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Logical Fallacies
AkosGyarmathy
What is an Argument?
An argument is a presentation of reasons for a particularstandpointIt is composed of premisesPremises are statements that express your reason or evidenceThese premises must be arranged in an appropriate way in order to support your conclusion
What is an argument?
To craft a strong argument, one must…Possess a certain degree of familiarity with the subjectUse good premisesFind good support for one’s conclusionFocus only on the most relevant part of the issueDon’t get sidetracked by rabbit trails!Only make claims that are capable of being supportedThis means avoiding sweeping claims, as those are rarely supportable
What is a fallacy?
When an argument fails in one of the previously mentioned ways, that failing is called a fallacyEssentially, fallacies are defects in an argumentThey are very common and can be quite convincingMost of us have likely been convinced by a fallacious argument before. In fact, we’ve likely presented one!
Pro-life ArgumentsIs this argument convincing?
Debate the issue in groups – prepare in 10 minutes(1) It is always morally wrong to kill a human being.(2) Abortion involves killing a humanfetus.(3) A humanfetusis a human being.C:Abortion is always morally wrong.
Pro-choiceArgumentsIs this argument convincing?
Debate the issue in groups – prepare in 10 minutes(1) An action that best increases overall human welfare is not morallywrong.(2) Abortion is sometimes the best way of increasing overall humanwelfare.C:Abortion is sometimes not morally wrong.
Reconstruct the argument in groupsPreparation time: 10 minutes
You wake up in the morning and find yourself back to back in bed withan unconsciousviolinist.A famousunconscious violinist. He has been found to havea fatalkidney ailment, and the Society of Music Lovers has canvassed all theavailable medicalrecords and found that you alone have the right blood type to help.They havetherefore kidnapped you, and last night the violinist’s circulatory systemwas pluggedinto yours, so that your kidneys can be used to extract poisons fromhis bloodas well as your own. The director of the hospital now tells you, “Look,we’re sorrythe Society of Music Lovers did this to you—we would never have permittedit ifwe had known. But still, they did it, and the violinist now is plugged into you.To unplugyou would be to kill him. But never mind, it’s only for nine months. Bythen hewill have recovered from his ailment, and can safely be unplugged from you.”Judith Jarvis Thomson – A defence of abortion
Is this argument convincing?
(1) If two actions are similar in all morally relevant respects, and if oneof the acts is not morally wrong, then the other act is alsonot morallywrong.(2) It is not morally wrong for you to unplug the violinistin Thomson’sexample.(3) To unplug the violinist and to abort a pregnancy due to rape aresimilar in all morally relevant respects.C:It is not morally wrong for a woman to abort a pregnancy due torape.
Slipperyslope fallacy
A man is clocked at fifty-six miles per hour by a radar detectionunit of thehighway patrol in a fifty-five mile per hour speed limit zone. Heargues tothe patrolman that he should not get a ticket because the differenceof onemile per hour in speed is insignificant: “After all it’s really arbitrarythat theagreed-upon speed limit is fifty-five rather than fifty-six isn’t it? It’sjust becausefifty-five is a round number that it is chosen as the limit.”
Types of Fallacies
There are many, many fallacies – far too many for us to look at them all in this presentationWe will be examining 16 of the more common fallaciesFormal fallacyAn argument A commits a formal fallacy (in the strict sense) if and only if A has F as its logical form, F is a fallacious form, and A inherits the fallacy form F.Informal fallacyFormally explicable fallacyAn argument A commits a formally explicable fallacy of type T if and only if there is at least one logical form F that enters into the explanation of how A comes to commit fallacy T and yet F not itself exhibit that fallacy.Formally inexplicable fallacyAn argument that cannot be reduced to a formally invalid argumentscheme.
1.Equivocation
Usingan ambiguous term in aquestion.Whyis it aproblem?Thequestion itselfwillbecomeambiguous,TheAnswerer may grant the premise asked fortakingthequestion in one sense, whereas the Questioner uses it in another sense ashededuceshis conclusion.Ifthe ambiguous term occurs in the theses oftheAnswererand of the Questioner, it may be that it has adifferentsense ineachthesis, so that there is no realcontradiction.
1.Equivocation
Usingan ambiguous term in a questionExample:A feather is light.What is light cannot be dark.Therefore, a feather cannot be dark.“And so, my fellow Americans: ask not what your country can do for you – ask what you can do for your country.”JFKMargarine is better thannothing.Nothingis better thanbutter.Therefore, margarine is better than butter.
2.Amphiboly
Ifa sentence contains no ambiguous words, it may still beanambiguoussentence because it allows two ways of being parsed.Whyis it aproblem?The question itself willbecome ambiguous,The Answerer may grant the premise asked for takingthe question in one sense, whereas the Questioner uses it in another sense as hededuces his conclusion.If the ambiguoussentenceoccurs in the theses of theAnswerer and of the Questioner, it may be that it has adifferentsense in eachthesis, so that there is no real contradiction.
2.Amphiboly
Ambiguoussentence because it allows two ways of being parsedExample:Noperson shall be held to answer for a capital, or otherwise infamous crime, unless on a presentment or indictment of a grand jury, except in cases arising in the land or naval forces, or in the militia, when in actual service in time of war or public danger…(Fifthamendment of USconstitution)
3.Composition
Fallaciesdependent on the use of languageandconcernthe groupings of words.– shiftingfromthedividedreadingof asentencetothecomposedreading.Whyis it aproblem?May bedifferentfromamphibolyifonesentencecanbereadastwodifferentsentences.The question itself willbecome ambiguous,The Answerer may grant the premise asked for takingthe question in one sense, whereas the Questioner uses it in another sense as hededuces his conclusion.If the ambiguoussentenceoccurs in the theses of theAnswerer and of the Questioner, it may be that it has adifferentsense in eachthesis, so that there is no real contradiction.
3.Composition
Example:“[he is]beingableto walk while sitting”Wordscanbe grouped either as“[he is] ((being able to (walk))(while sitting))”(divided reading: “while sitting” is placed at the same level as “beingableto”)or“[he is] (being able to ((walk) (while sitting)))”(composed reading:“while sitting” is brought into the scope of “being able to”).
3.Composition
Example:“This fragment of metal cannot be broken with a hammer, therefore the machine of which it is a part cannot be broken with a hammer.”Human cells are invisible to the naked eye.Humans are made up of human cells.Therefore, humans are invisible to the naked eye.
4.Division
Fallaciesdependent on the use of language andconcern the groupings of words.– shiftingfromthecomposedreadingof asentencetothedividedreading.Whyis it aproblem?May bedifferentfromamphibolyifonesentencecanbereadastwodifferentsentences.The question itself willbecome ambiguous,The Answerer may grant the premise asked for takingthe question in one sense, whereas the Questioner uses it in another sense as hededuces his conclusion.If the ambiguoussentenceoccurs in the theses of theAnswerer and of the Questioner, it may be that it has adifferentsense in eachthesis, so that there is no real contradiction.
4.Division
Fallaciesdependent on the use of language andconcern the groupings of words.– shiftingfromthecomposedreadingof asentencetothedividedreading.ExamplesA Boeing 747 can fly unaided across the ocean.A Boeing 747 has jet engines.Therefore, one of its jet engines can fly unaided across the ocean.Functioning brains think.Functioning brains are nothing but the cells that they are composed of.If functioning brains think, then the individual cells in them think.
5.Fallacyofaccentorintonation
Shiftingfromoneinterpretationof asentenceto anotherbychangingaccent/intonation.Forancientgreek, insome cases, two words that were indistinguishable when written, orsloppilypronounced, could be distinguished by their different accents, ifpronouncedcorrectly.Ifan utterance of a sentenceScontainssuchaword, the utterance could sometimes be taken to correspond also toanothersentenceS’, and thus to carry two distinct messages: S and S’.IftheQuestionertakesadvantage of this fact by shifting from one message to theotherone, he will commit the fallacy ofaccent.
5.Fallacyofaccentorintonation
Shiftingfromoneinterpretationof asentenceto anotherbychangingaccent/intonation.ExamplesIdidn't take the test yesterday. (Somebody else did.)Ididn'ttake the test yesterday. (I did not take it.)Ididn'ttakethe test yesterday. (I did something else with it.)Ididn't takethetest yesterday. (I took a different one.)Ididn't take thetestyesterday. (I took something else.)Ididn't take the testyesterday. (I took it some other day.)
5.Fallacyofaccentorintonation
Shiftingfromoneinterpretationof asentenceto anotherbychangingaccent/intonation.ExamplesIlove your mother’s cooking.Iloveyour mother’s cooking.I loveyourmother’s cooking.I love yourmother’scooking.I love your mother’scooking.
6.PetitioPrincipii- Begging the Question
The arguer asks the audience to simply accept the conclusion without providing any real evidence, either through the use of circular reasoning or by simply ignoring an important (but questionable) assumption that the argument rests on.Circular reasoning occurs when the premise states the same thing as the conclusion.Harder to detect than many otherfallaciesExample 1:Adam: God must exist.Josh: How do you know?Adam: Because the Bible says so.Josh: Why should I believe the Bible?Adam: Because the Bible was written by God.Example 2:“If such actions were not illegal, then they would not be prohibited by the law.”
7.Post hoc(False Cause)
Post hoccomes from the Latin phrase,post hoc, ergo propter hocwhich, when translated, is “after this, because of this.”This fallacy assumes that because X precedes Y, therefore X caused Y.Superstitiousbeliefs are often due to the Post Hoc Fallacy: an athlete wears their “lucky socks” and wins the game, etc.Example:(1) Cell phone usage has increased exponentially in the last 20 years.(2) Researchers discovered that the incidences of brain cancer have also increased in that time.(3) Therefore, cell phone usage must cause brain cancer.
8.Hasty Generalization
Making assumptions about an entire group of people, or a range of cases based on an inadequately small sampleCreates a general rule based on a single caseStereotypes are a common exampleExample:(1) My roommate from Maine loves lobster ravioli.(2) Therefore, all people from Maine must lovelobsterravioli.
9.Missing the Point
The premise supports a conclusion other than the one it is meant to supportExample:(1) There has been an increase in burglary in thearea.(2) More people are moving into the area.(3) Therefore, the burglary is directly caused by theincreasednumber of people moving into thearea.
10.Slippery Slope
Falsely assuming that one thing will inevitably lead to another, and another, and another, until we have reached some unavoidable dire consequence!It does not allow for the idea that one can stop at any point on the slope – it does not necessarily have to lead to the inevitable dire consequence.Restraint is possible!Example:(1) If you buy a Green Day album, then you will buy The Avengers.(2) Before you know it, you’ll be a punk with green hair and tats.(3) If you don’t want to have green hair, then you can’t buy a GreenDayalbum.
11.Weak Analogy
Many arguments rely on an analogy between two or more objects, ideas, or situationsHowever, drawing an analogy alone is not enough to prove anythingIt is crucial to make sure that the two things being compared are truly alike in the relevant areasExample:-“Life is like a box of chocolates – you never know what you’regoingto get.”-How similar are life and a box of chocolates?
12.Appeal to Authority
This does not refer to appropriately citing an expert, but rather when an arguer tries to get people to agree with him/her by appealing to a supposed authority who isn’t much of an expert.Example:“Gun laws should be extremely strict and it should be incrediblydifficultto acquire a gun. Many respected people, such asactorBrad Pitt, have expressed their support of thismovement.”
13.Appeal to Pity
Attempting to convince an individual to accept a conclusion by making them feel sorry for someoneExample:“I know the paper was due today, but my computer died last week, and then the computer lab was too noisy, so while I was on my way to the library, a cop pulled me over and wrote me a ticket, and I was so upset by the ticket that I sat by the side of the road crying for 3 hours! You should give me an A for all the trouble I’ve been through!”((These fallacies are quite common around the due date of the final paper!))
14.Appeal to Ignorance
Essentially, this fallacy states that because there is no conclusive evidence, we should therefore accept the arguer’s conclusions on the subject.The arguer attempts to use the lack of evidence as support for a positive claim about the truth of a conclusion.The exception to this fallacy is in the case of qualified scientific researchExample:(1) Not a single report of a flying saucer has ever beenauthenticated.(2) Therefore, flying saucers don’t exist.
15.Adpopulum(Bandwagon)
Also referred to as the bandwagon fallacy, the arguer tries to convince the audience to do or believe something because everyone else (supposedly) doesExample:(1) An increasing number of people are turning to yoga as awayto get in touch with their inner-being(2) Therefore, yoga helps one get in touch with theirinner-being
16.Ad hominem
Attacking the opponent instead of the opponent’s argumentExample:“Allison Smith is a bad mother, whose idea of parenting is leaving her children with the nanny. Therefore, we shouldn’t listen to her ideas on improvements in the college classroom.”
17.Tuquoque- appeal to hypocrisy
In this fallacy, the arguer points out that the opponent has actually done the thing he or she is arguing against, and concluding that we do not have to listen to the argument.Example:Mother: Smoking is bad for your health and expensive! I hopetonever see you do it.Daughter: But you did it when you were my age! Therefore,Icando it too!
18.Straw Man
The arguer sets up a weaker version of the opponent’s position and seeks to prove the watered-down version rather than the position the opponent actually holds.Through this misrepresentation, the arguer concludes that the real position has been refuted.Example:“Those who seek to abolish the death penalty are seeking to allowmurderersand others who commit heinous crimes to simply get offscot-freewith no consequence for their actions!”
19.Red Herring
The arguer goes off on a tangent midway through the argument, raising a side issue that distracts the audience from the actual argument.Example:“We admit that this measure is unpopular. But wealsourge you to note that there are so many issuesonthis ballot that the whole thing is gettingridiculous.”
20.False Dichotomy
In this fallacy, the arguer sets up the situation so that it looks as though there are only two choices. When the arguer then eliminates one of the choices, it appears that there is only one option left – the arguer’s assertion!There is rarely only 2 choices – if we were to think about them all, it may not appear to be as clear a choice.Example:(1) I can’t find my book! It was either stolen, or I never had it.(2) I know I had it;(3) Therefore, it must have been stolen!
How To Prevent Fallacies
Pretend to argue against yourselfList the evidence for each of your main pointsInvestigate your own personal fallaciesGive the appropriate amount of proofs for your claimsRemember, broad claims need more proof than narrow claims!Fairly characterize the arguments of others

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