www.commoncc.com
commoncc.jpgTwo_Men_Confabulating.jpg

The Missing High School Class

The commoncc of Decision-Making

2011-10-15

Critical Reasoning has been around since the days of Socrates, and it is essential to a successful and happy life, yet educators leave most of us to figure it out “on the fly”.  Studies have found that an inability to express oneself with language and reasoning skills can lead to frustration and anger.  Here’s a crash course in critical reasoning; become an expert, right here, right now. 

 

First, when reasoning, we use the word “argument” to mean the structure: premises followed by a conclusion…not to mean a disagreement. 

 

The simplest structure of an argument is this:

     Premise1 + Premise2 = Conclusion

 

When we say that an argument is true, we mean the whole argument is right, and straight, and correct, and proper, and including the conclusion.  We are looking for two things, and two things only, in an argument:

1.     “the truth of the premises”, and

2.     validity

 

TRUTH:  The first test is for the truth of an argument, and is straightforward.  Are the premises true or not?  For an argument to be true,

1.     The premises (the “facts” being stated) must be true, and

2.     The argument must be “valid”.  (The conclusion must necessarily follow from the premises.)

 

VALIDITY:  The second test is for the “validity” of the argument, and it goes like this.

If the premises are true, then must the Conclusion be true?

Does P1 + P2 necessarily = C?  That’s validity.

 

CRITICAL REASONING: Finally, we put them together.  If the premises are true and the argument is valid, then the conclusion must necessarily also true.

 

Examples help here.  For this illustration to work, we will simply agree in advance, that Spot is a scientist, and also that all scientists give to charity...just for our examples…to make it uncomplicated.

 

Example 1

     Premise 1: All scientist give to charity.

     Premise 2: Spot is a scientist.

     Conclusion: Therefore, Spot gives to charity.

 

Premises 1 and 2 are both true, and this argument is “valid”.  (Remember: It’s valid if the premises are true, then the conclusion must be true.)

Therefore, this argument is true, and the conclusion of this argument is true.

We can be certain that, in the universes of “Everyone who gives to charity” and “Scientists”, Spot fits in like this.

 

Diagram_Example_1.jpg

Example 2

     Premise1: All scientists give to charity.

     Premise 2: Spot is an Economist.

     Conclusion: Spot gives to charity.

 

Premises1 is true.

Premise2 is not true.

And this argument is not valid.  (That is, even if the premises are true, the conclusion may or may not be true.  the conclusion does not necessarily follow from the premises.  The premises do not line-up together to create a must-be-true conclusion.)

In this case, while the conclusion may be true, the argument is not true.

 

For example 2, from our premises, we know that in the universes of “Everyone who gives to charity” and “Scientists”, Spot could fit in like this,

 

Diagram_Example_2.jpg

Example 3 (a tougher one to see, sometimes)

     Premise1: All scientists give to charity.

     Premise2: Spot gives to charity.

     Conclusion: Spot is a scientist.                                                        

Premises1 is true.

Premise2 is true.

However, this argument is not valid.  (That is, even if the premises are true, the conclusion may or may not be true.  the conclusion does not necessarily follow from the premises.  The premises do not line-up together to create a must-be-true conclusion.)

In this case, while the conclusion may be true, the argument is not valid.

 

In the universes of “Everyone who gives to charity” and “Scientists”, we are uncertain how Spot fits in.  Because, it could be either one of these, the argument is not valid.

 

Diagram_Example_3.jpg

Now that you’re an expert logician…People say stuff that doesn’t “add up”.  Now that you know what to look for.  Here are some favorite games people play.

1.     Invalid arguments

a.     The conclusion does not necessarily follow from the premises.

b.     Some evidence, but not enough premises to connect the dots, to say “The conclusion must be true.”

2.     Untrue arguments

a.     False premises

b.     Unstated (and unproven) assumptions for premises

c.      Confusing or vague premises that may or may not support the conclusion.

3.     Circular arguments

a.     “The conclusion is true…Therefore, the conclusion must be true.”

4.     Presuppositions

a.     “You will of course agree that…”

 

…Okay, one last one, then we are getting into negotiating and counter-negotiating…

 

5.     Bullying

a.     Raising the volume (to bully) or talking faster (to confuse), as if talking louder or faster makes premises suddenly true, or arguments suddenly valid.

 

Only with argument valid,

And premises true,

Will we accept the conclusion;

We have a clue.

 

 

 

 

How say you?

 

 

commoncc@commoncc.com