Tuesday, June 12, 2012

Logic Lesson pt 1

I've decided to add another regular feature:  Logic Lessons.

As a teacher, I have found that this skill is sorely lacking in many.  In young people, this is understandable, and it is the job of their teachers to show them.  But I think we have moved away from a systematic explanation of logic.  One of the problems is that many people do not see the consequences of their thoughts.  I had a dialogue in class once that went like this:

Me: Ash Wednesday is tomorrow, so that means that some of us will fast.
Student: (under her breath) That's stupid.
Me:  So fasting is foolish?
Student:  Yeah.
Me: So someone who told you to do something foolish, like fasting, would be a fool.
Student:  Yeah.
Me: So Jesus was a fool?
Me:  But if Jesus told us to fast, and someone who tells you to fast is a fool, then you called Jesus a fool.
Student:  But I didn't!
Me:  Yes, you did.  By logic.

The mighty Dr. Peter Kreeft has written extensively on this subject and I would recommend anything that he writes.

To understand the consequences of our positions can be a very eye-opening process.

To understand logic, we have to remember that the mind performs 3 main acts:

    1. UNDERSTANDING: simple apprehension.  This is what a baby does when it learns what a thing is.  The baby points to a ball and says "ball."  Understanding is about having the a concept in mind.  This act is primarily concerned with defining terms.
    2. JUDGING what is true.  Not all ideas can be true.  Some are false.  Judging is the act that determines whether a statement is true or false.   This act is primarily concerned with propositions
    3. REASONING:  taking 2 or more propositions and finding an new conclusion.  This act is primarily concerned with arguments.

Now, there are 2 kinds of logic

Inductive Logic starts with examples and draws a general conclusion.
 E.g.) “Socrates, Plato, and Aristotle are mortal” “THEREFORE Men are mortal. 

This method an only yield probability, not certainty.  Pointing to several examples is like sampling in a poll.  The larger the sample, the greater the probability, but it cannot be certain unless every single member of the group is in the sample.

Deductive Logic starts with General Principles and draws specific conclusions.
E.g.) “Men are Mortal” “Socrates is a Man” “THERFORE Socrates is Mortal”

Deductive logic can yield certainty if:
a. All terms are clear.   A term = Subject or a predicate.  It is either clear or unclear
b. All premises are true.  A Proposition (or a premise)  = Declarative Sentence.  It is either true or false
c. The argument is logically valid.  An Argument = a logical move from premises to conclusion.  It is either valid or invalid

To disagree with a deductively logical argument, it must have at least one of the following:
1. An ambiguous term
2. A false premise
3. A logical fallacy

If it does not have any of these, then the conclusion must be true.

Next time we will focus on the different types of terms.   I am convinced that the majority of our major arguments come from a misunderstanding of the subject.  That is why whenever I begin a debate, I ask the participants to define their terms.  You have no idea how much of a headache that saves in the long run.  More on this later.

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