Propaganda - Fallacies

Argument Fallacies

An argument fallacy is a reasoning "trick" made up of faulty logic, erroneous assumptions, or irrelevant information meant to distract. it may look like a consistent and compelling argument but is not. You will need to becopme familiar with the fallacies in order to recognize them.


Faulty Logic

There is a form of logic based on the construction
    a -> b
which represents the premise that the presence of a implies that b is also present. For example, if a is "you go outside into a heavy rain" then b is "you are very wet." If a occurs, then b will follow. It looks like:

Go outside in heavy rain -> Get very wet
There are four ways to use this structure.
  1. Assert that a is true. This is Modus Ponens (affirming the antecedent) reasoning. If a is true, then you can conclude that b is also true. You have gone outside into the rain, so you are soaked. This reasoning is valid.
  2. Assert that a is not true. This attempt at reasoning doesn't work. Consider the above example. Suppose you didn't go out in the rain.. Maybe you took a shower, or fell in the indoor swimming pool. You are very wet, but not from rain. b might be true for some other reason. This reasoning is not valid.
  3. Assert that b is true. This doesn't tell you anything about a. b might be true for more than one reason. You are very wet - for one of a number of possible reasons. This reasoning is not valid.
  4. Assert that b is not true. This is Modus Tollens (denying the consequent) reasoning. If b is not true, then a must also be not true. You are NOT wet, therefore you must not have gone out in the rain. This reasoning is valid.
Notice that only two of the four possibilities are valid. The other two provide no evidence for a conclusion. Detection of either of the two invalid reasonings is cause for caution.

General Fallacies

What follows is a summary of common reasoning fallacies. These things appear to support the conclusion of an argument but really don't. You will notice that the number of these fallacies is large, too large for us to list all of them..



References