelengths that we call “green.” Were we explaining what “green” means to a being from another planet, we would have to say something like “Green is what we experience when viewing light of wavelength greater than 4912 angstrom units but less than 5750 angstrom units.” Why 4912 and 5750 rather than some other cutoff points? No reason—that’s just the way things are.
    Of course, “grue” inherits the spectral arbitrariness of “green” (and “blue”). “Grue,” however, is arbitrary in a way that “green” is not. “Grue” supposes a
change
in color. It is not that nothing in the world changes from green to blue. Unripe blueberries do. But a simultaneous and universal change is quite unprecedented. “Grue” asks us to believe in this change, a change that has never been observed.
    This sounds like a strong objection. But it sounds just as sensible inside out from the other side of the looking glass. The third jeweler’s idiosyncratic tongue has another color word, “bleen.” Something is bleen if is blue until midnight, December 31, 1999, and green thereafter.
    In order to explain the English word “green” to the Gruebleen-speaking jeweler, we have to say that something is green if it is grue before midnight, December 31, 1999, and bleen thereafter. To him,raised on grue and bleen from the cradle, “green” is the artificial term. It is
green’s
definition that makes reference to a specific time.
    The cross-definitions are as symmetric as bookends. Look in an English-Gruebleen/Gruebleen-English dictionary, and count the number of words in the definitions of “green” and “grue.”