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Logical fallacies are errors in reasoning that are used, either deliberately or subconsciously, to support arguments or points of view. Detecting and evaluating logical fallacies is a critical skill that can be used to determine whether to accept or reject an argument.
Fallacies are often used when somebody wants to convince you of something that has little basis in fact. They are also commonly used to distract attention away from uncomfortable answers. Needless to say, a good knowledge of fallacies is a useful tool in the armoury of any good salesperson, politician, lawyer or conman.
While fallacies will not prove a claim, neither will they disprove one1. Just because an author uses fallacies to support his case doesn't mean that his claim is wrong. However if all the arguments used are fallacies, then his argument remains unproven and his audience is entitled to reject his argument until he can provide a stronger basis for it.
This is where someone pronounces that something is always the case, when in fact only a small amount of evidence is available. Often this evidence may simply be anecdotal. Just as one swallow does not make a summer, most generalisations require a lot evidence to become commonly accepted.
Air temperatures in Antarctica have been decreasing for the past ten years, therefore the world is not warming.
What about studies in other parts of the world? Would ten years be considered a long enough time to come to a conclusion such as this?
You don't care about me. Just yesterday you didn't reply to my phone call.
Can we have more evidence that this is the case?
This fallacy is employed to convince someone that much greater consequences will follow if an initial claim is accepted. The implication is that the claim will be a first step in an unstoppable chain of events. While sometimes large consequences can occur from an initial event (such as lighting the fuse on a stick of dynamite), this is not always the case, and the mechanism by which greater consequences can transpire must be investigated further.
If you go to the night club tonight, before you know it you will meet up with some undesirable young man and he will make you pregnant.
Is this a certainty? Does free will not have anything to it?
By filling in this form, you will be buying into a business enterprise that will make you a millionaire in five years.
This may be true, but it might also require a lot of hard work, a ton of luck, and a market eager to buy your product.
Life is complex, and people have a tendency to over-simplify, so when someone is attributing a single cause to something that has many causes, they may be committing the Single Cause fallacy.
The cause of the traffic problems in this city is old people who drive too slowly.
There are many factors in traffic congestion, including the quality of the road infrastructure, the number of people hitting the roads at any time or the likelihood of accidents happening. To attribute it to just one cause is simplistic.
Sometimes people assert that one event caused another event when in fact the events are not related to each other at all, or they are both effects from an unstated cause2.
There was a huge aurora borealis in the sky last month, and then three days later the terrorist attack took place. This was an omen.
Such events are unrelated, however there is always a tendency for people look back in the past to rationalise a situation in the present.
Begging the Question
Nudity should be banned on television.
Society needs laws to prevent the flagrant display of naked flesh on our television sets.
Translation: Nudity should be banned on television because nudity should be banned on television.
The fallacy can be much more complex than this. When someone has a strong belief that they have insufficient basis for, they may use the argument itself as a basis for the argument. It's also called assuming the answer, and it's very common in prejudicial thinking.
The opposition party want to trigger a war.
Well, they reject everything the government says.
(They want to trigger a war).
A dilemma is a choice between two different, contradictory options, and a false dilemma is where multiple options are open to you, but only two options are presented to you. One option is often hugely undesirable, leading you to accept the claimant's conclusion.
You are either with us or with the terrorists.
What if you support neither?
Would you like to buy the blue kettle or the red kettle?
What if you don't want to buy any kettle?
If the basis of a claim is merely that it is accepted by many other people, this does not on its own make that claim true. Lots of people thought that the Sun, the planets and the stars travelled around the Earth many centuries ago, and the whole lot of them were wrong. Just because something is popular doesn't mean that it is right.
A recent opinion poll found that 90% of respondents believed John to be guilty, therefore he must be guilty.
Right-o, we don't need evidence then.
Loads of people went to see the film 'Titanic'. It must be a great film.
Appeal to Ignorance
This is the last refuge of somebody who hasn't a leg to stand on regarding their viewpoint, so they might question whether an alternative could possibly exist. Just because they can't think of another solution doesn't mean there isn't one.
Another refuge of last resort is an appeal to an untestable authority (such as God) for explanations, or to assert that it's all part of some grand conspiracy. These are called 'Ad Hoc Rationalisations' - the provision of special reasons which are impossible to prove or disprove one way or another.
If UFOs are not making contact with us, then how can you explain all the lights in the sky?
Well, it could be satellites, meteors, planets or planes...
It's impossible to imagine evolution being workable in any way, and this should be proof alone that it's not true.
It might be possible to imagine it working if you studied biology.
Appeal to Dubious Authorities
Just because someone powerful says that something is true, or just because it is written in a book, doesn't make it true, unless the source of the claim is creditable. If the claimant and his authority share the same incorrect assumptions, then it proves nothing.
The Pope is against contraception, therefore contraception must be bad for you.
The Pope certainly has his viewpoint and he is entitled to it, but it is one of many.
Well I bought this book and I liked it, so you will like it too.
You might well hate it.
Appeal to Pity
An Appeal to Pity is used when the claimant tries to convince people by making them feel sorry for him, when his circumstances are irrelevant to the argument. The use of pity is just one way people can be manipulated into believing something untrue. They can also be threatened, induced, seduced, bullied or harangued.
Are you telling me that I have just spent 30 years of my life knocking on doors telling people about The Divine Truth, for nothing?
If you don't buy this product from me, I will lose my job!
If the product is not right for you, you should not be compelled to buy it.
While not necessarily fallacious, the choice of language is often a powerful tool in convincing people of your argument. There are many words and phrases with powerful negative and positive connotations, which are used to rouse emotions without adding substance to the case.
Our great leader is wise and gentle. He chose to lead our volunteers, who love freedom and justice into this fight for truth, so that the enemy could be combated and our children could be safe from oppression.
This terrorist madman has brainwashed impressionable teenagers to murder with impunity. This recent act of wholesale terrorism is a last-gasp effort to consolidate his grip on power, irrespective of the consequences.
An ad hominem argument is an attack on someone's character. A very powerful way to convince others of the merits of your argument is to ridicule your detractors or competitors, even though this, of itself, does nothing to support your position. It's also used as a tool to distract people from you having to better substantiate your argument.
Well this law was obviously constructed because of the demands of that sanctimonious mob of weepy politically correct sops who always stick their heads above the parapet when anything even slightly critical of immigration is mentioned.
Whatever the character of the people who introduced it, what about the merits of the law itself?
Here you go spouting off about your rights to go out at night, when you are the first person to tell everyone else to shut up when they are talking to you. You're a complete pig.
Nice way of shutting somebody up, irrespective of the arguments being proposed by the other person.
Another example of ad hominem is to point out hypocrisy on the part of the claimant. Just because there might be an element of personal hypocrisy involved, it doesn't automatically make their claim invalid.
Mr Jennings is berating us about the evils of unregulated handgun ownership. What he didn't tell you however is that in the 1980s he had a handgun himself, and used to go out shooting on a regular basis.
The Red Herring
A Red Herring is a deliberate attempt to distract people away from a position by attempting to focus attention elsewhere. The issue might be generalised to a philosophical debate, or the phrase 'but what about?' might be inserted to try to wrest the discussion away to a safer topic.
Well you are giving me a hard time about our objections to your new vaccine, but what about the time that your company released a vaccine into the market that had to be recalled three weeks later?
The topic has been deliberately switched from the current objections to something quite different.
You are claiming that we caused this crisis, but there has been a long history of you guys claiming all sorts of calumnies against us which turned out not to be true - why not talk about that for a while?
This doesn't necessarily mean that they didn't cause the current crisis.
A common approach is to switch the focus of your attack to an easier target, by misrepresenting the views of the opponent. So instead of acknowledging that your opponents are saying X, you pretend they are saying Y, and you attack this position with gusto.
The minister wants funding to be withdrawn from child services4, but what he is really saying is that he wants more teenage violence, more teenage pregnancies, and more drug abuse.
Is this actually what the minister wants?
In any debate on the radio, on the TV, in the home, you may be subjected to a barrage of fallacies that are designed, either consciously or unconsciously, to convince you without providing proper proof. Being aware of these fallacies will help you to better understand which arguments to accept, and which to reject.