
Math General Math Forum  For general math related discussion and news 
 LinkBack  Thread Tools  Display Modes 
April 17th, 2019, 03:22 AM  #1 
Member Joined: Apr 2011 Posts: 35 Thanks: 0  implication
How can I convince students of the truth value of if P is false then P implies Q is true independent of what truth value Q takes? Is there any real life or a convincing argument for this? I have given the analogy of if being elected then you will abolish the death penalty which seems ok but rather crass. Are there any other examples?
Last edited by skipjack; April 17th, 2019 at 03:27 AM. 
April 17th, 2019, 06:27 AM  #2 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 14,597 Thanks: 1038 
You've managed to completely confuse me!!

April 17th, 2019, 07:48 AM  #3 
Math Team Joined: May 2013 From: The Astral plane Posts: 2,205 Thanks: 901 Math Focus: Wibbly wobbly timeywimey stuff.  
April 17th, 2019, 08:41 AM  #4 
Senior Member Joined: Jun 2015 From: England Posts: 915 Thanks: 271 
OK so your proposal depends upon the nature of P. It is not true for all possible statements P. Your example introduces the conditional 'if' another example might be Whether in Rome or not, I eat pasta. This implies I always eat pasta, but of course may be factually incorrect, depending upon Q. A plain statement for P such as My bike is broken, so I can't go to the fair does indeed depend upon the truth of P. So you should gather a few examples like this and have you students work through possible types of statements for P and Q and predict the effects of the truth values of P, Q and P implies Q. 
April 17th, 2019, 10:38 AM  #5 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 14,597 Thanks: 1038  

Tags 
implication, logic 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
A weird implication of LW  J Thomas  Physics  8  February 27th, 2015 08:34 AM 
implication  ungeheuer  Applied Math  6  November 27th, 2012 03:44 PM 
Trouble with logical implication  aphex221  Applied Math  3  June 6th, 2011 05:37 PM 
Need help on a implication proof  Selena  Applied Math  7  February 21st, 2010 06:33 PM 
Need help with implication and induction  Karenin  Applied Math  3  May 11th, 2009 05:25 PM 