Fallacies of Ambiguity


Explanation


Fallacies of ambiguity appear to support their conclusions only due to their imprecise use of language. , , Once terms are clarified, fallacies of ambiguity are exposed. , , It is to avoid fallacies of this type that philosophers often carefully define their terms before launching into an argument.


Examples


The accent fallacy, and the fallacy of equivocation, are classic examples of fallacies of ambiguity. , , Equivocation is particularly important to look out for in evaluating philosophical arguments.


Accent Fallacies


Explanation


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.


Equivocation Fallacy


Explanation


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.


Straw Man Fallacy


Explanation


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.


Fallacies of Presumption


Explanation


Fallacies of presumption are not errors of reasoning in the sense of logical errors, but are nevertheless commonly classed as fallacies. , , Fallacies of presumption begin with a false (or at least unwarranted) assumption, and so fail to establish their conclusion.


Examples


Arguments involving false dilemmas, complex questions, or circularity all commit fallacies of presumption: false dilemmas assume that there are no other options to consider; , , complex questions assume that a state of affairs holds when it may not; , , circular arguments assume precisely the thing that they seek to prove. , , In each case, the assumption is problematic, and prevents the argument from establishing its conclusion.


Affirming the Consequent


Explanation


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.


Arguing from Ignorance


Explanation


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.


Begging the Question / Circular Reasoning


Explanation


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.


Complex Question Fallacy


Explanation


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.


Cum Hoc Fallacy


Explanation


The cum hoc fallacy is committed when it is assumed that because two things occur together, they must be causally related. , , This, however, does not follow; , , correlation is possible without causation. , , This fallacy is closely related to the post hoc fallacy.


Example


As the graph below (taken from the Church of the Flying Spaghetti Monster website) shows, two things have happened since the early 19th-century: one is that the number of pirates has declined, the other is that global average temperatures have risen.


Graph showing a correlation between an increase in global average temperatures and a rise in incidences of piracy


If correlation implied causation, we would be able to infer a connection between these two events. , , It is not the case, however, that global warming is an effect of the decline in piracy. , , Neither is the decline in piracy the result of increasing temperatures. , , Mere correlation does not imply a causal connection.


Real-World Example


Nestle, the makers of the breakfast cereal Shredded Wheat, once ran an advertising campaign in which the key phrase was this: "People who eat Shredded Wheat tend to have healthy hearts." , , This is very carefully phrased. , , It does not explicitly state that there is any causal connection between eating Shredded Wheat and having a healthy heart, but it invites viewers of the advertisements to make the connection; , , the implication is there. , , Whether or not there is any such connection, the mere fact that the two things are correlated does not prove that there is such a connection. , , In tempting viewers to infer that eating Shredded Wheat is good for your heart, Nestle are tempting viewers to commit a fallacy.


False Dilemma / Bifurcation Fallacy


Explanation


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.


Hasty Generalisation Fallacy


Explanation


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.


'No True Scotsman' Fallacy


Explanation


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.


Post Hoc Fallacy


Explanation


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.


Slippery Slope Fallacy


Explanation


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.


Sweeping Generalisation Fallacy


Explanation


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.


Sweeping Generalisation Fallacy


Explanation


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.


Subjectivist Fallacy


Explanation


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.


Tu Quoque Fallacy


Explanation


The tu quoque fallacy is committed when it is assumed that because someone else has done a thing there is nothing wrong with doing it. , , This fallacy is classically committed by children who, when told off, respond with "So and so did it too", with the implied conclusion that there is nothing wrong with doing whatever it is that they have done. , , This is a fallacy because it could be that both children are in the wrong, and because, as we were all taught, two wrongs don't make a right.


Example


(1) The Romans kept slaves.


Therefore:


(2) We can keep slaves too.


This argument commits the tu quoque fallacy because it assumes that if someone else does a thing then it's okay for us to do it too. , , It does not follow, however, from the simple fact that the Romans kept slaves, that there is nothing wrong with keeping slaves. , , It is plausible to think that the Romans acted immorally in keeping slaves, and that we would act immorally if we followed their example. , , The conclusion of the argument therefore does not follow from its premise.


Examples of the tu quoque fallacy occur all the time. , , For instance, in an article entitled Man United defend ticket price rise, BBC Sport reported:


"Manchester United have hit their fans with a 12.3% average rise in season ticket prices for the next campaign. , , A top-price ticket will cost £38 and the cheapest £23… But United have defended the price rises, saying they compare favourably with the rest of the Premiership. , , 'We do not know what most of our rivals will charge next year, buy even a price freeze across the rest of the Premiership would mean that next year only seven clubs will have a cheaper ticket than £23 and nine clubs will have a top price over £39 – in some cases almost double,' said Humby [Manchester United finance director]."


The representative of Manchester United's argument was essentially this: "Other Premiership clubs charge more, therefore our ticket prices are justified." , , This commits the tu quoque fallacy because it's quite possible that all clubs, including Manchester United, overcharge for their tickets.