Drexel dragonThe Math ForumDonate to the Math Forum

Ask Dr. Math - Questions and Answers from our Archives
_____________________________________________
Associated Topics || Dr. Math Home || Search Dr. Math
_____________________________________________

Disjunctive Syllogism


Date: 09/25/98 at 10:51:45
From: Lauren Ray
Subject: Disjunctive Syllogism

I am enrolled in a Elementary Logic and Set Theory class, and we have 
an assignment to find out definitions of the words: Modus Ponens, 
Modus Tollens, and Disjunctive Syllogism. I have already found the 
first two, but am stuck on the last one. So my question is, what does 
it mean?  

Thank you,
Lauren


Date: 09/25/98 at 11:28:48
From: Doctor Mike
Subject: Re: Disjunctive Syllogism

Hi Lauren,  
   
See Stefan Waner and Steven R. Costenoble's "Introduction to Logic" on 
the Web. It has the definition of Disjunctive Syllogism and other logic 
terms.
 
   http://www.hofstra.edu/~matscw/logic/logic4.html   
   
The disjunctive syllogism is  (P v Q) and notQ --> P. In words:

   "If one or the other is true, and one of them is false, the other 
   must be true."

Here is an example:

   -  Given: Either Congress meets in Washington D.C. OR pigs can fly.
   -  Given: Scientific evidence shows conclusively that pigs cannot 
             fly.
   -  Conclusion: Congress meets in Washington D.C.   
   
I hope this helps. 
   
"Thanks for writing."  OR  "Pigs can fly."
    
- Doctor Mike, The Math Forum
  http://mathforum.org/dr.math/   
    
Associated Topics:
High School Definitions
High School Logic

Search the Dr. Math Library:


Find items containing (put spaces between keywords):
 
Click only once for faster results:

[ Choose "whole words" when searching for a word like age.]

all keywords, in any order at least one, that exact phrase
parts of words whole words

Submit your own question to Dr. Math

[Privacy Policy] [Terms of Use]

_____________________________________
Math Forum Home || Math Library || Quick Reference || Math Forum Search
_____________________________________

Ask Dr. MathTM
© 1994-2013 The Math Forum
http://mathforum.org/dr.math/