True or false: Bananas are the most popular fruit.

8 Jul

Well, what do you think? Can you even say?  (yes, you can!)  Isn’t that being….. narrow or intolerant to say?  Besides who are YOU to say that!  Horrors!

Most Westerners in the 21st century don’t like to come right out and make categorical statements.  They are afraid of being labelled the J-word!  judgmental

Put your mind at ease:  saying that something IS or IS NOT is perfectly logical!


We’ve looked at terms, one or more words used to describe a concept (something one can either see or picture in one’s mind) and discussed how terms are either CLEAR or UNCLEAR.  (not T/F, not  logical/ illogical not  right/wrong)  This is the Question you should be asking as you choose your terms:  Does your language recipient understand what you mean, you the originator of the spoken or written term?  That’s clarity.

Next in constructing a logical argument come the propositions.  A subject term, a copula (is/am/are) and a predicate term are the parts of a proposition.  There are 4 possible propositional forms:

  • All S is P  – All girls (subject)  are people who wear skirts(predicate)
  • Some S is P – Susie is a person who wears a skirt or  Some girls are people who wear skirts  (1 or more exemplars of your subject , but not all)
  • No S is P – No boys are people who wear skirts
  • Some S is not P –  Some girls are not people who wear skirts

What all these have in common is that they are either True or False statements/sentences.

That is how we evaluate propositions.

For example:   All killing is condemned by God   (as in, ‘Thou shall not murder.)

We can’t say:  That statement isn’t logical….that statement isn’t clear.  But we CAN say:  That statement is true or it’s false.

So how do we prove the proposition true or false? :  All killing is condemned by God.

This is what is so cool.  All we have to do is find ONE SINGLE SOLITARY CASE where a killing is NOT condemned by God. That one case will make our proposition false.  What we DON’T have to show is:  No killing is condemned by God.   That is TOTALLY and extravagantly unnecessary.  Let’s take just one example of God-approved killing, say defending your family. THAT would render the proposition false.  The proposition that IS true, i.e that corresponds to reality  would be this:  Some killing is condemned by God.  (or equally true:  Some killing is NOT condemned by God)

This principle is called the Law of Non-Contradiction.  It goes like this:  Contradictory statements cannot both be true or both be false at the same time and in the same way.  This specific stipulation means that you can’t equivocate (change the meaning) of the term, “Killing”.  You have to be referring to the exact same concept in both propositions.  (All killing is condemned by God and Some killing is NOT condemned by God)

Truth (aka ‘reality’) is so clean and precise, if you handle it correctly. 

PS:  there is one other contradictory pair – and we’ll talk about that next time.

HW: Listen for and notice a ‘general statement’ that are not true and see if you can come up with the counter-example that proves it false.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: