Logical Gal and the Law of Excluded Middle

2 Oct

Have you ever been frustrated by someone’s quibbling?

Mom – “Who ate my chocolate?”

Kid – silence….Shrug of shoulder

Mom – “Listen, you either KNOW or you DON’T KNOW, which is it? “

Kids – “Maybe it just vaporized?”

Mom – “So you know!”

Kid – “I didn’t say I know.”

Mom – “So you don’t know!”

Kid – “I didn’t say that either,” whining because he knows he’s been caught by a logical mom!

Mom – “Based on the Law of the Excluded Middle, you have only 2 choices:  Either…….A – you know what happened to my chocolate .  Or……B – you don’t know…..Which is it, Buddy?”

Mom is relying on the 2nd of the 3 basic laws of Classical Thought – the Law of Excluded Middle.  (last time we talked about the Law of Identity)

This is very useful because it forces you to categorize an issue.   Something is either A or non-A.  There are no other choices.  This isn’t rocket science, just common intuition!

  • You’re either pregnant or you’re NOT pregnant (no such thing as a little pregnant)
  • My car is painted either black or non-black
  • You either speak Chinese or you don’t.  (What about if you speak just a little?  Then you speak Chinese!)

Turning to a deeper issue that often comes up, do you see how this law could help in a discussion about the existence of God? He either exists, or He doesn’t.  We might not know, but it’s either one or the other.

What other possibility could there be?  The picture below is TRYING to get you to think that there might be a 3rd choice, but there isn’t!   (the supposed 3rd option of ” Probably”  is meaningless!)

Here’s one guideline in organizing your either/or statement: 

  • Whatever predicate you are using, you have to frame it as A or non-A

You can’t say:  Either my car is blue or white.  That’s not true, for there are other possibilities.

So you would have to claim: “ Either my car is blue or it is non-blue”

What issues does the Law of Excluded Middle simplify for you?

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