Logic

Fallacies of Ambiguity (Types)

Accent Fallacies Equivocation Fallacies Straw Man Fallacy

Fallacies of Presumption (Types)

- Affirming the Consequent - Arguing from Ignorance - Begging the question / circular reasoning - Complex question fallacy - Cum Hoc Fallacy - False dilemma / bifurcation fallacy - Hasty generalization fallacy - No True Scotsman Fallacy - Post Hoc Fallacy - Slippery Slope Fallacy - Sweeping Generalization Fallacy - Subjectivist Fallacy - Tu Quoquo Fallacy

Fallacies of Ambiguity

Arguments that commit fallacies of ambiguity, such as equivocation or the straw man fallacy, manipulate language in misleading ways

Fallacies of Presumption

Arguments that commit fallacies of presumption contain false premises, and so fail to establish their conclusion. For example, arguments based on a false dilemma or circular arguments both commit fallacies of presumption.

Informal / Inductive Fallacy

An inductive fallacy is less formal than a deductive fallacy. They are simply "arguments" which appear to be inductive arguments, but the premises do not provided enough support for the conclusion. In such cases, even if the premises were true, the conclusion would not be more likely to be true. Example -- Premise 1: Having just arrived in Ohio, I saw a white squirrel. Conclusion: All Ohio Squirrels are white. (While there are many, many squirrels in Ohio, the white ones are very rare).

Irrelevant Appeals

Irrelevant appeals attempt to sway the listener with information that, though persuasive, is irrelevant to the matter at hand. There are many different types of irrelevant appeal, many different ways of influencing what people think without using evidence. Each is a different type of fallacy of relevance. Appeal to: - Antiquity/Tradition

Deductive Argument

A deductive argument is an argument such that the premises provide (or appear to provide) complete support for the conclusion. A good deductive argument is known as a valid argument and is such that if all its premises are true, then its conclusion must be true. If all the argument is valid and actually has all true premises, then it is known as a sound argument. If it is invalid or has one or more false premises, it will be unsound. Valid or Sound / Invalid or Unsound

Straw Man Fallacy

A straw man argument is one that misrepresents a position in order to make it appear weaker than it actually is, refutes this misrepresentation of the position, and then concludes that the real position has been refuted. This, of course, is a fallacy, because the position that has been claimed to be refuted is different to that which has actually been refuted; the real target of the argument is untouched by it. Example (1) Trinitarianism holds that three equals one. (2) Three does not equal one. Therefore: (3) Trinitarianism is false. This is an example of a straw man argument because its first premise misrepresents trinitarianism, its second premise attacks this misrepresentation of trinitarianism, and its conclusion states that trinitarianism is false. Trinitarianism, of course, does not hold that three equals one, and so this argument demonstrates nothing concerning its truth.

Appeal to Novelty

An appeal to novelty is the opposite of an appeal to antiquity. Appeals to novelty assume that the newness of an idea is evidence of its truth. They are thus also related to the bandwagon fallacy. That an idea is new certainly doesn't entail that it is true. Many recent ideas have no merit whatsoever, as history has shown; every idea, including those that we now reject as absurd beyond belief, were new at one time. Some ideas that are new now will surely go the same way. Examples (1) String theory is the most recent development in physics. Therefore: (2) String theory is true. (1) Religion is old-fashioned; atheism is a much more recent development. Therefore: (2) Atheism is true. Each of these arguments commits the appeal to novelty fallacy. The former takes the newness of string theory to be evidence that string theory is true; the latter takes the newness of atheism to be evidence that atheism is true. Merely being a new idea, of course, is no guarantee of truth. The newness of string theory and atheism alone, then, should not be taken to be evidence of the truth of these two positions.

Appeal to Wealth

The appeal to wealth fallacy is committed by any argument that assumes that someone or something is better simply because they are wealthier or more expensive. It is the opposite of the appeal to poverty. In a society in which we often aspire to wealth, where wealth is held up as that to which we all aspire, it is easy to slip into thinking that everything that is associated with wealth is good. Rich people can be thought to deserve more respect than poorer people; more expensive goods can be thought to be better than less expensive goods solely because of their price. This is a fallacy. Wealth need not be associated with all that is good, and all that is good need not be associated with wealth. Examples (1) My computer cost more than yours. Therefore: (2) My computer is better than yours. (1) Warren is richer than Wayne. Therefore: (2) Warren will make a better dinner-guest than Wayne. Each of these arguments takes an association with money to be a sign of superiority. They therefore both commit the appeal to wealth fallacy.

Fallacy

A fallacy is, very generally, an error in reasoning. This differs from a factual error, which is simply being wrong about the facts. To be more specific, a fallacy is an "argument" in which the premises given for the conclusion do not provide the needed degree of support.

Gambler's Fallacy

Belief that independent phenomena are subject to statistical "runs" The gambler's fallacy is the fallacy of assuming that short-term deviations from probability will be corrected in the short-term. Faced with a series of events that are statistically unlikely, say, a serious of 9 coin tosses that have landed heads-up, it is very tempting to expect the next coin toss to land tails-up. The past series of results, though, has no effect on the probability of the various possible outcomes of the next coin toss. Example (1) This coin has landed heads-up nine times in a row. Therefore: (2) It will probably land tails-up next time it is tossed. This inference is an example of the gambler's fallacy. When a fair coin is tossed, the probability of it landing heads-up is 50%, and the probability of it landing tails-up is 50%. These probabilities are unaffected by the results of previous tosses. The gambler's fallacy appears to be a reasonable way of thinking because we know that a coin tossed ten times is very unlikely to land heads-up every time. If we observe a tossed coin landing heads-up nine times in a row we therefore infer that the unlikely sequence will not be continued, that next time the coin will land tails-up. In fact, though, the probability of the coin landing heads-up on the tenth toss is exactly the same as it was on the first toss. Past results don't bear on what will happen next.

Appeal to Poverty

The appeal to poverty fallacy is committed when it is assumed that a position is correct because it is held by the poor. The opposite of the appeal to poverty is the appeal to wealth. There is sometimes a temptation to contrast the excesses, greed, and immorality of the rich with the simplicity, virtue, and humility of the poor. This can give rise to arguments that commit the appeal to poverty fallacy. The poverty of a person that holds a view, of course, does not establish that the view is true; even the poor can sometimes err in their beliefs. Example (1) The working classes respect family and community ties. Therefore: (2) Respect for family and community ties is virtuous. This argument is an appeal to poverty because it takes the association between a position and poverty as evidence of the goodness of that position. There is, however, no necessary connection between a position being associated with poverty and its being true, and so the argument is fallacious.

False Dilemma / Bifurcation Fallacy

The bifurcation fallacy is committed when a false dilemma is presented, i.e. when someone is asked to choose between two options when there is at least one other option available. Of course, arguments that restrict the options to more than two but less than there really are are similarly fallacious. Examples (1) Either a Creator brought the universe into existence, or the universe came into existence out of nothing. (2) The universe didn't come into existence out of nothing (because nothing comes from nothing). Therefore: (3) A Creator brought the universe into existence. The first premise of this argument presents a false dilemma; it might be thought that the universe neither was brought into existence by a Creator nor came into existence out of nothing, because it existed from eternity. Another example emerged when George W Bush launched the war on terror, insisting that other nations were either for or against America in her campaign, excluding the quite real possibility of neutrality. Complex questions are subtle forms of false dilemma. Questions such as "Are you going to admit that you're wrong?" implicitly restrict the options to either being wrong and admitting it or being wrong or not admitting it, thus excluding the option of not being wrong.

Moralistic Fallacy

The moralistic fallacy is the opposite of the naturalistic fallacy. The naturalistic fallacy moves from descriptions of how things are to statements of how things ought to be, the moralistic fallacy does the reverse. The moralistic fallacy moves from statements about how things ought to be to statements about how things are; it assumes that the world is as it should be. This, sadly, is a fallacy; sometimes things aren't as they ought to be. Examples Have you ever crossed a one-way street without looking in both directions? If you have, reasoning that people shouldn't be driving the wrong way up a one way street so there's no risk of being run over from that direction, then you've committed the moralistic fallacy. Sometimes things aren't as they ought to be. Sometimes people drive in directions that they shouldn't. The rules of the road don't necessarily describe actual driving practices.

Fallacies of Relevance

Arguments that commit fallacies of relevance rely on premises that aren't relevant to the truth of the conclusion. The various irrelevant appeals are all fallacies of relevance, as are ad hominems.

Red Herring

The red herring is as much a debate tactic as it is a logical fallacy. It is a fallacy of distraction, and is committed when a listener attempts to divert an arguer from his argument by introducing another topic. This can be one of the most frustrating, and effective, fallacies to observe. The fallacy gets its name from fox hunting, specifically from the practice of using smoked herrings, which are red, to distract hounds from the scent of their quarry. Just as a hound may be prevented from catching a fox by distracting it with a red herring, so an arguer may be prevented from proving his point by distracting him with a tangential issue. Example Many of the fallacies of relevance can take red herring form. An appeal to pity, for example, can be used to distract from the issue at hand: "You may think that he cheated on the test, but look at the poor little thing! How would he feel if you made him sit it again?"

Naturalistic Fallacy

There are two fundamentally different types of statement: statements of fact which describe the way that the world is, and statements of value which describe the way that the world ought to be. The naturalistic fallacy is the alleged fallacy of inferring a statement of the latter kind from a statement of the former kind. Arguments cannot introduce completely new terms in their conclusions. The argument, "(1) All men are mortal, (2) Socrates is a man, therefore (3) Socrates is a philosopher" is clearly invalid; the conclusion obviously doesn't follow from the premises. This is because the conclusion contains an idea—that of being a philosopher—that isn't contained in the premises; the premises say nothing about being a philosopher, and so cannot establish a conclusion about being a philosopher. Arguments that commit the naturalistic fallacy are arguably flawed in exactly the same way. An argument whose premises merely describe the way that the world is, but whose conclusion describes the way that the world ought to be, introduce a new term in the conclusion in just the same way as the above example. If the premises merely describe the way that the world is then they say nothing about the way that the world ought to be. Such factual premises cannot establish any value judgement; you can't get an 'ought' from an 'is'. Examples (1) Feeling envy is only natural. Therefore: (2) There's nothing wrong with feeling envy. This argument moves from a statement of fact to a value judgement, and therefore commits the naturalistic fallacy. The argument's premise simply describes the way that the world is, asserting that it is natural to feel envious. To describe the way that the world is, though, is to say nothing of the way that it ought to be. The argument's conclusion, then, which is value judgement, cannot be supported by its premises. It is important to note that much respectable moral argument commits the naturalistic fallacy. Whether arguments of the form described here are fallacious is controversial. If they are, then the vast majority of moral philosophy commits a basic logical error.

Argument

an argument consists of one or more premises and one conclusion. A premise is a statement (a sentence that is either true or false) that is offered in support of the claim being made, which is the conclusion (which is also a sentence that is either true or false).

Hasty Generalization

A hasty generalisation draws a general rule from a single, perhaps atypical, case. It is the reverse of a sweeping generalisation. Example (1) My Christian / atheist neighbour is a real grouch. Therefore: (2) Christians / atheists are grouches. This argument takes an individual case of a Christian or atheist, and draws a general rule from it, assuming that all Christians or atheists are like the neighbour. The conclusion that it reaches hasn't been demonstrated, because it may well be that the neighbour is not a typical Christian or atheist, and that the conclusion drawn is false.

Formal / Deductive Fallacy

A pattern of reasoning rendered invalid by a flaw in its logical structure that can neatly be expressed in a standard logic system. The conclusion does not follow from the premises in the manner described. A deductive fallacy is a deductive argument that is invalid (it is such that it could have all true premises and still have a false conclusion). Example -- Premise 1: If Portland is the capital of Maine, then it is in Maine. Premise 2: Portland is in Maine. Conclusion: Portland is the capital of Maine. (Portland is in Maine, but Augusta is the capital. Portland is the largest city in Maine, though.)

Sweeping Generalization Fallacy

A sweeping generalisation applies a general statement too broadly. If one takes a general rule, and applies it to a case to which, due to the specific features of the case, the rule does not apply, then one commits the sweeping generalisation fallacy. This fallacy is the reverse of a hasty generalisation, which infers a general rule from a specific case. Example (1) Children should be seen and not heard. (2) Little Wolfgang Amadeus is a child. Therefore: (3) Little Wolfgang Amadeus shouldn't be heard. No matter what you think of the general principle that children should be seen and not heard, a child prodigy pianist about to perform is worth listening to; the general principle doesn't apply.

Accent Fallacies

Accent fallacies are fallacies that depend on where the stress is placed in a word or sentence. The meaning of a set of words may be dramatically changed by the way they are spoken, without changing any of the words themselves. Accent fallacies are a type of equivocation. Example Suppose that two people are debating whether a rumour about the actions of a third person is true. The first says, "I can imagine him doing that; it's possible." The second replies, "Yes, it's possible to imagine him doing that." This looks like agreement. If however, the second person stresses the word imagine, then this appearance vanishes; "Yes, it's possible to imagine him doing that." This now sounds like a pointed comment meaning that though it may just about be possible to imagine him doing that, there's no way that he would actually do it.

Appeal to Antiquity/Tradition

An appeal to antiquity is the opposite of an appeal to novelty. Appeals to antiquity assume that older ideas are better, that the fact that an idea has been around for a while implies that it is true. This, of course, is not the case; old ideas can be bad ideas, and new ideas can be good ideas. We therefore can't learn anything about the truth of an idea just by considering how old it is. Example (1) Religion dates back many thousands of years (whereas atheism is a relatively recent development). Therefore: (2) Some form of religion is true. This argument is an appeal to antiquity because the only evidence that it offers in favour of religion is its age. There are many old ideas, of course, that are known to be false: e.g. that the Earth is flat, or that it is the still centre of the solar system. It therefore could be the case that the premise of this argument is true (that religion is older than atheism) but that its conclusion is nevertheless false (that no religion is true). We need a lot more evidence about religion (or any other theory) than how old it is before we can be justified in accepting it as true. Appeals to antiquity are therefore fallacious.

Appeal to Force

An appeal to force is an attempt to persuade using threats. Its Latin name, "argumentum ad baculum", literally means "argument with a cudgel". Disbelief, such arguments go, will be met with sanctions, perhaps physical abuse; therefore, you'd better believe. Appeals to force are thus a particularly cynical type of appeal to consequences, where the unpleasant consequences of disbelief are deliberately inflicted by the arguer. Of course, the mere fact that disbelief will be met with sanctions is only a pragmatic justification of belief; it is not evidence that the resultant belief will be true. Appeals to force are therefore fallacious. Example (1) If you don't accept that the Sun orbits the Earth, rather than the other way around, then you'll be excommunicated from the Church. Therefore: (2) The Sun orbits the Earth, rather than the other way around. This argument, if it can properly be called an argument, makes no attempt to provide evidence for its conclusion; whether or not you'll be excommunicated for disbelieving the geocentric model has no bearing on whether the geocentric model is true. The argument therefore commits the appeal to force fallacy.

Appeal to Pity

An appeal to pity attempts to persuade using emotion—specifically, sympathy—rather than evidence. Playing on the pity that someone feels for an individual or group can certainly affect what that person thinks about the group; this is a highly effective, and so quite common, fallacy. This type of argument is fallacious because our emotional responses are not always a good guide to truth; emotions can cloud, rather than clarify, issues. We should base our beliefs upon reason, rather than on emotion, if we want our beliefs to be true. Examples Pro-life campaigners have recently adopted a strategy that capitalises on the strength of appeals to pity. By showing images of aborted foetuses, anti-abortion materials seek to disgust people, and so turn them against the practice of abortion. A BBC News article, Jurors shown graphic 9/11 images, gives another clear example of an appeal to pity: "A US jury has been shown graphic images of people burned to death in the 11 September 2001 attack on the Pentagon. The jurors will decide whether al-Qaeda plotter Zacarias Moussaoui should be executed or jailed for life... Prosecutors hope such emotional evidence will persuade the jury to opt for the death penalty."

Begging the Question / Circular Reasoning

An argument is circular if its conclusion is among its premises, if it assumes (either explicitly or not) what it is trying to prove. Such arguments are said to beg the question. A circular argument fails as a proof because it will only be judged to be sound by those who already accept its conclusion. Anyone who rejects the argument's conclusion should also reject at least one of its premises (the one that is the same as its conclusion), and so should reject the argument as a whole. Anyone who accepts all of the argument's premises already accepts the argument's conclusion, so can't be said to have been persuaded by the argument. In neither case, then, will the argument be successful. Example (1) The Bible affirms that it is inerrant. (2) Whatever the Bible says is true. Therefore: (3) The Bible is inerrant. This argument is circular because its conclusion—The Bible is inerrant—is the same as its second premise—Whatever the Bible says is true. Anyone who would reject the argument's conclusion should also reject its second premise, and, along with it, the argument as a whole. Real-World Examples The above argument is a straightforward, real-world example of a circular argument. Other examples can be a little more subtle. Typical examples of circular arguments include rights-claims: e.g., "I have a right to say what I want, therefore you shouldn't try to silence me"; "Women have a right to choose whether to have an abortion or not, therefore abortion should be allowed"; "The unborn has a right to life, therefore abortion is immoral". Having a right to X is the same as other people having an obligation to allow you to have X, so each of these arguments begs the question, assuming exactly what it is trying to prove.

Inductive Argument

An inductive argument is an argument such that the premises provide (or appear to provide) some degree of support (but less than complete support) for the conclusion. A good inductive argument is known as a strong (or "cogent") inductive argument. It is such that if the premises are true, the conclusion is likely to be true. Strong / Weak Inductive Argument Premise 1: Most American cats are domestic house cats. Premise 2: Bill is an American cat. Conclusion: Bill is domestic house cat.

Appeal to Popularity

Appeals to popularity suggest that an idea must be true simply because it is widely held. This is a fallacy because popular opinion can be, and quite often is, mistaken. Hindsight makes this clear: there were times when the majority of the population believed that the Earth is the still centre of the universe, and that diseases are caused by evil spirits; neither of these ideas was true, despite its popularity. Example (1) Most people believe in a god or 'higher power'. Therefore: (2) God, or at least a higher power, must exist. This argument is an appeal to popularity because it suggests that God must exist based solely on the popularity of belief in God. An atheist could, however, accept the premise of this argument (the claim that belief in God is widespread) but reject its conclusion without inconsistency.

Appeal to Consequences

Argument from the consequence of something An appeal to consequences is an attempt to motivate belief with an appeal either to the good consequences of believing or the bad consequences of disbelieving. This may or may not involve an appeal to force. Such arguments are clearly fallacious. There is no guarantee, or even likelihood, that the world is the way that it is best for us for it to be. Belief that the world is the way that it is best for us for it to be, absent other evidence, is therefore just as likely to be false as true. Examples Appeal to Good Consequences: (1) If believe in God then you'll find a kind of fulfilment in life that you've never felt before. Therefore: (2) God exists. Appeal to Bad Consequences: (1') If you don't believe in God then you'll be miserable, thinking that life doesn't have any meaning. Therefore: (2) God exists. Both of these arguments are fallacious because they provide no evidence for their conclusions; all they do is appeal to the consequences of belief in God. In the case of the first argument, the positive consequences of belief in God are cited as evidence that God exists. In the case of the second argument, the negative consequences of disbelief in God are cited as evidence that God exists. Neither argument, though, provides any evidence for Santa's existence. The consequences of a belief are rarely a good guide to its truth. Both arguments are therefore fallacious. Real-World Examples Each of the arguments above features in real-world discussions of God's existence. In fact, they have been developed into an argument called Pascal's Wager, which openly advocates belief in God based on its good consequences, rather than on evidence that it is true. Another example occurs in the film The Matrix. There Neo is asked whether he believes in fate; he says that he doesn't. He is then asked why, and replies, "I don't like the thought that I'm not in control." This is not an appeal to evidence, but to the unpleasantness of believing in fate: Fate would imply that the world is a way that I don't want it to be, therefore there is no such thing.

Weak Analogy

Arguments by analogy rest on a comparison. Their logical structure is this: (1) A and B are similar. (2) A has a certain characteristic. Therefore: (3) B must have that characteristic too. For example, William Paley's argument from design suggests that a watch and the universe are similar (both display order and complexity), and therefore infers from the fact that watches are the product of intelligent design that the universe must be a product of intelligent design too. An argument by analogy is only as strong as the comparison on which it rests. The weak analogy fallacy (or "false analogy", or "questionable analogy") is committed when the comparison is not strong enough. Example The example of an argument by analogy given above is controversial, but is arguably an example of a weak analogy. Are the similarities in the kind and degree of order exhibited by watches and the universe sufficient to support an inference to a similarity in their origins?

Arguing from Ignorance

Arguments from ignorance infer that a proposition is true from the fact that it is not known to be false. Not all arguments of this form are fallacious; if it is known that if the proposition were not true then it would have been disproven, then a valid argument from ignorance may be constructed. In other cases, though, arguments from ignorance are fallacious. Example (1) No one has been able to disprove the existence of God. Therefore: (2) God exists. This argument is fallacious because the non-existence of God is perfectly consistent with no one having been able to prove God's non-existence.

Ad Hominem (Personal Attack)

It is important to note that the label "ad hominem" is ambiguous, and that not every kind of ad hominem argument is fallacious. In one sense, an ad hominem argument is an argument in which you offer premises that you the arguer don't accept, but which you know the listener does accept, in order to show that his position is incoherent (as in, for example, the Euthyphro dilemma). There is nothing wrong with this type of argument ad hominem. The other type of ad hominem argument is a form of genetic fallacy. Arguments of this kind focus not on the evidence for a view but on the character of the person advancing it; they seek to discredit positions by discrediting those who hold them. It is always important to attack arguments, rather than arguers, and this is where arguments that commit the ad hominem fallacy fall down. Example (1) William Dembski argues that modern biology supports the idea that there is an intelligent designer who created life. (2) Dembski would say that because he's religious. Therefore: (3) Modern biology doesn't support intelligent design. This argument rejects the view that intelligent design is supported by modern science based on a remark about the person advancing the view, not by engaging with modern biology. It ignores the argument, focusing only on the arguer; it is therefore a fallacious argument ad hominem.

Slippery Slope

Slippery slope arguments falsely assume that one thing must lead to another. They begin by suggesting that if we do one thing then that will lead to another, and before we know it we'll be doing something that we don't want to do. They conclude that we therefore shouldn't do the first thing. The problem with these arguments is that it is possible to do the first thing that they mention without going on to do the other things; restraint is possible. Example (1) If you buy a Green Day album, then next you'll be buying Buzzcocks albums, and before you know it you'll be a punk with green hair and everything. (2) You don't want to become a punk. Therefore: (3) You shouldn't buy a Green Day album. This argument commits the slippery slope fallacy because it is perfectly possible to buy a Green Day album without going on to become a punk; we could buy the album and then stop there. The conclusion therefore hasn't been proven, because the argument's first premise is false.

Appeal to Authority

Something is right/good/correct because an authority figure said so. An appeal to authority is an argument from the fact that a person judged to be an authority affirms a proposition to the claim that the proposition is true. Appeals to authority are always deductively fallacious; even a legitimate authority speaking on his area of expertise may affirm a falsehood, so no testimony of any authority is guaranteed to be true. However, the informal fallacy occurs only when the authority cited either (a) is not an authority, or (b) is not an authority on the subject on which he is being cited. If someone either isn't an authority at all, or isn't an authority on the subject about which they're speaking, then that undermines the value of their testimony. Example (1) Marilyn vos Savant says that no philosopher has ever successfully resolved the problem of evil. Therefore: (2) No philosopher has ever successfully resolved the problem of evil. This argument is fallacious because Marilyn vos Savant, though arguably an authority, is not an authority on the philosophy of religion. Her judgement that no philosopher has ever successfully resolved the problem of evil therefore carries little evidential weight; if there were a philosopher somewhere that had successfully resolved the problem then there's a good chance that Marilyn vos Savant wouldn't know about it. Her testimony is therefore insufficient to establish the conclusion of the argument.

Post Hoc Fallacy

The Latin phrase "post hoc ergo propter hoc" means, literally, "after this therefore because of this." The post hoc fallacy is committed when it is assumed that because one thing occurred after another, it must have occurred as a result of it. Mere temporal succession, however, does not entail causal succession. Just because one thing follows another does not mean that it was caused by it. This fallacy is closely related to the cum hoc fallacy. Example (1) Most people who are read the last rites die shortly afterwards. Therefore: (2) Priests are going around killing people with magic words! This argument commits the post hoc fallacy because it infers a causal connection based solely on temporal order. Real-World Examples One example of the post hoc flaw is the evidence often given for the efficacy of prayer. When someone reasons that as they prayed for something and it then happened, it therefore must have happened because they prayed for it, they commit the post hoc fallacy. The correlation between the prayer and the event could result from coincidence, rather than cause, so does not prove that prayer works. Superstitions often arise from people committing the post hoc fallacy. Consider, for example, a sportsman who adopts a pre-match ritual because one time he did something before a game he got a good result. The reasoning here is presumably that on the first occasion the activity preceded the success, so the activity must have contributed to the success, so repeating the activity is likely to lead to a recurrence of the success. This is a classic example of the post hoc fallacy in action.

Bandwagon Fallacy

The bandwagon fallacy is committed by arguments that appeal to the growing popularity of an idea as a reason for accepting it as true. They take the mere fact that an idea suddenly attracting adherents as a reason for us to join in with the trend and become adherents of the idea ourselves. This is a fallacy because there are many other features of ideas than truth that can lead to a rapid increase in popularity. Peer pressure, tangible benefits, or even mass stupidity could lead to a false idea being adopted by lots of people. A rise in the popularity of an idea, then, is no guarantee of its truth. The bandwagon fallacy is closely related to the appeal to popularity; the difference between the two is that the bandwagon fallacy places an emphasis on current fads and trends, on the growing support for an idea, whereas the appeal to popularity does not. Example (1) Increasingly, people are coming to believe that Eastern religions help us to get in touch with our true inner being. Therefore: (2) Eastern religions help us to get in touch with our true inner being. This argument commits the bandwagon fallacy because it appeals to the mere fact that an idea is fashionable as evidence that the idea is true. Mere trends in thought are not reliable guides to truth, though; the fact that Eastern religions are becoming more fashionable does not imply that they are true.

Cum Hoc Fallacy

The complex question fallacy is committed when a question is asked (a) that rests on a questionable assumption, and (b) to which all answers appear to endorse that assumption. Examples "Have you stopped beating your wife?" This is a complex question because it presupposes that you used to beat your wife, a presupposition that either answer to the question appears to endorse. "Are you going to admit that you're wrong?" Answering yes to this question is an admission of guilt. Answering no to the question implies that the accused accepts that he is in the wrong, but will not admit it. No room is left to protest one's innocence. This is therefore a complex question, and a subtle false dilemma.

Complex Question

The complex question fallacy is committed when a question is asked (a) that rests on a questionable assumption, and (b) to which all answers appear to endorse that assumption. Examples "Have you stopped beating your wife?" This is a complex question because it presupposes that you used to beat your wife, a presupposition that either answer to the question appears to endorse. "Are you going to admit that you're wrong?" Answering yes to this question is an admission of guilt. Answering no to the question implies that the accused accepts that he is in the wrong, but will not admit it. No room is left to protest one's innocence. This is therefore a complex question, and a subtle false dilemma.

Fallacist's Fallacy

The fallacist's fallacy involves rejecting an idea as false simply because the argument offered for it is fallacious. Having examined the case for a particular point of view, and found it wanting, it can be tempting to conclude that the point of view is false. This, however, would be to go beyond the evidence. It is possible to offer a fallacious argument for any proposition, including those that are true. One could argue that 2+2=4 on the basis of an appeal to authority: "Simon Singh says that 2+2=4". Or one could argue that taking paracetamol relieves headaches using a post hoc: "I took the paracetamol and then my headache went away; it worked!" Each of these bad arguments has a true conclusion. A proposition therefore should not be dismissed because one argument offered in its favour is faulty. Example "People argue that there must be an afterlife because they just can't accept that when we die that's it. This is an appeal to consequences; therefore there is no life after death."

Affirming the Consequent

The fallacy of affirming the consequent is committed by arguments that have the form: (1) If A then B (2) B Therefore: (3) A The first premise of such arguments notes that if a state of affairs A obtained then a consequence B would also obtain. The second premise asserts that this consequence B does obtain. The faulty step then follows: the inference that the state of affairs A obtains. Examples (1) If Fred wanted to get me sacked then he'd go and have a word with the boss. (2) There goes Fred to have a word with the boss. Therefore: (3) Fred wants to get me sacked. This argument is clearly fallacious; there are any number of reasons why Fred might be going to have a word with the boss that do not involve him wanting to get me sacked: e.g. to ask for a raise, to tell the boss what a good job I'm doing, etc. Fred's going to see the boss therefore doesn't show that he's trying to get me fired. (1) If Zeus was a real, historical figure, but the Catholic Church covered up his existence, then we wouldn't have any evidence of a historical Zeus today. (2) We don't have any evidence of a historical Zeus today. Therefore: (3) Zeus was a real, historical figure, but the Catholic Church covered up his existence.

Fallacy of Composition

The fallacy of composition is the fallacy of inferring from the fact that every part of a whole has a given property that the whole also has that property. This pattern of argument is the reverse of that of the fallacy of division. It is not always fallacious, but we must be cautious in making inferences of this form. Examples A clear case of the fallacy of composition is this: (1) Every song on the album lasts less than an hour. Therefore: (2) The album lasts less than an hour. Obviously, an album consisting of many short tracks may itself be very long. Not all arguments of this form are fallacious, however. Whether or not they are depends on what property is involved. Some properties, such as lasting less than an hour, may be possessed by every part of something but not by the thing itself. Others, such as being bigger than a bus, must be possessed by the whole if possessed by each part.

Fallacy of Division

The fallacy of division is the reverse of the fallacy of composition. It is committed by inferences from the fact that a whole has a property to the conclusion that a part of the whole also has that property. Like the fallacy of composition, this is only a fallacy for some properties; for others, it is a legitimate form of inference. Example An example of an inference that certainly does commit the fallacy of division is this: (1) Water is liquid. Therefore: (2) H2O molecules are liquid. This argument, in attributing a macro-property of water, liquidity, to its constituent parts, commits the fallacy of division. Though water is liquid, individual molecules are not. Note, however, that an argument with the same logical form but inferring from the fact that a computer is smaller than a car that every part of the computer is smaller than a car would not be fallacious; arguments with this logical form need not be problematic.

Equivocation Fallacy

The fallacy of equivocation is committed when a term is used in two or more different senses within a single argument. For an argument to work, words must have the same meaning each time they appear in its premises or conclusion. Arguments that switch between different meanings of words equivocate, and so don't work. This is because the change in meaning introduces a change in subject. If the words in the premises and the conclusion mean different things, then the premises and the conclusion are about different things, and so the former cannot support the latter. Example (1) The church would like to encourage theism. (2) Theism is a medical condition resulting from the excessive consumption of tea. Therefore: (3) The church ought to distribute tea more freely. This argument is obviously fallacious because it equivocates on the word theism. The first premise of the argument is only true if theism is understood as belief in a particular kind of god; the second premise of the argument is only true if theism is understood in a medical sense. Real-World Examples (1) Christianity teaches that faith is necessary for salvation. (2) Faith is irrational, it is belief in the absence of or contrary to evidence. Therefore: (3) Christianity teaches that irrationality is rewarded. This argument, which is a reasonably familiar one, switches between two different meanings of "faith". The kind of faith that Christianity holds is necessary for salvation is belief in God, and an appropriate response to that belief. It does not matter where the belief and the response come from; someone who accepts the gospel based on evidence (e.g. Doubting Thomas) still gets to heaven, according to Christianity. For the kind of faith for which (1) is true, (2) is therefore false. Similarly, for the kind of faith for which (2) is true, (1) is false. There is no one understanding of faith according to which both of the argument's premises are true, and the argument therefore fails to establish its conclusion. Another argument relating to Christianity that crops up from time to time goes like this: (1) Jesus is the Word of God. (2) The Bible is the Word of God. Therefore: (3) Jesus is the Bible. This is usually used to to support some further conclusion about the authority of the Bible or something similar, but there's no need to go any further to see that there's a problem here: the phrase "Word of God" means very different things in the two premises, so this argument rests on an equivocation.

Genetic Fallacy

The genetic fallacy is committed when an idea is either accepted or rejected because of its source, rather than its merit. Even from bad things, good may come; we therefore ought not to reject an idea just because of where it comes from, as ad hominem arguments do. Equally, even good sources may sometimes produce bad results; accepting an idea because of the goodness of its source, as in appeals to authority, is therefore no better than rejecting an idea because of the badness of its source. Both types of argument are fallacious. Examples (1) My mommy told me that the tooth fairy is real. Therefore: (2) The tooth fairy is real. (1) Eugenics was pioneered in Germany during the war. Therefore: (2) Eugenics is a bad thing. Each of these arguments commits the genetic fallacy, because each judges an idea by the goodness or badness of its source, rather than on its own merits.

No True Scotsman Fallacy

The no true scotsman fallacy is a way of reinterpreting evidence in order to prevent the refutation of one's position. Proposed counter-examples to a theory are dismissed as irrelevant solely because they are counter-examples, but purportedly because they are not what the theory is about. Example The No True Scotsman fallacy involves discounting evidence that would refute a proposition, concluding that it hasn't been falsified when in fact it has. If Angus, a Glaswegian, who puts sugar on his porridge, is proposed as a counter-example to the claim "No Scotsman puts sugar on his porridge", the 'No true Scotsman' fallacy would run as follows: (1) Angus puts sugar on his porridge. (2) No (true) Scotsman puts sugar on his porridge. Therefore: (3) Angus is not a (true) Scotsman. Therefore: (4) Angus is not a counter-example to the claim that no Scotsman puts sugar on his porridge. This fallacy is a form of circular argument, with an existing belief being assumed to be true in order to dismiss any apparent counter-examples to it. The existing belief thus becomes unfalsifiable. Real-World Examples An argument similar to this is often arises when people attempt to define religious groups. In some Christian groups, for example, there is an idea that faith is permanent, that once one becomes a Christian one cannot fall away. Apparent counter-examples to this idea, people who appear to have faith but subsequently lose it, are written off using the 'No True Scotsman' fallacy: they didn't really have faith, they weren't true Christians. The claim that faith cannot be lost is thus preserved from refutation. Given such an approach, this claim is unfalsifiable, there is no possible refutation of it.

Tu Quoquo Fallacy

There are two types of claim: objective and subjective. Objective claims have the same truth-value for everyone. For example, the claim that the Earth is cuboid is an objective claim; it's either true for everyone or false for everyone. It isn't possible for the Earth to be cuboid for me, spherical for you, but flat for everyone else, because whatever shape the Earth is it is only one shape. Subjective claims can have different truth-values for different people. For example, the claim that running a marathon takes more than three hours is a subjective claim: for many people it is true, but for a good number of runners it is false. The subjectivist fallacy is committed when someone resists the conclusion of an argument not by questioning whether the argument's premises support its conclusion, but by treating the conclusion as subjective when it is in fact objective. Typically this is done by labelling the arguer's conclusion as just an "opinion", a "perspective", a "point of view", or similar. This is one of those cases where the objectionable logic is so underdeveloped that it is difficult to pin down precisely what is wrong with it. Someone who just grunts "that's just your opinion" is clearly trying to imply something, but their reasoning isn't explicit. They might have in mind something like the following: (1) Your argument concludes that p is objectively true. (2) P is subjective. Therefore: (3) Your argument fails. This argument is fine as long as its premises are true, but where (2) is false it commits the subjectivist fallacy. Alternatively, they might mean something like this: (1) Your argument concludes that p is true. (2) Many people don't accept that p is true. Therefore: (3) Your argument fails. This argument doesn't commit the subjectivist fallacy; it has nothing to do with objectivity and subjectivity. Instead it is an example of an appeal to popularity, giving far too much weight to the opinion of those who don't accept the conclusion of the argument, failing to recognise that even an argument for a conclusion that many people don't accept can be sound.

Subjectivist Fallacy

There are two types of claim: objective and subjective. Objective claims have the same truth-value for everyone. For example, the claim that the Earth is cuboid is an objective claim; it's either true for everyone or false for everyone. It isn't possible for the Earth to be cuboid for me, spherical for you, but flat for everyone else, because whatever shape the Earth is it is only one shape. Subjective claims can have different truth-values for different people. For example, the claim that running a marathon takes more than three hours is a subjective claim: for many people it is true, but for a good number of runners it is false. The subjectivist fallacy is committed when someone resists the conclusion of an argument not by questioning whether the argument's premises support its conclusion, but by treating the conclusion as subjective when it is in fact objective. Typically this is done by labelling the arguer's conclusion as just an "opinion", a "perspective", a "point of view", or similar. This is one of those cases where the objectionable logic is so underdeveloped that it is difficult to pin down precisely what is wrong with it. Someone who just grunts "that's just your opinion" is clearly trying to imply something, but their reasoning isn't explicit. They might have in mind something like the following: (1) Your argument concludes that p is objectively true. (2) P is subjective. Therefore: (3) Your argument fails. This argument is fine as long as its premises are true, but where (2) is false it commits the subjectivist fallacy. Alternatively, they might mean something like this: (1) Your argument concludes that p is true. (2) Many people don't accept that p is true. Therefore: (3) Your argument fails. This argument doesn't commit the subjectivist fallacy; it has nothing to do with objectivity and subjectivity. Instead it is an example of an appeal to popularity, giving far too much weight to the opinion of those who don't accept the conclusion of the argument, failing to recognise that even an argument for a conclusion that many people don't accept can be sound.