From ucleaar@UCL.AC.UK Sat Mar 6 22:44:56 2010 Date: Mon, 29 May 1995 10:04:00 +0100 From: ucleaar Subject: Re: A Fuzzy Ship from Theseus To: Bob LeChevalier X-From-Space-Date: X-From-Space-Address: LOJBAN%CUVMB.BITNET@uga.cc.uga.edu Message-ID: Steven: > >I believe in fuzzy categories, and I recognize that this example is > >from time to time used to exemplify the notion, but I think it is > >not in the least fuzzy. Eagles, pigeons, penguins are all indubitably > >birds, and bats, squirrels are indubitably not birds. These are > >on a TYPICALITY GRADIENT [emphasis, not yelling] but not a > >MEMBERSHIP GRADIENT. Contrast this with the category Square: the > >further something is from having four sides of equal length and four > >angles of 90 degrees, the less it is a square, but it isn't possible > >to say when it becomes definitely not a square. A category has gradient > >membership iff it has defining features. > >This is not necessarily the standard view, but at any rate it's what I > >teach my students. > Sure, eagles, pigeons, penguins, and ostriches are genetically birds. I > certainly think genetics are important. But to me birdishness is more than > genes. An eagle gets a higher birdish score, because it swoops about so > birdishly, displaying several different modes of flight-soaring, diving, > climbing. Pigeons seem to fly mainly to avoid being stepped on. Penguins > fly, sure, but underwater! Ostriches just run. Those students' experiments have confirmed that if you ask people "Is an ostrich a bird?" and let their answer be somewhere on a scale from "yes, definitely" through "yes, probably", "not sure", to "no, definitely not", they'll say "yes, definitely". In contrast, if you show them a wonky, somewhat irregular quadrilateral & ask "Is this a square?", they'll mostly answer "not sure". If, however, you ask people "Is an ostrich a typical bird", they'll all say "no, definitely not". And if you ask someone to think of a bird, they'll not think of an ostrich. In sum, it is necessary to distinguish the matter of how much X is a member of category Y from the matter of how central a member of Y X is. > Imagine that I incrementally replace an eagle's genes with the > analogous iguana genes. With which substitution does the eagle > abruptly cease being a bird? Since we don't have much experience of such phenomena, I'm rather short of reliable intuitions on this. But I think it might show that in principle the category Bird does have a defining feature, namely possession of bird genes, and therefore has gradient membership. I said: > For meanings like "ish", "sort of". I agree {jei} doesn't really > have the right syntax to do the job. Something in NA would be more > appropriate. Jorge: > je'ucai absolutely true > je'usai > je'u > je'uru'e > je'ucu'i > je'unairu'e > je'unai > je'unaisai > je'unaicai absolutely false These have the right meaning. Do we know how they interact with {na} and {jaa}? Dylan: > Aren't {traji}, {banli}, {mutce}, {nutli}, and {milxe} just what's wanted? They may have the right meaning, but I guess you'd use them in tanru, which are doomed to ineluctable vagueness. > > The relevant distinction is the structure of the scale. Ni is bounded > > at the negative end of the scale and unbounded at the positive end of > > the scale. True/false in fuzzy logic is bounded at both ends of the > > scale. True/false, correct/incorrect in English lexical semantics is > > bounded at the positive (true/correct) end of the scale and unbounded > > at the negative end. Whichever scale structure you choose for true/false, > > it's different from the scale structure for ni. > Hum. The reason {lo ni gusni} is bounded on one end is a absolute > minimum to the amount of brightness: total darkness, while the > absolute maximum is far beyond our experience. (At a certain point > the energy density of the photons would create a black hole, I > believe.) But this is particular to {gusni}. That's true, I think. The scale structure of ni but not of jei is affected by the semantics of the subordinate bridi. > Is {lo jei broda} equivalent to {lo ni lodu'u broda cu fatci}? to {lo ni loe duu broda cu jeftu} is better, I think, but yes. The redundancy of {jei} has been remarked upon before. > Would {ka} be more appropriate? I don't immediately see why. > Is the difference that truth values are usually quite near one end of > the scale? The difference between what? > Wow, do we have a live professor on the list? You teach logic, I take > it? God no. Linguistics. I don't know anything about logic except what I glean from jbomri. Pc is the logician. --- And noi nae logji