What is Debate?
Debate is, fortunately or not, an exercise in persuasion, wit, and rhetoric, not just logic.
Reasonable Expectations
In a debate format that limits each debater's speaking time, it is simply not reasonable to expect every proposition or conclusion to follow precisely and rigorously from a clear set of premises stated at the outset.
The Debater's Task
Instead, debaters have to bring together various facts, insights, and values that others share or can be persuaded to accept, and then show that those ideas lead more or less plausibly to a conclusion. Logic is a useful tool in this process, but it is not
The Judge's Task
Ultimately, the judge in a debate round has to decide which side's position is more plausible in light of the arguments given -- and the judge is required to pick one of those sides, even if logic alone dictates that "we do not know" is the answer to the
The "truth" of the matter- winning
Besides, let's be honest: debate is not just about finding truth, it's also about winning. If you think a fallacious argument can slide by and persuade the judge to vote for you, you're going to make it, right? The trick is not getting caught.
Why learn them?
I can think of a couple of good reasons. First, it makes you look smart. If you can not only show that the opposition has made an error in reasoning, but you can give that error a name as well (in Latin!), it shows that you can think on your feet and that
Removing an Argument due to Fallacious Reasoning
Second, and maybe more importantly, pointing out a logical fallacy is a way of removing an argument from the debate rather than just weakening it.
Exposing a Fallacy
The opposition points out that the voters supported X by a wide margin in last year's referendum. But this is just the logical fallacy of argumentum ad populum, appeal to public opinion!
Exposure Example
Tell everybody what the fallacy means and why it is wrong. But be careful -- you have to do this without sounding pedantic. You should state the fallacy's meaning as though you are reiterating what you assume your intelligent judge already knows. To conti
When to Commit Logical Fallacies
And there are some types of argument that are listed as logical fallacies in logic textbooks, but that are perfectly acceptable in the context of the rules of debate. The most important guideline for committing such fallacies yourself is to know when you
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 st
Argumentum ad hominem (argument directed at the person
Argumentum ad hominem (argument directed at the person). This 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 char
Argumentum ad ignorantiam (argument to ignorance).
Assumption that Lack of information proves validity of something (stupidity)
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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 co
Argumentum ad nauseam (argument to the point of disgust; i.e., by repitition)
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
Argumentum ad populum (argument or appeal to the public).
This is the fallacy of trying to prove something by showing that the public agrees with you. For an example, see above. This fallacy is nearly identical to argumentum ad numerum, which you should see for more details.
Argumentum ad verecundiam (argument or appeal to authority).
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,
Complex question.
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 b
Argumentum ad numerum (argument or appeal to number
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
Cum hoc ergo propter hoc (with this, therefore because of this)
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 thi
Circulus in demonstrando (circular argument
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
Dicto simpliciter (spoken simply, i.e., sweeping generalization).
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 an
Nature, appeal to.
Nature, appeal to. 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 functio
Naturalistic fallacy.
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
Non Sequitur ("It does not follow").
Non Sequitur ("It does not follow"). 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
Petitio principii (begging the question).
Petitio principii (begging the question). 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 r
Post hoc ergo propter hoc (after this, therefore because of this). T
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. A favorite example: "Most rapists read pornography when they were teenagers; obviously, pornography ca
Red herring
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 su
Slippery slope.
Slippery slope. 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 con
Straw man.
Straw man. This 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
Tu quoque ("you too").
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. For example, "They accuse us of making unju