Expanded Notes on Argument Forms


We have indicated that argument forms are repeatable, like building structures.  Thus, we should expect to find arguments about a variety of topics that are set up in the same way.  We just determined the form for argument (I).  Consider the following two arguments that have the same form as (I):

Argument (I-A):

  1. If Bush can convince the American people that we shouldn't "switch horses midstream", then he will win re-election.

  2. Bush can convince the American people that we shouldn't "switch horses midstream".

  3. Therefore, he will win re-election.

Argument (I-B):

  1. If time travelers from the future live among us, then time travel is possible.

  2. Time travelers from the future live among us.

  3.  Therefore, time travel is possible.

If you replaced the sentence after the "If" in the first reason in each with "A" and the sentence after the "then" with "B", you would get the same form as the one we extracted from (I).  There are many such forms.  Here are three more, just to demonstrate the range:

Form (2):

  1. X is either P or it's Q.

  2. X is not P.

  3. Therefore, X is Q.

Form (3):

  1. All As are Bs.

  2. X is an A.

  3. Therefore, X is a B.

Form (4):

  1. The first X observed could fly.

  2. The second X observed could fly.

  3. The third X observed could fly.

  4. The fourth X observed could fly.


  5. Therefore, all Xs can fly.

Forms (2) and (3) are what we will call CPAs below, whereas (4) is an example of a PPA. For more about the details of these arguments, see the Expanded Notes sections associated with CPAs and PPAs.

A final note about form.  You might agree with (I-A) or you might not.  Chances are that unless you are a die-hard Terry Gilliam fan, you aren't impressed by (I-B).  What this shows us is that when it comes to argument quality, form isn't everything.  As we will see in the next section, content matters a great deal too.