T2: 10 of 13

Part IV of Tutorial Two: Fallacies

A fallacy is an argument that misleads. It's a "trick" of reasoning. There are two main types of fallacious reasoning: Formal and informal.

next, formal fallacies...

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Formal Fallacies

These are arguments which are fallacious because of bad form. We've already seen an example of this: the Sanchez case.

Sanchez stays at her banking job only if she gets a raise. So, if she gets a raise, she'll continue at the bank.

This reasoning may at first seem OK. But it's not. To see the problem, notice that the same form of reasoning is obviously wrong in a different context:

There is fire only if there's oxygen. So, if we add oxygen to an area, there will be fire.

But of course this is wrong. Often we have oxygen but no fire: oxygen is a necessary but not sufficient condition for burning.

Notice that both the last two arguments are of this form:

_____ only if _ _ _ _ _. So, if _ _ _ _ _, then ______.

The problem with the argumentation is the form.

Note: Formal fallacies are always or almost always invalid deductive arguments.

OK, to finish...

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

...which of the following are examples of formal fallacies?
  1. All readers of Steven Pinker understand evolutionary psychology. Otem does not read Pinker. So, Otem does not understand evolutionary psychology.
  2. All readers of Steven Pinker understand evolutionary psychology. Otem does not understand evolutionary psychology. So, Otem does not read Pinker.
  3. If n>2, then 2n>4. Suppose n=3, then 2n must be greater than 4.
  4. If Dennett is a believer, then God is satisfied with her creation. God is satisfied with her creation, so Dennett is a believer.