For specific popular misconceptions, see List of common misconceptions.
In reasoning to argue a claim, a fallacy is reasoning that is evaluated as logically incorrect and that undermines the logical validity of the argument and permits its recognition as unsound. Regardless of their soundness, all registers and manners of speech can demonstrate fallacies.
Because of their variety of structure and application, fallacies are challenging to classify so as to satisfy all practitioners. Fallacies can be classified strictly by either their structure or content, such as classifying them as formal fallacies or informal fallacies, respectively. The classification of informal fallacies may be subdivided into categories such as linguistic, relevance through omission, relevance through intrusion, and relevance through presumption. On the other hand, fallacies may be classified by the process by which they occur, such as material fallacies (content), verbal fallacies (linguistic), and again formal fallacies (error in inference). In turn, material fallacies may be placed into the more general category of informal fallacies as formal fallacies may be clearly placed into the more precise category of logical or deductive fallacies[clarification needed]. Yet, verbal fallacies may be placed in either informal or deductive classifications; compare equivocation which is a word or phrase based ambiguity, e. g. "he is mad", which may refer to either him being angry or clinically insane, to the fallacy of composition which is premise and inference based ambiguity, e. g. "this must be a good basketball team because each of its members is an outstanding player".
Faulty inferences in deductive reasoning are common formal or logical fallacies. As the nature of inductive reasoning is based on probability, a fallacious inductive argument or one that is potentially misleading, is often classified as "weak".
The conscious or habitual use of fallacies as rhetorical devices are prevalent in the desire to persuade when the focus is more on communication and eliciting common agreement rather than the correctness of the reasoning. One may consider the effective use of a fallacy by an orator as clever but by the same token the reasoning of that orator should be recognized as unsound, and thus the orator's claim, supported by an unsound argument, will be regarded as unfounded and dismissed.
Main article: Formal fallacy
A formal fallacy is an error in logic that can be seen in the argument's form. All formal fallacies are specific types of non sequiturs.
A propositional fallacy is an error in logic that concerns compound propositions. For a compound proposition to be true, the truth values of its constituent parts must satisfy the relevant logical connectives that occur in it (most commonly: <and>, <or>, <not>, <only if>, <if and only if>). The following fallacies involve inferences whose correctness is not guaranteed by the behavior of those logical connectives, and hence, which are not logically guaranteed to yield true conclusions.
Types of propositional fallacies:
A quantification fallacy is an error in logic where the quantifiers of the premises are in contradiction to the quantifier of the conclusion.
Types of Quantification fallacies:
Formal syllogistic fallacies
Syllogistic fallacies – logical fallacies that occur in syllogisms.
Main article: Informal fallacy
Informal fallacies – arguments that are fallacious for reasons other than structural (formal) flaws and usually require examination of the argument's content.
- Appeal to the stone (argumentum ad lapidem) – dismissing a claim as absurd without demonstrating proof for its absurdity.
- Argument from ignorance (appeal to ignorance, argumentum ad ignorantiam) – assuming that a claim is true because it has not been or cannot be proven false, or vice versa.
- Argument from incredulity (appeal to common sense) – "I cannot imagine how this could be true; therefore, it must be false."
- Argument from repetition (argumentum ad nauseam, argumentum ad infinitum) – signifies that it has been discussed extensively until nobody cares to discuss it anymore; sometimes confused with proof by assertion
- Argument from silence (argumentum ex silentio) – assuming that a claim is true based on the absence of textual or spoken evidence from an authoritative source, or vice versa.
- Argument to moderation (false compromise, middle ground, fallacy of the mean, argumentum ad temperantiam) – assuming that the compromise between two positions is always correct.
- Begging the question (petitio principii) – providing what is essentially the conclusion of the argument as a premise.
- Circular reasoning (circulus in demonstrando) – the reasoner begins with what he or she is trying to end up with; sometimes called assuming the conclusion.
- Circular cause and consequence – the consequence of the phenomenon is claimed to be its root cause.
- Continuum fallacy (fallacy of the beard, line-drawing fallacy, sorites fallacy, fallacy of the heap, bald man fallacy) – improperly rejecting a claim for being imprecise.
- Correlative-based fallacies
- Divine fallacy (argument from incredulity) – arguing that, because something is so incredible/amazing/ununderstandable, it must be the result of superior, divine, alien or paranormal agency.
- Double counting – counting events or occurrences more than once in probabilistic reasoning, which leads to the sum of the probabilities of all cases exceeding unity.
- Equivocation – the misleading use of a term with more than one meaning (by glossing over which meaning is intended at a particular time).
- Ambiguous middle term – a common ambiguity in syllogisms in which the middle term is equivocated.
- Definitional retreat – changing the meaning of a word to deal with an objection raised against the original wording.
- Motte-and-bailey fallacy – The arguer conflates two similar positions, one modest and easy to defend (the "motte") and one much more controversial (the "bailey"). The arguer advances the controversial position, but when challenged, they insist that they are only advancing the more modest position.
- Ecological fallacy – inferences about the nature of specific individuals are based solely upon aggregate statistics collected for the group to which those individuals belong.
- Etymological fallacy – reasoning that the original or historical meaning of a word or phrase is necessarily similar to its actual present-day usage.
- Fallacy of accent – a specific type of ambiguity that arises when the meaning of a sentence is changed by placing an unusual prosodic stress, or when, in a written passage, it's left unclear which word the emphasis was supposed to fall on.
- Fallacy of composition – assuming that something true of part of a whole must also be true of the whole.
- Fallacy of division – assuming that something true of a thing must also be true of all or some of its parts.
- False attribution – an advocate appeals to an irrelevant, unqualified, unidentified, biased or fabricated source in support of an argument.
- Fallacy of quoting out of context (contextomy, quote mining) – refers to the selective excerpting of words from their original context in a way that distorts the source's intended meaning.
- False authority (single authority) – using an expert of dubious credentials or using only one opinion to sell a product or idea. Related to the appeal to authority fallacy.
- False dilemma (false dichotomy, fallacy of bifurcation, black-or-white fallacy) – two alternative statements are held to be the only possible options when in reality there are more.
- False equivalence – describing a situation of logical and apparent equivalence, when in fact there is none.
- Fallacy of many questions (complex question, fallacy of presuppositions, loaded question, plurium interrogationum) – someone asks a question that presupposes something that has not been proven or accepted by all the people involved. This fallacy is often used rhetorically so that the question limits direct replies to those that serve the questioner's agenda.
- Fallacy of the single cause (causal oversimplification) – it is assumed that there is one, simple cause of an outcome when in reality it may have been caused by a number of only jointly sufficient causes.
- Furtive fallacy – outcomes are asserted to have been caused by the malfeasance of decision makers.
- Gambler's fallacy – the incorrect belief that separate, independent events can affect the likelihood of another random event. If a fair coin lands on heads 10 times in a row, the belief that it is "due to the number of times it had previously landed on tails" is incorrect.
- Historian's fallacy – 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. (Not to be confused with presentism, which is a mode of historical analysis in which present-day ideas, such as moral standards, are projected into the past.)
- Historical fallacy – a set of considerations is thought to hold good only because a completed process is read into the content of the process which conditions this completed result.
- Homunculus fallacy – a "middle-man" is used for explanation; this sometimes leads to regressive middle-men. Explains without actually explaining the real nature of a function or a process. Instead, it explains the concept in terms of the concept itself, without first defining or explaining the original concept. Explaining thought as something produced by a little thinker, a sort of homunculus inside the head, merely explains it as another kind of thinking (as different but the same).
- Inflation of conflict – The experts of a field of knowledge disagree on a certain point, so the scholars must know nothing, and therefore the legitimacy of their entire field is put to question.
- If-by-whiskey – an argument that supports both sides of an issue by using terms that are selectively emotionally sensitive.
- Incomplete comparison – insufficient information is provided to make a complete comparison.
- Inconsistent comparison – different methods of comparison are used, leaving one with a false impression of the whole comparison.
- Intentionality fallacy – the insistence that the ultimate meaning of an expression must be consistent with the intention of the person from whom the communication originated (e.g. a work of fiction that is widely received as a blatant allegory must necessarily not be regarded as such if the author intended it not to be so.)
- Ignoratio elenchi (irrelevant conclusion, missing the point) – an argument that may in itself be valid, but does not address the issue in question.
- Kettle logic – using multiple, jointly inconsistent arguments to defend a position.[dubious– discuss]
- Ludic fallacy – the belief that the outcomes of non-regulated random occurrences can be encapsulated by a statistic; a failure to take into account unknown unknowns in determining the probability of events taking place.
- McNamara fallacy (quantitative fallacy) – making a decision based only on quantitative observations, discounting all other considerations.
- Mind projection fallacy – one's subjective judgments are "projected" to be inherent properties of an object, rather than being related to personal perception of that object.
- Moralistic fallacy – inferring factual conclusions from purely evaluative premises in violation of fact–value distinction. For instance, inferring is from ought is an instance of moralistic fallacy. Moralistic fallacy is the inverse of naturalistic fallacy defined below.
- Moving the goalposts (raising the bar) – argument in which evidence presented in response to a specific claim is dismissed and some other (often greater) evidence is demanded.
- Naturalistic fallacy – inferring evaluative conclusions from purely factual premises in violation of fact–value distinction. For instance, inferring ought from is (sometimes referred to as the is-ought fallacy) is an instance of naturalistic fallacy. Also naturalistic fallacy in a stricter sense as defined in the section "Conditional or questionable fallacies" below is an instance of naturalistic fallacy. Naturalistic fallacy is the inverse of moralistic fallacy.
- Naturalistic fallacy fallacy (anti-naturalistic fallacy) – inferring an impossibility to infer any instance of ought from is from the general invalidity of is-ought fallacy, mentioned above. For instance, is does imply ought for any proposition , although the naturalistic fallacy fallacy would falsely declare such an inference invalid. Naturalistic fallacy fallacy is an instance of argument from fallacy.
- Nirvana fallacy (perfect solution fallacy) – solutions to problems are rejected because they are not perfect.
- Onus probandi – from Latin "onus probandi incumbit ei qui dicit, non ei qui negat" the burden of proof is on the person who makes the claim, not on the person who denies (or questions the claim). It is a particular case of the argumentum ad ignorantiam fallacy, here the burden is shifted on the person defending against the assertion. Also known as shifting the burden of proof.
- Post hoc ergo propter hoc Latin for "after this, therefore because of this" (faulty cause/effect, coincidental correlation, correlation without causation) – X happened, then Y happened; therefore X caused Y. The Loch Ness Monster has been seen in this loch. Something tipped our boat over; it's obviously the Loch Ness Monster.
- Proof by assertion – a proposition is repeatedly restated regardless of contradiction; sometimes confused with argument from repetition (argumentum ad infinitum, argumentum ad nauseam)
- Prosecutor's fallacy – a low probability of false matches does not mean a low probability of some false match being found.
- Proving too much – using a form of argument that, if it were valid, could be used to reach an additional, undesirable conclusion.
- Psychologist's fallacy – an observer presupposes the objectivity of his own perspective when analyzing a behavioral event.
- Red herring – a speaker attempts to distract an audience by deviating from the topic at hand by introducing a separate argument the speaker believes is easier to speak to.
- Referential fallacy – assuming all words refer to existing things and that the meaning of words reside within the things they refer to, as opposed to words possibly referring to no real object or that the meaning of words often comes from how we use them.
- Regression fallacy – ascribes cause where none exists. The flaw is failing to account for natural fluctuations. It is frequently a special kind of post hoc fallacy.
- Reification (concretism, hypostatization, or the fallacy of misplaced concreteness) – a fallacy of ambiguity, when an abstraction (abstract belief or hypothetical construct) is treated as if it were a concrete, real event or physical entity. In other words, it is the error of treating as a "real thing" something that is not a real thing, but merely an idea.
- Retrospective determinism – the argument that because an event has occurred under some circumstance, the circumstance must have made its occurrence inevitable.
- Special pleading – a proponent of a position attempts to cite something as an exemption to a generally accepted rule or principle without justifying the exemption.
- Wrong direction – cause and effect are reversed. The cause is said to be the effect and vice versa.
Faulty generalizations – reach a conclusion from weak premises. Unlike fallacies of relevance, in fallacies of defective induction, the premises are related to the conclusions yet only weakly buttress the conclusions. A faulty generalization is thus produced.
- Accident – an exception to a generalization is ignored.
- No true Scotsman – makes a generalization true by changing the generalization to exclude a counterexample.
- Cherry picking (suppressed evidence, incomplete evidence) – act of pointing at individual cases or data that seem to confirm a particular position, while ignoring a significant portion of related cases or data that may contradict that position.
- Survivorship bias – a small number of survivors of a given process are actively promoted while completely ignoring a large number of failures
- False analogy – an argument by analogy in which the analogy is poorly suited.
- Hasty generalization (fallacy of insufficient statistics, fallacy of insufficient sample, fallacy of the lonely fact, hasty induction, secundum quid, converse accident, jumping to conclusions) – basing a broad conclusion on a small sample or the making of a determination without all of the information required to do so.
- Inductive fallacy – A more general name to some fallacies, such as hasty generalization. It happens when a conclusion is made of premises that lightly support it.
- Misleading vividness – involves describing an occurrence in vivid detail, even if it is an exceptional occurrence, to convince someone that it is a problem.
- Overwhelming exception – an accurate generalization that comes with qualifications that eliminate so many cases that what remains is much less impressive than the initial statement might have led one to assume.
- Thought-terminating cliché – a commonly used phrase, sometimes passing as folk wisdom, used to quell cognitive dissonance, conceal lack of thought-entertainment, move on to other topics etc. but in any case, end the debate with a cliché—not a point.
Red herring fallacies
A red herring fallacy, one of the main subtypes of fallacies of relevance, is an error in logic where a proposition is, or is intended to be, misleading in order to make irrelevant or false inferences. In the general case any logical inference based on fake arguments, intended to replace the lack of real arguments or to replace implicitly the subject of the discussion.
Red herring – argument given in response to another argument, which is irrelevant and draws attention away from the subject of argument. See also irrelevant conclusion.
- Ad hominem – attacking the arguer instead of the argument.
- Poisoning the well – a subtype of ad hominem presenting adverse information about a target person with the intention of discrediting everything that the target person says.
- Abusive fallacy – verbally abusing the opponent rather than arguing about the originally proposed argument.
- Appeal to motive – dismissing an idea by questioning the motives of its proposer.
- Kafka-trapping – A sophistical and unfalsifiable form of argument that attempts to overcome an opponent by inducing a sense of guilt and using the opponent's denial of guilt as further evidence of guilt.
- Tone policing – focusing on emotion behind (or resulting from) a message rather than the message itself as a discrediting tactic.
- Traitorous critic fallacy (ergo decedo) – a critic's perceived affiliation is portrayed as the underlying reason for the criticism and the critic is asked to stay away from the issue altogether.
- Appeal to authority (argumentum ad verecundiam) – an assertion is deemed true because of the position or authority of the person asserting it.
- Appeal to consequences (argumentum ad consequentiam) – the conclusion is supported by a premise that asserts positive or negative consequences from some course of action in an attempt to distract from the initial discussion.
- Appeal to emotion – an argument is made due to the manipulation of emotions, rather than the use of valid reasoning.
- Appeal to fear – an argument is made by increasing fear and prejudice towards the opposing side
- Appeal to flattery – an argument is made due to the use of flattery to gather support.
- Appeal to pity (argumentum ad misericordiam) – an argument attempts to induce pity to sway opponents.
- Appeal to ridicule – an argument is made by presenting the opponent's argument in a way that makes it appear ridiculous.
- Appeal to spite – an argument is made through exploiting people's bitterness or spite towards an opposing party.
- Wishful thinking – a decision is made according to what might be pleasing to imagine, rather than according to evidence or reason.
- Appeal to nature – judgment is based solely on whether the subject of judgment is 'natural' or 'unnatural'. (Sometimes also called the "naturalistic fallacy", but is not to be confused with the other fallacies by that name)
- Appeal to novelty (argumentum novitatis, argumentum ad antiquitatis) – a proposal is claimed to be superior or better solely because it is new or modern.
- Appeal to poverty (argumentum ad Lazarum) – supporting a conclusion because the arguer is poor (or refuting because the arguer is wealthy). (Opposite of appeal to wealth.)
- Appeal to tradition (argumentum ad antiquitatem) – a conclusion supported solely because it has long been held to be true.
- Appeal to wealth (argumentum ad crumenam) – supporting a conclusion because the arguer is wealthy (or refuting because the arguer is poor). (Sometimes taken together with the appeal to poverty as a general appeal to the arguer's financial situation.)
- Argumentum ad baculum (appeal to the stick, appeal to force, appeal to threat) – an argument made through coercion or threats of force to support position.
- Argumentum ad populum (appeal to widespread belief, bandwagon argument, appeal to the majority, appeal to the people) – a proposition is claimed to be true or good solely because majority or many people believe it to be so.
- Association fallacy (guilt by association and honor by association) – arguing that because two things share (or are implied to share) some property, they are the same.
- Bare assertion fallacy, also known as ipse dixit – a claim that is presented as true without support, as self-evidently true, or as dogmatically true. This fallacy relies on the implied expertise of the speaker or on an unstated truism.
- Bulverism (psychogenetic fallacy) – inferring why an argument is being used, associating it to some psychological reason, then assuming it is invalid as a result. It is wrong to assume that if the origin of an idea comes from a biased mind, then the idea itself must also be a falsehood.
- Chronological snobbery – a thesis is deemed incorrect because it was commonly held when something else, clearly false, was also commonly held.
- Fallacy of relative privation ("not as bad as") – dismissing an argument or complaint due to the existence of more important problems in the world, regardless of whether those problems bear relevance to the initial argument. For example, First World problem.
- Genetic fallacy – a conclusion is suggested based solely on something or someone's origin rather than its current meaning or context.
- Judgmental language – insulting or pejorative language to influence the recipient's judgment.
- Moralistic fallacy (the inverse of naturalistic fallacy) – statements about what is, on the basis of claims about what ought to be.
- Naturalistic fallacy (is–ought fallacy, naturalistic fallacy) – claims about what ought to be, on the basis of statements about what is.
- Pooh-pooh – dismissing an argument perceived unworthy of serious consideration.
- Straw man fallacy – an argument based on misrepresentation of an opponent's position.
- Texas sharpshooter fallacy – improperly asserting a cause to explain a cluster of data.
- Tu quoque ("you too", appeal to hypocrisy, I'm rubber and you're glue, Whataboutism) – the argument states that a certain position is false or wrong or should be disregarded because its proponent fails to act consistently in accordance with that position.
- Two wrongs make a right – occurs when it is assumed that if one wrong is committed, an "equal but opposite" wrong will cancel it out.
- Vacuous truth – a claim that is technically true but meaningless, in the form of claiming that no A in B has C, when there are no A in B. For example, claiming that no mobile phones in the room are on when there are no mobile phones in the room at all.
Conditional or questionable fallacies
- Broken window fallacy – an argument that disregards lost opportunity costs (typically non-obvious, difficult to determine or otherwise hidden) associated with destroying property of others, or other ways of externalizing costs onto others. For example, an argument that states breaking a window generates income for a window fitter, but disregards the fact that the money spent on the new window cannot now be spent on new shoes.
- Definist fallacy – involves the confusion between two notions by defining one in terms of the other.
- Naturalistic fallacy – attempts to prove a claim about ethics by appealing to a definition of the term "good" in terms of either one or more claims about natural properties (sometimes also taken to mean the appeal to nature) or God's will.
- Slippery slope (thin edge of the wedge, camel's nose) – asserting that a relatively small first step inevitably leads to a chain of related events culminating in some significant impact/event that should not happen, thus the first step should not happen. It is, in its essence, an appeal to probability fallacy.
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Three Critical Questions
The goals of rational criticism can be formulated by three more or less distinct questions.
(1) Is the reasoning well-formulated?
(2) Is the reasoning well-connected?
(3) Is the reasoning well-established?
Questions of formulation relate to the attempt to understand exactly what the person is saying and the background against which he or she is saying it. It is here that we sometimes find that a person has gotten off on the wrong foot by misrepresenting a person's views, or conflating different kinds of statements, or misconstruing the nature of the problem at issue.
Questions of connection relate to the attempt to understand how what a person is saying is relevant to the conclusion s/he appears to be drawing. It is here that we sometimes find that a person has said things that are logically irrelevant to the question at issue, but which might nevertheless persuade people on non logical grounds (e.g. by confusing them, or appealing to their emotions or self-interest.)
The question whether a person's reasoning is well-established raises issues of confirmation and credibility. It is here that we sometimes find that the reasoning being offered rests on weak principles or reasons that have not been adequately supported.
What Is a Fallacy?
Some errors in reasoning are simply the result of the fact that people aren't perfect. Sometimes we hit the wrong letter on the keyboard, sometimes we get on the wrong bus, sometimes we swing at the ball and miss, and sometimes we draw the wrong conclusion. Stuff like this just happens. Sometimes, however, our errors are the result of a fundamental problem that will cause us to repeat the same mistakes over and over. E.g., you may not know how to type; you may not understand how to read the bus schedule, or you may have a bad batting stance. In logic, mistakes due to some fundamental problem are called fallacies. A fallacy is a systematic error, as opposed to a random error. We usually say that fallacies are a systematic error in reasoning , which is true, but only if you understand reasoning very broadly as the process of formulating, connecting, and establishing the reasons for your conclusions. (Some people think of reasoning as just the process of connecting reasons to conclusions, and only some of the fallacies relate to this.) We are going to begin developing the tools of rational criticism by discussing some basic fallacies relevant to the categories introduced above. Later on we will discuss more specific sorts of fallacies and other problems that are not simple enough to be defined as fallacies at all.
Two Fallacies of Formulation: Straw Person, False Alternatives
Two of the most common mistakes people make in formulating their reasoning are: (1) misrepresenting views they want to refute; (2) misrepresenting the nature of the problem they are addressing. The first mistake is traditionally called the Straw Person Fallacy. An important form of the second mistake is called False Alternatives (or False Dilemma).
Def.: Attempting to discredit a view by criticizing a weak version of it or the reason given in support of it.
The idea behind Straw Person is that if you can get people to think that a "straw" version (think of a scarecrow) of what a person is saying is the real version, then you can appear to be refuting what the person has said without actually addressing it at all. This sounds like it takes a lot of cunning and deceit, but the fact is that we all do it spontaneously. It takes a great deal of discipline and intellectual honesty to listen carefully to what someone is saying and represent it accurately before going on to criticize it. If you feel from the beginning that a person is wrong, you will naturally think that it isn't worth your time to listen very carefully to what they are saying.
E.g. 1: Barb feels ill one morning and asks Butch to inform the instructor that this is the reason why she will not be in class. Butch carries out Barb's request as follows: "Barb isn't here today because she didn't feel like coming." Obviously, Barb would not be happy with this version of her absence because Butch has stated in a way that is easy to criticize. Now it sounds more like an unexcused absence than an excused one.
E.g. 2.: Butch claims that, generally speaking, women are far more concerned about their personal appearances than men, pointing out that most make-up is sold to women and that popular women's clothing is often very uncomfortable, but women buy it because it is attractive to men.. Barb replies: "That's totally ridiculous, not all women wear that kind of stuff and lots of men are using make-up these days, too." This is a straw person because Butch didn't make a claim about all women or men. Understood in this way, Butch's statements are obviously false.
E.g 3: Butch is beside himself with anger because the construction workers across the street have been shouting lewd comments at him all week. Barbs says, "Well, if you don't like it maybe you should stop running around in your Speedo." Butch responds, "That is just so unfair! I have a right to be comfortable in my own yard." Here, Butch has interpreted Barb's remark as an implicit criticism of his Speedo outfit, rather than simply a piece of advise about how to avoid being teased. (This example has an interesting connection to Innunendo.)
E.g. 4: A defense attorney argues that, even though expert testimony has established that the defendant knew that she was breaking the law when she bombed the abortion clinic, she should be found not guilty by reason of insanity. The attorney reminds the jury that a person is legally insane when they do not know the difference between right and wrong. The fact that she knew the difference between what is legal and illegal does not mean she knew the difference between right and wrong, for the two issues are distinct. If it were always wrong to do things that are illegal, then civil disobedience (disobeying the law for a higher moral cause) would be impossible. The prosecuting attorney responds to this line of reasoning as follows: "The defense has asked us to find the defendant not guilty on the grounds that bombing an abortion clinic is essentially like an act of civil disobedience. It is difficult to think of anything more preposterous than to compare this act of sheer violence with peaceful acts of civil disobedience." Again, in this example, the defense attorney would object to the prosecutions characterization of her reasoning. This version does sound preposterous, though the original reasoning was not.
Def.: Misformulating a problem as a choice between two (or more) alternatives, when there exist other alternatives that have not been considered.
False Alternatives is essentially a problem of oversimplification. Its usual form is: "You have a choice between A and B. A is obviously unacceptable, therefore you must do B." This is actually a perfectly acceptable form of inference known as the Disjunctive Syllogism. The problem is that the choice itself may be misrepresented; i.e., the real choice might be between A, B, C &D. Also, sometimes more than one option can be available to you at the same time. It is worth pointing out that choices are not always expressed as "Either...or." Sometimes people will say "If you don't do B, then A is going to happen." If you think about it, you'll see that this is just another way of saying that you have a choice between A and B.
E.g. 1: "I don't want to hear anything more about your mother being black and your father being white. Sooner or later you are going to have to admit that you are a black man and accept the responsibilities that go along with that." A statement like this rests on characterizing the problem of understanding ones true nature as a choice between two simple alternatives, black and non black. It does not allow that a person may regard neither category as an accurate reflection of who they are.
E.g. 2: In response to the problem of illegal immigration from Mexico someone might argue that the only way to deal with the problem of illegal immigration is to massively increase our border controls, and vigorously pursue and deport all illegal aliens. This characterizes the situation as a choice between two alternatives; viz., increased law enforcement or an unacceptably high level of illegal immigrants. However, these may not be the only alternatives. For example, one might suggest that the problem would be better addressed by increasing trade with Mexico, thereby improving the economy and reducing people's incentive to immigrate.
Two Fallacies of Connection: Red Herring, Ad Hominem
Under certain situations it is possible to say things that are logically irrelevant to the issue at hand, but which nevertheless succeed in having some effect on the way in which people understand it. There are two standard ways of doing this. (1) Introduce an issue that is superficially similar to the one being discussed; (2) Focus attention on the speaker rather than what the speaker is saying. The first of these fallacies is called Red Herring. The second is called Ad Hominem. (These, by the way, are not totally distinct fallacies; technically, an Ad Hominem is a Red Herring.)
Def.: Distracting attention from an issue by introducing an irrelevant issue or one that is only superficially related to the one being discussed. The mechanism of this fallacy is similar to that of Straw Person. Both depend on creating something that has a deceptive resemblance to the genuine article. Also, like Straw Person, Red Herring does not depend on intentionally deceiving someone. More often than not people commit Red Herring because they don't know or can't keep their minds focused on the real issue.
E.g. 1: Suppose people in our community are drawing graffiti on public buildings. I point out that it is an illegal activity and suggest that we should make a more concerted effort to apprehend and prosecute the offenders. You respond as follows: "But graffiti is art and the people who do it are artists." This is a Red Herring, because the artistic value of graffiti is unrelated to the question of its legality. However, because you are still talking about graffiti and saying something that I might disagree with, you may succeed in distracting my attention from the real issue.
E.g., 2: Suppose I claim that homosexuality is a disease and that the proper approach is to try to cure it rather than to integrate it into our society. To this you respond "That's outrageous. People don't choose to be homosexuals, they are born that way." This, too, may succeed in distracting me from my point, but it is irrelevant to the question whether homosexuality is a disease. Many people are born with diseases.
E.g., 3: Suppose we are members of a jury trying to determine whether the evidence we have just heard is sufficient to convict the defendant of robbing a bank. In his defense, you point out that the defendant is destitute, that his family was hungry, and that he was wrongly fired from his previous job. This is a specific kind of Red Herring called Appeal to Emotion. What you have said is irrelevant to the question whether he committed the crime, but it may influence the decision by making us feel sorry for him.
Def.: Any attempt to discredit a view by calling attention to the character, actions or personal circumstances of those who hold it rather than the reasoning they provide in support of it.
"Ad hominem" is Latin for "against the person." Anything that involves an attack on a person's character we call an Abusive Ad Hominem. Anything that appeals to a person's unique circumstances we call a Circumstantial ad Hominem. These are both fallacious for the simple reason that the personal character and circumstances of the individual reasoner are logically irrelevant to the question whether the reasoning itself is any good.
E.g. 1: Suppose a very rich person like Ross Perot gives a speech in which he argues that it is not such a great thing to be rich and that, in fact, people who are poor are likely to live better lives on the whole. Of course, we want to respond: "Oh, sure, that's easy for you to say, but I don't see you giving away all your money." This is an abusive Ad Hominem, because we are attacking Perot as a hypocrite rather than examining the argument itself. It is also known at the fallacy of Tu Quoque, which is Latin for "You do it, too."
E.g. 2: Suppose I am a member of an ethnic minority and I am arguing against affirmative action. You may be inclined to give me the following advice: "You are foolish to adopt this view. Don't you realize that as a member of an ethnic minority you stand to benefit from affirmative actions programs?" This is a Circumstantial Ad Hominem because you are using my personal circumstances in order to try to discredit my view or encourage me to adopt a different one. You do not actually examine the reasoning I have produced.
Two Fallacies of Establishment: Appeal to Questionable Authority and Questionable Analogy
There are many ways to make it seem as if our claims are more credible than they actually are. Two of the most common are: (1) Appealing to a questionable source of authoritative information; (2) Making superficial comparisons. The first of these is called Appeal to Questionable Authority. The second is called Questionable Analogy.
Appeal to Questionable Authority
Def.: Accepting or recommending a claim on the basis of an appeal to an authoritative source of information when there are reasons for doubting the source in question. This fallacy has many forms. We sometimes make inappropriate appeals to the authority of common opinion and tradition. We also sometimes appeal to individual organizations and people as authoritative sources even though we are uncertain who they are, what their claim to authority is, or whether they should be trusted. Questionable authority is a fallacy that is often misused, however, as our first example shows.
E.g. 1: Suppose you explain to me why the Federal Reserve Board is going to raise interest rates. You tell me that the Feds are concerned about rising inflation, and that raising interest rates tend to reduce consume borrowing, which reduces consumer demand, which reduces the amount that manufacturers can charge for their products, which reduces inflation. Now, suppose I respond as follows: "Are you some sort of authority on economics or something? Why should I listen to you?" Now, this would not be a legitimate thing for me to say. You never claimed to be an authority. You gave me some reasoning and I have ignored it, preferring to talk about your personal qualifications instead. In fact, I have just committed an Abusive Ad Hominem. The moral of this example is: An appeal to Questionable Authority occurs only when somebody uses authority in order to legitimate something they say. If they do not use authority, then it is illegitimate to raise the issue.
E.g. 2: Suppose I own a music store and am also an accomplished musician on several instruments. I sell pianos but no string instruments like guitars or cellos. You ask me what's the best instrument to start out learning on and I say, unequivocally, a piano. When you ask me why, I say that you can trust me on this. I play all sorts of instruments and the piano is by far the best one to start out on. In fact, I explain, that's why I only sell pianos. Notice that in this situation I haven't given you a single reason for believing the piano is the best instrument to learn on except my authority. But, knowing that my livelihood depends on the sale of pianos, it would be wrong to accept my appeal to authority. I have what is commonly called a "conflict of interest."
E.g. 3: Suppose the issue is whether we should allow prayer in public schools. You argue that we should because disallowing prayer is a violation of religious freedom, and that individual freedom is what the United States stands for. I say we should not because everybody who understands the Constitution realizes that the separation of church and state is fundamental. I have made an appeal to Questionable Authority because the sole reason I give is that "everybody who understands the Constitution" agrees with me. I have not identified who these people are. Also I have made an appeal to the Constitution as a kind of time-honored document that should not be tampered with. This an appeal to the authority of tradition. I haven't given any actual reason for thinking the Constitution can not be amended which, of course, it can.
Def.: Any reasoning based on the assumption that two or more things that are alike in one respect must be alike in other respects when there are independent grounds for doubting this. We draw an analogy whenever we claim that two different things are similar in significant respects. However, sometimes we draw an analogy when there is, in fact, an important difference that may undermine the conclusion the analogy is meant to support. For example, it would be ridiculous for me to say "Gina and Lisa are both girls. Gina is five feet tall, so I guess Lisa is probably five feet tall, too." Here, you would want to point out that there is no principle that say "If X is a girl, then X is five feet tall." Another way of making this point is to accuse me of a questionable analogy by observing that just because Gina and Lisa are similar in one physical respect (viz., sex) doesn't mean they are similar in other physical respects (viz., height). This depends on other factors like age and genetic makeup.
However, there are other examples that are not quite as easy to deal with. Sometimes we feel that someone has drawn a questionable analogy, but it takes some effort and careful thinking to say why. Consider the following example:
E.g. 1 "I think people who use the toilet stall designed for people with physical disabilities should be fined. After all, that's what we do to people who use their parking spaces." This sounds ridiculous, and what you want to say is that parking facilities are one thing and toilet facilities are another. But why? What's the real difference between them such that it makes sense to fine non disabled people for using one, but not the other? The answer here might be that it is a much more serious inconvenience to disabled people to use their parking facilities than to use their bathroom facilities. But until you make this point clearly, your claim that there is a false or questionable analogy has not been adequately supported.
Sometimes we might think that someone has drawn a questionable analogy when in fact it is a perfectly good analogy. Suppose you heard the following argument
E.g. 2 "The right way for people to get things from others is to pay for them. So, if what we want is from the people of Brazil is for them not to destroy their rain forests, we should pay them not to do it." This sounds a little bit peculiar, but does it rest on a false analogy? Are these different kinds of wants, such that it makes sense to pay for one and not the other? You might say that they are because ordinarily when you pay for something you get ownership of it, but in fact that's not actually true. What about renting? Or you might say that it just doesn't make any sense to pay people not to destroy their own property. But that's only true given that you have no personal interest in it being maintained. This analogy is, in fact, not an obviously bad one at all. Many economists take it very seriously.
Questionable analogies are very common, but it is also common to accuse people of drawing a questionable analogy when they are actually pointing out an interesting similarity between two otherwise very different things. So whenever you charge someone with drawing a questionable analogy, be sure that the problem is not just a failure of intellect or imagination on your part.