Gotta stay positive

28 Aug

All Chocolate is satisfying

Ghirardelli is chocolate

Tf, Ghirardelli is not satisfying   

What???  That doesn’t make sense!

You’re right.  Our mind easily balks because Premise 1 and Premise 2 are both affirmative propositions, they are A statements.  And the senseless conclusion is a negative proposition, an E statement (No Ghirardelli is satisfying).

Below is the chart that shows the 4 kinds of propositions and their Quality (Affirmative or Negative)

Affirmative  Propositions                      Negative Propositions

in this column                                         in this column

A – All dogs are cuddly E – No dogs are cuddly
I – Some dogs are cuddly O – Some dogs are not cuddly

So, back to chocolate and the question of validity – We are continuing with our extended lesson of

  • “How to examine a syllogism and see if it’s valid”

There are 7 rules in our Validity Checklist that we must run down to determine if a syllogism is valid , that is, in the correct form.  Last time, we showed that NO conclusion whatsoever can be drawn from 2 negative propositions.  Today, we see from Rule # 6 that

  • if premise 1 & 2 are affirmative, then the conclusion MUST be affirmative as well.

So what happens if someone has asserted a negative claim about health care such as:

  • No costly plans are possible

and when you ask the person WHY??? (Whoever makes an assertion is required to back it up with reasons) he/she says:

Premise 1 – All government plans are possible

Premise 2 – All costly plans are government plans

They’ve JUST articulated two affirmative reasons for their NEGATIVE conclusion of “ No costly plans are possible”

Before you jump in (or down your conversation partner’s throat) and start giving YOUR reasons why you disagree, you have every right to encourage this person to explain what she has either

  • left out on purpose
  • left out because she is not THINKING

Remember, there is absolutely NO point in arguing about an invalid argument.  And a negative conclusion drawn from 2 affirmative premises is one of the 7 ways an argument can be deemed invalid.

An argument (syllogism) must win the ‘Good Logician’s Stamp of Validity ‘ to be considered ready to meet the next criterion – are the premises TRUE.

Leave a Reply

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

WordPress.com Logo

You are commenting using your WordPress.com 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 )

Google+ photo

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

Connecting to %s

%d bloggers like this: