Prologue:

In response to requests from my logically-sound readers, you can now find links to Logic 101 (which covers the basic structure of logical arguments) and Logic 103 (which covers the Argumentum ad Populum , Argumentum ad Verecundiam, Petitio Principii, Complex Question, The Ignoratio Elenchi, Fallacies of Ambiguity, The Fallacy of Composition , and Fallacy of Division) here.

Begin Actual Article:

In the first article in this series, Logic 101, we looked at the basic structure of a logical argument. We went over what a logical ARGUMENT is (as differentiated from where you are screaming epithets at your spouse and the neighbors start banging on the floor), what a PROPOSITION is (hint: this is not the same thing as the pick up line you offer to the pretty goth girl in the corner, though in my experience it may get you farther), what PREMISES and CONCLUSIONS are. We also went over the two basic kinds of logical arguments: DEDUCTIVE and INDUCTIVE, how they work, and (in the comment thread) why some folks think inductive reasoning sucks.

Now, as promised, I present to you part two: The Attack of the Evil Fallacies

My Mom (um, with me as translator):

Sometimes it is not easy to recognize that there is something wrong with an argument you are hearing. A deductive argument that may sound persuasive to people but is in fact not valid is called a FALLACY. Oddly enough, people keep on using some of these same arguments every day to try to prove their points, even though the flaws with their arguments are well known.

Let’s look at some invalid arguments (fallacies) that you might run into in everyday life.
Many common fallacies are what logicians refer to as fallacies of relevance. These are arguments where the premises are LOGICALLY irrelevant (not related) to the conclusion – although there may be some reason why they have an emotional impact on the listener that makes him tend to assume that the premises and conclusion are related.

Some of the traditional types of irrelevant arguments have been used so often throughout history that they have been given Latin names. But don’t let that scare you. Almost nobody knows Latin anymore, so you’re not really expected to. Breaking out with the Latin terminology sounds really impressive, though, so it’s good to remember if you’re into impressing people (like cute goth girls).

For instance:

1. The Argumentum ad Baculum is one that involves an APPEAL TO FORCE. Usually, this sort of fallacy is committed when evidence or rational arguments have already failed. For instance, if you were trying to convince someone at your office not to do something, and he totally ignored your reasoning, you might finally in desperation say something like, “If you do that, the boss will demote you to cleaning toilets, and we’ll hang your underwear from the flagpole.” On the assumption that the other person really likes his job (and his underwear), then this Argumentum ad Baculum might just get his attention – even though it has absolutely nothing to do with what you were originally arguing about!

2.An Argumentum ad Hominem translates literally as an “argument directed to the man.” There are two sorts of common ways in which people resort to an Argumentum ad Hominem. In one such case, instead of trying to disprove the truth of what has been said, someone attacks the person who made the assertion. For instance, a politician may have made very strong statements about our country and what needs to change. If his opponents can’t successfully argue that what the politician is saying is not true, it has become pretty common to try instead to prove that the guy has done something completely unrelated that a lot of people in this country don’t approve of. For example, they may try to prove that the politician is gay or has cheated on his wife or that he evaded the draft during the Vietnam war. If they can get enough people angry about things he has done that are totally irrelevant to what he is arguing, then even though what he is arguing is true and can’t be shown not to be true, they can still get people to vote against him because the people don’t like things he has done previously that are totally irrelevant to the current election issues.

Another example of an Argumentum ad Hominem would be when, instead of arguing against something someone has said, his opponent will say, “And you claim to be a Democrat … but that is totally contrary to the Democratic Party Platform.” In regular life, this would be like you were playing a drinking game with some of your friends, and one friend challenges you to do something that you tell him is dangerous and would hurt you. Since in fact the friend knows you are probably right, instead of arguing that the action is not dangerous, he could turn around and say something like, “And you claim to be adventurous; you’re not adventurous, you’re a coward.” If you were very silly, you could let yourself be persuaded to do what you know you shouldn’t by this sort of argument. People do, unfortunately. Or consider a well known book title of a few years ago, Real Men Don’t Eat Quiche. What does a statement like this imply? By suggesting that what you are doing is inconsistent with what you want to be, somebody is trying to make you conclude that his or her idea about what you should do is the (only) right way.

3. An Argumentum ad Ignorantiam (argument from ignorance) is a fallacy committed whenever it is argued that a proposition is true simply on the basis that it has not been proved false, or conversely, that it is false because it has not been proved true. For example, someone might argue that there are ghosts, because nobody has ever been able to prove that there are not any. Similarly, people have argued that, since nobody has ever seen (or otherwise proved the existence of) a soul, souls don’t exist. However, our ignorance of how to prove or disprove a proposition does not establish either its truth or its falsehood.

4. An Argumentum ad Misericordium (appeal to pity) is a fallacy committed whenever pity is appealed to as a reason that a conclusion should be accepted. For instance, when someone breaks the law, a lawyer might argue that the person should not be punished because he or she is poor, comes from a family with little money, his or her mother has been abandoned by the father and has to work two jobs, etc. These statements may all be true and pity may be justified, but the statements are quite irrelevant to the question of whether the person actually committed the crime and, assuming so, what the prescribed legal punishment for breaking the law is. Likewise the aforementioned cute goth girl might be prevailed upon with the argument that you haven’t gotten anyone to sleep with you in six months…but this is both unlikely to succeed and logically unsound.

(just) Me Again:

What we have here are four of the most basic fallacies in common use: Argumentum ad Baculum (an appeal to force), Argumentum ad Hominem (an attack against your opponent, rather than their argument), Argumentum ad Hominem (arguing something is true only on the basis that it has not been proved untrue), and Argumentum ad Misericordium (the pity trick). We all encounter these on a pretty regular basis, especially if you frequent the bar scene or pay attention to politics. I challenge you good folks to note down the best example of any of these fallacies that your hear in the next 24 hours and post it here. I promise to send the person who supplies the best one a lollipop.

In our next exciting episode, we will expose more nefarious fallacies and why they won’t help you pick up the goth girl in the corner. Make sure you check it out, because anyone who is a good Newsvine user of course wants to know how to make a logical argument, and if you don’t we’ll run your underwear up a flagpole and my heart will be broken.