Persuasion

Using Rhetorical Strategies for Persuasive purposes

There are three types of rhetorical appeals, or persuasive strategies, used in arguments to support claims and respond to opposing arguments. A good argument will generally use a combination of all three appeals to make its case.

Logos

Logos or the appeal to reason relies on logic or reason. Logos often depends on the use of inductive or deductive reasoning.

Inductive reasoning takes a specific representative case or facts and then draws generalizations or conclusions from them. Inductive reasoning must be based on a sufficient amount of reliable evidence, in other words the facts you draw on must fairly represent the larger situation or population. Example:

Fair trade agreements have raised the quality of life for coffee producers, so fair trade agreements could be used to help other farmers as well.

In this example the specific case of fair trade agreements with coffee producers is being used as the starting point for the claim. Because these agreements have worked the author concludes that it could work for other farmers as well.

Deductive reasoning begins with a generalization and then applies it to a specific case. The generalization you start with must have been based on a sufficient amount of reliable evidence.Example:

Genetically modified seeds have caused poverty, hunger, and a decline in bio-diversity everywhere they have been introduced, so there is no reason the same thing will not occur when genetically modified corn seeds are introduced in Mexico.

In this example the author starts with a large claim, that genetically modified seeds have been problematic everywhere, and from this draws the more localized or specific conclusion that Mexico will be affected in the same way.

Avoid Logical Fallacies

These are some common errors in reasoning that will undermine the logic of your argument. Also, watch out for these slips in other people’s arguments.

Ad hominem: attacking the person instead of attacking his argument. For example, “Von Daniken’s books about ancient astronauts are worthless because he is a convicted forger and embezzler.” (Which is true, but that’s not why they’re worthless.) This is an attack on the character of a person rather than their opinions or arguments. Argumentum ad hominem (argument directed at the person) is the error of attacking the character or motives of a person who has stated an idea, rather than the idea itself. The most obvious example of this fallacy is when one debater maligns the character of another debater (e.g, “The members of the opposition are a couple of fascists!”), but this is actually not that common. A more typical manifestation of argumentum ad hominem is attacking a source of information — for example, responding to a quotation from Richard Nixon on the subject of free trade with China by saying, “We all know Nixon was a liar and a cheat, so why should we believe anything he says?” Argumentum ad hominem also occurs when someone’s arguments are discounted merely because they stand to benefit from the policy they advocate — such as Bill Gates arguing against antitrust, rich people arguing for lower taxes, white people arguing against affirmative action, minorities arguing for affirmative action, etc. In all of these cases, the relevant question is not who makes the argument, but whether the argument is valid.Example:

Green Peace’s strategies aren’t effective because they are all dirty, lazy hippies.

In this example the author doesn’t even name particular strategies Green Peace has suggested, much less evaluate those strategies on their merits. Instead, the author attacks the characters of the individuals in the group.
It is always bad form to use the fallacy of argumentum ad hominem. But there are some cases when it is not really a fallacy, such as when one needs to evaluate the truth of factual statements (as opposed to lines of argument or statements of value) made by interested parties. If someone has an incentive to lie about something, then it would be naive to accept his statements about that subject without question. It is also possible to restate many ad hominem arguments so as to redirect them toward ideas rather than people, such as by replacing “My opponents are fascists” with “My opponents’ arguments are fascist.”
Another example is this syllogism, which alludes to Alan Turing’s homosexuality:

Turing thinks machines think.
Turing lies with men.
Therefore, machines don’t think.

(Note the equivocation in the use of the word “lies”.)
A common form is an attack on sincerity. For example, “How can you argue for vegetarianism when you wear leather shoes?” The two wrongs make a right fallacy is related.
A variation (related to Argument By Generalization) is to attack a whole class of people. For example, “Evolutionary biology is a sinister tool of the materialistic, atheistic religion of Secular Humanism.” Similarly, one notorious net.kook waved away a whole category of evidence by announcing “All the scientists were drunk.”
Another variation is attack by innuendo: “Why don’t scientists tell us what they really know; are they afraid of public panic?”
There may be a pretense that the attack isn’t happening: “In order to maintain a civil debate, I will not mention my opponent’s drinking problem.”
Sometimes the attack is on intelligence. For example, “If you weren’t so stupid you would have no problem seeing my point of view.” Or, dismissing a comment with “Well, you’re just smarter than the rest of us.” (In Britain, that might be put as “too clever by half”.) This is related to Not Invented Here, but perhaps it is more connected to Dismissal By Differentness and Changing The Subject.
Ad Hominem is not fallacious if the attack goes to the credibility of the argument. For instance, the argument may depend on its presenter’s claim that he’s an expert. (That is, there is an Argument From Authority.) Trial judges allow this category of attacks.

Ambiguous Assertion: a statement is made, but it is sufficiently unclear that it leaves some sort of leeway. For example, a book about Washington politics did not place quotation marks around quotes. This left ambiguity about which parts of the book were first-hand reports and which parts were second-hand reports, assumptions, or outright fiction.
Of course, lack of clarity is not always intentional. Sometimes a statement is just vague.
If the statement has two different meanings, this is Amphiboly. For example, “Last night I shot a burglar in my pyjamas.”

Appeal To Anonymous Authority: an Appeal To Authority is made, but the authority is not named. For example, “Experts agree that ..”, “scientists say ..” or even “they say ..”. This makes the information impossible to verify, and brings up the very real possibility that the arguer himself doesn’t know who the experts are. In that case, he may just be spreading a rumor.
The situation is even worse if the arguer admits it’s a rumor.

Appeal To Authority: “Albert Einstein was extremely impressed with this theory.” (But a statement made by someone long-dead could be out of date. Or perhaps Einstein was just being polite. Or perhaps he made his statement in some specific context. And so on.)
To justify an appeal, the arguer should at least present an exact quote. It’s more convincing if the quote contains context, and if the arguer can say where the quote comes from.
A variation is to appeal to unnamed authorities .

Appeal To Coincidence: asserting that some fact is due to chance. For example, the arguer has had a dozen traffic accidents in six months, yet he insists they weren’t his fault. This may be Argument By Pigheadedness. But on the other hand, coincidences do happen, so this argument is not always fallacious.

Appeal To Complexity: if the arguer doesn’t understand the topic, he concludes that nobody understands it. So, his opinions are as good as anybody’s.

Appeal To Common Sense: unfortunately, there simply isn’t a common-sense answer for many questions. In politics, for example, there are a lot of issues where people disagree. Each side thinks that their answer is common sense. Clearly, some of these people are wrong.
The reason they are wrong is because common sense depends on the context, knowledge and experience of the observer. That is why instruction manuals will often have paragraphs like these:
When boating, use common sense. Have one life preserver for each person in the boat.
When towing a water skier, use common sense. Have one person watching the skier at all times.
If the ideas are so obvious, then why the second sentence? Why do they have to spell it out? The answer is that “use common sense” actually meant “pay attention, I am about to tell you something that inexperienced people often get wrong.”
Science has discovered a lot of situations which are far more unfamiliar than water skiing. Not surprisingly, beginners find that much of it violates their common sense. For example, many people can’t imagine how a mountain range would form. But in fact anyone can take good GPS equipment to the Himalayas, and measure for themselves that those mountains are rising today.

Appeal To False Authority: a variation on Appeal to Authority , but the Authority is outside his area of expertise.
For example, “Famous physicist John Taylor studied Uri Geller extensively and found no evidence of trickery or fraud in his feats.” Taylor was not qualified to detect trickery or fraud of the kind used by stage magicians. Taylor later admitted Geller had tricked him, but he apparently had not figured out how.
A variation is to appeal to a non-existent authority. For example, someone reading an article by Creationist Dmitri Kuznetsov tried to look up the referenced articles. Some of the articles turned out to be in non-existent journals.
Another variation is to misquote a real authority. There are several kinds of misquotation. A quote can be inexact or have been edited. It can be taken out of context. (Chevy Chase: “Yes, I said that, but I was singing a song written by someone else at the time.”) The quote can be separate quotes which the arguer glued together. Or, bits might have gone missing. For example, it’s easy to prove that Mick Jagger is an assassin. In “Sympathy For The Devil” he sang: “I shouted out, who killed the Kennedys, When after all, it was … me.”

Appeal to Nature: this is the fallacy of assuming that whatever is “natural” or consistent with “nature” (somehow defined) is good, or that whatever conflicts with nature is bad. For example, “Sodomy is unnatural; anal sex is not the evolutionary function of a penis or an anus. Therefore sodomy is wrong.” But aside from the difficulty of defining what “natural” even means, there is no particular reason to suppose that unnatural and wrong are the same thing. After all, wearing clothes, tilling the soil, and using fire might be considered unnatural since no other animals do so, but humans do these things all the time and to great benefit.
The appeal to nature appears occasionally in debate, often in the form of naive environmentalist arguments for preserving pristine wilderness or resources. The argument is very weak and should always be shot down. It can, however, be made stronger by showing why at least in specific cases, there may be a (possibly unspecifiable) benefit to preserving nature as it is. A typical ecological argument along these lines is that human beings are part of a complex biological system that is highly sensitive to shocks, and therefore it is dangerous for humans to engage in activities that might damage the system in ways we cannot predict. Note, however, that this approach no longer appeals to nature itself, but to the value of human survival.
For further comment on this subject, see the naturalistic fallacy.

Appeal To Pity (Appeal to Sympathy, The Galileo Argument): “I did not murder my mother and father with an axe! Please don’t find me guilty; I’m suffering enough through being an orphan.”
Some authors want you to know they’re suffering for their beliefs. For example, “Scientists scoffed at Copernicus and Galileo; they laughed at Edison, Tesla and Marconi; they won’t give my ideas a fair hearing either. But time will be the judge. I can wait; I am patient; sooner or later science will be forced to admit that all matter is built, not of atoms, but of tiny capsules of TIME.”
There is a strange variant which shows up on Usenet. Somebody refuses to answer questions about their claims, on the grounds that the asker is mean and has hurt their feelings. Or, that the question is personal.

Appeal To Force: threats, or even violence. On the Net, the usual threat is of a lawsuit. The traditional religious threat is that one will burn in Hell. However, history is full of instances where expressing an unpopular idea could you get you beaten up on the spot, or worse.

Argument By Fast Talking: if you go from one idea to the next quickly enough, the audience won’t have time to think. This is connected to Changing The Subject and (to some audiences) Argument By Personal Charm.
However, some psychologists say that to understand what you hear, you must for a brief moment believe it. If this is true, then rapid delivery does not leave people time to reject what they hear.

Argument By Generalization: drawing a broad conclusion from a small number of perhaps unrepresentative cases. (The cases may be unrepresentative because of Selective Observation.) For example, “They say 1 out of every 5 people is Chinese. How is this possible? I know hundreds of people, and none of them is Chinese.” So, by generalization, there aren’t any Chinese anywhere. This is connected to the Fallacy Of The General Rule.
Similarly, “Because we allow terminally ill patients to use heroin, we should allow everyone to use heroin.”
It is also possible to under-generalize. For example,
“A man who had killed both of his grandmothers declared himself rehabilitated, on the grounds that he could not conceivably repeat his offense in the absence of any further grandmothers.”
— “Ports Of Call” by Jack Vance

Argument By Gibberish (Bafflement): this is the extreme version of Argument By Prestigious Jargon. An invented vocabulary helps the effect, and some net.kooks use lots of CAPitaLIZation. However, perfectly ordinary words can be used to baffle. For example, “Omniscience is greater than omnipotence, and the difference is two. Omnipotence plus two equals omniscience. META = 2.” [From R. Buckminster Fuller's No More Secondhand God.]
Gibberish may come from people who can’t find meaning in technical jargon, so they think they should copy style instead of meaning. It can also be a “snow job”, AKA “baffle them with BS”, by someone actually familiar with the jargon. Or it could be Argument By Poetic Language.
An example of poetic gibberish: “Each autonomous individual emerges holographically within egoless ontological consciousness as a non-dimensional geometric point within the transcendental thought-wave matrix.”

Argument By Half Truth (Suppressed Evidence): this is hard to detect, of course. You have to ask questions. For example, an amazingly accurate “prophecy” of the assassination attempt on President Reagan was shown on TV. But was the tape recorded before or after the event? Many stations did not ask this question. (It was recorded afterwards.)
A book on “sea mysteries” or the “Bermuda Triangle” might tell us that the yacht Connemara IV was found drifting crewless, southeast of Bermuda, on September 26, 1955. None of these books mention that the yacht had been directly in the path of Hurricane Iona, with 180 mph winds and 40-foot waves.

Argument By Laziness (Argument By Uninformed Opinion): the arguer hasn’t bothered to learn anything about the topic. He nevertheless has an opinion, and will be insulted if his opinion is not treated with respect. For example, someone looked at a picture on one of my web pages, and made a complaint which showed that he hadn’t even skimmed through the words on the page. When I pointed this out, he replied that I shouldn’t have had such a confusing picture.

Argument By Question: asking your opponent a question which does not have a snappy answer. (Or anyway, no snappy answer that the audience has the background to understand.) Your opponent has a choice: he can look weak or he can look long-winded. For example, “How can scientists expect us to believe that anything as complex as a single living cell could have arisen as a result of random natural processes?”
Actually, pretty well any question has this effect to some extent. It usually takes longer to answer a question than ask it.
Variants are the rhetorical question, and the loaded question, such as “Have you stopped beating your wife?”

Argument By Personal Charm: getting the audience to cut you slack. Example: Ronald Reagan. It helps if you have an opponent with much less personal charm.
Charm may create trust, or the desire to “join the winning team”, or the desire to please the speaker. This last is greatest if the audience feels sex appeal.

Argument By Poetic Language: if it sounds good, it must be right. Songs often use this effect to create a sort of credibility – for example, “Don’t Fear The Reaper” by Blue Oyster Cult. Politically oriented songs should be taken with a grain of salt, precisely because they sound good.

Argument By Prestigious Jargon: using big complicated words so that you will seem to be an expert. Why do people use “utilize” when they could utilize “use” ?
For example, crackpots used to claim they had a Unified Field Theory (after Einstein). Then the word Quantum was popular. Lately it seems to be Zero Point Fields.

Argument By Repetition (Argument Ad Nauseam): if you say something often enough, some people will begin to believe it. There are some net.kooks who keeping reposting the same articles to Usenet, presumably in hopes it will have that effect.

Argument by Rhetorical Question: asking a question in a way that leads to a particular answer. For example, “When are we going to give the old folks of this country the pension they deserve?” The speaker is leading the audience to the answer “Right now.” Alternatively, he could have said “When will we be able to afford a major increase in old age pensions?” In that case, the answer he is aiming at is almost certainly not “Right now.”

Argument By Slogan: if it’s short, and connects to an argument, it must be an argument. (But slogans risk the Reductive Fallacy.)
Being short, a slogan increases the effectiveness of Argument By Repetition. It also helps Argument By Emotive Language (Appeal To The People), since emotional appeals need to be punchy. (Also, the gallery can chant a short slogan.) Using an old slogan is Cliche Thinking.

Argument By Selective Observation: also called cherry picking, the enumeration of favorable circumstances, or as the philosopher Francis Bacon described it, counting the hits and forgetting the misses. For example, a state boasts of the Presidents it has produced, but is silent about its serial killers. Or, the claim “Technology brings happiness”. (Now, there’s something with hits and misses.)
Casinos encourage this human tendency. There are bells and whistles to announce slot machine jackpots, but losing happens silently. This makes it much easier to think that the odds of winning are good.

Argument By Selective Reading: making it seem as if the weakest of an opponent’s arguments was the best he had. Suppose the opponent gave a strong argument X and also a weaker argument Y. Simply rebut Y and then say the opponent has made a weak case.
This is a relative of Argument By Selective Observation, in that the arguer overlooks arguments that he does not like. It is also related to Straw Man (Fallacy Of Extension), in that the opponent’s argument is not being fairly represented.

Argument From Authority: the claim that the speaker is an expert, and so should be trusted.
There are degrees and areas of expertise. The speaker is actually claiming to be more expert, in the relevant subject area, than anyone else in the room. There is also an implied claim that expertise in the area is worth having. For example, claiming expertise in something hopelessly quack (like iridology) is actually an admission that the speaker is gullible.

Argument From Adverse Consequences (Appeal To Fear, Scare Tactics):
saying an opponent must be wrong, because if he is right, then bad things would ensue. For example: God must exist, because a godless society would be lawless and dangerous. Or: the defendant in a murder trial must be found guilty, because otherwise husbands will be encouraged to murder their wives.
Wishful thinking is closely related. “My home in Florida is six inches above sea level. Therefore I am certain that global warming will not make the oceans rise by one foot.” Of course, wishful thinking can also be about positive consequences, such as winning the lottery, or eliminating poverty and crime.

Argument From False Authority: a strange variation on Argument From Authority. For example, the TV commercial which starts “I’m not a doctor, but I play one on TV.” Just what are we supposed to conclude?

Argument From Small Numbers: “I’ve thrown three sevens in a row. Tonight I can’t lose.” This is Argument By Generalization, but it assumes that small numbers are the same as big numbers. (Three sevens is actually a common occurrence. Thirty three sevens is not.)
Or: “After treatment with the drug, one-third of the mice were cured, one-third died, and the third mouse escaped.” Does this mean that if we treated a thousand mice, 333 would be cured? Well, no.

Argument From Spurious Similarity: this is a relative of Bad Analogy. It is suggested that some resemblance is proof of a relationship. There is a WW II story about a British lady who was trained in spotting German airplanes. She made a report about a certain very important type of plane. While being quizzed, she explained that she hadn’t been sure, herself, until she noticed that it had a little man in the cockpit, just like the little model airplane at the training class.

Argument Of The Beard: assuming that two ends of a spectrum are the same, since one can travel along the spectrum in very small steps. The name comes from the idea that being clean-shaven must be the same as having a big beard, since in-between beards exist.
Similarly, all piles of stones are small, since if you add one stone to a small pile of stones it remains small.
However, the existence of pink should not undermine the distinction between white and red.

Argument To The Future: arguing that evidence will someday be discovered which will (then) support your point.

Argumentum ad antiquitatem (the argument to antiquity or tradition). This is the familiar argument that some policy, behavior, or practice is right or acceptable because “it’s always been done that way.” This is an extremely popular fallacy in debate rounds; for example, “Every great civilization in history has provided state subsidies for art and culture!” But that fact does not justify continuing the policy. Snobbery that very old (or very young) arguments are superior. This is a variation of the Genetic Fallacy, but has the psychological appeal of seniority and tradition (or innovation).
Products labelled “New! Improved!” are appealing to a belief that innovation is of value for such products. It’s sometimes true.
Because an argumentum ad antiquitatem is easily refuted by simply pointing it out, in general it should be avoided. But if you must make such an argument — perhaps because you can’t come up with anything better — you can at least make it marginally more acceptable by providing some reason why tradition should usually be respected. For instance, you might make an evolutionary argument to the effect that the prevalence of a particular practice in existing societies is evidence that societies that failed to adopt it were weeded out by natural selection. This argument is weak, but better than the fallacy alone.

Argumentum ad ignorantiam (argument to ignorance). This is the fallacy of assuming something is true simply because it hasn’t been proven false. For example, someone might argue that global warming is certainly occurring because nobody has demonstrated conclusively that it is not. But failing to prove the global warming theory false is not the same as proving it true.
Whether or not an argumentum ad ignorantiam is really fallacious depends crucially upon the burden of proof. In an American courtroom, where the burden of proof rests with the prosecution, it would be fallacious for the prosecution to argue, “The defendant has no alibi, therefore he must have committed the crime.” But it would be perfectly valid for the defense to argue, “The prosecution has not proven the defendant committed the crime, therefore you should declare him not guilty.” Both statements have the form of an argumentum ad ignorantiam; the difference is the burden of proof.
In debate, the proposing team in a debate round is usually (but not always) assumed to have the burden of proof, which means that if the team fails to prove the proposition to the satisfaction of the judge, the opposition wins. In a sense, the opposition team’s case is assumed true until proven false. But the burden of proof can sometimes be shifted; for example, in some forms of debate, the proposing team can shift the burden of proof to the opposing team by presenting a prima facie case that would, in the absence of refutation, be sufficient to affirm the proposition. Still, the higher burden generally rests with the proposing team, which means that only the opposition is in a position to make an accusation of argumentum ad ignorantiam with respect to proving the proposition.

Argumentum ad logicam (argument to logic). This is the fallacy of assuming that something is false simply because a proof or argument that someone has offered for it is invalid; this reasoning is fallacious because there may be another proof or argument that successfully supports the proposition. This fallacy often appears in the context of a straw man argument.
This is another case in which the burden of proof determines whether it is actually a fallacy or not. If a proposing team fails to provide sufficient support for its case, the burden of proof dictates they should lose the debate, even if there exist other arguments (not presented by the proposing team) that could have supported the case successfully. Moreover, it is common practice in debate for judges to give no weight to a point supported by an argument that has been proven invalid by the other team, even if there might be a valid argument the team failed to make that would have supported the same point; this is because the implicit burden of proof rests with the team that brought up the argument. For further commentary on burdens of proof, see argumentum ad ignorantiam, above.

Argumentum ad misericordiam (argument or appeal to pity). The English translation pretty much says it all. Example: “Think of all the poor, starving Ethiopian children! How could we be so cruel as not to help them?” The problem with such an argument is that no amount of special pleading can make the impossible possible, the false true, the expensive costless, etc.
It is, of course, perfectly legitimate to point out the severity of a problem as part of the justification for adopting a proposed solution. The fallacy comes in when other aspects of the proposed solution (such as whether it is possible, how much it costs, who else might be harmed by adopting the policy) are ignored or responded to only with more impassioned pleas. You should not call your opposition down for committing this fallacy unless they rely on appeals to pity to the exclusion of the other necessary arguments. It is perfectly acceptable to use appeal to pity in order to argue that the benefits of the proposed policy are greater than they might at first appear (and hence capable of justifying larger costs).

Argumentum ad nauseam (argument to the point of disgust; i.e., by repitition). This is the fallacy of trying to prove something by saying it again and again. But no matter how many times you repeat something, it will not become any more or less true than it was in the first place. Of course, it is not a fallacy to state the truth again and again; what is fallacious is to expect the repitition alone to substitute for real arguments.
Nonetheless, this is a very popular fallacy in debate, and with good reason: the more times you say something, the more likely it is that the judge will remember it. The first thing they’ll teach you in any public speaking course is that you should “Tell ‘em what you’re gonna tell ‘em, then tell ‘em, and then tell ‘em what you told ‘em.” Unfortunately, some debaters think that’s all there is to it, with no substantiation necessary! The appropriate time to mention argumentum ad nauseam in a debate round is when the other team has made some assertion, failed to justify it, and then stated it again and again. The Latin wording is particularly nice here, since it is evocative of what the opposition’s assertions make you want to do: retch. “Sir, our opponents tell us drugs are wrong, drugs are wrong, drugs are wrong, again and again and again. But this argumentum ad nauseam can’t and won’t win this debate for them, because they’ve given us no justification for their bald assertions!”

Argumentum ad numerum (argument or appeal to numbers). This fallacy is the attempt to prove something by showing how many people think that it’s true. But no matter how many people believe something, that doesn’t necessarily make it true or right. Example: “At least 70% of all Americans support restrictions on access to abortions.” Well, maybe 70% of Americans are wrong!
This fallacy is very similar to argumentum ad populum, the appeal to the people or to popularity. When a distinction is made between the two, ad populum is construed narrowly to designate an appeal to the opinions of people in the immediate vicinity, perhaps in hope of getting others (such as judges) to jump on the bandwagon, whereas ad numerum is used to designate appeals based purely on the number of people who hold a particular belief. The distinction is a fine one, and in general the terms can be used interchangeably in debate rounds. (I’ve found that ad populum has better rhetorical effect.)

Argumentum ad populum. This is the fallacy of trying to prove something by showing that the public agrees with you. This fallacy is nearly identical to argumentum ad numerum, which you should see for more details. This is an emotional appeal that speaks to positive (such as patriotism, religion, democracy) or negative (such as terrorism or fascism) concepts rather than the real issue at hand. Example:
If you were a true American you would support the rights of people to choose whatever vehicle they want.
In this example the author equates being a “true American,” a concept that people want to be associated with, particularly in a time of war, with allowing people to buy any vehicle they want even though there is no inherent connection between the two.

Argument By Pigheadedness (Doggedness): refusing to accept something after everyone else thinks it is well enough proved. For example, there are still Flat Earthers.

Complex Question (Tying): unrelated points are treated as if they should be accepted or rejected together. In fact, each point should be accepted or rejected on its own merits.
For example, “Do you support freedom and the right to bear arms?”
Appeal to the public uses emotionally loaded words to sway the audience’s sentiments instead of their minds. Many emotions can be useful: anger, spite, condescension, and so on.
For example, argument by condescension: “Support the ERA? Sure, when the women start paying for the drinks! Hah! Hah!”

Appeal To Widespread Belief (Bandwagon Argument, Peer Pressure, Appeal to Common Practice): the claim, as evidence for an idea, that many people believe it, or used to believe it, or do it.)
If the discussion is about social conventions, such as “good manners”, then this is a reasonable line of argument.
However, in the 1800′s there was a widespread belief that bloodletting cured sickness. All of these people were not just wrong, but horribly wrong, because in fact it made people sicker. Clearly, the popularity of an idea is no guarantee that it’s right.
Similarly, a common justification for bribery is that “Everybody does it”. And in the past, this was a justification for slavery.
Cliche Thinking and Argument By Slogan are useful adjuncts, particularly if you can get the audience to chant the slogan. People who rely on this argument may seed the audience with supporters or “shills”, who laugh, applaud or chant at proper moments. This is the live-audience equivalent of adding a laugh track or music track. Now that many venues have video equipment, some speakers give part of their speech by playing a prepared video. These videos are an opportunity to show a supportive audience, use emotional music, show emotionally charged images, and the like. The idea is old: there used to be professional cheering sections. (Monsieur Zig-Zag, pictured on the cigarette rolling papers, acquired his fame by applauding for money at the Paris Opera.)
If the emotion in question isn’t harsh, Argument By Poetic Language helps the effect. Flattering the audience doesn’t hurt either.

Argumentum ad verecundiam (argument or appeal to authority). This fallacy occurs when someone tries to demonstrate the truth of a proposition by citing some person who agrees, even though that person may have no expertise in the given area. For instance, some people like to quote Einstein’s opinions about politics (he tended to have fairly left-wing views), as though Einstein were a political philosopher rather than a physicist. Of course, it is not a fallacy at all to rely on authorities whose expertise relates to the question at hand, especially with regard to questions of fact that could not easily be answered by a layman — for instance, it makes perfect sense to quote Stephen Hawking on the subject of black holes.
At least in some forms of debate, quoting various sources to support one’s position is not just acceptable but mandatory. In general, there is nothing wrong with doing so. Even if the person quoted has no particular expertise in the area, he may have had a particularly eloquent way of saying something that makes for a more persuasive speech. In general, debaters should be called down for committing argumentum ad verecundiam only when (a) they rely on an unqualified source for information about facts without other (qualified) sources of verification, or (b) they imply that some policy must be right simply because so-and-so thought so.

Bad Analogy: claiming that two situations are highly similar, when they aren’t. For example, “The solar system reminds me of an atom, with planets orbiting the sun like electrons orbiting the nucleus. We know that electrons can jump from orbit to orbit; so we must look to ancient records for sightings of planets jumping from orbit to orbit also.”
Or, “Minds, like rivers, can be broad. The broader the river, the shallower it is. Therefore, the broader the mind, the shallower it is.”
Or, “We have pure food and drug laws; why can’t we have laws to keep movie-makers from giving us filth?”

Petitio principii (begging the question, Assuming The Answer, Tautology): reasoning in a circle. The thing to be proved is used as one of your assumptions. For example: “We must have a death penalty to discourage violent crime”. (This assumes it discourages crime.) Or, “The stock market fell because of a technical adjustment.” (But is an “adjustment” just a stock market fall?) This is the fallacy of assuming, when trying to prove something, what it is that you are trying prove. For all practical purposes, this fallacy is indistinguishable from circular argumentation.
The main thing to remember about this fallacy is that the term “begging the question” has a very specific meaning. It is common to hear debaters saying things like, “They say pornography should be legal because it is a form of free expression. But this begs the question of what free expression means.” This is a misuse of terminology. Something may inspire or motivate us to ask a particular question without begging the question. A question has been begged only if the question has been asked before in the same discussion, and then a conclusion is reached on a related matter without the question having been answered. If somebody said, “The fact that we believe pornography should be legal means that it is a valid form of free expression. And since it’s free expression, it shouldn’t be banned,” that would be begging the question.

Begging the Claim: The conclusion that the writer should prove is validated within the claim. Example:

Filthy and polluting coal should be banned.

Arguing that coal pollutes the earth and thus should be banned would be logical. But the very conclusion that should be proved, that coal causes enough pollution to warrant banning its use, is already assumed in the claim by referring to it as “filthy and polluting.”

Burden Of Proof: the claim that whatever has not yet been proved false must be true (or vice versa). Essentially the arguer claims that he should win by default if his opponent can’t make a strong enough case.
There may be three problems here. First, the arguer claims priority, but can he back up that claim? Second, he is impatient with ambiguity, and wants a final answer right away. And third, “absence of evidence is not evidence of absence.”

Causal Reductionism (Complex Cause): trying to use one cause to explain something, when in fact it had several causes. For example, “The accident was caused by the taxi parking in the street.” (But other drivers went around the taxi. Only the drunk driver hit the taxi.)

Changing The Subject (Digression, Red Herring, Misdirection, False Emphasis): this is sometimes used to avoid having to defend a claim, or to avoid making good on a promise. In general, there is something you are not supposed to notice.
For example, I got a bill which had a big announcement about how some tax had gone up by 5%, and the costs would have to be passed on to me. But a quick calculation showed that the increased tax was only costing me a dime, while a different part of the the bill had silently gone up by $10.
It is connected to various rhetorical tricks, such as announcing that there cannot be a question period because the speaker must leave. (But then he doesn’t leave.)

Circulus in demonstrando (circular argument). Circular argumentation occurs when someone uses what they are trying to prove as part of the proof of that thing. Here is one of my favorite examples (in pared down form): “Marijuana is illegal in every state in the nation. And we all know that you shouldn’t violate the law. Since smoking pot is illegal, you shouldn’t smoke pot. And since you shouldn’t smoke pot, it is the duty of the government to stop people from smoking it, which is why marijuana is illegal!”
Circular arguments appear a lot in debate, but they are not always so easy to spot as the example above. They are always illegitimate, though, and pointing them out in a debate round looks really good if you can do it. The best strategy for pointing out a circular argument is to make sure you can state clearly the proposition being proven, and then pinpoint where that proposition appears in the proof. A good summing up statement is, “In other words, they are trying to tell us that X is true because X is true! But they have yet to tell us why it’s true.”
Circular Argument restates the argument rather than actually proving it. Example:
George Bush is a good communicator because he speaks effectively.
In this example the conclusion that Bush is a “good communicator” and the evidence used to prove it “he speaks effectively” are basically the same idea. Specific evidence such as using everyday language, breaking down complex problems, or illustrating his points with humorous stories would be needed to prove either half of the sentence.

Cliche Thinking: using as evidence a well-known wise saying, as if that is proven, or as if it has no exceptions.
Exception That Proves The Rule: a specific example of Cliche Thinking. This is used when a rule has been asserted, and someone points out the rule doesn’t always work. The cliche rebuttal is that this is “the exception that proves the rule”. Many people think that this cliche somehow allows you to ignore the exception, and continue using the rule.
In fact, the cliche originally did no such thing. There are two standard explanations for the original meaning.
The first is that the word “prove” meant test. That is why the military takes its equipment to a Proving Ground to test it. So, the cliche originally said that an exception tests a rule. That is, if you find an exception to a rule, the cliche is saying that the rule is being tested, and perhaps the rule will need to be discarded.
The second explanation is that the stating of an exception to a rule, proves that the rule exists. For example, suppose it was announced that “Over the holiday weekend, students do not need to be in the dorms by midnight”. This announcement implies that normally students do have to be in by midnight. Here is a discussion of that explanation.
In either case, the cliche is not about waving away objections.

Complex question. A complex question is a question that implicitly assumes something to be true by its construction, such as “Have you stopped beating your wife?” A question like this is fallacious only if the thing presumed true (in this case, that you beat your wife) has not been established.
Complex questions are a well established and time-honored practice in debate, although they are rarely so bald-faced as the example just given. Complex questions usually appear in cross-examination or points of information when the questioner wants the questionee to inadvertently admit something that she might not admit if asked directly. For instance, one might say, “Inasmuch as the majority of black Americans live in poverty, do you really think that self-help within the black community is sufficient to address their problems?” Of course, the introductory clause about the majority of black Americans living in poverty may not be true (in fact, it is false), but an unwary debater might not think quickly enough to notice that the stowaway statement is questionable. This is a sneaky tactic, but debate is sometimes a sneaky business. You wouldn’t want to put a question like that in your master’s thesis, but it might work in a debate. But be careful — if you try to pull a fast one on someone who is alert enough to catch you, you’ll look stupid. “The assumption behind your question is simply false. The majority of blacks do not live in poverty. Get your facts straight before you interrupt me again!”

Confusing Correlation And Causation: earthquakes in the Andes were correlated with the closest approaches of the planet Uranus. Therefore, Uranus must have caused them. (But Jupiter is nearer than Uranus, and more massive too.)
When sales of hot chocolate go up, street crime drops. Does this correlation mean that hot chocolate prevents crime? No, it means that fewer people are on the streets when the weather is cold.
The bigger a child’s shoe size, the better the child’s handwriting. Does having big feet make it easier to write? No, it means the child is older.

Cum hoc ergo propter hoc (with this, therefore because of this). This is the familiar fallacy of mistaking correlation for causation — i.e., thinking that because two things occur simultaneously, one must be a cause of the other. A popular example of this fallacy is the argument that “President Clinton has great economic policies; just look at how well the economy is doing while he’s in office!” The problem here is that two things may happen at the same time merely by coincidence (e.g., the President may have a negligible effect on the economy, and the real driving force is technological growth), or the causative link between one thing and another may be lagged in time (e.g., the current economy’s health is determined by the actions of previous presidents), or the two things may be unconnected to each other but related to a common cause (e.g., downsizing upset a lot of voters, causing them to elect a new president just before the economy began to benefit from the downsizing).
It is always fallacious to suppose that there is a causative link between two things simply because they coexist. But a correlation is usually considered acceptable supporting evidence for theories that argue for a causative link between two things. For instance, some economic theories suggest that substantially reducing the federal budget deficit should cause the economy to do better (loosely speaking), so the coincidence of deficit reductions under Clinton and the economy’s relative health might be taken as evidence in favor of those economic theories. In debate rounds, what this means is that it is acceptable to demonstrate a correlation between two phenomenon and to say one caused the other if you can also come up with convincing reasons why the correlation is no accident.
Cum hoc ergo propter hoc is very similar to post hoc ergo propter hoc, below. The two terms can be used almost interchangeably, post hoc (as it is affectionately called) being the preferred term.

Dicto simpliciter (spoken simply, i.e., sweeping generalization). This is the fallacy of making a sweeping statement and expecting it to be true of every specific case — in other words, stereotyping. Example: “Women are on average not as strong as men and less able to carry a gun. Therefore women can’t pull their weight in a military unit.” The problem is that the sweeping statement may be true (on average, women are indeed weaker than men), but it is not necessarily true for every member of the group in question (there are some women who are much stronger than the average).
As the example indicates, dicto simpliciter is fairly common in debate rounds. Most of the time, it is not necessary to call an opposing debater down for making this fallacy — it is enough to point out why the sweeping generalization they have made fails to prove their point. Since everybody knows what a sweeping generalization is, using the Latin in this case will usually sound condescending. It is also important to note that some generalizations are perfectly valid and apply directly to all individual cases, and therefore do not commit the fallacy of dicto simpliciter (for example, “All human males have a Y chromosome” is, to my knowledge, absolutely correct).

Disproof By Fallacy: if a conclusion can be reached in an obviously fallacious way, then the conclusion is incorrectly declared wrong. For example,
“Take the division 64/16. Now, canceling a 6 on top and a six on the bottom, we get that 64/16 = 4/1 = 4.”
“Wait a second! You can’t just cancel the six!”
“Oh, so you’re telling us 64/16 is not equal to 4, are you?”
Note that this is different from Reductio Ad Absurdum, where your opponent’s argument can lead to an absurd conclusion. In this case, an absurd argument leads to a normal conclusion.

Either/or: This is a conclusion that oversimplifies the argument by reducing it to only two sides or choices. Example: We can either stop using cars or destroy the earth.
In this example where two choices are presented as the only options, yet the author ignores a range of choices in between such as developing cleaner technology, car sharing systems for necessities and emergencies, or better community planning to discourage daily driving.

Error Of Fact: for example, “No one knows how old the Pyramids of Egypt are.” (Except, of course, for the historians who’ve read the records written by the ancient Egyptians themselves.) Typically, the presence of one error means that there are other errors to be uncovered.

Equivocation: using a word to mean one thing, and then later using it to mean something different. For example, sometimes “Free software” costs nothing, and sometimes it is without restrictions. Some examples:
“The sign said ‘fine for parking here’, and since it was fine, I parked there.”
All trees have bark.
All dogs bark.
Therefore, all dogs are trees.

“Consider that two wrongs never make a right, but that three lefts do.”
– “Deteriorata”, National Lampoon

Euphemism: the use of words that sound better. The lab rat wasn’t killed, it was sacrificed. Mass murder wasn’t genocide, it was ethnic cleansing. The death of innocent bystanders is collateral damage. Microsoft doesn’t find bugs, or problems, or security vulnerabilities: they just discover an issue with a piece of software.
This is related to Argument By Emotive Language, since the effect is to make a concept emotionally palatable.

Excluded Middle (False Dichotomy, Faulty Dilemma, Bifurcation): assuming there are only two alternatives when in fact there are more. For example, assuming Atheism is the only alternative to Fundamentalism, or being a traitor is the only alternative to being a loud patriot.

Extended Analogy: the claim that two things, both analogous to a third thing, are therefore analogous to each other. For example, this debate:

“I believe it is always wrong to oppose the law by breaking it.”
“Such a position is odious: it implies that you would not have supported Martin Luther King.”
“Are you saying that cryptography legislation is as important as the struggle for Black liberation? How dare you!”

A person who advocates a particular position (say, about gun control) may be told that Hitler believed the same thing. The clear implication is that the position is somehow tainted. But Hitler also believed that window drapes should go all the way to the floor. Does that mean people with such drapes are monsters?
Failure To State: if you make enough attacks, and ask enough questions, you may never have to actually define your own position on the topic.

Fallacy Of Composition: assuming that a whole has the same simplicity as its constituent parts. In fact, a great deal of science is the study of emergent properties. For example, if you put a drop of oil on water, there are interesting optical effects. But the effect comes from the oil/water system: it does not come just from the oil or just from the water.
Another example: “A car makes less pollution than a bus. Therefore, cars are less of a pollution problem than buses.”
Another example: “Atoms are colorless. Cats are made of atoms, so cats are colorless.”

Fallacy Of Division: assuming that what is true of the whole is true of each constituent part. For example, human beings are made of atoms, and human beings are conscious, so atoms must be conscious.

Fallacy Of The Crucial Experiment: claiming that some idea has been proved (or disproved) by a pivotal discovery. This is the “smoking gun” version of history.
Scientific progress is often reported in such terms. This is inevitable when a complex story is reduced to a soundbite, but it’s almost always a distortion. In reality, a lot of background happens first, and a lot of buttressing (or retraction) happens afterwards. And in natural history, most of the theories are about how often certain things happen (relative to some other thing). For those theories, no one experiment could ever be conclusive.

Fallacy Of The General Rule: assuming that something true in general is true in every possible case. For example, “All chairs have four legs.” Except that rocking chairs don’t have any legs, and what is a one-legged “shooting stick” if it isn’t a chair?
Similarly, there are times when certain laws should be broken. For example, ambulances are allowed to break speed laws.

False Cause: assuming that because two things happened, the first one caused the second one. (Sequence is not causation.) For example, “Before women got the vote, there were no nuclear weapons.” Or, “Every time my brother Bill accompanies me to Fenway Park, the Red Sox are sure to lose.”
Essentially, these are arguments that the sun goes down because we’ve turned on the street lights.

False Compromise: if one does not understand a debate, it must be “fair” to split the difference, and agree on a compromise between the opinions. (But one side is very possibly wrong, and in any case one could simply suspend judgment.) Journalists often invoke this fallacy in the name of “balanced” coverage.
Television reporters like balanced coverage so much that they may give half of their report to a view held by a small minority of the people in question. There are many possible reasons for this, some of them good. However, viewers need to be aware of this tendency.

Genetic Fallacy: A conclusion is based on an argument that the origins of a person, idea, institute, or theory determine its character, nature, or worth. if an argument or arguer has some particular origin, the argument must be right (or wrong). The idea is that things from that origin, or that social class, have virtue or lack virtue. (Being poor or being rich may be held out as being virtuous.) Therefore, the actual details of the argument can be overlooked, since correctness can be decided without any need to listen or think. Example:
The Volkswagen Beetle is an evil car because it was originally designed by Hitler’s army.
In this example the author is equating the character of a car with the character of the people who built the car.

Hasty Generalization: This is a conclusion based on insufficient or biased evidence. In other words, you are rushing to a conclusion before you have all the relevant facts. Example:
Even though it’s only the first day, I can tell this is going to be a boring course.
In this example the author is basing their evaluation of the entire course on only one class, and on the first day which is notoriously boring and full of housekeeping tasks for most courses. To make a fair and reasonable evaluation the author must attend several classes, and possibly even examine the textbook, talk to the professor, or talk to others who have previously finished the course in order to have sufficient evidence to base a conclusion on.

Having Your Cake (Failure To Assert, or Diminished Claim): almost claiming something, but backing out. For example, “It may be, as some suppose, that ghosts can only be seen by certain so-called sensitives, who are possibly special mutations with, perhaps, abnormally extended ranges of vision and hearing. Yet some claim we are all sensitives.”
Another example: “I don’t necessarily agree with the liquefaction theory, nor do I endorse all of Walter Brown’s other material, but the geological statements are informative.” The strange thing here is that liquefaction theory (the idea that the world’s rocks formed in flood waters) was demolished in 1788. To “not necessarily agree” with it, today, is in the category of “not necessarily agreeing” with 2+2=3. But notice that writer implies some study of the matter, and only partial rejection.
A similar thing is the failure to rebut. Suppose I raise an issue. The response that “Woodmorappe’s book talks about that” could possibly be a reference to a resounding rebuttal. Or perhaps the responder hasn’t even read the book yet. How can we tell? [I later discovered it was the latter.]

Hypothesis Contrary To Fact: arguing from something that might have happened, but didn’t.

Inconsistency: for example, the declining life expectancy in the former Soviet Union is due to the failures of communism. But, the quite high infant mortality rate in the United States is not a failure of capitalism.
This is related to Internal Contradiction.

Inflation Of Conflict: arguing that scholars debate a certain point. Therefore, they must know nothing, and their entire field of knowledge is “in crisis” or does not properly exist at all.
For example, two historians debated whether Hitler killed five million Jews or six million Jews. A Holocaust denier argued that this disagreement made his claim credible, even though his death count is three to ten times smaller than the known minimum.
Similarly, in “The Mythology of Modern Dating Methods” (John Woodmorappe, 1999) we find on page 42 that two scientists “cannot agree” about which one of two geological dates is “real” and which one is “spurious”. Woodmorappe fails to mention that the two dates differ by less than one percent.

Internal Contradiction: saying two contradictory things in the same argument. For example, claiming that Archaeopteryx is a dinosaur with hoaxed feathers, and also saying in the same book that it is a “true bird”. Or another author who said on page 59, “Sir Arthur Conan Doyle writes in his autobiography that he never saw a ghost.” But on page 200 we find “Sir Arthur’s first encounter with a ghost came when he was 25, surgeon of a whaling ship in the Arctic..”
This is much like saying “I never borrowed his car, and it already had that dent when I got it.”
This is related to Inconsistency.

Outdated Information: information is given, but it is not the latest information on the subject. For example, some creationist articles about the amount of dust on the moon quote a measurement made in the 1950′s. But many much better measurements have been done since then.

Amazing Familiarity: the speaker seems to have information that there is no possible way for him to get, on the basis of his own statements. For example: “The first man on deck, seaman Don Smithers, yawned lazily and fingered his good luck charm, a dried seahorse. To no avail! At noon, the Sea Ranger was found drifting aimlessly, with every man of its crew missing without a trace!”

Least Plausible Hypothesis: ignoring all of the most reasonable explanations. This makes the desired explanation into the only one. For example: “I left a saucer of milk outside overnight. In the morning, the milk was gone. Clearly, my yard was visited by fairies.”
There is an old rule for deciding which explanation is the most plausible. It is most often called “Occam’s Razor”, and it basically says that the simplest is the best. The current phrase among scientists is that an explanation should be “the most parsimonious”, meaning that it should not introduce new concepts (like fairies) when old concepts (like neighborhood cats) will do.

Argument By Scenario: telling a story which ties together unrelated material, and then using the story as proof they are related.

Affirming The Consequent: logic reversal. A correct statement of the form “if P then Q” gets turned into “Q therefore P”.
For example, “All people whose surname begins with Mac are of Scottish ancestry. Dougal is of Scottish ancestry. Therefore his surname begins with Mac.” But actually his name is Campbell.
Another example: “If the earth orbits the sun, then the nearer stars will show an apparent annual shift in position relative to more distant stars (stellar parallax). Observations show conclusively that this parallax shift does occur. This proves that the earth orbits the sun.” In reality, it proves that Q [the parallax] is consistent with P [orbiting the sun]. But it might also be consistent with some other theory. (Other theories did exist. They are now dead, because although they were consistent with a few facts, they were not consistent with all the facts.)
Another example: “If space creatures were kidnapping people and examining them, the space creatures would probably hypnotically erase the memories of the people they examined. These people would thus suffer from amnesia. But in fact many people do suffer from amnesia. This tends to prove they were kidnapped and examined by space creatures.” This is also a Least Plausible Hypothesis explanation.

Lies: intentional Errors of Fact. If the speaker thinks that lying serves a moral end, this would be a Pious Fraud.

Meaningless Questions: irresistible forces meeting immovable objects, and the like.

Misunderstanding The Nature Of Statistics: President Dwight Eisenhower expressed astonishment and alarm on discovering that fully half of all Americans had below average intelligence. Similarly, some people get fearful when they learn that their doctor wasn’t in the top half of his class. (But that’s half of them.)
“Statistics show that of those who contract the habit of eating, very few survive.” — Wallace Irwin.
Very few people seem to understand “regression to the mean”. This is the idea that things tend to go back to normal. If you feel normal today, does it really mean that the headache cure you took yesterday performed wonders? Or is it just that your headaches are always gone the next day?

Moving The Goalposts (Raising The Bar, Argument By Demanding Impossible Perfection): if your opponent successfully addresses some point, then say he must also address some further point. If you can make these points more and more difficult (or diverse) then eventually your opponent must fail. If nothing else, you will eventually find a subject that your opponent isn’t up on.
This is related to Argument By Question. Asking questions is easy: it’s answering them that’s hard.
It is also possible to lower the bar, reducing the burden on an argument. For example, a person who takes Vitamin C might claim that it prevents colds. When they do get a cold, then they move the goalposts, by saying that the cold would have been much worse if not for the Vitamin C.

Naturalistic fallacy. This is the fallacy of trying to derive conclusions about what is right or good (that is, about values) from statements of fact alone. This is invalid because no matter how many statements of fact you assemble, any logical inference from them will be another statement of fact, not a statement of value. If you wish to reach conclusions about values, then you must include amongst your assumptions (or axioms, or premises) a statement of value. Once you have an axiomatic statement of value, then you may use it in conjunction with statements of fact to reach value-laden conclusions.
For example, someone might argue that the premise, “This medicine will prevent you from dying” immediately leads to the conclusion, “You should take this medicine.” But this reasoning is invalid, because the former statement is a statement of fact, while the latter is a statement of value. To reach the conclusion that you ought to take the medicine, you would need at least one more premise: “You ought to try to preserve your life whenever possible.”
The naturalistic fallacy appears in many forms. Two examples are argumentum ad antiquitatem (saying something’s right because it’s always been done that way) and the appeal to nature (saying something’s right because it’s natural). In both of these fallacies, the speaker is trying to reach a conclusion about what we ought to do or ought to value based solely on what is the case. David Hume called this trying to bridge the “is-ought gap,” which is a nice phrase to use in debate rounds where your opponent is committing the naturalistic fallacy.
One unsettling implication of taking the naturalistic fallacy seriously is that, in order to reach any conclusions of value, one must be willing to posit some initial statement or statements of value that will be treated as axioms, and which cannot themselves be justified on purely logical grounds. Fortunately, debate does not restrict itself to purely logical grounds of argumentation. For example, suppose your opponent has stated axiomatically that “whatever is natural is good.” Inasmuch as this statement is an axiom rather than the conclusion of a logical proof, there can be no purely logical argument against it. But some nonetheless appropriate responses to such an absolute statement of value include: (a) questioning whether anyone — you, your judge, or even your opponent himself — really believes that “whatever is natural is good”; (b) stating a competing axiomatic value statement, like “whatever enhances human life is good,” and forcing the judge to choose between them; and (c) pointing out logical implications of the statement “whatever is natural is good” that conflict with our most basic intuitions about right and wrong.

Needling: simply attempting to make the other person angry, without trying to address the argument at hand. Sometimes this is a delaying tactic.
Needling is also Ad Hominem if you insult your opponent. You may instead insult something the other person believes in (“Argumentum Ad YourMomium”), interrupt, clown to show disrespect, be noisy, fail to pass over the microphone, and numerous other tricks. All of these work better if you are running things – for example, if it is your radio show, and you can cut off microphones. A compliant host or moderator is almost as good.

Non Sequitur (“It does not follow”): something that just does not follow. For example, “Tens of thousands of Americans have seen lights in the night sky which they could not identify. The existence of life on other planets is fast becoming certainty!”
Another example: arguing at length that your religion is of great help to many people. Then, concluding that the teachings of your religion are undoubtably true.
Or: “Bill lives in a large building, so his apartment must be large.”
This is the simple fallacy of stating, as a conclusion, something that does not strictly follow from the premises. For example, “Racism is wrong. Therefore, we need affirmative action.” Obviously, there is at least one missing step in this argument, because the wrongness of racism does not imply a need for affirmative action without some additional support (such as, “Racism is common,” “Affirmative action would reduce racism,” “There are no superior alternatives to affirmative action,” etc.).
Not surprisingly, debates are rife with non sequitur. But that is partly just a result of having to work within the time constraints of a debate round, and partly a result of using good strategy. A debate team arguing for affirmative action would be foolish to say in their first speech, “We also believe that affirmative action does not lead to a racist backlash,” because doing so might give the other side a hint about a good argument to make. A better strategy (usually) is to wait for the other team to bring up an argument, and then refute it; that way, you don’t end up wasting your time by refuting arguments that the opposition has never made in the first place. (This strategy is not always preferable, though, because some counterarguments are so obvious and important that it makes sense to address them early and nip them in the bud.)
For these reasons, it is generally bad form to scream “non sequitur” just because your opposition has failed to anticipate every counterargument you might make. The best time to point out a non sequitur is when your opposition is trying to construct a chain of causation (A leads to B leads to C, etc.) without justifying each step in the chain. For each step in the chain they fail to justify, point out the non sequitur, so that it is obvious by the end that the alleged chain of causation is tenuous and implausible.

Not Invented Here: ideas from elsewhere are made unwelcome. “This Is The Way We’ve Always Done It.”
This fallacy is a variant of the Argument From Age. It gets a psychological boost from feelings that local ways are superior, or that local identity is worth any cost, or that innovations will upset matters. People who use the Not Invented Here argument are often accused of being stick-in-the-mud’s.
Conversely, foreign and “imported” things may be held out as superior.

Pious Fraud: a fraud done to accomplish some good end, on the theory that the end justifies the means.
For example, a church in Canada had a statue of Christ which started to weep tears of blood. When analyzed, the blood turned out to be beef blood. We can reasonably assume that someone with access to the building thought that bringing souls to Christ would justify his small deception.
In the context of debates, a Pious Fraud could be a lie. More generally, it would be when an emotionally committed speaker makes an assertion that is shaded, distorted or even fabricated. For example, British Prime Minister Tony Blair was accused in 2003 of “sexing up” his evidence that Iraq had Weapons of Mass Destruction.
Around the year 400, Saint Augustine wrote two books, De Mendacio[On Lying] and Contra Medacium[Against Lying], on this subject. He argued that the sin isn’t in what you do (or don’t) say, but in your intent to leave a false impression. He strongly opposed Pious Fraud. I believe that Martin Luther also wrote on the subject.

Poisoning The Wells: discrediting the sources used by your opponent. This is a variation of Ad Hominem.

Post hoc ergo propter hoc (after this, therefore because of this). This is the fallacy of assuming that A caused B simply because A happened prior to B. This is a conclusion that assumes that if ‘A’ occurred after ‘B’ then ‘B’ must have caused ‘A.’ A favorite example: “Most rapists read pornography when they were teenagers; obviously, pornography causes violence toward women.” The conclusion is invalid, because there can be a correlation between two phenomena without one causing the other. Often, this is because both phenomena may be linked to the same cause. In the example given, it is possible that some psychological factor — say, a frustrated sex drive — might cause both a tendency toward sexual violence and a desire for pornographic material, in which case the pornography would not be the true cause of the violence.
Another example:
I drank bottled water and now I am sick, so the water must have made me sick.
In this example the author assumes that if one event chronologically follows another the first event must have caused the second. But the illness could have been caused by the burrito the night before, a flu bug that had been working on the body for days, or a chemical spill across campus. There is no reason, without more evidence, to assume the water caused the person to be sick.
See:Cum hoc ergo propter hoc

Psychogenetic Fallacy: if you learn the psychological reason why your opponent likes an argument, then he’s biased, so his argument must be wrong.

Red herring. This means exactly what you think it means: introducing irrelevant facts or arguments to distract from the question at hand. For example, “The opposition claims that welfare dependency leads to higher crime rates — but how are poor people supposed to keep a roof over their heads without our help?” It is perfectly valid to ask this question as part of the broader debate, but to pose it as a response to the argument about welfare leading to crime is fallacious. (There is also an element of ad misericordiam in this example.)
This is a diversionary tactic that avoids the key issues, often by avoiding opposing arguments rather than addressing them. Example:
The level of mercury in seafood may be unsafe, but what will fishers do to support their families.
In this example the author switches the discussion away from the safety of the food and talks instead about an economic issue, the livelihood of those catching fish. While one issue may effect the other it does not mean we should ignore possible safety issues because of possible economic consequences to a few individuals.
It is not fallacious, however, to argue that benefits of one kind may justify incurring costs of another kind. In the example given, concern about providing shelter for the poor would not refute concerns about crime, but one could plausibly argue that a somewhat higher level of crime is a justifiable price given the need to alleviate poverty. This is a debatable point of view, but it is no longer a fallacious one.
The term red herring is sometimes used loosely to refer to any kind of diversionary tactic, such as presenting relatively unimportant arguments that will use up the other debaters’ speaking time and distract them from more important issues. This kind of a red herring is a wonderful strategic maneuver with which every debater should be familiar.

Reductio Ad Absurdum: showing that your opponent’s argument leads to some absurd conclusion. This is in general a reasonable and non-fallacious way to argue. If the issues are razor-sharp, it is a good way to completely destroy his argument. However, if the waters are a bit muddy, perhaps you will only succeed in showing that your opponent’s argument does not apply in all cases, That is, using Reductio Ad Absurdum is sometimes using the Fallacy Of The General Rule. However, if you are faced with an argument that is poorly worded, or only lightly sketched, Reductio Ad Absurdum may be a good way of pointing out the holes.
An example of why absurd conclusions are bad things:
Bertrand Russell, in a lecture on logic, mentioned that in the sense of material implication, a false proposition implies any proposition. A student raised his hand and said “In that case, given that 1 = 0, prove that you are the Pope”. Russell immediately replied, “Add 1 to both sides of the equation: then we have 2 = 1. The set containing just me and the Pope has 2 members. But 2 = 1, so it has only 1 member; therefore, I am the Pope.”

Reductive Fallacy (Oversimplification): over-simplifying. As Einstein said, everything should be made as simple as possible, but no simpler. Political slogans such as “Taxation is theft” fall in this category.

Reifying: an abstract thing is talked about as if it were concrete. (A possibly Bad Analogy is being made between concept and reality.) For example, “Nature abhors a vacuum.”

Short Term Versus Long Term: this is a particular case of the Excluded Middle. For example, “We must deal with crime on the streets before improving the schools.” (But why can’t we do some of both?) Similarly, “We should take the scientific research budget and use it to feed starving children.”

Slippery Slope Fallacy (Camel’s Nose): there is an old saying about how if you allow a camel to poke his nose into the tent, soon the whole camel will follow.
The fallacy here is the assumption that something is wrong because it is right next to something that is wrong. Or, it is wrong because it could slide towards something that is wrong.
For example, “Allowing abortion in the first week of pregnancy would lead to allowing it in the ninth month.” Or, “If we legalize marijuana, then more people will try heroin.” Or, “If I make an exception for you then I’ll have to make an exception for everyone.”
The Slippery Slope is a conclusion based on the premise that if A happens, then eventually through a series of small steps, through B, C,…, X, Y, Z will happen, too, basically equating A and Z. So, if we don’t want Z to occur A must not be allowed to occur either. A slippery slope argument is not always a fallacy. A slippery slope fallacy is an argument that says adopting one policy or taking one action will lead to a series of other policies or actions also being taken, without showing a causal connection between the advocated policy and the consequent policies. A popular example of the slippery slope fallacy is, “If we legalize marijuana, the next thing you know we’ll legalize heroin, LSD, and crack cocaine.” This slippery slope is a form of non sequitur, because no reason has been provided for why legalization of one thing leads to legalization of another. Tobacco and alcohol are currently legal, and yet other drugs have somehow remained illegal.
There are a variety of ways to turn a slippery slope fallacy into a valid (or at least plausible) argument. All you need to do is provide some reason why the adoption of one policy will lead to the adoption of another. For example, you could argue that legalizing marijuana would cause more people to consider the use of mind-altering drugs acceptable, and those people will support more permissive drug policies across the board. An alternative to the slippery slope argument is simply to point out that the principles espoused by your opposition imply the acceptability of certain other policies, so if we don’t like those other policies, we should question whether we really buy those principles. For instance, if the proposing team argued for legalizing marijuana by saying, “individuals should be able to do whatever they want with their own bodies,” the opposition could point out that that principle would also justify legalizing a variety of other drugs — so if we don’t support legalizing other drugs, then maybe we don’t really believe in that principle.
Example: If we ban Hummers because they are bad for the environment eventually the government will ban all cars, so we should not ban Hummers.
In this example the author is equating banning Hummers with banning all cars, which is not the same thing.

Sophistry: this is very much like Euphemism, except that the word changes are done to claim a new, different concept rather than soften the old concept. For example, an American President may not legally conduct a war without a declaration of Congress. So, various Presidents have conducted “police actions”, “armed incursions”, “protective reaction strikes,” “pacification,” “safeguarding American interests,” and a wide variety of “operations”. Similarly, War Departments have become Departments of Defense, and untested medicines have become alternative medicines. The book “1984″ has some particularly good examples.

Special Pleading (Stacking The Deck): using the arguments that support your position, but ignoring or somehow disallowing the arguments against.
Uri Geller used special pleading when he claimed that the presence of unbelievers (such as stage magicians) made him unable to demonstrate his psychic powers.

Statement Of Conversion: the speaker says “I used to believe in X”.
This is simply a weak form of asserting expertise. The speaker is implying that he has learned about the subject, and now that he is better informed, he has rejected X. So perhaps he is now an authority, and this is an implied Argument From Authority.

“X” has not actually been countered unless there is agreement that the speaker has that expertise. In general, any bald claim always has to be buttressed.
For example, there are a number of Creationist authors who say they “used to be evolutionists”, but the scientists who have rated their books haven’t noticed any expertise about evolution.

Stolen Concept: using what you are trying to disprove. That is, requiring the truth of something for your proof that it is false. For example, using science to show that science is wrong. Or, arguing that you do not exist, when your existence is clearly required for you to be making the argument.
This is a relative of Begging The Question, except that the circularity there is in what you are trying to prove, instead of what you are trying to disprove.
It is also a relative of Reductio Ad Absurdum, where you temporarily assume the truth of something.

Straw Man(Fallacy Of Extension) attacking an exaggerated or caricatured version of your opponent’s position.
For example, the claim that “evolution means a dog giving birth to a cat.”
Another example: “Senator Jones says that we should not fund the attack submarine program. I disagree entirely. I can’t understand why he wants to leave us defenseless like that.”
On the Internet, it is common to exaggerate the opponent’s position so that a comparison can be made between the opponent and Hitler.
Straw man is the fallacy of refuting a caricatured or extreme version of somebody’s argument, rather than the actual argument they’ve made. Often this fallacy involves putting words into somebody’s mouth by saying they’ve made arguments they haven’t actually made, in which case the straw man argument is a veiled version of argumentum ad logicam. One example of a straw man argument would be to say, “Mr. Jones thinks that capitalism is good because everybody earns whatever wealth they have, but this is clearly false because many people just inherit their fortunes,” when in fact Mr. Jones had not made the “earnings” argument and had instead argued, say, that capitalism gives most people an incentive to work and save. The fact that some arguments made for a policy are wrong does not imply that the policy itself is wrong.
In debate, strategic use of a straw man can be very effective. A carefully constructed straw man can sometimes entice an unsuspecting opponent into defending a silly argument that he would not have tried to defend otherwise. But this strategy only works if the straw man is not too different from the arguments your opponent has actually made, because a really outrageous straw man will be recognized as just that. The best straw man is not, in fact, a fallacy at all, but simply a logical extension or amplification of an argument your opponent has made.

Tu quoque (“you too”). This is the fallacy of defending an error in one’s reasoning by pointing out that one’s opponent has made the same error. An error is still an error, regardless of how many people make it.
A charge of wrongdoing is answered by a rationalization that others have sinned, or might have sinned. For example, Bill borrows Jane’s expensive pen, and later finds he hasn’t returned it. He tells himself that it is okay to keep it, since she would have taken his.
War atrocities and terrorism are often defended in this way.
Similarly, some people defend capital punishment on the grounds that the state is killing people who have killed.
This is related to Ad Hominem (Argument To The Man).

Ethos

Ethos or the ethical appeal is based on the character, credibility, or reliability of the writer.There are many ways to establish good character and credibility as an author:

* Use only credible, reliable sources to build your argument and cite those sources properly.
* Respect the reader by stating the opposing position accurately.
* Establish common ground with your audience, often this can be done by acknowledging values and beliefs shared by those on both sides of the argument.
* If appropriate for the assignment, disclose why you are interested in this topic or what personal experiences you have had with the topic.
* Organize your argument in a logical, easy to follow manner. You can use the Toulmin method of logic or a simple pattern such as chronological order, most general to most detailed example, earliest to most recent example, etc.
* Proofread the argument. Too many careless grammar mistakes cast doubt on your character as a writer.

Pathos

Pathos or the emotional appeal appeals to an audience’s needs, values, and emotional sensibilities.

Argument emphasizes reason, but used properly there is often a place for emotion as well. Emotional appeals can use sources such as interviews and individual stories to paint a more legitimate and moving picture of reality or illuminate the truth. For example, telling the story of a single child who has been abused may make for a more persuasive argument than simply the number of children abused each year because it would give a human face to the numbers.

Only use an emotional appeal if it truly supports the claim you are making, not as a way to distract from the real issues of debate. An argument should never use emotion to misrepresent the topic or frighten people.

This information is a reformatting of the information from the following three sources:
The Online Writing Lab at Purdue: http://owl.english.purdue.edu/owl/resource/588/04/
Logical Fallacies and the Art of Debate:http://www.csun.edu/~dgw61315/fallacies.html
and A List Of Fallacious Arguments:http://www.don-lindsay-archive.org/skeptic/arguments.html