The Use and Misuse of Logical Fallacies – Part 1

June 21, 2009

penguin logic As a casual student of debate, we were taught that arguments are not won on logic alone, that they are won by the copious application of wit, rhetoric, and most importantly – by the use and misuse of logical fallacies.

Unlike stating counter-arguments, by catching logical fallacies not only are you providing a valid response, but you are essentially rendering to oppositions arguments invalid. Of course, being the perpetrator of logical fallacies is not a very wise option, for a person with strong logic will always catch the same. But at times the clever use of some fallacies can decisively swing an argument in your favour. And let’s be honest, arguments and debates aren’t just about finding the truth; they’re also about *cough* winning *cough*.

“A fallacy is an argument which provides poor reasoning in support of its conclusion. Fallacies differ from other bad arguments in that many people find them psychologically persuasive. That is, people will mistakenly take a fallacious argument to provide good reasons to believe its conclusion. An argument can be fallacious whether or not its conclusion is true.”


A fallacy is simply an error in reasoning. These are flawed statements that often sound true. It is usually independent of the truth, although conclusion based on such statement might or might not be true.

Below are some of the more common fallacies found in the English language. The same is by no means an exhaustive list of logic fallacies, just some of the more common ones.

1. Ad Hominem

Latin for “argument against the man

This is a form of attack directed towards the character of a person rather than the argument at hand. Such arguments usually assume the following form:-

A makes argument X
B attacks the character of A
Thus A’s argument is false.

Ad Hominem is one of the most popular forms of attack adopted in an argument. And the reason why it is a fallacy is that the character, circumstances or actions of a person does not (in most cases, that is) have a bearing on the validity of the claim purported. Eg.

A: I am looking for some financial advice.
B: Why don’t you get in touch with X, he has a proven record of giving sound financial advice. Why, I myself made a small fortune with his help.
A: X!! How can you accept his advice?! Isn’t he the one who was convicted for armed robbery only a few years ago?

Now X’s supposed conviction does not in any capacity hinder his ability to provide sound financial advice. Thus, the fallacy in reasoning. Ad Hominem is generally not a suggested form of reasoning in an argument. But there are cases where such an attack is considered valid. For example, in a situation where a person would have an ‘incentive to lie’, it would be rather naïve to accept his claim without question.

A: XYZ are by far a most superior brand of cookies.
B: Of course you would say that. Your dad owns the company that makes them!

Now, since A would have an incentive to lie, such an attack would be considered valid.

In another case, when Bill Clinton lied on National television about his relations with Monica Lewinsky, questions were raised on his ability to govern a country. Supporters did argue that Clinton’s sex life would not have any impact on his ability to run a country. Although his willingness to lie could certainly put a question mark on his integrity and ability to adhere to the truth in other cases as well.

2. Slippery Slope (also known as ‘camels nose’)

dilbert-slippery slope

Very popular among housewives, priests and out of work politicians, a slippery slope is not always a logical fallacy. A slippery slope is a claim which states that one thing will lead to another thing (usually far fetched) without showing a plausible connection between the action taken and the stated outcome.

Such statements usually assume the following form :-

If ‘Event A’ occurs
Unrelated ‘Event B’ will occur

Such statements are fallacious because no conclusive evidence is given to show a connection between the two events. If plausible reasons are given as to why A would lead to B, which would in turn lead to C and so on, then the statement is not to be considered fallacious.

Eg. of  a Slipper slope :-

A: What do you think of the government’s move to ban pornography?

B: Absolutely ludicrous! Soon they’ll start burning all forms of literature. One can only image the fate of classics such as Shakespeare and Tolstoy!

When used in extremity (as in the example above), slippery slope arguments are very easy to catch and therefore, to refute. But if used cleverly, such arguments carry a lot of weight in debates.

One such case where a ‘slippery slope’ argument has often been implemented successfully is in the debate over the legalization of drugs.
We’ve often heard the following:-

“If marijuana is to be leglized, we might as well legalize heroin, LSD, and crack cocaine.”

But one could claim that the legalization of one form of drugs could (in principle, at least) open the possibility of other forms being considered for legalization. Thus a valid form of a ‘slippery slope’ argument.

3. Non Sequitur

non sequitur

Latin for “does not follow”

Similar to a ‘slippery slope’, non sequitur is a fallacy wherein the conclusion does not follow the premise, almost to the point of sounding confusing and absurd.

Eg :-

A: There aren’t enough open spaces near my apartment. So I’m thinking of purchasing a treadmill. I just haven’t been getting any exercise.
M: Now, if you can afford a treadmill you can certainly afford to buy a house in a posh locality where there would be sufficient open spaces.
A: Huh?

Such fallacies should be avoided as even a novice logician will catch these without a hitch.
The penguin illustration used at the beginning of the post is also a classic example of non sequitur.



Glasbergen (Penguin Illustration)