Intro to Fallacies

Intro to Logic, Class 19- The Fallacies


In this second part of an introduction to informal logic, Prof. Casey takes us through some of the most common fallacies of argument.  Since Aristotle’s original list of fallacies, philosophers and logicians since have been continually adding to that list.  It is important to remember that there is no finalized set of fallacies agreed upon by all.  Some are referred to by different names, some are seen as subsidiaries of others, and some are not agreed upon.  Recognizing the fallacies is more important than memorizing the names.

Methodological Skepticism– a general defense against fallacious arguments

One without statistical training should suspend judgment on an argument based on statistics until the stats presented are further examined by someone with further training.

While there are plenty of fallacies of formal logic to cover, we will be focusing on informal logical fallacies in this post.  Here are a few:

Appeal to Authority- While looking to an authority source for information regarding an issue they are well-versed in makes total sense, citing one who is not an authority in the relevant area or giving to much weight to one’s advice when the topic is still disputed is considered fallacious.

Accent- Implying contrast by putting emphasis on a particular word in a sentence.  This is considered fallacious when the implication being made by the emphasis is not supported by other evidence.

Ad Hominem– Attempting to undermine your opponent’s argument by launching a personal attack, questioning motives, or otherwise using personal characteristics instead focusing on the issue at hand.  Simply calling someone an offensive name is not an example of ad hominem, but calling in to question one’s knowledge of the economy because he/she was let go from a banking job would be.  Ad hominem is a widely used fallacy of argument.

Begging the Question (Assuming what you’re trying to prove)- When one’s conclusion is derived from a proposition that is that very conclusion (A –> A).  The two propositions may be worded differently, yet turn out to mean the same thing.  This term is often misused by saying “That begs the question…” but meaning “that gives rise to the question…”  To avoid confusion, it may be easier to use the more direct terminology assuming what you are trying to prove.

Circular Reasoning (Arguing in a Circle)- Argument begins at A and may take a tour through other propositions before arriving back at A again.  For example, “We should believe everything that the mainstream media tells us because the mainstream media is credible enough to believe.”  We can actually use eduction to expose this sort of a statement by identifying the four equivalent forms of a proposition.

Broken Window Fallacy- Focusing attention only on benefits or at least benefits to a specific group without taking into consideration the total cost.  This tends to occur after natural disasters, when someone makes the argument that a certain level of destruction will be good for the economy because it will create jobs.  In making this argument, the person overlooks the total cost and how the economy would have been otherwise affected had the damage not occurred in the first place.

Everybody’s doing it- This fallacy shouldn’t need much discussion.  Perhaps you used it on your parents when you were young, or you may be hearing it nowadays as a parent.  It is an attempt to justify a particular stance simply due to large numbers of people holding the same stance.

Prof. Casey has one more class concerning informal logic.  Please follow along in the next post and if you’d like further explanation, register at Liberty Classroom.  Thanks for reading.


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