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What if….it rains on my wedding day?

25 Sep

Saturday, it POURED in the Asheville area of Western NC. 

Normally we hike, my husband and I.  But as we went to bed Friday night, Mike gloomily looked up from checking his Weather Bug app and announced, “ 90 % chance of rain!”

So we did a field trip into the Big City of Asheville and walked around in the rain, stopping in at Topps for shoes and sampling good food at Black Bird Café.

On our way home in driving rain, I casually mentioned to Mike, “Pity the poor couple who planned a lovely Fall Wedding OUTDOORS!”    

Come to find out, a colleague at work WAS part of the bridal party in what was to be an outdoor wedding.

“ Hors de question!”  out of the question, as it turned out.

So here’s the syllogism:

If it rains, then we’ll have to move the wedding indoors

It’s raining,

Therefore, we must move the wedding indoors

This is called a conditional syllogism, part of the class of hypotheticals.

We test the validity of hypotheticals differently.

The major premise is the complex one, the “if/then statement” .

The normal categorical proposition that follows the IF – in this case, It rains

is called the Antecedent.  And the proposition that follows the THEN – in this case, we’ll have to moved the wedding indoors is called the consequent

There are 4 possibilities for arranging the minor premise and the conclusion.  Two are valid and 2 are invalid because they assume too much.

Here are the valid ones , side by side, with their names

If it rains, then we’ll move the wedding indoors          If it rains, then we’ll move the wedding indoors

It’s raining                                                                                    We’re not moving the wedding indoors

Tf, we’re moving the wedding indoors                             Tf, it’s not raining

Affirming the Antecedent                                                      Denying the consequent

(Modus Ponens in Latin)                                                         (Modus Tollens in Latin)

To remember which segment to affirm or deny to be valid, I created a silly statement.

“ AA (alcoholics anonymous) meets in DC (Washington) is valid”     

So we can either affirm the antecedent or deny the consequent and have a valid conditional argument.

If however, we propose the other 2 possibilities, we are stuck with INVALID arguments.

If we DENY the antecedent we get the following:

If it rains, then we will move the wedding indoors

It’s not raining                       

Tf, we’re not moving the wedding indoors

This is not valid, because there are OTHER possible reasons one might be forced to move the wedding indoors.  There could be a snow storm…..the beach could have been eroded….the patio of the Historic Inn could have been double booked.

The other invalid version is this:

If it rains, then we will move the wedding indoors

We’re moving the wedding indoors

Tf, it must be raining

Again, there are a range of other reasons that might cause the wedding to moved indoors.  We don’t have enough information to conclude that rain is the decisive factor.

The ONLY fact we had was this:  That if rain came, the wedding WOULD FOR SURE be moved indoors.  No other contingency plans were described in the syllogism.

Listen next time you hear an “if-then” statement and see if you can determine if it’s valid.

By the way, the bride owes a hearty thanks to her bridal party who pulled off the herculean task of last minute decorating inside!!

If-then statements and the abortion issue

6 Aug

“If you’re a man, you have no right to an opinion about abortion”


I read this statement in a letter to the editor the other day.  This assertion is useful for two reasons:

·         We can look at conditional if/then syllogisms that will support this assertion

·         AND we can practice teasing out the implications of this assertion by using something that sounds VERY sophisticated, but is actually quite simple – the “argumentum ad absurdum”

First, let’s consider a conditional argument:

If A, then B         If it is sunny today, then we will go on a picnic

A                           It’s sunny (we affirmed the 1st clause, the antecedent)

Tf, B                     Tf, we will go on a picnic (resulting in the 2nd clause, the  consequent)

The form of this hypothetical conditional syllogism is valid if we AFFIRM the “if-clause” (or the antecedent).  The other valid form that works is when we DENY the “then- clause” (called the consequent).

If it’s sunny today, (the antecedent) then we will go on a picnic (the consequent)

We didn’t go on a picnic (we denied the consequent)

Tf, it wasn’t sunny (resulting in a denial of the antecedent)


Now let’s look at the actual MEANING of the statement at the top.  The full argument looks like this:

           If you’re a man, then you have no right to an opinion about abortion

          You’re a man

          Tf, you have no right to an opinion about abortion


We affirmed the antecedent in Premise 2, resulting in a valid conclusion. What would the other valid form look like?

If you’re a man, then you have no right to an opinion about abortion

You have a right to an opinion about abortion

Tf, you must be a woman (you’re not a man)


We denied the consequent in Premise 2, resulting also in a valid conclusion.  But as we’ve seen before, just because an argument is VALID, the TRUTH of the premises is a separate issue.

This assertion in Premise 1 seems ridiculous at face value, but how do we approach it through reason?  We can show it to be false by applying the same ‘logic’ to other situations and seeing the results.

For example, would we apply the same reasoning to these circumstances?

  • ·         If you are not a concentration camp victim, then you have no right to an opinion about Nazis.
  • ·         If you are not a cancer patient, then you have no right to an opinion about meds.
  • ·         If you are not a teacher, then you have no right to an opinion about how children learn best.

Think about how government works – we elect men and women to represent us at the local, state and federal levels. We trust that they will be able to decide issues wisely AFTER studying the details. We don’t limit them to voting issues that they have ONLY personally experienced.   We don’t even hold our President, the Commander-in-Chief of the military to that standard.  Barack Obama has never served in the military, but we expect him to make informed decisions that impact the armed forces.

Where else do you see this smug assertion clobbering folks on both the left and the right? Remember how much easier it is to see others doing that to which we are blind in ourselves.  Humility heals.