Arguments can be affected by logical fallacies, meaning errors in logic that invalidate the reliability of an argument. Sometimes, writers or speakers purposefully use logical fallacies to make an argument seem more persuasive or valid. To know what fallacies are and how to recognise them, is very important for a critical thinker, because fallacious arguments are very common in newspapers, advertisements, political speeches and other sources and can be quite persuasive, at least to the casual reader or listener.
Here below are some of the most common fallacies to be aware of.
Making assumptions about a whole group or range of cases based on a sample that is inadequate (usually because it is atypical or just too small), drawing conclusions from too little evidence and often relying on stereotypes.
A group of teenagers vandalized the park downtown. Teenagers are irresponsible and destructive.
Post hoc (false cause)
Assuming that because B comes after A, A caused B. Just because two events chronologically follow each other, does not necessarily mean that a cause and effect relationship exists.
The president raised taxes, and then the rate of violent crime went up. The president is responsible for the rise in crime.
I forgot to do my homework yesterday and we had a pop quiz.
I laid out my clothes to dry and it just started to rain.
Slippery Slope (Bad Precedent)
Assuming that a proposed step will set off an uncontrollable chain of undesirable events. The arguer claims that a sort of chain reaction, usually ending in some dire consequence, will take place, but there’s really not enough evidence for that assumption.
If you don’t stop smoking cigarettes, then you are going to start shooting heroin.
Many arguments rely on an analogy between two or more objects, ideas, or situations. If the two things that are being compared aren’t really alike in the relevant respects, the analogy is a weak one, and the argument that relies on it commits the fallacy of weak analogy.
Guns are like hammers – they’re both tools that could be used to kill someone. If we restrict the purchase of guns, we should restrict the purchase of hammers as well!
Partway through an argument, the arguer goes off on a tangent, raising a side issue that distracts the audience from what’s really at stake. The arguer avoids the main argument by diversionary tactics such as following tangents and never returns to the original issue.
I forgot to go grocery shopping for you, but I did buy you a dozen roses because I love you.
Yes, my grades are low, but I volunteer a lot of time to the nonprofit sector.
In false dichotomy, the arguer sets up the situation so it looks like there are only two choices. The arguer then eliminates one of the choices, so it seems that we are left with only one option: the one the arguer wanted us to pick in the first place. It is an oversimplification that assumingly reduces several alternatives to a mere binary opposition. It is a false dilemma that presents a “black and white” kind of thinking when there are actually many shades of grey.
The school is in bad shape. Either we tear it down and put up a new building, or we continue to risk students’ safety. Obviously, we shouldn’t risk anyone’s safety, so we must tear the building down.”
(The argument neglects to mention the possibility that we might repair the building or find some way to protect students from the risks in question, for example, if only a few rooms are in bad shape, perhaps we shouldn’t hold classes in those rooms).
Begging the Question (Petitio Principii)
Premises that are passed on as being valid without supporting evidence. Sometimes the premise is proven by the conclusion itself, making the argument circular, restating the premise in the conclusion rather than proving or disproving.
President Kennedy was an excellent speech giver because he delivered exceptional speeches.
Distorting, misrepresenting or exaggerating someone’s position so it’s easier to refute. A straw man fallacy occurs when someone takes another person’s argument or point, distorts it or exaggerates it in some kind of extreme way, and then attacks the extreme distortion, as if that is really the claim the first person is making, concluding that the original position is incorrect or ridiculous.
A: “Let’s go to the movies tonight”
B: “No, thank you, I’d rather not today”
A: “You never want to have fun!”
Mr. and Mrs. Smith are arguing about cleaning out their basement.
Mr. Smith: “Why, we just did it last year. “Do we have to clean it out every day?”
Mrs Smith: “You just want to keep everything around forever, and that’s ridiculous.”
Common Sense Fallacy
An argument is held to be true because of practical truths and common sense.
If it looks bad, it tastes bad.
Argumentum Ad Hominem
Criticizing the person who’s making an argument, rather than the argument itself.
Candidate A will not maintain his electoral promises: he cheated on his wife!
Argumentum ad Ignoratiam
An argument is true because no evidence disproves its validity.
No one has complained about this public policy, so it is not unjust.
Appeal to Fear
This type of fallacy is one that, as noted in its name, plays upon people’s fear. In particular, this fallacy presents a scary future if a certain decision is made today.
Candidate A doesn’t understand foreign policy. If you elect her as president, we will be attacked by terrorists.
Authority of Tradition
Justify an idea based on tradition.
We have always written the report this way.
Supporting a claim by stating that “everyone” believes or acts a particular way.
I support the war, because every patriotic citizen does.
The error of thinking that a random event can be influenced by past random events.
The lottery was won in this city last year; buying a ticket this year is a waste of money.
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Coordinator – Centro per lo Sviluppo Creativo Danilo Dolci – Italy