On 01-02-98 William Elliot wrote to John Boone... 
 
        Hello William and thanks for writing, 
  
 WE>  JB> Yep, and I was using the exclusive -OR-.  
 
 WE> Logicians use 'xor' to denote exclusive or and 'or' to 
 WE> denote inclusive or.  So when you use or I assume that you  
 WE> mean inclusive or.  Note that 'P or P' but not 'P xor P'.   
 
  If you recall, -the- ORIGINAL post was TO Clarence 
and NOT to YOU (the one you started this with remember). 
From prior conversations with Clarence, he indicated 
he wasn't "formally" educated which indicated to me 
-any- posts to -him-, Clarence- using xor would most 
likely gone misunderstood.  
  Granted, in my discussions to you, I did not use xor, 
however, the intent was there.  I am sorry this was not 
evident.  I will endeavour to be more limpid in the future. 
  
 WE> Also note that P xor Q implies P or Q while the reverse is 
 WE> false. 
    
  The truth tables are not the same.  Let us look at the 
truth tables for these two functions (obtained from 
"Logic and Philosophy" Third Edition by Kahane). 
  The first one is P xor Q: 
 
            P          Q    ------------    xor 
 
            T          T                     F 
            F          T                     T    
            T          F                     T 
            F          F                     F 
 
  The second one is P or Q: 
 
            P          Q    -------------    or 
 
            T          T                      T   
            T          F                      T 
            F          T                      T 
            F          F                      F 
  
 WE>  WE> Hence the expression stereotypical 'black and white' thinking. 
 WE>  JB> Yep, but binary logic is such a case.  
 
 WE> Not familiar with that term.  Binary data and two value 
 
  Binary logic is another term used for Aristotlian logic, 
zeros and ones.  
  Since you aren't familar with it, let me share so that you 
too may become aware of different terms for the same thing. 
  From "Fuzzy Logic" by Bart Kosko preface xvi: 
 
        At the core is the paradigm shift from black and white 
        to the gray----- from bivalence to multivalence...... 
 
from page 6: 
 
        This faith in the black and the white, this BIVALENCE,  
        reaching back in the West to at least the ancient Greeks. 
         
from page 18, 19: 
 
        Fuzziness has a formal name in science: multivalence. 
        The opposite of fuzziness is BIVALENCE or TWO-valuedness. 
 
  Please notice, the words "BIVALENCE" kept appearing 
and further notice "bivalence" and "binary" are different 
words for the same thing with the words "BIVALENCE or 
TWO-valuedness." 
 
Take care, 
John 
 
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