Know Your Logical Fallacies
- False Dilemma -- A limited number of options (usually two) is given, while in reality there are more options. A false dilemma is an illegitimate use of the "or" operator. Putting issues or opinions into "black or white" terms is a common instance of this fallacy. (Example: Every person is either wholly good or wholly evil.)
- Argumentum Ad Ignorantiam (argument from ignorance) - Arguments of this form assume that since something has not been proven false, it is therefore
true. Conversely, such an argument may assume that since something has not been proven true, it is therefore false. (This is a special case of a false dilemma, since it assumes that all propositions must either be known to be true or known to be false.) (Example: Since scientists cannot prove that global warming will occur, it probably won't.)
- Argumentum ad consequentiam - The author points to the disagreeable consequences of holding a particular belief in order to show that this belief is false. (Ex. You can't agree that evolution is true, because if it were, then we would be no better than monkeys and apes.)
- Argumentum ad hominem - The person presenting an argument is attacked instead of the argument itself. This takes many forms. For example, the person's character, nationality or religion may be attacked. Alternatively, it may be pointed out that a person stands to gain from a favorable outcome. Or, finally, a person may be attacked by association, or by the company he keeps.
There are three major forms of Attacking the Person: (1) ad hominem (abusive): instead of attacking an assertion, the argument attacks the person who made the assertion. (2) ad hominem (circumstantial): instead of attacking an assertion the author points to the relationship between the person making the assertion and the person's circumstances. (3) ad hominem (tu quoque): this form of attack on the person notes that a person does not practice what he preaches.
- Appeal to Authority -- While sometimes it may be appropriate to cite an authority to support a point, often it is not. In particular, an appeal to authority is inappropriate
if: (i) the person is not qualified to have an expert opinion on the subject, (ii) experts in the field disagree on this issue; (iii) the authority was making a joke, drunk, or otherwise not being
serious. (Ex: Economist John Kenneth Galbraith argues that a tight money policy s the best cure for a recession. (Although Galbraith is an expert, not all economists agree on this point.))
- Hasty Generalization -- The size of the sample is too small to support the conclusion. (Ex. - I asked six of my friends what they thought of the new spending restraints and they agreed it is a good idea. The new restraints are therefore generally popular.)
- Coincidental Correlation (post hoc ergo propter hoc) -- The name in Latin means "after this therefore because of this". This describes the fallacy. An author commits the fallacy when it is assumed that because one thing follows another that the one thing was caused by the other. (Ex. Immigration to Alberta from Ontario increased. Soon after, the welfare rolls increased. Therefore, the increased immigration caused the increased welfare rolls.
- Fallacy of the Four Terms -- A standard form categorical syllogism contains four terms. (Ex. All dogs are animals, and all cats are mammals, so all dogs are mammals. The four terms are: dogs, animals, cats and mammals.) [Note: In many cases, the fallacy of four terms is a special case of equivocation. While the same word is used, the word has different meanings, and hence the word is treated as two different terms. Consider the following example: Only man is born free, and no women are men, therefore, no women are born free. The four terms are: man (in the sense of 'humanity'), man (in the sense of 'male'), women and born free.]
- Undistributed Middle -- The middle term in the premises of a standard form categorical syllogism never refers to all of the members of the category it describes. (Ex. All Russians were revolutionists, and all anarchists were revolutionist, therefore, all anarchists were Russians. The middle term is 'revolutionist'. While both Russians and anarchists share the common property of being revolutionist, they may be separate groups of revolutionists, and so we cannot conclude that anarchists are otherwise the same as Russians in any way.)
- Illicit Major -- The predicate term of the conclusion refers to all members of that category, but the same term in the premises refers only to some members of that category. (Ex. "All Texans are Americans, and no Californians are Texans, therefore, no Californians are Americans." The predicate term in the conclusion is 'Americans'. The conclusion refers to all Americans (every American is not a Californian, according to the conclusion). But the premises refer only to some Americans (those that are Texans).)
- Fallacy of Exclusion -- Important evidence which would undermine an inductive argument is excluded from consideration. The requirement that all relevant information be included is called the "principle of total evidence." (Ex: The Leafs will probably win this game because they've won nine out of their last ten. (Eight of the Leafs' wins came over last place teams, and today they are playing the first place
- Coincidental Correlation (post hoc ergo propter hoc) -- The name in Latin means "after this therefore because of this". This describes the fallacy. An author commits the fallacy when it is assumed that because one thing follows another that the one thing was caused by the other. (Ex. Immigration to Alberta from Ontario increased. Soon after, the welfare rolls increased. Therefore, the increased immigration caused the increased welfare rolls.)
- Joint Effect -- One thing is held to cause another when in fact both are the effect of a single underlying cause. This fallacy is often understood as a special case of post hoc ergo prompter hoc. (Ex. "You have a fever and this is causing you to break out in spots." (In fact, both symptoms are caused by the measles.))
- Genuine but Insignificant Cause - The object or event identified as the cause of an effect is a genuine cause, but insignificant when compared to the other causes of that event. Note that this fallacy does not apply when all other contributing causes are equally insignificant. Thus, it is not a fallacy to say that you helped cause defeat the Tory government because you voted Reform, for your vote had as much weight as any other vote, and hence is equally a part of the cause. (Ex. Smoking is causing air pollution in Edmonton. (True, but the effect of smoking is insignificant compared to the effect of auto exhaust.))
- Wrong Direction -- The relation between cause and effect is reversed. (Ex. The increase in AIDS was caused by more sex education. (In fact, the increase in sex education was caused by the spread of AIDS.))
- Complex Cause -- The effect is caused by a number of objects or events, of which the cause identified is only a part. A variation of this is the feedback loop where the effect is itself a part of the cause. (Ex. The accident was caused by the poor location of the bush. (True, but it wouldn't have occurred had the driver not been drunk and the pedestrian not been jaywalking.))
- Begging the Question (petitio principii) The truth of the conclusion is assumed by the premises. Often, the conclusion is simply restated in the premises in a slightly different form. In more difficult cases, the premise is a consequence of the conclusion. (We know that God exists, since the Bible says God exists. What the Bible says must be true, since God wrote it and God never lies. (Here, we must agree that God exists in order to believe that God wrote the Bible.))
- Irrelevant Conclusion (ignoratio elenchi) You should support the new housing bill. We can't continue to see people living in the streets; we must
have cheaper housing. (We may agree that housing s important even though we disagree with the housing bill.)
- Straw Man -- The author attacks an argument which is different from, and usually weaker than, the opposition's best argument. (Example: "We should have conscription. People don't want to enter the military because they find it an inconvenience. But they should realize that there are more important things than convenience.")
- Equivocation - The same word is used with two different meanings. (Example: "Criminal actions are illegal, and all murder trials are criminal actions, thus all murder trials are illegal." (Here the term "criminal actions" is used with two different meanings.)
- Amphiboly - An amphiboly occurs when the construction of a sentence allows it to have two different meanings. (Ex: Last night I shot a burglar in my pajamas.)
- Retrospective determinism -- the logical fallacy that because something happened, it was therefore bound to
happen. Example: "When he declared himself dictator of the Roman Republic, Julius Caesar was bound to be assassinated sooner or later.")
- Historian's fallacy -- a logical fallacy that occurs when one assumes that decision makers of the past viewed events from the same perspective and having the same information as those subsequently analyzing the decision. (Example: "Japan's surprise attack on Pearl Harbor should have been predictable in the United States because of the many indications that an attack was imminent.")
- Incomplete comparison -- a misleading argument popular in advertising. For example, an advertisement might say "product X is better". This is an incomplete assertion, so can't be refuted. A complete assertion, such as "product X sells for a lower price than product Y" or "the new product X lasts longer than the old product X" could be tested and possibly refuted.
- Juxtaposition -- logical fallacy on the part of the observer, where two items placed next to each other imply a correlation, when none is actually claimed. For example, an illustration of a politician and Adolf Hitler on the same page would imply that the politician had a common ideology with Hitler. Similarly, saying "Hitler was in favor of gun control, and so are you" would have the same effect.
- Middle Ground (argumentum ad temperantiam) -- The fallacy of assuming that the middle ground between extreme points of view is the logical place to find truth. The middle ground is most often invoked when there are sharply contrasting views which are deeply entrenched. (Example: "Opinions on abortion range from banning it altogether to allowing it on demand; thus the correct view is restricted abortions.")
- Non sequitur -- Latin for "it does not follow." In formal logic, an argument is a non sequitur if the conclusion does not follow from the premise. It should be stressed that in a non sequitur, the conclusion can be either true or false, but the argument is a fallacy because the conclusion does not follow from the premise. (Example: "If my hair looks nice, all people will love me.")
- Overwhelming Exception -- a generalization which is accurate, but comes with one or more qualifications which eliminate so many cases that what remains is much less impressive than the initial statement might have led one to assume. (Example: "All right, but apart from the sanitation, the medicine, education, wine, public order, irrigation, roads, a fresh water system, and public health, what have the Romans ever done for us?" (The attempted implication (fallaciously false in this case) is that the Romans did nothing for us). This is a quotation from Monty Python's Life of Brian.)
- Poisoning the well -- a logical fallacy where adverse information about someone is
preemptively presented to an audience, with the intention of discrediting or ridiculing everything that person is about to say. Poisoning the well is a special case of argumentum ad hominem. (Example: "Don't listen to what he says, he's a lawyer.")
- Reification -- treating a concept, an abstraction, as if it were a real, concrete thing. (Example: "Their ideology is going to ruin this country.")
- Statistical special pleading -- a logical fallacy which occurs when the interpretation of the relevant statistic is "massaged" by looking for ways to reclassify or requantify data from one portion of results, but not applying the same scrutiny to other categories. (Example: "A study of teenage gang members has shown that 40% of those who are atheists have been convicted of a violent offence. This is hundreds of times the number of people in the general population who are convicted of such offences. This clearly shows that atheism leads to violence.")
- Tu quoque -- (Latin for "You, too" or "You, also") is a line of one's defensive argument based on the concept that the adversary party also engages (or has engaged in the past) in the act for which one is accused by that party. This argumentative move works by showing that a criticism or objection applies equally to the person making it. It can be considered an ad hominem argument, since it focuses on the opposite party itself, rather than its positions.
- Suppressed correlative -- (A type of argument which tries to redefine a correlative (two mutually exclusive options) so that one alternative encompasses the other, i.e. making one alternative impossible. (Example: "All dogs are black when it is dark. Therefore, Lassie is a black dog because it is dark outside.")
- Appeal to consequences -- an argument that concludes a premise (typically a belief) to be either true or false based on whether the premise leads to desirable or undesirable consequences. (Example: ""Real estate markets will continue to rise this year because home owners enjoy the capital gains.")
- Argument from ignorance -- (argumentum ad ignorantiam a logical fallacy in which it is claimed that that a premise is true only because it has not been proven false, or that a premise is false only because it has not been proven true. (Example: "A thousand-ton piece of metal could never float. Ships need to be made of wood, or at least something that floats.")
- Argumentum ad populum -- (Latin for "appeal to the people") a fallacious argument that concludes a proposition to be true because many or all people believe it; it alleges that "If many believe so, it is so." (Example: "It's silly for you to claim that Hitler would not have attacked the United States if they hadn't entered World War II. Everyone knows that he planned to conquer the world.")
These argument tactics are dishonest. Christians would be sinning to
use these. These are here for you to correct an opponent toward
honesty. If you have used these in the past, confession would be
"Be ye wise as serpents, yet as innocent as doves."