How to Identify Fallacies and Logical Errors

The Identification of fallacies  is a three step process.  
1.  Name the fallacy.
2.  Define the fallacy.
3.  Show how the definition fits the example in question.

The first two steps are simply a matter of copying the name and the definition from the Index of Fallacies.  Step 3, however, is very exacting.  You'll notice that each fallacy in the index is supported by an ID and an MID.  The ID is a set of instructions for completing step 3.  The MID identifies ways that people typically botch step 3.  

You are already familiar with the kind of reasoning required to identify fallacies.  To see this, think about how you would answer the following question.  

Is the following reasoning deductively valid?
Monkeys love to play backgammon.
Sirius is a monkey.
Sirius loves to play backgammon.


You would say:
1.  It is deductively valid.
2.  In a deductively valid argument it is impossible for the premises to be true and the conclusion false.
3.  In this example, the premises are "Monkeys love to play backgammon" and "Sirius is a monkey".  If both of these statements are true, then the conclusion "Sirius loves  to play backgammon" must be true.  Hence, it is impossible for the premises to be true and the conclusion false.


Step 1 names the property in question, in this case deductive validity.   Step 2 defines deductive validity.  Step 3 shows exactly how the example fits the definition.  Fallacy identification works in exactly the same way.  Consider the following example.
    Barb: I think capital punishment should be abolished because it is cruel and unusual punishment, and that's prohibited by the Constitution.

    Butch:  Right, I feel sorry for those poor little murderers, too.  Let's just release them all and tell them to be nice from now on.

This is a straightforward example of the fallacy of Straw Person.  Before showing how to identify the fallacy correctly, let's look at a typical example of a botched identification.
1.  Straw Person.
2.  Attempting to discredit a view by criticizing a weak version of the view or the reasoning given in support of it.
3.  In this example Butch is just totally ridiculing what Barb is saying by making it seem like she thinks all murderers should be released from prison.  But that's not what she is saying at all.


You'll notice that what is said in step 3 is vaguely correct and vaguely related to the fallacy of straw person, but it does not fit precisely fit the definition of Straw Person. Notice the ID on Straw Person.  It says
ID: Identify both the original view and the weak version of that view.  Show (a) why the weak version is a version of the view and (b) why it  is weak.

 Hence, step 3 above should read something like this.
3.  The original view is:  Capital punishment should be abolished.  The weak version of the view is something like: Murderers shouldn't receive any punishment at all.  This is a weak version of the previous view because it entails the abolishment of capital punishment.  It is weak, because not punishing murderers is both absurd, and not implied by the original view.


As you learn more fallacies and become more adept at their identification, you'll often find that one example of fallacious reasoning commits more than one fallacy. Sometimes this is just because the example contains multiple errors. Other times it is because the fallacies in question have overlapping boundaries.  The above example can be plausibly analyzed as the fallacy of false Alternatives and the fallacy of innuendo.
1.  False alternatives.
2.  Misformulating a problem as a choice between two (or more) alternatives when there exist other alternatives that have not been considered.
3.  In this example Butch misformulates the problem raised as a choice between two alternatives:  either retain capital punishment or have no punishment at all.  He neglects the fact that there are other plausible alternatives, such as long term prison sentences.

1. Innuendo.
2. Insinuating or suggesting a conclusion under conditions that suggest that one would be reluctant to claim it explicitly.
3. In this example Butch suggests without stating or implying that Barb's view requires us to release murderers on death row from prison.  Butch would probably not claim this explicitly, since it is obviously not implied by Barb's view that capital punishment should be abolished.  

Both of these analyses are accurate.  False alternatives and straw person are equally penetrating analyses. Innuendo is a little less so, since the suggested view is itself fallacious.